Time on Their Hooves

Chapters

Chapter 0: Twilight Time Away Day
Chapter 1: The Liturgy of the Minute
Chapter 2: Nocturn
Chapter 3: Prime Time Riddles
Chapter 4: A Time of Climate Change
Chapter 5: The First Second
Chapter 6: A Brief History of Equestrian Time

Chapter 0: Twilight Time Away Day

Twilight Sparkle stood across the Canterlot Meridian, with her left hooves in the western hemisphere of Equestria, and her right hooves in the east. The tip of her horn and the pink streak of her tail perfectly aligned with zero degrees longitude. She looked up at the clock tower of the Abbey of the Time Turners in front of her, lost in thought.

It was said that there were worlds where the movement of the heavens was set by the laws of physics. Where planets would circle around stars, spinning such that each side experienced alternately day, then night. Moons would cycle through monthly phases set by their orbital motion. Any creatures on such a world, Twilight speculated, would recognise patterns in the movements of lights in the sky, and thus learn to tell the time and decipher the laws of nature. It must be fun to study astronomy in such a world.

But here in the magical land of Equestria, the movement of the heavens was controlled by magical beings. The stars were kicked about in games of hoofball by the ursas. The planets would wander across the sky to visit friends. The sun and moon had to be coaxed above the horizon by alicorn princesses, and gently directed back to bed when the day or night was done. This made the business of telling the time a bit more complicated, and even more important.

The abbey was a group of ancient stone buildings built around a plaza on a ledge in the cliff high above Canterlot. Here, a stream flowed out of the rock—fed by whatever magic it was that brought fresh water to the surface hundreds of miles from the ocean. The water cascaded down into the abbey compound, where it was collected in a large cuboid cistern, and then fed through a complicated mechanism into a narrow precision cut channel. This ran across the plaza, between Twilight’s legs, then through a grating in the wall, where it cascaded further down the cliff to Canterlot and beyond.

She had always loved visiting the abbey, ever since Princess Celestia had first brought her here as a young student, and explained to her about the principle of keeping time. And this visit would be especially fun as she was sharing it with her young friends who loved learning new things. She turned around and walked across the plaza to a stone parapet where the Cutie Mark Crusaders were admiring the view.

“Wow,” cried Scootaloo, with her fore-hooves placed on the stone wall staring over the cliff edge and flapping her small wings in excitement. “This is awesome. You can see the entire world—there's Cloudsdale, and Ponyville, and the Everfree forest.”

“You can see the old castle in the middle of the forest,” said Sweetie Belle.

“I think I can make out Sweet Apple Acres—that’s our barn,” said Apple Bloom. “And there’s the river. And that must be the scariest cave in Equestria.” She pointed her hoof over the landscape. “And there's the valley where we tried to get our cutie marks in zip-lining.”

Twilight Sparkle smiled and let them admire the panorama. Once they had fallen silent, she said, “When you're ready, there's something I want to show you. This place is the home of a very special group of ponies, and some personal heroes of mine: The Order of the Time Turners.”

“Order of the time turnips?” said Apple Bloom. “What d’they do?”

“They keep time. They keep track of every second which passes. And they publish an excellent range of calendars and diaries, including my favourite week-to-two-pages personal organiser.”

“Keep—time?” Apple Bloom pulled a face. This was not a concept that the Apple family were familiar with, being more used to keeping apples, pigs, sheep, and track of the weather schedule and fruit price index.

“You mean, they like have a stopwatch, and they time how fast Rainbow Dash can fly?” cried Scootaloo.

“It's much more than that,” said Twilight. “They keep track of time itself.”

She looked at the faces of three thoroughly puzzled little ponies.

“How do you tell the time?” she asked them.

“Ooo, ooo,” replied Sweetie Belle, “I know! You look at the clock face, and the little hand shows what hour it is, and the big hand shows how much past the hour it is, and...”

“But what do you do if your clock has stopped?”

“You wind it up and set it to the correct time,” said Apple Bloom.

“But how do you know the correct time?”

“Well... You find another clock. Or go and look at the Ponyville clock tower.”

Twilight smiled. They were starting to get it. “But suppose the Ponyville clock tower clock stops. How do we know what time to set it to?”

There was a pause while the crusaders pondered this problem. Then Sweetie Belle's face lit up.

“You can use a sundial!” she cried. “It always gives the right time, as Celestia raises the sun at the same time each day!”

“Well not quite the same time every day,” said Twilight. “She has to raise it earlier in the summer, than in the winter. But you're right, we can use Celestia's sun to tell the time, as every day, it's at its highest point at noon.”

Sweetie Belle beamed with the satisfaction of having got it right.

“But,” said Twilight, moving on to the next stage of the tutorial, “that’s only because Celestia puts it there. How does she know when to raise the sun?”

“She must have her own clock,” cried Apple Bloom.

“Yes,” added Scootaloo. “She must have a super fancy pony princess watch. Bet it's digital!”

“And what does Celestia use to set her watch?”

“The sun of course!” said Scootaloo.

“No silly,” said Apple Bloom. “She can't set her watch by the sun, because she sets the sun by her watch.”

“That’s right,” said Twilight with a satisfied grin.

“So she must use the clock tower,” continued Apple Bloom. Twilight stopped grinning.

“I'm not sure that works,” said Sweetie Belle.

“Yes it does,” insisted Apple Bloom. “Celestia sets her watch by the Ponyville clock tower. Then she raises the sun according to the time on her watch. And the clock tower keeper sets the clock when Celestia's sun is at noon. It all makes sense!” She traced out a circle in the air in front of her with a hoof to illustrate the line of her reasoning. Then gave a puzzled look as if she didn't entirely believe it.

Twilight explained: “If we want to set the time on any clock, we need another clock to do it. Celestia needs a standard clock to tell her when to raise the sun. We can only tell the time as accurately as the best clock we have.”

“Can’t you tell the time by magic?” asked Sweetie Belle.

“Not very well,” said Twilight. “Magical clocks are notoriously unreliable. Anything magic has a tendency to take on a life of its own. They get bored of running at the correct speed, and decide to run slower or faster, and sometimes play pranks on unsuspecting ponies. We need a super-regular, one hundred percent reliable, non-magical clock to keep proper time. Running that clock is a very important task. It's the duty of the ponies of the Order of the Time Turners.”

As she was talking, a familiar earth pony stallion, wearing a collar and tie, with an hour glass cutie mark walked up to join them.

“You remember Doctor Hooves from Ponyville?” said Twilight.

“Sure. Hello Doctor,” said Apple Bloom. “Do you need any apples?”

“The Doctor is a member of the Order,” said Twilight. “He has agreed to give us a tour of the abbey.”

“Hello,” said the Doctor. “Hello Apple Bloom. Hello Sweetie Belle. Hello Scootaloo. And hello Princess Twilight Sparkle. Come on, come on. There's lots to see and we haven't much time if we're to see everything in the abbey and learn all about the history of the Order, stop for tea, and get through everything before dinner. Let's start over here.” Beckoning them with a hoof, he trotted across the plaza. The four ponies followed him over to a curious contraption built just below the large water cistern fed by the spring.

“Behold the Equestrian Universal Absolute Time Standard Mark One.”

A steady flow of water was trickling out the tank. This flowed along a short chute, and then into a large metal bucket connected to one arm of a large balance. The other end being terminated with a metal counterweight. The balance see-sawed on a pivot. For a while it was resting with the water bucket high in the air, but as they were watching, the bucket filled with water. Once full, its weight tipped the balance over, sending the counterweight into the air, and the water bucket downward, until it was tipped over and emptied its contents into a stone basin on the ground. It then swung back upwards, and the counterweight fell back down. The movement of the counterweight pushed a lever, which in turn pushed a circle of pegs on a wheel driving a clock mechanism. As the see-saw fell, it moved the wheel around by one ratchet, and the long hand on a small clock face, mounted to one side, advanced by six degrees. Looking upwards, they saw that it matched the time shown by the large clock at the top of the tower.

“Wow! This is great—what is it?” cried Scootaloo.

“It is The Minute,” replied the Doctor. “An ancient water clock, so-called because it counts the time of one minute. We have a steady flow of water out of the cistern. Every sixty seconds, the bucket fills with water and its weight tips the lever arm, and the clock hand moves forward one sixtieth of the hour. A basic, but functional timepiece. It was built nearly two thousand years ago by ponies searching for a way to regulate time which didn't require them to keep turning hour-glasses. A simple water wheel wouldn’t do as it would turn at a different rate depending on the flow of the stream, but here, the water flows from the stone cistern, fed by the stream and kept full, so with a constant head of water, the rate at which the water flows into the bucket is steady and is used to set the clock. For hundreds of years, this was the clock which kept Equestria running to time, telling Celestia when to raise the sun, Luna when to raise the moon, and everypony else when it was time for lunch, dinner and supper. These days, of course, we just run it for fun—and for its heritage value. But in the olden days, Luna and Celestia would fly up here to the abbey twice a day to make sure they raised and lowered the moon and sun at the correct time.”

“Why don't you use it anymore?” asked Apple Bloom.

“It's not nearly accurate enough. It can gain or lose many minutes a day.”

“Does that really matter?” asked Sweetie Belle.

This was not a good thing to say to a member of the Order of the Time Turners. The Doctor gave Sweetie Belle a stern look. “It matters very much indeed. If we cannot keep accurate time, Celestia and Luna would raise and lower the sun and moon at the wrong time.”

“What's the problem?” asked Scootaloo. “So what if Celestia's a few minutes late raising the sun? Then we just get a few minutes extra in bed.”

“That would have very serious consequences. As was discovered by the ponies of this Order many hundreds of years ago. Now that is an interesting tale, and it includes the story of how a young filly got her cutie mark. Would you like to hear it?”

“A cutie mark story! Yes!” answered the three fillies in unison. They sat down on the ground and looked up at the Doctor expectantly. The stallion assumed the pose of a story-teller, with a sly smile and a twinkle in his eye. He opened a book he had left lying on the ground with a hoof.

“It’s all explained in this journal. It all began on a cold winter day.”

Author's Note

These notes are intended to provide some more information for anyone interested in the real world science and history behind this story. Feel free to ignore.

Zero Longitude

Our story begins on the prime meridian of Equestria—the zero point for measuring your position East of West of that line. As currently published maps of Equestria have strangely omitted such information, I figure I am free to set the location of this prestigious coordinate.

In our world, all sorts of places have been used as a prime meridian, causing no end of confusion for navigators, until it was decided at the International Meridian Conference in 1884 in Washington DC, that the international standard for zero longitude should be the Royal Observatory, Greenwich, London.

From then on, the time measured by the position of the sun and stars at Greenwich was the International Standard Time, disseminated across the globe by that fancy new technology, the electric telegraph. This system worked well for many years, but with the development of atomic clocks, it was found that the Earth was not such a good timepiece—it wobbles a bit and is gradually slowing down. Thus in 1972 Greenwich Mean Time was replaced by Coordinated Universal Time as the worldwide standard. This is set by a network of atomic clocks, with one second defined as a fixed number of oscillations of a caesium atom. Whenever it gets out of sync with our spinning planet, it is corrected by the insertion of a leap second, and we get an extra second in bed, or at work or school, depending on which side of the planet you live on.

Leap seconds cause all sorts of problems for telecom engineers in our world. However, in Equestria, they would not have to worry about this as Celestia and Luna would keep the sun and moon properly aligned. No doubt there is an Equestrian Atomic Standard to define this. But this does raise the question of what they did before ponies invented atomic clocks. This is the subject of this story.

Chapter 1: The Liturgy of the Minute

“Saturday 14th January, 748th year of the reign of the two Pony Sisters.
Today temperatures fell to the lowest level this winter. The Order continues in our duty to monitor the passage of time and record the events of history. We have plenty of fuel, yet every member looks forward to the spring, with the exception of the Treasurer who appears quite indifferent to the climate. Preparations for tomorrow's feast, marking the five hundredth anniversary of the defeat of the draconequus and the end of Reign of Chaos, are almost complete. We have brought in ample supplies of food and drink. The princesses have accepted our invitations.”

The Abbess of the Order of the Time Turners, Prime Meridian, finished writing her daily entry in the log book and wiped the excess ink off her quill. As the daylight was fading she needed the light of her horn to read her script. Glancing at the level of sand in the hourglass on her desk, she saw that she still had ten minutes before she had to leave for the evening ceremony. She walked across the stone floor of her chamber and stood to stare out of the south window. As the head of the Order, she had personal quarters in a prime position, with windows looking over the abbey complex on one side, and on the other, directly above the cliff face, she could look out across the vast expanse of the densely forested central Equestrian plain. As there was no need for heavy rain until spring, the pegasi had cleared the sky of clouds to reduce the risk of winter storms. But the clear skies led to cold nights this high up in the mountain.

In the distance, surrounded by the dark Everfree forest, she could just make out the castle of the pony sisters. Once the home of the two alicorns crowned Princesses of Equestria, the castle had been uninhabited for over twenty years since Celestia and Luna had chosen to live apart. Celestia had a tower in the mountains to the east of Everfree, while Luna had raised a citadel in the range to the west.

The relationship of the two sisters had swung back and forth, from good to bad, over the centuries. For centuries they had been best of friends, living in the same castle. Then they had argued and parted. In due course becoming lonely, and eventually coming back together to live as best friends for another century or so. This cycle had repeated several times since the start of their reign.

“But why did Celestia and Luna fall out?” asked Sweetie Belle.

“They loved pranking one another. But occasionally a prank went too far and hurt one of their feelings. They had many arguments over the years and there were times when they stopped talking to one another. If you remember, that eventually drove Luna to turn into Nightmare Moon.”

“Like you and Rarity,” said Apple Bloom.

“That was different! That was just because Rarity started being a totally stuck-up, snooty unsister who wouldn’t do anything fun. But she made up for it in the end.”

“Exactly, I bet Celestia was just the same.”

“Let the Doctor continue the story,” said Twilight.

The Abbess knew this as it was all documented in the annals of the abbey. The duties of the Order, beyond measuring time, included keeping records of historical events and mediating between the princesses. When Starswirl had founded the Order, shortly after Celestia and Luna had gained their cutie marks and taken on their roles as guardians of the sun and moon, he had rightly guessed that regulating the length of the day and night was best undertaken by an independent body. He had also foreseen—maybe as a consequence of his dabbling in time travel, or maybe just because he knew what sisters can be like—that while they were at the time the best of friends, this would not always be true. At the present moment the princesses’ feelings towards one another were as cold as the weather. However they both respected the Order, and would meet at the abbey twice a day to participate in the ceremonies of sunrise and sunset.

Five hundred years previously, the two sisters had stood together and wielded the elements of harmony to defeat Discord, the Master of Chaos. A triumph of friendship and a great relief for the Order[1]. The Abbess had hoped that the anniversary of this event would provide an occasion for the princesses to come back together. But this hope had faded as she had counted down the days and saw no sign of a thawing of their feelings to one another.

[1] During the Reign of Chaos, the terrified members of the Order had dutifully kept to their station, counting the passage of the minutes while the sun and moon flittered overhead at random, chocolate milk rained down upon them, and the rocks beneath their feet turned to jelly. It was said by a historian of wit, long after the defeat of Discord, that the princesses had fought the monster, while the Order held the stopwatch. But the Order saw no shame in this division of labour. Holding the stopwatch was their mission. They were proud to have kept track of time such that, when the chaos had passed, they could tell Celestia and Luna where to position the sun and moon, and the cycle of day and night could continue exactly as it should.

Staring across the landscape, the Abbess noted a small dot move away from the castle. At first she took this to be a raven, but as it grew larger, she realised it was a winged pony, and a minute later she could see that it was Princess Celestia flying towards the mountain. The princess had been visiting the old castle. That was noteworthy.

A bell rang out from a tower on the other side of the plaza, signalling to the ponies of the Order that sunset would be in eight minutes. The Abbess threw her black hooded gown—which marked her as a Fellow of the Order—over her cream coat and curly orange mane, and left her chamber, closing the heavy oak door behind her. She walked down the spiral staircase, down four floors, and then into the great hall. The kitchen ponies were busy lighting candles and laying out plates along the long wooden tables, which ran the length of the hall, in preparation for dinner. The walls were covered with portraits of the previous ponies who had held her office as head of the abbey and the Order. With the largest portrait of all, hung above the high table at the end of the hall, depicting Canonical Hours—the first abbot of the Order, and the inventor of the hourglass.

“Did he have an hourglass cutie mark like yours?” said Apple Bloom.

“He did,” replied the Doctor. “But when he got his cutie mark, he thought his special talent was in making abstract glass sculptures. He only later found that it was one of the greatest inventions in Equestria.”

“We should try to get our cutie marks in glass sculpture,”

“If you let the Doctor finish the story, you might learn how to get your cutie mark,” said Twilight.

Life in the abbey ran to a rigid schedule, befitting a community of ponies united by their common special talent in keeping time. The day and night were divided up into the eight three-hour periods of: nocturn, matins, prime, terce, sext, none, vespers and compline. The precise times of the ceremonies of daybreak and nightfall were changed throughout the year to set the seasons. All the Order would rise before dawn and assemble at the scheduled time to watch Celestia raise the sun, after her sister had withdrawn the moon to mark the end of the night. They would then eat breakfast together in the great hall before setting about their own work or studies.

The duties of the Order were divided into different categories. Their primary task, which the Abbess administered as her personal responsibility, was to keep time: to maintain the ancient water mechanism which defined the minute, and ensure the spindles, cogs, and other mechanics driving the clocks were in full working order. She would then direct Celestia and Luna as to when they should move the heavens accordingly.

But the abbey had secondary functions. It was, at the time, the greatest centre of learning in Equestria. The library held records going back to the dawn of pony literacy, and grew larger every year. A small herd of scholars collected stories of happenings from around the kingdom, and beyond, and copied these into the great bound volumes which made up the ever growing History of Equestria. There were also many talented artists who produced beautifully illuminated manuscripts, with strips of comics depicting the better stories. Other scholars wrote treatises on every topic under the sun and moon: natural philosophy, magic, legal codes, medicine, botany, astronomy and many more. The library collected books from far afield, and had many volumes in exotic languages such as Camel, Griffon, and Llama, which only a few of the senior scholars could read. There were also extensive workshops, where craftsponies assembled the precision instruments and timepieces for which the order was famous. Glass-blowers, metal workers, carpenters and others were all hard at work somewhere within the walls.

All in all, the abbey housed several hundred ponies. Who all required regular meals. Hence the third, and in the opinion of most members of the Order, the most important role of the abbey was its culinary function. Tunnels into the mountain led to extensive cellars, stocked with the produce of the abbey's terraced gardens, and with more exotic foodstuffs imported from around the world. Barrels of the best wine, beer, mead—

“And cider?” said Apple Bloom.

“Plenty of cider,” said the Doctor.

Twilight stared at Apple Bloom.

“Let the Doctor—”

“Yeah, okay, I was just askin’.”

—the best cider, brandy and exotic liqueurs; jars of honey, jam, chutneys and other preserves; nuts, berries, cheeses, cakes. The kitchen ponies took great pride in preparing daily feasts, and their skill in making sweet pastries, baking cakes, and mixing salads was known throughout the kingdom.

The education of the next generation was vital to the continuity of the Order. Any pony with a special talent for keeping time could join their community, and most arrived as young fillies or colts. They filled the ranks of the novices, and spent five years studying all aspects of time keeping, including mathematics, physics, history, metrology, as well as more practical skills such as glass blowing, metal working and cider making. Once they graduated as full members of the Order, many would leave the abbey and travel throughout Equestria, using their knowledge and skills to help other ponies and ensure the country ran to order. Some, however, would stay to run the abbey, rising up the hierarchy to the rank of Fellows of the Order, which included the Abbess, the Dean—who oversaw the education of the novices, the Practical Scholar—who took charge of the workshops, the Librarian, the Treasurer, and the Steward and Cellarer—who together had the all-important job of maintaining the stocks of food and drink, and providing meals for everypony.

The Abbess walked out of the hall and along the short passageway which led to the outside doorway. A steady stream of young novices, clad in brown hoods, were running outside. Among them she caught sight of the fire-like red mane and green wings of her friend Median Measure—the Dean—descending another staircase. They exchanged smiles and walked through the ornate stone doorway together and out onto the plaza. A porter, clad in the grey hood that marked him as a full member, but not a Fellow, of the Order held the wooden door ajar with a hoof.

Most of the ponies were now assembled. Braziers, filled with burning charcoals, had been positioned across the courtyard to provide warmth against the winter chill. But the ponies still huddled together with their hoods firmly wrapped around their ears. The full members of the Order were standing in lines on the north wall, either side of the clock tower. The novices were assembled on the south side, in two groups on either side of the straight water channel which carried the water flowing from the Minute, the zero longitude of Equestria, which cut the plaza into two halves. The Dean walked along the line of assembled novices, inspecting them with a critical eye.

“Peony Poset—take that silly pink thing out of your mane. It makes you look ridiculous—like you're some sort of children's toy. Pumpkin Strudel—Look at those shoes—fancy coming before the princesses with such dirty hooves. Stand up tall everypony.”

Raised podia in the eastern and western hemispheres were set up for the princesses. The Fellows stood on a stone platform at the south, straddling the meridian. From this point, which jutted out over the cliff edge, the Abbess had a wider angle of view than the rest of the congregation, and thus she was the first to see Princess Luna approaching from the west, a silhouette in front of the red sun just above the horizon.

Luna flew around the western side of the mountain, accompanied by a small guard of bat ponies. In recent years, the princess of the night had formed a strong friendship with the nocturnal tribe of winged ponies, who now made up the greater part of her retinue. She landed on her platform and bowed to the Abbess. All eyes then turned to the south-east, to watch Princess Celestia approach, with her guard of gleaming white pegasus stallions, illuminated by the evening rays of her sun.

Celestia landed on the eastern platform as the clock face indicated another three minutes before the given time for sunset. All the assembly watched in solemn silence as the bucket filled with water, the lever arm fell, and the mechanism moved the clock hand once, twice, and finally reached the awaited minute. A moment before this, unseen by the audience who were looking at the clock, the Abbess withdrew a tuning fork from her robe—

“What’s a tuning fork?” said Scootaloo.

“It’s from the kitchen. It’s what you need to turn over hot apple fritters in the pan,” said Apple Bloom.

“That’s a turning fork,” said Sweetie Belle. “You use a tuning fork to tune a piano.”

“How can you tune a piano with a fork?”

“Do you need a knife and spoon too?”

“Hey—we never tried getting our cutie marks in piano tuning.”

“Will you let the Doctor continue the story?”

The Abbess took her tuning fork from her robes, hit it against a hoof and raised it to her ear. Then, in perfect tune, she sang out the words to start the ceremony.

“By the authority vested in me as the head of the Order of the Time Turners I hereby ask Her Royal Highness Princess Celestia to lower the sun—”

She hung onto the final note, as Celestia lit up her horn and bowed to direct the sun below the mountains to the west. The twilight faded to darkness and the stars appeared in the sky above. The congregation waited, in the light of the burning braziers. The Abbess turned her head to the princess of the night.

“Now that the day has finished and the night is begun I hereby ask Her Royal Highness Princess Luna to lift the moon—”

Luna raised her head, horn aglow, and the moon rose steadily above the eastern horizon, shedding a soft light onto the snow-capped mountains.

“We thank you the Royal Pony Sisters in the name of the Unicorns and the Pegasi and the Earth Ponies.”

Upon completing the liturgy, the chorus of novices intoned, “Amen.” Thus marking the end of the short ceremony.

The daily ceremony was an impressive spectacle to behold—at least the first time you saw it. After a week in the Order, it was a tedium. Occasionally one of the more uninhibited novices would ask the Abbess why it was necessary to go through the rites every day. Was it really necessary for the entire Order to assemble every day at sunrise and sunset?

The Abbess would reply that it was a tradition that had been followed for over six hundred years. Most novices would accept that. Occasionally one would ask why it was necessary to continue with a tradition just because it had been done for over six hundred years. At which the Abbess would admit that it was not strictly necessary to continue with any tradition, but one should certainly be wary of changing one which had served them well for six hundred years. Very occasionally an exceptionally pert novice would suggest that maybe it wasn't really necessary for them to get out of bed before dawn every single day. At this the Abbess would sternly explain that the ceremonies of daybreak and nightfall was what brought order to Equestria. That it ensured the proper movement of the sun and moon. Without it, chaos would come to their world. The many other abbeys around Equestria—satellites of the Order, who set their clocks by the sun and moon—would be unable to keep accurate time. Farmers would not know when to plant their crops. Sailors would be unable to navigate the oceans. And while it may be that time would continue to pass without their presence each morning, did they really want to risk the consequences of being absent and failing their duty as novice members of the Order?

The brighter novices just pretended not to hear the bell, pulled their blankets over their heads, stayed in bed and didn't ask questions.

“They didn’t have Applejack as a sister. That never works. If there’s chores to be done—”

“Let the Doctor continue the story.”

What was not generally revealed to the junior members was that the most important audience for the ceremony was not them but the princesses. Regular routine was important in the training of alicorns. Celestia and Luna, while over seven centuries old, were still young by alicorn standards. Nopony questioned the sincerity of their promises to serve and protect Equestria. But they did sometimes have trouble getting up in the morning (or evening), and the Fellows of the Order knew well that the best way to ensure their timely arrival was to make sure that there would be over a hundred ponies looking at them if they turned up late.

The evening ceremony now over, the rows of hooded ponies made their way towards the hall, already thinking about dinner. The two princesses walked towards the Abbess, as it was the custom for them to exchange a few words.

“We thank thee Abbess for presiding over the ceremony,” said Luna, in the traditional Royal Canterlot Voice. She was facing the Abbess and ignoring her sister. “Thy voice is in perfect tune as usual.”

The Abbess nodded to acknowledge the formality. She noticed that Celestia was watching Luna. Was this a sign that she wanted to make peace with her younger sister? Had her evening visit to the old castle made her miss her old friend?

“We also extend our thanks Abbess, to you and your Order,” said Celestia. “And we greet thee, younger sister.”

It was hardly an expression of friendship. But it was the first time Celestia had directly addressed Luna in over two years. Both the Abbess and Luna realised the significance of this gesture. However if Celestia had been hoping for a warm reply, she was to be disappointed. Luna seemed more surprised than touched by the direct address. Unsure how to reply for a moment, she quickly rallied.

“A cold day to greet us, in this most bitter of winters. Canst thou not return thy sun to its earlier power?”

Celestia's face instantly hardened at this comment. “The sun shines as hot today as it did ten, twenty and indeed a hundred years past.”

“Then why is the weather so much colder? Thy sun is the source of the energy to heat the world, and what else has changed over the centuries? Thou art shirking thy duty sister.” Luna stared into her sister’s eyes. It seemed that this brought back bitter memories.

“Just as you did in times past,” she said, dropping the Royal Canterlot Voice. “When you let that fiend of a phoenix set fire to my favourite poetry notebook.”

Celestia thrust her head forwards towards her sister until their horns were touching.

“Am I to blame if Philomena dislikes bad verse? And you accuse me of not controlling my pet? You who left a dozen moon frogs in my bed!”

“They were just searching for somewhere warm to hibernate. It was cruel of you to throw them in the moat.”

“They’re frogs! They’re supposed to like water.”

“There is no water on the moon! Of course you would not know—you never paid it any attention.”

At this point small sparks were flying between the two alicorns’ horns. The Abbess coughed nervously. The princesses suddenly remembered she was present and each took a step back. There was an awkward silence for a few seconds as the three ponies looked at each other, then Celestia turned and flew off to the east without saying another word, leaving Luna and the Abbess.

“Until dawn,” said Luna, bowing slightly to the Abbess, then she turned and took flight back towards her home.

Standing alone on the podium, the Abbess turned first to the east, then west, watching the two princesses fly apart. She would gladly give half the gold in the abbey treasury to see the two sisters on friendly terms again, as they had been in her youth[2]. But friendship could not be bought. She could only wait. A reunion would come at some point in the future. She could only hope that it would be within her lifetime. And, she reminded herself, the important thing was that they continued to respect the Order, and perform their duties in raising and lowering the sun and moon at the required time.

[2] Although the Treasurer would not agree to such a transaction.

She walked alone, across the now empty plaza, into the main hall where the Order were waiting for her to begin the evening dinner.

Author's Note

Monastic Orders

Monasteries were a key part of life in medieval Europe. Large residential communities—some had hundreds of members—who had dedicated their lives to serving God. Some were based in towns and cities, other were deliberately build in remote, isolated locations. The Abbey of the Time Turners is vaguely based on my memories of hill-top abbeys I saw during my time backpacking around Italy.

Life in monasteries followed a regular routine of prayer, work, and reading. Members had taken solemn vows to follow the rule of the order. Monastic discipline was strict. In order to keep to their schedule, they needed some way to tell the time when the sun or stars were hidden by clouds. This was done using various methods including chanting hymns, candle clocks, and water clocks of various designs. All of these had limitations, and this provided the incentive to investigate new ways of keeping time.

In addition to their spiritual role they were also centres of learning (predating universities), storehouses, libraries and hospitals. European scientists of this period were friars such as Roger Bacon (1214-1292) a pioneer of the scientific method, or William of Occam (1285-1347) famous for his razor.

Chapter 2: Nocturn

The Abbess walked through the doorway and along the main hall, past the long wooden tables aligned parallel to the length of the room, where the novices were all sat on low benches chattering away waiting for the meal to begin, and up to the high table, set across the hall on a raised platform beneath the portrait of Canonical Hours. Here the rest of the Fellows were waiting for her arrival, seated on plush cushions. The room was lit by candles, positioned in circular chandeliers hanging by chains from the high ceiling, and in forked candelabra set on the tables, among the many plates, trays and dishes of good food.

In the middle of the high table was a large ornate hourglass, used to ensure that dinner ran to proper time and that the ponies of the Order did not dawdle to excess over their food. On taking her place, the Abbess levitated this in the air, turning it over, before replacing it. Then she picked up a wooden gavel and signalled the start of dinner by hammering it firmly against a sounding block, creating a loud sharp noise which instantly silenced the chattering ponies. Except one pegasus filly with a pink bow in her mane, who let out a terrified squeak and leapt high in the air, knocking a chandelier to one side.

The Dean exchanged a look with the Abbess, shaking her red mane and tutting despairingly. “That Peony Poset. Frightened by a loud noise… Really… She’s lucky she’s under our care—she wouldn't last long in the outside world.”

The Steward, who was levitating dishes of hot steaming vegetables onto the table, paused a moment to defend the young filly. “We’re lucky to have her,” he said. “She has a lovely singing voice, and we have a shortage of good sopranos in the choir.” He was an ivory unicorn with an immaculately groomed mahogany mane. Whereas the rest of the Fellows were content to dress in their simple hooded gowns, he chose to wear an elegant frock coat, cravat and gleaming white shirts with extra lace.

They all piled food onto their plates: roast vegetable pastries, steamed butternut squash, fresh beans, potatoes, pickles. The ponies of the Order enjoyed their food, and the abbey took pride in providing the best for its members. Most were content to eat straight off their plates, although some of the unicorns chose to show off their skill at manipulating the latest instrument technology—knives, forks and spoons. The Abbess surveyed the hall checking that every table was well provided, nodding at the Cellarer, sitting at the end of the table, to acknowledge that everything was in order. She watched the disturbed chandelier swing back and forth across the central table, casting moving shadows onto the surface, then turned her attention to the high table conversation.

“This weather is getting very tiresome,” complained the Practical Scholar, a yellow earth pony with a curly blue mane. “The workshops are freezing. Well… It's okay for the glass blowers next to their furnaces, but the rest of us are trying to piece together precision timepieces with hooves numb from the cold.” He rubbed his forelegs together to make the point. His pale yellow coat was covered with specks of oil acquired from an afternoon of tinkering with gearwheels. “Can't we bring spring forwards a bit?”

He did not mean this seriously. Everypony knew that the calendar was set to a fixed scheduled drawn up by Starswirl the Bearded before the foundation of the Order [1]. This pattern had been followed for over seven centuries, and nopony considered changing it now.

[1] His original vision called for a year of three hundred and sixty days, divided into twelve months of thirty days. This was certified by the unicorns, as in line with the cosmic order; by the pegasi, as optimum for managing weather patterns; and by the Earth ponies, as ensuring a good length of growing season to produce the food they needed. There had been a few modifications, following a process of public consultation, which added an extra five days of public holidays. A late request by the Show Jumpers League for an extra day to hold their annual gala was permitted one year in four (so-called leap years).

“The winter always seems to last. While summer comes and goes so fast,” mused the Librarian, Azalay, an old zebra mare who had joined the abbey after many years travelling the world [2].

[2] Her full name was Azalay Asfar as Time-Buck-To, identifying the distant foreign priory where she had joined the Order many years ago.

“That is just how it seems to ponies,” said the Abbess. “Time always seems to pass quicker during warm summer days, and slower during the cold winter nights. That's why we have a mechanical timepiece to regulate the seasons.”

“But,” said the Practical Scholar, “the Minute is running slightly slower than it used to.”

“It can't,” said the Abbess, helping herself to a portion of daisy and buttercup salad.

“It is,” insisted the scholar, “I timed it with an hourglass that was filled with sand some time ago to mark a one hour period. During that period, the Minute counted only fifty-eight minutes – it's going slow.”

“It can't,” repeated the Abbess, levitating a fork above her plate to select potatoes and parsnips.

“But—”

“You misunderstand me. The Minute cannot run slow by definition. It always runs at one minute per minute because it is what defines the minute. It is the absolute time standard, so it can't run slow. Instead your hourglass was running fast. Pass the sprouts.”

The Practical Scholar could not dispute her logic. He passed the sprouts.

“That is not to say,” continued the Abbess while spooning the vegetables onto her plate, “that it is necessarily a perfect timepiece. Let us suppose—as a thought experiment—that there exists a perfect clock, which could measure the length of a time period to perfect precision. It is quite conceivable that our imperfect Minute would run fast or slow relative to such a clock. However the Minute is the best timepiece we have—the hourglasses are fine for measuring short periods, but we must have a clock which does not require a pony to turn it every hour. Maybe one day we will build a better chronometer. Until that point we must trust the Minute.”

“I read of a world, very far away,” said the Librarian.
“With no alicorns to make night or day.
Around the sun, the world is fixed in orbit.
So regular you can set the clock by it.”

“That would make things easy,” said the Abbess, in between mouthfuls of food. “But I can’t see it working. The sun and moon are so easily disturbed by stray magic, we need the princesses to control them.”

“Sounds like an old mares' tale to me,” said the Dean. “Like those stories about magic clocks controlled by fairy ponies, and pumpkins which turn into rocks at midnight.”

“There's a way to build a better clock using atomic theory,” said the Practical Scholar. The Dean groaned. Atomic theory, a radical new intellectual idea that all the matter in the world was made of tiny indivisible particles, was the Practical Scholar's pet subject. She did not share his enthusiasm.

“No really,” he said. “If we can just produce a coherent cloud of cold atoms, all spinning in unison, then we could build a super accurate clock!”

“And how will you build it?” asked the Dean.

“I'm working on it.”

After they had finished the main course, the Steward brought in sticky sweet pastries made with soft cheese, honey and raisins, and a vessel of cream which they each poured over their portions.

“Is everything prepared for the feast tomorrow?” the Abbess asked the Cellarer. “Do we have enough cider in stock?”

“Eeyup,” she said. “More than enough. The Practical Scholar sent the last order to the cider press, written using metric units. But they assumed it was in hogsheads. So we now have nine hundred and twenty barrels to drink up.”

The Dean sighed. “Why do you have to count everything in different measures to everypony else?” she asked the Practical Scholar.

“Why does everypony else still use such silly archaic units? The metric system is much more logical. It’s all based on multiples of ten. I’ve also been working out a system for metric time which will have ten minutes to the hour, and ten hours to the day, and…”

“Anypony would think you had ten legs.”

“Can I remind you all,” said the Abbess, “that it is very important that everything goes smoothly tomorrow. It will be the five hundredth anniversary of the defeat of chaos and the restoration of order. Everything needs to be precise and on time or it will give a bad impression to the novices and the princesses. Dinner will start at seven o’clock precisely. We have plenty of time to get through all five courses before eleven o’clock. That was the precise hour that Discord was vanquished, so I will propose a toast to the princesses at that point. Don’t drink too much cider or fall asleep.”

The Fellows nodded their heads, but were not paying much attention. The Practical Scholar stared vacantly into the air, musing on further innovative time keeping instruments.

“If we could excite a mechanical resonance in a rock crystal,” he mused, “it would oscillate at a precise frequency and make an accurate clock. But how do we start a mechanical vibration?”

“Try bashing your head against it,” suggested the Dean.

“This cream's a bit thick,” said the Steward, lifting the jug in the air and watching the viscous liquid slowly drain onto his pudding.

“It's the cold weather,” explained the Cellarer, “let me warm it up.” She took the jug and left the table.

The Abbess stopped listening to the Fellows’ random conversations and stared over their heads at the novices, engaged in their own conversations, then up at the ceiling, where the chandelier was still swinging back and forth following the earlier disturbance. She noted the level of sand in the upper half of the table hourglass was almost finished—less than a minute to go. She placed one fore hoof against the other, feeling her pulse, and counted the passage of time steadily, as was her habit. One, two, three... The chandelier swung to the left... Four, five, six... Back to the right... Seven, eight, nine... Left again. She watched the final grain of sand fall, then stood up, pausing briefly to let the chandelier swing fully to the right, so that when she banged the gavel sharply down to signal the end of dinner, it was clear of Peony Poset’s vertical trajectory.

The sound abruptly cut off the Fellows' and novices' conversations and all ponies stood in silence. Now that the formal meal was completed, the ponies were free to do as they wished until it was time for bed. Some would return to the workshops or the library to work on their projects. The novices would mostly stay chatting and playing games in the hall. The Abbess and the Dean left the table and walked out of the hall with stern faces as the entire order watched them.

The two friends kept up this demeanour as they walked up the tower staircase, but once they reached the Abbess's chamber, they both started giggling. They closed the door and sat down on a pile of cushions. The Abbess withdrew a bottle of port from her habit—

“What’s port?” said Apple Bloom.

“It's a place where you park boats,” said Scootaloo.

“It's the left-hoof side of a boat, opposite to starboard,” said Sweetie Belle.

“Port is a type of sweet wine,” said Twilight. “It comes from Portugallop. Now please let the Doctor continue the story.”

The Abbess levitated two glasses off a shelf, filling them with the sweet wine.

“You’re getting better at making them jump out their skin with that gavel,” said the Dean.

“They get more jumpy every year,” said the Abbess.

“We need to toughen them up. Maybe we should get them to run up to the summit every morning.”

“How are they doing with their studies?”

“Progressing at their usual pace,” replied the Dean. “How are things with the princesses?”

The Abbess outlined her earlier observations and the brief conversation between Celestia and Luna. The Dean listened with interest.

“So Luna blames Celestia for the cold weather? Is there any truth in that?”

“I don't see how,” said the Abbess, “but I don't have any better explanation.”

“Maybe if we can find an explanation—assuming it isn't the sun—and explain it to Luna, she might soften up.”

The Abbess nodded.

“It would be good to get them together again.”

The two Fellows continued chatting late into the evening. They were old friends, and it was their custom to spend this time of the day talking privately about the affairs of the abbey. Eventually the Dean stood up.

“Well, I better go and check the novices are all in bed and not reading under the covers. Goodnight.” The two mares exchanged a short hug, then the Dean left closing the door behind her.

The Abbess walked over to the window and stared out at the stars. The moon had now risen high into the sky, and its light shone onto the plaza illuminating the flagstones, the water channel and the clock face. She watched the Minute mechanism move up and down for several cycles, listening to the soft clang of the metal arm, then she walked back to the centre of the room, blew out the candles, threw off her gown, and climbed into bed. Before she closed her eyes, she turned over an hourglass on her bedside table—actually an eight-hour-glass—which would time her sleeping period. Then she fell asleep with the ease which comes to ponies who live their lives to a strict regular schedule.

The Abbess's room was on the top floor, separated from the roof by a layer of wooden floor boards, and a very small attic space, too low to allow an adult pony to stand without hitting his or her head on the roof-trusses. There was, however, just enough space for a small foal, and while the Abbess was enjoying her evening chat with the Dean, this space was occupied by a little pegasus filly named Rappel (or Rap to her friends—and to us, as we shall assume that role), lying on the floor with her ear to a crack between the boards, listening to the private conversation.

As soon as Rap heard the Dean leave the room, she got to her hooves, and quickly, but quietly, ran along the narrow attic passage. Halfway across the building there was a sky-light, which she pushed open, then she jumped out onto the roof, skidding down the tiles into a valley between two gables. She then set off racing across the slates in the moonlight in order to reach the other side of the building.

Rap was a light blue pony with a perpetually messy purple mane. Her coat was covered in small scratches and grazes. Her small wings had not yet allowed her to achieve sustained flight, a fact which irritated her greatly—although she would never admit as much—but this handicap had failed to prevent her from exploring every rooftop and high location within the abbey. Possessing a natural gift, cultivated by much practice, to fit her hooves around the tiniest ledge in any rock or brickwork, and flapping her small wings to maintain balance with a highly individual application of pegasus magic, she could scale any cliff face or building wall. She also knew some neat tricks with a length of rope. Nonetheless, scarcely a week went by without suffering at least one minor fall.

“A pegasus filly who couldn't fly—like you Scootaloo,” said Apple Bloom.

“Yeah,” said Scootaloo. “Hey—do you think I can climb that wall—let me try!”

Without waiting for a reply, she galloped up to the clock tower and set off up the stone wall. Buzzing her wings, and sustained by her momentum, she propelled herself up hoof-by-hoof past the lowest windows, then onwards and upwards, and had nearly reached the next window when she slipped off a support. Falling back she flapped her wings wildly and made a grab for a windowsill with another hoof. But to no avail. Just before hitting the ground, she was caught in a pink magical aura. Twilight rotated the floating filly the right way up, put her down on her hooves and gave her a stern look.

“Let the Doctor continue the story.”

She reached the far end of the roof and grabbed the end of a rope, left tied around a chimney stack, in her teeth, then swung herself off the gable. She hit the wall of the tower with all four hooves, and abseiled quickly down three floors. On reaching her destination floor, she pushed against a window, then on finding it shut, hammered loudly.

A light-green unicorn filly opened the window and Rap dropped into the room. It was a small bedroom, containing two bunks and other basic furniture, lit by a single candle.

“Why did you shut the window?” she asked, turning back outside, and pulling the rope into the room, letting it coil up on the floor.

“It's cold,” replied the other filly. She had a pretty, curly grey mane and a light green coat. She wore thick rimmed glasses. Next to her stood an earth pony filly of the same age with a brown coat and orange mane.

Rap kicked the rope behind a cupboard, closed the window, then scrambled up onto a bunk and pulled a blanket over her head.

“Quick—get into bed,” she said to her roommates.

Unfortunately before they could do this, the door to the room opened, and in walked the Dean.

“Patina, Ginger Root,” said the Dean, sternly addressing the two fillies. “What are you doing out of bed? The bell for lights-out was twenty minutes ago.

Patina and Ginger Root stood in the middle of the room looking slightly lost.

“We… err…” began Patina.

“We thought we heard a noise,” improvised Ginger Root.

The Dean gave them a long hard stare until they both looked away. Eventually she just said, “Well, don't let me find you out of bed out of hours again.”

Patina and Ginger Root were both novices who had entered the abbey the previous summer. Patina came from a unicorn family in Canterlot and had earned her cutie mark—a splendid hourglass—after revising her school’s exam timetable to show that it was possible to take courses in unicorn history, levitation, chamber music, and Equestrian literature without any clashes. Her teacher had suggested that the Order of the Time Turners might be a better place to continue her studies. Ginger Root came from the small coastal village of Manehattan, which was rapidly growing due to the profitable trade in spices from the South Seas. After gaining her cutie mark—a set of scales—she had worked in her merchant family’s shop for a year, before leaving home, seeking adventure, and had ended up at the abbey. The two fillies shared a room with Rap and had become best friends.

Once the Dean had left the room. Patina immediately walked over to the bunk and prodded the blanket covering Rap. “You've been eavesdropping on her and the Abbess again!” she accused.

“Yes,” admitted Rap proudly. “Best way to find out what's going on around here. Quizzing the Steward after he's drunk too much claret sometimes works, but the Abbess doesn't tell him everything.”

“It's not right to listen in on other ponies conversations,” said Patina.

“Don't you want to know what I heard?”

Patina was not sure whether she wanted to know or not.

“It's about the princesses!” said Rap with a tempting smile.

“Tell us,” said Ginger Root.

Rap grinned. “Celestia wants to make peace with her sister. But Luna blames her for the freezing weather. The Abbess thinks if she can show that Celestia is not at fault, then they will be friends again and everything will be clockwork.”

Rap had lived in the abbey for her entire life. After her parents—both members of the Order—had died when she was very young, she had been adopted by the Steward and Cellarer and taken into the community. Having grown up within (or as often as not, climbing up) the abbey walls, she knew far more about the buildings and ponies of the Order than any of the novices: the secret passages, the rooms which nopony ever visited, the best route to scale the cliff, how to get into the wine and food cellars, and up on the roofs. She also knew which adult ponies were most prone to gossip, and had a better understanding of the internal politics of the institution than many of the senior members.

Despite this, she was officially not yet a novice. The regulations stated that membership of the Order was only open to ponies with a special talent for keeping time[3]. None of the Order doubted that Rap would one day be initiated as a novice. But it was a formality that it could not happen until she had demonstrated her special talent and got her cutie mark. At this point in the story, Rap was still a blank flank. This was a point of considerable frustration to her, and she was forever scheming how best to demonstrate her skill in keeping time, get a cutie mark, and enter the Order as a novice.

[3] This was interpreted fairly liberally. Keeping time was the collective duty of the order and required many ponies with diverse talents. So a pony with a special talent for making sugar pastries, would be admitted, provided she could make them in good time.

“She was a Cutie Mark Crusader! That’s so cool! Why didn’t you say so before?” said Scootaloo.

“But she can’t have been a crusader,” said Apple Bloom. “They didn’t have crusaders in the old days. We’ve only just invented crusading.”

“But she would have been a crusader if they’d had crusaders then.”

Twilight glared at them.

“Will you please stop interrupting and let the Doctor finish the story.”

“So,” said Rap, “I just need to find out the reason why it's so cold, then I can save us all from the tyranny of two sulking princesses, get my cutie mark, and prove to the Abbess that I should be a member of the Order.” She paused while drawing up a mental checklist of the tasks ahead. “But first, let's get some snacks.”

She jumped out of bed and made for the door. Patina and Ginger Root stood where they were.

“We’ll get in deeper trouble it the Dean finds us out of bed,” Patina said.

“Relax,” replied Rap. “She will be in bed herself now. And if we do meet her, what can she do?”

“She’ll give us one of her cold hard stares.”

Ginger Root shivered. The Dean’s stares could make a pony feel very uncomfortable. Rap, however, never stayed still long enough to encounter one.

“Come on Pat,” she pleaded.

“But we shouldn’t be roaming around the abbey at night. It’s against the rules.”

“They’re not strict rules.”

“That’s not the point. You’re supposed to respect the rules, as if you don’t, you’re not respecting proper order, and if you don’t respect that then you shouldn’t be here. You’ll never be admitted into the Order if you keep breaking all the rules.”

Rap turned to face her reluctant friends with another smile. “They had those delicious cannulicchi pastries at dinner, with ricotta and honey and berries. And I bet there's still some marzipan fruits and that liqueur soaked sponge cake with the candied peel.”

“Let’s go,” said Ginger Root, giving the deciding vote.

In addition to knowing about the confidential politics of the Order, Rap also had a considerable knowledge of the contents of the Fellow's pantry. As befitted their senior status within the abbey hierarchy, the food served to the Fellows was of significantly higher quality than that dished up to the novices. The Cellarer always prepared more desserts and sweets than were consumed at dinner, and left the remainder in the pantry for any Fellow to partake of as and when they felt hungry. Rap and her friends helped the senior members finish the leftovers during midnight visits to the pantry, having long ago noted the shelf where the Steward hid the key.

The three fillies crept out of their room, along the corridor, and down the spiral stone staircase into the hall. After rummaging among a pile of napkins and cutlery in an ancient carved wooden cupboard, they found the key. Rap pushed this into the lock of the pantry door while standing on Ginger's back as Patina levitated a candle above the keyhole. Turning the key with her mouth, she opened the door and they entered the food store. Rap immediately walked along the shelves surveying the contents.

“Pastries will be in that tin. What's new? Oh good, they've brought in some more dried dates and figs... And what's this? Hey—it's got almonds in it—try some. Another carafe of port—they do like that stuff—and what's this green one? I've got to try this.”

She pulled the stopper out of a tall glass bottle full of a bright green liquid. It contained a highly praised liqueur produced by a satellite abbey in the Unicorn Range to a secret recipe containing over a hundred herbs and plants. The bottle was a rare gift from the abbot of that Order. Rap took a swig, then promptly sprayed the liqueur into Ginger's face—using the natural pony magic to turn a small mouthful into a voluminous spray to full comic effect.

“Urgh! That tastes awful.”

There were however plenty of the promised ricotta, honey and fruit filled pastries. The three friends sat down on the cold stone floor to enjoy the clandestine meal.

“What do you think is causing the cold weather?” ask Ginger.

“Well,” said Rap, “if it was something to do with sun, Celestia would know. If it concerned the moon, Luna would know. If it was about the clouds and stuff, the pegasi weather patrol would know. In any case they would tell the Abbess...”

“In which case you would know,” said Patina.

“Exactly,” said Rap. “So it must be something completely different. I was thinking there must be some sort of mysterious ice monster sucking all the heat out of the sun. So if we can figure out what it is, we could set a trap for it, and catch it, and save Equestria from eternal winter, and I can get my cutie mark.”

“It's not eternal winter,” said Patina. “It's just rather cold.”

“And I'm not sure there are any ice monsters,” said Ginger.

“That's because they're so mysterious,” said Rap. “Maybe it's an ice dragon which sleeps in a cave and only sticks its head out when nopony is looking to suck in some warmth. But it's been growing bigger and bigger for the last hundred years so it's eating more and more heat.”

“I'm not sure ice dragons exist,” said Patina.

“They must do. Just as there are fire-dragons which breathe fire, making the world hotter, there must be ice-dragons which breathe ice and make it colder. That's logic.”

“But how can we catch it?” said Ginger.

Rap thought about this while finishing off another pastry.

“We need to know more about them. Where they live and so on.” She paused, licking the soft cheese and honey off her hooves. “There must be a book about them in the library—lets go and find it.”

The three friends left the pantry (being careful to tidy up and lock the door behind them—they didn't want any fuss) and walked across the dining hall in the darkness, with the glow of moonlight entering through the high windows casting bars of light onto the walls. The library was located on the second floor of an octagonal tower at the other end of the building.

At this time of night they did not expect to meet any other ponies. They tip-hooved carefully past the Steward’s room—a quick glance through his door showed he was busy ironing his dress shirts next to the fire. They walked through a small passageway joining the two buildings and up a spiral stone staircase. They kept silent and moved slowly until they were into the library tower.

On pushing through the heavy curtain which marked the entrance to the library, Rap ran forwards. Then suddenly froze, her hooves rooted to the floor, staring straight ahead. Patina and Ginger Root ran into her and they were all thrown to the floor.

“Ow, why d'you stop like that!” said Patina. In reply, Rap just pointed a hoof forwards. It was nearly pitch black. Their large pony eyes were good at picking up even the faintest illumination, but they could not resolve anything in any detail. On the other side of the room, at a large wooden table, a single candle was lit, shining onto piles of books and casting shadows. Behind this they could make out a hooded figure. The flickering candle just revealed two sinister glowing yellow eyes beneath a black hood.

“A-a ghost?” whispered Patina. She clutched a hoof around Rap, who was also visibly shaking.

Ginger Root, however, ignored them both and trotted forwards confidently.

“It's just the Librarian,” she said.

As she approached the desk, the figure pushed back her hood to reveal the black and white head of the zebra scholar.

“Hi Azalay,”

The zebra's old eyes were not as sharp as the young fillies, but on hearing her name, she peered down to make out who had addressed her.

“Why is that young Ginger Root there?
I can see your orange hair,
I hope I did not give you a fright,
What brings you to the library this night?”

“We kinda got an idea we want to check out. Are you working late too?”

She looked at the scrolls covering the table, covered with writing in an alphabet unknown to her, interspersed by exotic symbols.

“It's true I work late into the night,
Studying these scrolls by candle light,
For I am old, but you instead,
Should by now be asleep in bed.”

Ginger Root ignored this comment and pointed a hoof at the paper scrolls.

“Is that zebra writing?”

The Librarian smiled, always happy to discuss her work.

“No my friend, this script is not a tongue of mine,
Zebra is but a dialect of Equine,
These are Griffon words, and the coloured inks,
Are the hieroglyphs of ancient Sphinx.”

Rap and Patina, overcoming their initial fear moved close up to the table and stared at the scrolls. The Librarian was in the process of copying text from several scrolls, with the different languages in different colours. None of it made any sense to the little fillies. Some lines looks like a train of wiggling worms, other seemed more pictures than letters, some shaped like birds and animals.

“What's Sphinx?” asked Patina.

“The hieracosphinx was an ancient beast,
Of which we scholars understand the least,
A lions body, a falcon's head,
They left inscriptions, which cannot be read,
While on my travels in lands to the south,
On an island in a great river mouth,
I saw many statues, with strange inscriptions,
And on my scrolls I copied these depictions.
Tonight I am still quite perplexed,
But one day I shall read these texts,
And thus their story I will trace,
And learn the riddles of this race.”

“She did! She did! She was the first pony—or zebra—to read Sphinx. I did a course on ancient Sphinx at Canterlot. She deciphered the hieroglyphs by comparing them to similar old Griffon texts. It was an amazing piece of scholarship and laid the ground for a generation of future research. Of course there’s still a lot we still don’t understand to this day—”

Apple Bloom, Scootaloo and Sweetie Belle all glared at Twilight, who stopped talking. She turned to the Doctor with a guilty face.

“Please Doctor, continue the story.”

“But enough from me, it's now your turn,
Tell me what you wish to learn.”

“We want to know how to catch an ice dragon,” said Rap.

“That is not an animal I know,
Dragons are creatures of fire, not snow.”

“The dragons we know of, yes,” said Rap. “But there must be other ice-breathing dragons for the sake of balance. But we think they're getting a bit out of hoof and that's why it's so cold. So we need to stop them. So we need a book to tell us where they live.”

The Librarian thought through this statement before replying kindly,

“If you ask for my advice,
I'd say that dragons can't breathe ice,
But there could be something that I miss,
My knowledge is not complete in this,
There may be a book on such a beast,
Or a general guide, at the least.”

Azalay lit an oil lamp and holding this in her mouth, she led the three fillies through the maze of shelves that made up the library. Stopping at the shelves where the books on dragons were stored.

“Here you will find the books you seek,
On magical creatures, the most mystique,
Now, I bid you goodnight, for I must return,
I hope you find the knowledge you yearn.”

The zebra placed the lamp on the floor and walked away. The three fillies lost no time in pulling books off the shelves and scanning pages for something of interest.

“Earth dragons, green dragons, oriental dragons, sea dragons, snapdragons,” said Patina. “'Ice dragons' aren't in the index.”

“There must be something somewhere,” said Rap, flipping through the pages of a large richly illustrated tome, with her hooves, pausing now and then to inspect a picture.

“I dunno…” said Ginger.

After an initial scan through a pile of books didn't reveal anything, they settled down to a more systematic literature search. Rap climbed up to the top shelf and pulled off any titles which looked vaguely interesting. Patina levitated these into neat piles and built a small book fort to demarcate a patch of floor space which they claimed for their investigation. Ginger Root found a few cushions and dragged these over. They then settled down to serious study.

Twenty minutes later, when the Librarian returned to check their progress, the three friends were all fast asleep. She extinguished the lamp and gently draped a blanket across the fillies before leaving them to return to her quarters smiling softly. It was good to see young foals passionate about scholarship.

A little more than six hours later, the Abbess awoke. By this time, the moon had moved around to the other side of the hall, but as dawn approached, there was a faint twilight brightness. Nonetheless she had to light up her horn to read her hourglass, and saw, to her surprise, that it was half an hour earlier than usual. The Abbess was a very regular sleeper and this early awakening puzzled her, but with no explanation in sight, she shook her head, climbed out of bed and set about her morning routine of brushing her mane and washing her face in an earthenware basin. Then, with time to spare, she stood at her desk and stared up at the old volumes of the journals of the abbey compiled by her predecessors, which where neatly ordered on the shelf above her, together Starswirl the Bearded’s Inquiry into the Nature of Time, Space and Facial Hair, the thirteen volumes of Commander Hurricane’s Comentarii de Bello Equestri, and other history books.

The records in the abbey went back many centuries, to the time before Celestia and Luna's reign, and before the foundation of Equestria. Some of the earliest texts were unreliable legends, and nopony was entirely sure how old they were. Or for that matter, how old was the world?

Ancient books described how the world was created by the gods in seven days. While the Abbess knew better than to treat these as accurate accounts, she saw no reason to question this particular detail. A day was defined as the time taken for the sun to move around the earth. And as the movement of the sun was controlled by super-magical beings, there was no reason why the creators should not have kept the sun above the horizon while they finished their work. No doubt the first seven days were much longer than contemporary reckoning, allowing all the time necessary for the deities to carve the mountains, fill the oceans, grow the first lifeforms, which would then die and turn into fossilised hydrocarbons, to be spun into polymers and turned into plastic pony dolls by the giants and brought to life by magic[4].

[4] Or so one story said. An old earth pony legend told another, in which when the world was created, all animals lived in harmony in a beautiful garden. But ponies were expelled from this paradise for stealing apples. The Practical Scholar preferred an alternative explanation that all hooved creatures were descended from lobe-finned fish. The Dean had pointed out numerous flaws with his theory.

The Abbess wondered if it would ever be possible to learn the age of the earth by modern reckoning. During one of his monologues about atomic theory, the Practical Scholar had talked about how some species of atoms could decay into others, with lifetimes ranging from a tiny fraction of a minute, to many years. Maybe you could count the number of different types of atom in a rock and from the relative amounts, determine when the rock was first formed. She dismissed the idea as ridiculous—how could any pony count the number of atoms in anything?

In a sudden revelation, which sent a shiver down her spine, chilling her bone-marrow, the Abbess realised why she had woken up early. She had not heard the sound of the Minute for—she did not have the mental terminology to accurately complete that thought. Forcing herself to keep calm, she walked to the window and looked down into the plaza. The clock-face was showing 6:47. Sunrise was scheduled for 7:24. It had evidently been 6:47 at least since she woke up, as the water in the chute leading to the minute was frozen solid, and the clock mechanism lay quite stationary.

Author's Note

Defining the Minute and Second

The Abbess claim that “The Minute cannot run slow by definition. It always runs at one minute per minute because it is what defines the minute” deserves a little further comment. In our world a minute was traditionally defined at 1/60th of 1/24th of a solar day. As the length of the day was the most regular thing anyone could imagine, that seemed incontestable. But as it was, in due course, found that spinning planets are not as regular as atomic transitions, the minute is now 60 seconds, where a second is the time period of 9,192,631,770 cycles of the radiation corresponding to a particular transition of the caesium atom.

Any unit of measurement is only as precise as the instrument used to measure it. So if you define a unit of time by a particular clock, and that clock slows down, then by definition, the rate of everything else is the universe is increasing. This is why a particularly stable atomic transition was chosen to fix the second.

The parallel story is our world is the problem of weighing the kilogram. At the time of writing the kilogram is defined as the weight of a particular lump of platinum kept in a vault in Paris. If it sheds a little material, then by definition everything else in the universe increases in mass. Silly, but true.

The Metric System

The many different measurements units used across our world over the centuries is far too long a list to itemize here. So let us jump to the metric system, introduced by the First French Republic in 1799, and eventually adopted, with various levels of enthusiasm, by every country in the world (except for Burma, Liberia and the USA). The metric system was envisaged a universal system for all humanity.

The idea of basing it on a decimal pattern had obvious advantages for doing arithmetic. Although it was noted that traditional measures divided into twelve, made division by three and four easier. The suggestion of moving to a duodecimal (base-12) counting system was seriously considered, but not officially adopted. Decimal time was indeed briefly introduced in revolutionary France but never really caught on.

The question of why ponies should use a decimal counting system when they have only four hooves is a fair one, and many commentators have pointed out that they really should use something else. But my own interpretation of the show is that there is pretty strong evidence they count in base 10.

Hieroglyphs

The translation of books from other languages was one of the more important activities of the monastic orders in the twelfth century, when many important works by Arab and Greek scientists were translated into Latin.

Egyptian hieroglyphs were a mystery to medieval scholars, and were not deciphered until 1820 following the discovery of the Rosetta Stone, which recorded parallel text in Greek and Egyptians.

As the sphinx is a half-human creature it has no place in Equestria, so I was pleased to learn of the hieracosphinx (head of a hawk, body of a lion). Evidently related to the eagle-headed Griffons, so there should be some similarity in language. Some of the griffons of Griffonstone look like they might have some hieracosphinx ancestry.

Chapter 3: Prime Time Riddles

“So what happened then?” asked Apple Bloom.

“Tell us what happened next!” said Sweetie Belle.

“All in good time Miss Apple Bloom, Miss Sweetie Belle,” replied the Doctor. “I will tell you later, but we must take a break from the story right now.”

“What! You can’t stop at a point like that—tell us what happened!” said Scootaloo. “Did Rap find a way to catch the ice dragon?”

“I will tell you everything in due course. But right now it is four o’clock, which means it’s time for tea. And we have freshly baked scones with strawberry jam this afternoon—we don’t want to miss that.”

He trotted off across the plaza. Twilight and the three crusaders followed through the doorway into the west hall, where the ponies of the modern-day Order were serving tea. They sat down at one of the long wooden tables and helped themselves to tea and cakes. Twilight politely levitated a knife to slice the scones in two and applied butter and jam. She then lifted her teacup to her snout and sipped it like a princess. The Doctor tipped his into the saucer and slurped it up. The crusaders followed his example. They all bit into the deliciously fresh scones.

“Now will you tell us what happened?” asked Apple Bloom.

The Doctor drained his saucer and restarted the story.

For the first time in five years, the Abbess's heartbeat rose above a hundred beats per minute. But she quickly composed herself, and with total calm, put on her gown, and walked out of her room, down the staircase, across the hall and out onto the plaza.

By now there was a small crowd of ponies gathering around the frozen Minute, including the Practical Scholar, the Dean, and the porters. They were all looking at the mechanism in dismay. The chute from the cistern, where the water should be flowing, just supported a glittering arc of solid ice connected to the half-full bucket. The lever arm was quite stationary and the clock-face—and time itself, as they defined it—was frozen at 6:47.

“How was this allowed to happen?” asked the Abbess.

It was a fair question. Given the low temperatures, it was hardly an unforeseen risk that the water would freeze. The streams higher up in the mountain had been frozen since early December. However the main source filling the cistern was a hot natural spring piped directly into the side of the tank. Thanks to deep geothermal heating, this water remained warm throughout the year. Once it left the ground, however, it would quickly cool, and it was the duty of the porters to heat the chutes and channels of the Minute in mid-winter to ensure an uninterrupted flow.

The head porter—a brown stallion with a black mane—looked a bit embarrassed.

“We kept the channels clear of ice as always,” he said, then paused and looked at his hooves. “There was a layer of ice at the top of the tank, as always happens, but it was water underneath… At least… it was… it seems the entire tank is now a frozen block.”

The Abbess took in a deep breath.

“We'll melt it as soon as we can,” said the porter. A group of unicorns were already standing on step ladders around the tank focussing their magic on the top. Other ponies were bringing the burning braziers close by. “But it could take some time until the water is flowing.”

The Abbess and the Dean exchanged a solemn look. This was the gravest catastrophe to hit the Order in over a generation. Before they could discuss it, their attention was distracted by further events. With a clatter of hooves hitting flagstones, Princess Luna and her retinue landed on the plaza. At almost the same instance, Celestia arrived with the solar guard.

“It seems we have arrived early,” said Luna, looking up at the clock face.

“We have a technical issue,” said the Abbess. “Time has stopped temporarily. We are working to resolve the problem and it will restart as soon as possible.”

“But time hadn’t really stopped?” ask Apple Bloom.

“Technically, yes,” said the Doctor. “Of course, things continued to happen. Nopony can stop time in that sense, or at least, if they did, nopony would have time to notice. But time, as in the number of minutes past the hour it was, was set by the water clock, and that had stopped.”

“But couldn’t they find another clock?”

“They could—but remember that the Order followed their rules to the letter—at least the rules concerning the keeping of time. If they used a different clock, they would have to change the way they defined time. And they didn’t have time for that.”

“So what did they do?”

Luna laughed, but without much merriment. “Please make haste. While we do not object to the night lasting forever, in principle, we would like to go to bed soon.”

“You need the heat of the sun,” said Celestia. “I could raise it… Before it is time?” She said this cautiously knowing that the suggestion would not be well received.

The Abbess did not reply. In theory Celestia's suggestion was reasonable. If the clock had not frozen, it must now be about time for sunrise, so why not start the day, then thaw the ice under the sun? However the statutes of the Order, as written by Starswirl the Bearded seven centuries ago, clearly stated that the sun could not be lifted above the horizon until the prescribed time for that day, as set by the water clock in front of them. In such a crisis it was important to follow the statute to the letter, otherwise who would ever respect it again? If she allowed Celestia to lift the sun thirty-seven minutes early, then Luna might ask to raise the moon at any time she liked. Of course it might be okay, but it would set a very dangerous precedent. She stared at the clock, willing the hands to start moving. She could push it forwards with her magic, but that would not keep it moving, and there was a strict rule forbidding spells around the cogs and axles, due to the fear that residual magic would interfere with the movement. They had to get it moving again by restarting the water flow as soon as possible. At the top of the cistern, a row of unicorns, horns aglow, were doing their best to melt the ice, but had so far just produced a small puddle of water at the top. The braziers brought in below had warmed the metal pipes and open channels, but there was no water flowing from the stone tank—it was just a huge block of ice—and nothing would flow until the ice at the bottom melted. But to get to that, they first had to melt the ice above it. This could take a while.

The Abbess looked at the Dean. They were both thinking of the same obvious solution to the problem. Neither of them liked the idea, but the simple necessity of the situation compelled them.

“Strombol?” said the Dean.

The Abbess nodded. She turned to the princesses and said, “Please excuse us.” Then, together with the Dean, walked away from the clock towards the door to the east hall.

Strombol was the Treasurer of the order, with the responsibility for guarding and administering the gold, silver, jewels and other financial assets of the abbey. He was also a grown fire-breathing dragon, who could melt a large block of ice in less than a minute. And he was a thorn in the Abbess's and Dean's side.

Strombol had arrived in the abbey, nearly two hundred years before the time of this story, as an egg. This had been a gift from a pilgrim, who had travelled in many distant lands, and presented the curiosity to the Abbot of the day in return for the hospitality received. For years it had sat on a shelf in the library, until the Practical Scholar of the day, a talented unicorn wizard, decided it would be a fun exercise to hatch it. After extensive research, practice with chickens, and a few miss-spells [1], he succeeded, and the resulting hatchling was adopted by the abbey community.

[1] One of which turned the Dean of the day into a cactus.

This was all recorded in the abbey records, which the Abbess had studied well. The accounts described how adorably cute the little baby dragon had been. How he would waddle around on two legs. He quickly learnt to read and write, clutching a quill in his tiny claws. As he grew older, he was always willing to help the ponies where possible, running errands, fetching books, sweeping the floor, and taking notes for the scholars. He was much loved by all.

Dragons grow up slowly. When he reached the age of fourteen, he was still only a tiny little creature. But as he was by then such a part of the abbey community, it was felt only fair that he should join the Order as a novice member. The Abbess could understand this decision, and also why, ten years later, he was allowed to graduate as a full member. However she felt it had been somewhat short-sighted of the head of the Order twenty years hence, to allow Strombol to become a full Fellow of the Order. They really hadn't thought through the implications.

Fellows of the Order were appointed for life. In return for their services to the abbey, they received lodging, meals, and as much cider, ale and wine as they could drink. They would then enjoy this lifestyle for another thirty to fifty years, before passing on quietly, and leaving the next generation to maintain order, keep time, and drink up the barrels and bottles which their predecessors hadn't managed to finish.

Strombol had been a Fellow of the Order for one hundred and fifty-six years. And he was still young for a dragon.

As he had grown too large to move through most of the abbey interior rooms, he had moved into the undercroft beneath the east hall. This was the space used to store the treasure of the abbey. Piling all this into a large hoard, he then lay down on top of it, and fell asleep. This was, of course, all part of the life-cycle of a dragon. The Librarian had studied many ancient texts on the behaviour of magical creatures, and explained this to the Abbess. He would spend most of his time snoozing, and only an hour a day, at most, awake.

Strombol explained that he was fulfilling his duty to the abbey by safeguarding the treasure. And he pointed out a footnote in the statutes which stated that attendance at the ceremonies was not compulsory for members over the age of seventy.

The Abbess disagreed with this interpretation of the regulations. But she was powerless to do anything about it. As the oldest Fellow, Strombol had the privilege of seniority. This presented another serious potential worry. The fellowship elected an abbot or abbess from their own ranks to lead the Order, with the Dean the acknowledged deputy. However if both of them were not available, authority automatically passed to the oldest Fellow. It was a worry for the Abbess, that if the fellowship could not agree on her successor, then the constitutional crisis could see this lazy dragon given ultimate responsibility for keeping time and maintaining order in all Equestria.

For a while she had hoped she could gather enough support within the Order to persuade Strombol that he might like to move to a quiet cave in the mountains, or go and live with other dragons. But he insisted that it was his duty as a Fellow of the Order, and as a Noble Dragon, to stay in the abbey. He made his own allies, befriending the novices, especially the pretty unicorn mares, giving them little necklaces and other trinkets made from his gems so they all thought he was wonderful. The Abbess and the Dean could barely stand him. But on this occasion, they could not deny that they needed his help.

“Will he cooperate?” asked the Dean as they walked around the east hall, and down a set of steps and a short passage which led below the ground floor.

“He can hardly refuse,” said the Abbess. “But he will do all he can to make us grovel first.”

She opened a huge wooden door—several times her height—and they walked into the dragon’s lair.

The undercroft covered the entire hoofprint of the hall, divided by numerous brick columns and arches which supported the weight of the building. A few lamps were burning in holders attached to the columns. This light reflected off the piles of gold coins and gems. The abbey was extremely wealthy—the hourglasses they made were regarded as the finest in the world, and sold for a high price, and the prestige of the Order meant that many foreign ambassadors felt obliged to pay a visit and offer valuable gifts from their homelands. In addition to the gold and jewels, the room was lined with exquisite works of art. Stone and metal sculptures, oil paintings, tapestries, intricately carved caskets were all stored here. The long term investment strategy of the Treasurer ensuring that no abbot or abbess was tempted to solve a short term budget problem by selling off any part of such a priceless collection.

Stretching the full length of the room, lay a large green dragon with purple spikes along his back, lying in a pile of gold, with his head by the main doorway, and his tail bent around through a brick archway and along the full length of the cloister to one side. The Abbess walked up to the head and shouted with the full authority of her position.

“Strombol! Wake-up!”

The dragon's body did not move, but a single eyelid—the size of a small cartwheel—flicked open and looked at the visitor.

“Oh it's you Abbess Prime Meridian,” said Strombol. “So nice of you to visit. And Dean Median Measure too. Welcome. What time is it?”

“It's 6:47,” replied the Abbess.

“Oh so you just popped in before sunrise. So sorry I can't join you for the ceremony, but you know how stiff my joints are—especially in this weather. I hardly ever get out these days.”

“Strombol. The Minute has stopped at 6:47. The water tank has frozen solid. It is imperative that you use your fire to thaw it this instant.”

The dragon did not visibly smile, but the Abbess could tell from the glitter in his huge eye that he found this very amusing. His other eye flicked open but he remained silent for a while before replying.

“Until I am measured,
I am not known,
Yet how you miss me,
When I have flown.”

“What was all that?” asked Apple Bloom.

“It’s an old riddle,” said Twilight. “The answer is time.”

“Strombol. This is not a time for games,” said the Abbess.

“Indeed. It is a tragedy! How did the Order allow such a thing to happen? To think of all the ponies we are letting down...”

“Exactly. Which is why we need you to get outside now and fix it.”

“Of course. I do wish I could help—I really do. But it is so painful for me to move.” To emphasize this he pulled up his forelegs, and raised his neck, twitching with each movement. “Oh! Oh! The pain! Would you be so kind as to rub some mineral oil on my back? I'm sure that would help.”

The Abbess bristled at this suggestion, but there was no way she would let this dragon make her lose her cool.

“Strombol. As the head of the Order, I command you to go outside and assist in melting the ice block, to restart the Minute.”

“Now now—let us not be too hasty. Foals rush in where alicorns fear to tread, you know. At my age, I have found it is best to take life at a steady pace, and think things through before jumping into action. If time has stopped, as you say, then you need not fear missing your next appointment. That reminds me, I heard another riddle the other day. Would you care to hear it? It goes—

“I never was, am always to be,
No one ever saw me, nor ever will,
And yet I am the confidence of all,
To live and breathe on this terrestrial ball.”

The Abbess knew what he was playing at. He was trying to stall her with a diversion. Riddles were a favourite game within the Order, and he knew that once asked, no Fellow could resist trying to guess the answer. Even as the Abbess forced herself to ignore this, a part of her brain was already distracted. Fortunately the Dean came to her aid.

“All the order are waiting for you,” she said.

Strombol did not reply.

“All the novices, and members and Fellows,” continued the Dean. “They're all so scared now that time has frozen—especially the young fillies—some of them are crying—they don't know what's going to happen. But we told them that you would surely come and save the day and then they were all happy and reassured. You won't let them down, will you? They're all waiting for you: Lovedot, Peony Poset, Paragon...”

At the mention of the final name, Strombol lifted his head—the first significant body movement he had made. “Well... I suppose I could...”

“And the answer to your riddle is tomorrow,” said the Abbess.

Strombol bent his neck ever so slightly, as if to acknowledge defeat, then raised his long body off the ground and crawled out of the undercroft through the open doorway. The Abbess and Dean followed, greatly relieved that they had not been obliged to prostrate themselves, or get mineral oil and dragon scales on their hooves.

“Who's Paragon?” asked the Abbess.

“Third year novice,” replied the Dean. “A rather pretty white unicorn mare. Whom Strombol has taken a certain shine to.”

“Should we be concerned?”

“I think she can deal with it.”

Rap dug her small hooves into the ice cliff on the side of the mountain, pulling her body upwards while flapping her small wings to maintain balance. Her iron horseshoes chipped a foothold into the ice, and she propelled herself higher. Reaching the summit, she briefly planted four hooves into the snow, then leapt high into the air, and away from the cliff. Spreading her wings, she sailed across the sky, landing on another peak, then leaping onwards and gliding across the mountain landscape. She landed on a crevice marking the edge of a broad valley, and looked down to the foe she sought. The ice dragon was asleep on the gravel-strewn stony landscape. It's long pale blue body curled around a collection of loose boulders, the moonlight glittered off the ice crystals attached to its scales. Every time it breathed out, a huge cloud of cold vapour formed in the air beside its head, which would condense into snowflakes and fall to the ground.

Rap grinned to herself. This was going to be perfect.

Too perfect. The realization that she was dreaming hit her, throwing the vision into her infinite mental chasm of unfulfilled desires. Shucks.

She shook herself awake and remembered that she was lying on the library floor. It was dark but she could make out the shapes of Patina and Ginger asleep beside her, breathing steadily. She had no idea what hour it was. Evidently still some time until sunrise.

She became aware of the sound of dozens of hooves pounding against flagstones. Ponies were descending the stairs in large numbers. But she hadn't heard the bell to mark the call to the sunrise ceremony. She prodded her friends with a hoof.

“Wake up!”

“W-what?” said Patina, yawning. “Oh no! We fell asleep in the library—I hope we weren’t snoring—it’s against the rules to make loud noises in the library. What time is it?”

“I don't know. But something is happening. Something interesting.”

The three fillies left their book fortress and trotted out of the library and down the wide spiral staircase. On the ground floor they joined a steady stream of ponies all filing out of the main doorway and onto the plaza.

Outside a large number of ponies were all crowding around the Minute in an atmosphere of chaos and confusion. Any pony could instantly comprehend what had happened—the clock-face was fixed with the hands showing thirteen minutes to the seventh hour, and the mechanism was quite still. The water in the meridian channel was frozen. But the clarity of the situation did not stop countless individuals asking what had happened? What did it mean? If time had stopped what were they all supposed to do with their time? And the most urgent and important question of all—when would they get breakfast?

The unicorns standing on ladders around the tanks, who had been focussed on the glacial job of thawing the huge block of ice by magic, were now being continuously disturbed by other ponies trying to get a view of the top of the tank, or ask what was going on, or offer to help. The Steward, Cellarer and Librarian walked back and forth in front of the crowd pleading for everypony to remain calm, in a futile attempt to maintain some level of order.

“Please keep yer calm everypony,” said the Cellarer. “It’s just a little temporary temporal trouble, which the Abbess and Dean will sort out. There is no need to panic.”

Watching over the situation, Princess Celestia stood on her podium with a look of concern. Luna watched from the western hemisphere with more relaxed look of mild amusement, but not without some anxiety. The librarian walked up to Celestia and spoke to her.

“You have magic beyond what we know. Can you restart the water flow?”

Celestia shook her head. “My power is tied to the sun. It must be in the sky to let me try such magic. I cannot lift the sun until the head of the Order asks me to.”

At the back of the crowd, Rap jumped up and down in the air with excitement.

“This is so awesome!”

“It is nothing of the sort,” said Patina, looking at her friend sternly. “Don't you see what has happened? The primary duty of the Order is to keep track of time, and the Minute has stopped completely.”

“But it's such a good opportunity. If I can find a way to melt the ice and get it started, then I'll get my cutie mark for sure.”

“How will you do that? You can't do magic. And if there was a simple way to do it, the Abbess would have already fixed the problem.”

Rap paused a moment to think. Her creative imagination quickly brainstorming ideas.

“We need a lava flow. There must be a volcano somewhere higher up the mountain. I could climb up and get it to erupt and direct some hot magma onto the ice, which would melt it...”

“That won't work.”

“Maybe not... Let me think...”

On the other side of the plaza, the Steward was listening to a not dissimilar monologue from the Practical Scholar.

“This is a situation for a clear application for atomic theory. When heavy atoms such as uranium break apart they release large amounts of heat. We just need to find a way to inject a small amount of uranium into the ice, and get them to undergo spontaneous fission. It would melt it all in no time...”

These discussions were halted by the arrival of the dragon. Strombol walked through the main arched gateway, which connected the courtyard to the road down the mountain and the main door to the eastern hall. The crowd of ponies instantly stopped talking and watched, gasping, as he raised a leg to salute the Order. He then turned to the Minute and jauntily waved a claw at the unicorns standing on ladders around the stone cistern to signal that they should get out of the way. They did so quickly.

Strombol paused for a moment and waited for the agitated crowd of ponies to fall quiet. Once he was satisfied that every pony was watching him, he took deep breath and blew a perfectly formed jet of flame onto the top of the stone tank. The wooden poles of the ladders were turned to charcoal. The puddle of water created on the top by the effort of a dozen unicorns was instantly vaporised sending a cloud of steam into the air. By the mysterious, and somewhat unphysical, thermodynamics of dragon breath, the block of ice quickly melted, and a steady flow of water emerged from the chute and ran into the metal bucket.

For a minute, nopony dared to say anything. Although they could see that the water was flowing and everything was back to normal, they did not dare believe it. Then once the bucket was filled, the lever arm swung down, shifting the cog-wheel by one pin. The long hand on the clock face moved forwards such that the time now read 6:48.

The crowd burst into spontaneous applause, hammering their hooves on the flagstones. Strombol turned to face them, lifting his neck, then bowing to the audience.

“Thank you, thank you everypony. Now you must excuse me, but I shall leave you with a riddle to ponder:

“I build up castles,
I tear down mountains,
I make some ponies blind,
I help others to see.
What am I?”

“Sand.” The Abbess shouted out the answer from the back of the crowd in a loud clear voice.

“How does that one work?” ask Sweetie Belle.

“Sand is part of the mortar used to build castles,” said Twilight. “Mountains are eroded away by tiny grains of sand. If you get it in your eye, it can blind you. But we can also turn it into glass, to make spectacle lenses.”

“That was a tricky one.”

“Well done Abbess,” said the Treasurer, not sounding too pleased at her quick reply. “How did you know that? Since you are so smart, I will leave you with another question to ponder. I have watched the water freely flowing from this rock for over a hundred and ninety years and it has never, until this night, turned to ice. What is the reason for this? Why has it only now become so cold?”

He took his leave, and falling to the ground, moved his huge body out of the courtyard and back towards his undercroft lair.

Some of the younger novices cheered as he departed. Celestia and Luna politely joined in. At the back of the crowd there was slightly less enthusiasm.

“Strombol. We should have thought of that after all the reading we did on dragons last night,” said Patina.

“That dragon is such a show-off,” said Rap, pulling a face.

She was overheard by the Abbess and Dean, standing behind her, who suddenly felt considerable warmth towards the little pegasus filly.

The excitement of the crowd was soon abated once everypony realised that there was nothing to do now except wait for the remaining twenty-two minutes until the scheduled time for sunrise. There followed a lot of awkward attempts at conversation until the bell rang out to mark the eight minute warning. Then the ponies knew what to do and swung into their usual roles for the morning ceremony. Directed by a solo chant from the Abbess, Luna moved the moon from the low angle where it had been waiting to beneath the horizon. Celestia then dutifully lifted the sun into the sky and the plaza was illuminated with the dawn rays. Everypony smiled at the sun with joy and relief that the night would not last forever and everything was back to normal.

Once day had clearly broken, the crowd all remembered that the next event on the schedule was breakfast and there was a stampede towards the dining hall as they all raced to get first in line for pancakes, oatmeal, fruit and toast.

The Abbess and the other Fellows lingered in the courtyard. The princesses walked over to greet them as diplomacy required.

“That was something which should never have happened,” said the Abbess. “We must ensure it is never repeated. I suggest that we meet at the third hour after noon for a council of the Fellowship.” She turned first to Celestia then Luna. “Will your highnesses be so kind as to join us? We will conclude the meeting before the evening ceremony and feast.”

The two alicorns nodded in agreement. They then turned away and took flight in opposite directions. The Abbess's face was neutral but the Dean could read her friends emotions.

“It's not your fault,” she said. “This could not have been foreseen. We haven't had weather this cold since—since before our records began.”

“We can’t afford to let this happen again,” said the Abbess.

The Dean nodded. “Strombol will become even more unbearable if we need to ask for his help again. But we can find a way to heat the water cistern so it doesn’t turn to ice again. It only happened this time because the porter never thought the whole tank could freeze.”

“But what if the water spring which feeds it freezes? Right into the mountain? Then no amount of dragon fire could help us?”

“Could that ever happen?”

“If it keeps getting colder, it will happen one day. I hate to admit it, but our Treasurer was right to ask his final question. We need to understand why it is getting so cold. And maybe we should look into building another sort of clock.”

“Not the Practical Scholar’s famous atomic clock? All we need is some way to get a billion atoms singing and dancing in unison on the head of a pin.”

“Maybe not that one.” For the first time since she had woken up the Abbess smiled, and walked with her friend in the morning sunlight, across the plaza, to the main hall for breakfast.

“So did they find out why it was so cold?”

“Did they make another sort of clock? How did it work?”

“Did Rap get her cutie mark?”

“What did they have for breakfast?”

“All in good time, my little ponies.”

Author's Note

Water Clocks

A water clock or clepsydra measures time through the flow of water. At its simplest, this could be just a jar of water with a small hole at the bottom, which could time the duration it took the water to flow out. For a more precise measurement, you could collect and measure the volume of water. Then you realise that the flow rate depends on the pressure difference on either side of the hole, so the height of water in the jar has a big effect on the flow, and you need some way to keep the jar full to provide a constant head. Next step is to use this to drive a water wheel, or some other automata to drive a needle around a dial.

Water clocks date back to ancient times, and were found, in various forms, all over the world. By the twelfth and thirteenth centuries some of water clocks in European monasteries had quite sophisticated mechanics, incorporating many design ideas from the Middle East, introduced through Islamic Spain.

One of their biggest problems was their tendency to freeze in winter.

Chapter 4: A Time of Climate Change

Rap, Ginger Root and Patina sat together in the main hall eating breakfast. In between licking bits of fried egg, potato and cabbage off their plates, Rap and Ginger listened to Patina read out the schedule of lessons for the next month.

“We should finish geometry this week, then we will move on to studying algebra, the Griffon calendar, old Equine scripts, and long term weather patterns. And our usual classes on chronometry, mechanics, cake baking and needlework.”

“But what do we have today?” asked Rap.

“Nothing. It’s a holiday today as the Fellows are all busy preparing for the feast tonight.”

“Cool. What shall we do?”

“Do you want to keep looking for something on ice dragons?”

“I’m not sure that’s going to work…” Rap’s enthusiasm for hunting dragons had abated since the previous night. “I mean, the ice dragon probably lives a long way from the abbey. So we probably won’t have time to track it down, catch it, and get back home in time for the feast. Let’s leave it for another day.”

“So what shall we do?” said Patina.

“Let’s go and visit the Practical Scholar,” said Ginger Root. “He’s always fun to talk to, and he won’t be busy as the Abbess never trusts anything important to him.”

The three fillies left the dining hall and walked up the staircase which led to the workshops. The Practical Scholar had a room on the second floor. They knocked on the door. There was no reply. On pushing it, it moved a short distance before sticking against a pile of cast iron metric-standard weights, but they were able to squeeze through the opening into the room.

The room was full of all sorts of random articles which the Practical Scholar considered essential for his work. The walls were covered with bookshelves, holding many old volumes, as well as collections of interestingly shaped rocks, shells, birds’ feathers and old horseshoes. A table in the middle was covered with cogs, spindles, hooks, and all sorts of oddly shaped pieces of metal that went in clockworks. Further shelves housed hourglasses, an abacus, astrolabe—

“What’s that?” asked Apple Bloom.

Twilight grinned. “An astrolabe is an instrument which you can use to measure the inclination of a star, or the sun, or another body, then if you know your latitude you can tell the time, or if you know the time, you can find your latitude and longitude. It’s made with a series of metal disks each marked with—”

“Okay, okay. Carry on Doctor.”

—protractors, dioptres, quadrants and sextants, scrolls, half-full bottles of wine. A pegasus skeleton was hanging from the ceiling (a former Librarian who had insisted, on his death, that his bones were to be used for anatomical research—no other member of the Order wanted to share their room with him). One side of the room was divided by a horizontal floor to create a sleeping platform, accessed by a ladder. From this was hung various models of prototype flying machines made from sticks and strips of paper, as well a hammock full of cans of paint, tools and other junk—this had been installed as a space saving idea by the Practical Scholar as an attempt to clear the floor space, but it had only worked temporarily and the floor was now covered with new debris.

The Practical Scholar, Spin Precession, was lying on the floor underneath an elaborate mechanism of interconnected wheels mounted in a metal frame. The three fillies could just see his tail and exposed flank baring his cutie mark—the image of a spinning top tilted at an angle.

“Hello?” said Ginger.

The noise made him drop the screwdriver he held in his mouth. The screw he had been tightening dropped out of space, releasing a spring, which flew out across the room and landed in a tea cup. He climbed up on his hooves. He had an elaborate headpiece strapped to his forehead, to which a large magnifying lens was attached by a spring. This hung down in front of his left eye, allowing him to focus on the tiny screws he needed to fix. His right eye, unobstructed, was able to focus on the fillies in front of him and on seeing Ginger Root, Rap and Patina he smiled broadly.

“Oh. Hi there!”

“What’s this thing?” asked Rap, staring at the mechanical contraption he had been working on. A long central spindle was sticking upwards out of an assembly of gears. To this was attached a series of rods, leading to the familiar face of a clock.

“It’s my latest invention,” he said. “I’m developing a new sort of clock, as an alternative to the hourglasses, and perhaps one day it could replace the Minute. If I can improve the accuracy.”

“How does it work?”

“It’s driven by the energy stored in the spring.” He pointed out a spiral spring tightly wound around an axis. “This makes the main wheel turn. Then the most important component is the escapement—which causes the gear wheel to advance at a regular interval.” He pointed to a metal wheel with triangular teeth pushed forwards by paddles connected to an axis, which pivoted back and forth. “We need something to prod the escapement at a regular rate, like the lever arm of the Minute. The best thing I’ve found so far is to connect two weights at the ends of a horizontal bar connected to the axis. By adjusting their position I can get it so it swings back and forth once a minute.”

To demonstrate this, he held a horizontal metal rod against the vertical axis and secured this with a pin. He then hung a metal weight on either end, and pushed it so it swung around in an arc, causing the paddle to push the escapement. It slowed, came to halt, then swung back in the other direction, but this time, the paddle was deflected by the slope of the teeth so it didn’t push it back. After completing one cycle, it swung back again to advance the mechanism another step. The escapement drove a train of gears, ultimately connected to clock hands which moved around a flat circular dial.

“That’s cool,” said Rap.

“Most of it is the same mechanism as we have in the main tower,” continued the Practical Scholar. “Which connects the Minute to the clock face and rings the bells at the correct time. But it has to be connected to something which moves back and forth in a super regular way. The best thing we have at the moment is the water-driven lever arm of the Minute. I thought this would work, but it doesn’t seem very accurate. But—” he paused a moment with a big smile. “I think I can do better.”

“How?” ask Patina.

“Atomic theory!” he announced gleefully, throwing his hooves in the air and knocking the lever arm of the escapement. The weight at the end fell off, falling against the spring. Knocked out of its holding cylinder, this sprang free and flew across the room, cutting through the cord holding a prototype model heavier-than-air flying machine from the ceiling and sending this crashing down onto a table of chemical glassware.

Ignoring this distraction, he beckoned them over to a table, pushing a pile of books to one side with a hoof. This in turn pushed a box of cogwheels on the far side of the table onto the floor. He picked up a scroll of paper and unrolled it onto the surface. Then, holding a pencil in his mouth, sketched a picture.

“Atomic theory says everything around us is made of tiny particles called atoms,” he said. “In every atom you have a nucleus in the middle, and lots of electrons circling around it. The electrons and the nucleus are spinning around like a spinning top.”

“How does that make a clock?” asked Ginger Root.

“There’s an intrinsic resonant frequency in the atom,” he said, “corresponding to the different ways the electrons dance around. If we can just give the atoms a kick and find a way to measure it. It must be have a super regular beat, jumping back and forth in a way fixed only by the atom, and not messed about by magic, the weather, ponies or dragons.”

“How fast does it jump?” asked Rap.

“A few hundred billion times a minute.”

“How can you keep count of that?” asked Patina.

“And how can that drive a clock?” said Ginger Root.

“I’m working on it.”

He picked up a small metal foal's toy—a spinning top—lying on the table in front of him, the same shape as his cutie mark, then with a skilled flick of a hoof, set it spinning around.”

“Atoms are like spinning tops on a microscopic scale. If we tip over the spin axis.” He gave the toy a tap with a hoof to tilt it to one side. This was not enough to cause it to fall over, but instead the spinning axis started to spiral outwards, swaying around. “The way it points moves around and around,” he explained, tracing out a circle in the air above the gyroscope with his hoof to illustrate the motion. “But the clever thing is that the rate which it does so stays constant.” The top finally slowed down and fell over, rolled across the table and crashed onto the floor. “Well, in this case it's not so stable, but that's because there are too many variables. We can’t make a clock out of a spinning top like this. But if it were an atom, it would keep spinning with a rhythm so stable we could use it as a clock.”

“That’s not quite true,” said Twilight. “Atoms and electrons have an intrinsic angular momentum, but it’s not correct to picture them as spinning solid bodies. This is where classical physics breaks down. You measure it by the interaction of the quantized spin with the magnetic field. The correct quantum mechanical interpretation would be—”

“Twilight—will you keep quiet and let the Doctor tell the story,” said Apple Bloom, Sweetie Belle and Scootaloo in unison.

As the Practical Scholar said this, the magnifying lens attached to his head was jumping up and down in front of his eyes. Rap stared at this with interest.

“So to drive a clock, you need something which bounces up and down in a regular way,” she said.

“That’s it. An isochronous mechanism.”

“Like a spring?”

“Oh I tried that but it doesn’t work very well—a springs only works for a while before it is dampened down. You would have to find a way to keep kicking it. But then that would interfere with the rhythm...”

Rap looked thoughtfully at the lens jumping up and down in front of the Practical Scholar’s face as he continued talking.

“This is the fundamental problem of timekeeping—finding something regular which we can use to count the passage of the minutes… The flow of water, the rate at which a candle burns, the swinging of an escapement. They all work up to a point, but they all have problems…” He shook his head while looking at his escapement mechanism. “There must be a simple way to do it.”

Clack, clack, clack, clack. The metal foliot swung back and forth, each time nudging a tooth of a cog driving a large gear wheel, which in turn pushed another. The interconnected components all jumping forward in a steady beat. Scootaloo, Apple Bloom and Sweetie Belle all stood staring at the mechanism watching the rocking levers and wheels, mesmerized by the movement. Behind them stood Twilight Sparkle and the Doctor. They had come into the East Hall of the abbey which now housed a museum of historical clocks and other instruments.

“So,” said the Doctor, “this is the verge-and-foliot escapement mechanism built by the Practical Scholar Spin Precession all those years ago. An early attempt to replace the Minute water clock. The position of the weights along the horizontal bars determines the period with which it swings back and forth, each time pushing the cog wheel. Unfortunately it didn’t keep very good time. The speed would change as the spring unwound. But they would soon make a major breakthrough.”

Scootaloo turned away from the museum piece to face the Doctor. “Is that how Rap got her cutie mark?”

Later that day, after lunch, the three fillies were sitting on the roof of the library having climbed up the stairs to the top of the tower and out of an attic window. The slates were warmed by the sun providing some comfort against the chill winter air. Rap outlined a new plan to prove her worth.

“So the Practical Scholar was saying you could keep time with a bouncing spring, but you need some way to keep it jumping up and down. So I was thinking, if I was at the end of the spring, I could always keep it going by flapping my wings or waving my legs or something.”

“But then you would have to be part of a clock forever after,” said Patina logically. “That would get very boring. And you would need to sleep and eat sometimes. And you would probably get seasick from all that bouncing up and down.”

Rap dismissed these technical issues with a casual wave of the hoof. “We’ll sort out the details later. The key thing to do now is to demonstrate the idea!”

“How? You would need a big spring.”

Rap grinned. “I thought of that. I had a look in the Steward’s sewing box while he was busy serving lunch. He had a large reel of elastic braid.” She dropped a reel of white elastic lace trim onto the roof tiles. “I just need to weave a rope from this.”

She held one end of the elastic between her teeth and kicked the reel off the roof so it fell six storeys to the ground. She was good at tying knots and braiding, and in a few minutes she secured the end of the elastic rope with a back splice. She then proceeded to tie one end to a protruding horizontal roof beam (the sort which are left sticking out the side of many pony buildings to provide a convenient perch for passing pegasi), and wrapped the other end around her rear hooves.

“Are you sure this is a good idea Rap?” asked Patina.

“Of course. What can go wrong? Here we go!”

She dived off the roof.

“We have got to try that! Cutie Mark Crusader Bungee Jumpers! That will get us our marks for sure. Where can we get some elastic rope?” said Scootaloo.

“Maybe Rarity has some sewing elastic,” said Sweetie Belle.

“Or we could use Pinkie Pie’s extra stretchy bubble gum,” said Apple Bloom.

“Don’t you want to hear the rest of the story?” said Twilight.

“Yes,” said Scootaloo. “Did Rap get her cutie mark in bungee jumping?”

“We will come back to Rap and her friends in a bit,” said the Doctor. “But first let us now return to the Princesses and the Fellows.”

The meeting of the Fellows and the princesses was held in the council room in the library tower. The library was made up of a large number of rooms, joined together by open doorways. Most of these were filled with shelves housing the tens of thousands of books and scrolls which made up the abbey's collection, but others were furnished with desks where the scholars of the Order worked, documenting the history of the world. Artists sat slowly decorating manuscripts with elaborate coloured strips of pictures. Other ponies were busy reading and scribbling notes onto scrolls.

At the centre of the network of rooms was the octagonal council room. In the geometric centre of this was a large stone table decorated with a beautiful mosaic. Around the edge, a series of images depicted scenes from the history of Equestria: the three ponies tribes coming together to found Equestria, Starswirl the Bearded founding the Order of the Time Turners, the building of the abbey, Canonical Hours demonstrating the first hourglass, the construction of the Minute, and Luna and Celestia defeating Discord and restoring order to the world. In the centre of the table was the emblem of the royal pony sisters chasing each-others' tails.

The table had been made by a team of outstanding craftsponies a century ago. It had served as the focal point for important meetings ever since. Thus it was here where the fellowship and the princesses assembled at none [1]. The princesses were rather less playful than the image on the table. Luna sat on the western side, flanked by two advisers. Celestia and her retinue on the other side. The Abbess, Dean and Librarian sat to the north, with the Cellarer, Steward and Practical Scholar facing them.

[1] 15:00—which would be the ninth hour after dawn at the spring and autumn equinoxes.

As was the custom, the Abbess began the meeting by turning a large hourglass in the centre of the table, and banging a gavel to formally mark the start.

“This meeting will last for two hours, after which we shall adjourn to prepare for the sunset ceremony,” she said. “I would like to begin, on behalf of the Order, by expressing our sincere apologies for the temporary lapse in timekeeping which occurred before sunrise this morning. This was a most unprecedented incident, precipitated by the extreme weather conditions. It is to endeavour to understand the cause of these conditions that I have summoned you all here.”

Princess Luna let out a loud audible yawn, staring out of the window. Her sister gave her a venomous stare, then turned to address the Abbess. “We request that the Lunar contingent keeps quiet.”

Luna gave her sister an icy glare. “Take that instruction thyself. We did not rise two hours before the norm to hear thy voice.”

The Abbess decided to ignore them and continue before Celestia could respond to her sister’s provocation. “To begin, the Librarian has examined the records of the abbey to see how the weather has changed over the last few hundred years.”

The zebra removed a large book from her saddle bag, with many pages of paper between dark blue cloth covers, ornamented with gold leaf. She placed this on the table and opened it at a spot marked by an embroidered bookmark.

“In this tome compiled by many an editor,
Is recorded the daily temperature,
We measure the height of a mercury column,
Through winter, spring, summer and autumn,

And over several hundred years,
A clear long term trend appears,
As the abbey has grown older,
The weather just keeps getting colder.”

“Is it steadily getting colder,” asked the Abbess. “Or has it just been unusually bitter for the last few winters?”

“A small change in living memory,
But it adds up over each century,
So that now, to our great unease,
It's not strange to see the Minute freeze.”

“And that is the problem,” said the Abbess.

“We can take measures to stop it freezing again,” said the Dean. “But we need to make sure it doesn't get any colder. If it gets any worse, it might freeze in the rock itself. Then no amount of dragon diplomacy will save us.”

The Abbess nodded. “Which is why it is imperative that we understand the cause of this long term trend.”

“Tis obvious, is it not?” said Luna. “The heat of the world comes from the sun.” She stared across the table at Celestia. “Explain why you cannot keep us warm sister.”

Celestia replied coldly, “The power of the sun does not waver. It is as hot today, as it was the first day I raised it.”

“There have been days when sunrise was late,” said the Cellarer [2], “is that significant?”

[2] The most common reasons for these events were: 1) Celestia oversleeping and not being available to raise the sun; 2) Luna waking up late and not being available to lower the moon; 3) In times past, when the princesses were on better terms, both sisters failing to turn up having been so engrossed in playing a board game that they forgot about the time.

“That could be it,” said Luna, “Celestia's getting lazy. We're all cold as she can't lift the sun on time.”

“I have been as punctual as the lunar guardian in recent times,” said Celestia.

The Librarian place another book on the table.

“We have recorded every date,
When sunrise was a little late,
Fortunately such events are rare,
But once it happened, we are aware,
That the sun was high for three whole days [3],
(As measured of course in other ways),
But over time it averages out,
There's no net effect, I have no doubt.
If sometimes we see too much of the sun,
At others, the night will overrun.”

[3] This incident occurred 274 years before this story. During a game of hide and seek Celestia managed to lock herself in a closet in the castle of the royal pony sisters. Desperate to beat Luna, after losing the previous three rounds, she had first charmed the cupboard to make it invisible. The royal guards and Luna spent over seventy hours searching the castle, during which the sun remained above the horizon.

It was the Practical Scholar's turn to make a suggestion. “Is it something to do with the way the pegasi are running the weather? Have they been making more clouds of late, which are blocking the sun?”

As the only pegasus present, the Dean responded to this by shaking her head. “The number of clouds hasn’t changed. They are valuable real estate for pegasi. If there was any increase in the cloud cover, property prices would fall, and we would hear about it.”

“Or,” continued the scholar. “Have you read about the greenhouse effect? Layers of air can trap the sun’s heat. Some gases can let light through, but trap heat, and could change the climate.”

“But why would the level of such gases change?” said the Dean.

“Well,” said the Scholar. “Hypothesis one: we are burning more wood, charcoal and oil…”

“That would mean more greenhouse gases,” said the Dean, “so it would be getting warmer, not colder.”

“Hypothesis two: As we ponies change our diet, it would change the gas produced in our guts.”

“But we've been eating more and more fine food over the years,” said the Cellarer. “The resulting extra farts would likewise heat the world up—not cool it down.”

“And to judge from our novices, ponies are getting more, not less, smelly over the years,” said the Dean.

As the meeting went on, the theories became wilder and wilder. As the Practical Scholar and Dean argued over the interpretation of the data, the Abbess looked up to the high windows above the table and watched the condensation forming on the cold glass. Through the glass she could make out a rope hanging in front of the window. She wondered how it had got there.

“As the sun is under suspicion,” said Celestia. “We should also look at the moon. How do we know it does not change the weather?” Evidently angered by Luna's accusations about her sun, she went on the attack. “Art thou sure thou art keeping it steady? A slight misalignment could change the tilt of axis of the world, and point it slightly away from the sun. A few degrees would be enough…”

“Ridiculous,” replied Luna. “The moon is what keeps the spin of our world stable!”

“That’s not exactly right,” said Twilight. “It’s true that the tidal forces from the moon will influence the axial precession but—”

“Twilight, will you keep quiet? We want to hear the rest of the story.”

The Abbess addressed both sisters. “Neither the Sun nor the Moon is at fault. Remember that the Order regulates the length of the day, so the solar power shining on Equestria is constant. There may be rare occasions—as today—when the sun remained down longer than it should. But they cannot explain the long term trend. As long as the Order counts the minutes, day is balanced by night. The days are longer in summer, but this is balanced by longer nights in winter. It is all as it has been for seven centuries, since the Order was founded, back in the days following the foundation of Equestria, as told in the tales of Hearth's Warming Eve.”

As she said this, the entire room fell quiet and stared at her.

“Hearth's Warming Eve...” said the Steward, pausing to think over the phrase. “Could it be... windigos?”

There was a long silence during which all the ponies present considered this new proposal. The Abbess turned her head away from the other ponies, and looked upwards in thought. Staring out of the high windows, a vision of a small blue pony suddenly flashed past the window, flying downwards. She blinked.

“Windigos—the winter spirits that feed off fighting and mistrust,” mused the Dean. “As the legend tells, when ponies were not friends, the spirits grew stronger, and the world became colder.”

The flying foal flashed past the window again, this time flying upwards at some speed. What was going on out there?

“But that was an era ago,” said the Practical Scholar. “All ponies are friends now. And it's not like anything has changed.”

The Abbess continued looking out of the window, not looking at the other Fellows. The blue filly flew back down.

“All ponies?” asked the Cellarer.

The Abbess’s attention was all on the window. As the filly did another fly by, this time going up, she tried to see who it was.

“Not wanting to make too fine a point of it,” said the Steward. “But your royal highnesses have not been quite so cordial to one another of late.”

The Fellows were all looking alternately at Celestia and Luna, except the Abbess, who kept staring at the window. What was that kid playing at?

“Now hang on,” said Celestia angrily. “Just because my sister and I have had an altercation, does not mean we’ve summoned a monster.”

“Quite,” said Luna, surprised to find herself agreeing with Celestia.

The Abbess stared out of the window waiting for another sight of the young pegasus, but it seemed the show was over. She noticed a frayed rope hanging down. Realising that she had been distracted, she brought her focus back to the foreground, and noticed the final grain of sand in the hourglass on the table was about to fall. Her instincts kicked in and before anypony could say another word, a sharp cracking sound echoed around the octagonal room as she brought her gravel down and duly brought the meeting to a close.

“We have had an interesting discussion,” she said. “We have heard many theories as to why the climate has become cooler in the last few hundred years. However we must now withdraw for the ceremony and feast. We shall continue this dialogue. Thank you.”

She got to her hooves and walked out of the room before anypony could add their own last word. The other ponies then followed her, aware that while the argument had been abruptly cut short, this was necessary if they were to achieve the higher priority of keeping to schedule.

The Abbess walked down the spiral staircase of the library tower, her black gown trailing on the steps behind her. All manner of ideas were buzzing around inside her head. Could the princesses’ quarrel have summoned a windigo? Was some long term change in the atmosphere cooling the world? Was the movement of the sun and moon as reliable as the sisters said? This was a riddle beyond anything else the Senior Fellow could set her, and her mind was anxious to tackle it. But she had to force herself to focus on the task in hand. She could not allow anything to go wrong with the evening ceremony.

Outside, sitting on the steps of the main doorway, was the young pegasus Rappel, being tended by her friends. Her feathers were all out of place and her coat was covered with fresh scratches. Evidently she had had another fall. But her face showed a bright grin.

“That was awesome! You saw me?” she said to her friends. “I so want to do that again. We just need to get some stronger elastic rope…”

“So did you make a good clock and keep good time?” asked Patina.

“I kinda forgot about that,” said Rap. “But it was great fun!”

The Abbess walked past them, out onto the plaza and took up her position on the podium. Then she forced herself to meditate, staring only at the clock face and the Minute mechanism, taking steady breaths. Around her the ponies of the order, and the two princesses, took up their positions. Then everypony waited in silence as the clock moved from 5:34, to 5:35, then 5:36. On the final point, she struck her tuning fork with her hoof and proceeded as she had the previous day.

Once the sun and moon had been duly rearranged, the ponies of the Order all walked into the hall together. The Fellows were in an ill humour. The day had started badly and not improved. On another occasion, they might have simply raided the kitchen for some snacks and retreated to their chambers with a bottle of wine. But tonight was the important anniversary which must be marked with a great feast. They had to entertain the princesses. And nopony wanted to challenge tradition. Discord was widely regarded as the arch nemesis of the Order, hence the special feast to celebrate the date of his defeat. The ponies of the Order took particular pride in marking the anniversary at the precise time when the reign of chaos had ended.

The novices, Rap among them, took their places at the low benches, all chattering excitedly. The Fellows walked up to the high table. The presence of the princesses complicated matters. They were known to have large appetites, and must be provided with extra helpings. And they were still not talking to one another. The Abbess arranged the cushions at the table such that Luna and Celestia were on the same side of the table, but separated by herself, the Dean and the Steward, such that they could not look one another in the eye.

The Steward, dressed in his finest frock coat and dress shirt, levitated a menu card before him and read out the schedule for the meal.

“Tonight we shall begin with a pea soup, followed by quails eggs and asparagus on a bed of hay; a daisy and fennel sorbet; carrot, squash, lentil and potato casserole; truffle polenta, avocado and glazed chestnuts; kale, root and peas shoot pie; then poached pears and blackberry and apple tart. We shall get through all main courses before 11 o’clock, in time to mark the moment of the defeat of chaos, then we shall finish off with dessert wines, cheese and chocolate.”

The Abbess nodded her head in approval, then rotated the table hourglass and brought her gavel down to mark the start of the feast.

Once the food was brought in, the two royal sisters both stuck their snouts into their dishes with equal enthusiasm, spraying food onto the Fellows from both sides. During the first course, the Practical Scholar described a new design of water clock to the Librarian, illustrating certain principles using his bowl of soup and a set of spoons. After spilling it all over the table they moved onto the next course. The Steward asked Celestia to tell him about the court fashion of the past two centuries, and she described how silly Luna had dressed at parties. The Librarian asked Luna what she knew about the Sphinx, which turned out to be very little, but she did tell a story about how Celestia once dressed up as a cat and spent two days playing with a ball of wool. The Cellarer rolled in extra barrels of cider and distributed this around the hall. After a few more tankards, some of the novices started singing, before being silenced by a cold hard stare from the Dean. After finishing her casserole, Luna announced that she would take a nap and slept through the next two courses, waking up for dessert. The Abbess sat calmly surveying the hall, saying very little.

Finally they reached the dessert course. By now they had run out of stories to tell. But the Practical Scholar tried to start up another conversation.

“I think the way forward has to be the development of an atomic clock.”

“Really?” The Dean answered without looking up from her food.

“Yes, let me show you how it works.” He took out his spinning top and put it on the table in front of him, then, with a skilled flick of a hoof, set it spinning around.

“All atoms are just like spinning tops on a microscopic scale, they are continuously rotating.”

“You don't say.”

“And if we tilt the spin—” He prodded his toy with a hoof. “The spinning axis wobbles around and around at a regular rate, just like atoms in a magnetic field, it’s a stable system…” The top fell over and rolled across the table crashing into a jug of cream.

“Well, in this case it's not so stable, but that's because there are too many other factors. If it were an atom, it would keep spinning at a fixed frequency so stable we could use it as a clock.”

“So how do you set an atom spinning how you want?”

“Not quite sure yet.”

“And how will you know when you've done it?”

“I'm working on that one.”

“And how will you use that to tell the time anyway?”

“It must be possible somehow, we just need to find a way to manipulate matter at the atomic level.”

“Meanwhile, pass the cream.”

Spin Precession pushed the jug of cream across the table. “You know sometimes I feel my talents are not appreciated here. Maybe I should go and found a satellite abbey on the other side of the mountain. A new community which would take atomic research seriously.”

“I would do that,” said the Dean, nodding vigorously.

“What?”

“Definitely,” she said while a smile and further nodding. “If you feel you are not appreciated here, go and found your own abbey. I would leave soon. No time like the present. I can give you a list of some of the novices who would most benefit from going with you.”

The Scholar looked up from his pear-poached-in-mulled-wine, a little taken aback by this enthusiastic endorsement.

“Err... I'll look into it.”

The Abbess had remained silent throughout this conversation. The steward had now brought in three huge blackberry and apple tarts, on plates which stretched across half the table. All the diners were in the process of cutting slices, shifting these onto these plates, then covering with cream poured from porcelain jugs. The cream was thick and fell onto the dessert as an irregular flow of globs. The Abbess watched this, while her mind was half following the Practical Scholars atomics, and half in an unfocused meditative state. Suddenly something clicked within her head.

She turned to face the Steward. “The cream was a fine liquid when you brought it in.”

The Steward nodded.

“But it's now much thicker.”

“It's getting cold,” he explained. “It's nice and runny when we warm it. But it quickly thickens in the cold. Eat it up quickly before it gets thicker. Or shall I warm it up for you?”

But the Abbess was not thinking about her food.

“Does water do the same thing?”

“Oh no. I've never seen water as thick as cream.”

“But could it get slightly thicker. So slight we would not notice?”

“I guess so, but why does that matter?”

“Suppose the water flowing through the Minute were to thicken, too little for us to notice, but enough to slow down the flow a little...”

The Dean was the first to spot what she was thinking.

“Then the Minute would run slow in cold weather.” She paused and then realised the faux-pas she had said. “Sorry—the Minute doesn't run slow because it runs at a minute per minute. But it would appear to run slow relative to an unaffected clock.”

The Practical Scholar smiled. “That would explain what I saw when I timed it against our best hourglasses!”

“And what happens,” continued the Abbess, talking more to herself than anypony in particular, “if we measure the length of the day and night by such a clock?”

“The day and night would be longer in colder weather,” answered the Dean.

“Would that make any difference?” asked the Cellarer. “It must be a very small effect or we would have noticed it. And it would affect both day and night equally.” The other ponies nodded their heads in agreement.

“But,” continued the Abbess, “if the days and nights are both longer than they should be in the cold of winter, that disproportionately affects the night—as it is longer in winter. And if the days and nights are shorter in the warmth of summer, then the long summer days would be not quite so long...”

“So with slightly longer cold winter nights and slightly shorter hot summer days, we would see slightly less of the sun...” said the Dean.

“Which would make the average annual weather slightly colder,” said the Abbess.

“Making the winters slightly longer and the summers slightly shorter,” continued the Dean, “making it colder still...”

“Which augments the effect even more. Colder weather means a slower Minute in winter, which means longer winter nights, which means colder weather, which means a slower Minute...”

The Abbess’s explanation trailed off as it became repetitive. The whole table fell into silence as they realised the full significance of this revelation. Celestia and Luna, who had not been paying much attention to the conversation until now, instead focussed on the food, realised that something was amiss and looked up.

“Positive feedback…” murmured the Practical Scholar.

“How long has this been going on for?” asked the Cellarer.

“Since the start of the Order,” said the Abbess. “Ever since the Minute was first used to set the sun and moon. A tiny effect. Not enough to notice from day to day, or even year by year. But over seven centuries, we have been cooling our world, little by little.”

“Can we be sure of this?”

The Abbess stood up. “We need to do an experiment,” she said.

“What?” exclaimed the Practical Scholar.

The head of the Order turned to the Steward and Cellarer.

“Bring that barrel of cider from over by the fireplace—the one that has not yet been opened and put it on the table. Then fetch a cold one from the cellar—the same size.” She turned to address the Scholar. “Bring a ten-minute-glass—the most precise we have.”

The instructions were given in a clear authoritative tone. The Fellows moved to follow her instructions straight away. In a short time the two casks of cider were positioned at either end of the table. And an ornate hour-glass—carved oak supporting the clear glass bulbs, filled with the finest coloured sand—was positioned in front of the Abbess.

“Okay,” said the Abbess, “we have two liquid vessels, identical, except they are at different temperatures. We shall measure the flow from each over a ten minute period.” She then banged her gavel to silence the chattering novices and addressed the hall. “Everpony bring your tankard and stand in line for a special holiday cider ration. If you like it warm, stand to the left, or if you prefer your cider chilled, take the right hoof line. Everypony is to take exactly one tankard, filled to the brim. Not a drop more or less.”

At the promise of extra cider, the novices jumped to their hooves and formed two lines on either side of the hall, leading up to the two ends of the high table, where the Steward and Cellarer each stood on either side, next to the spigots on the barrels. The first year novices, for whom this was their first experience of such a feast, assumed that this was all part of the ceremony that defined life in the abbey. The older members of the Order were a little puzzled by the novelty, but nopony was going to question the authority of the Abbess. Not when it meant extra cider.

“Ready?” said the Abbess, looking to the left, then the right, and nodding at the Steward and Cellarer, then she simultaneously turned the hour-glass and hammered her gavel. At this the two serving ponies opened the taps on the barrels, and the first novices in line thrust their tankards under the flow.

The Fellows sat without talking, their eyes flicking from one barrel, to the hour-glass, then the other barrel. As soon as each tankard was filled, the pony next in line pushed it away with his or her empty mug to take the place, and the pony ahead walked away with a full tankard and happy smile. As each tankard was filled, the Abbess marked a tally on a sheet of paper, filling two columns, for the warm and cold liquid.

After the ten minutes had passed, and the final grain of sand fell, the Abbess banged her gavel to mark the end of the experiment. The Cellarer and Steward instantly closed the spigot taps, leaving two ponies with incomplete measures somewhat miffed.

“The result,” said the Abbess. “Cold cider: Thirty-five and a quarter measures. Warm cider: thirty-eight and three sixteenths. The warm liquid flows faster. We have an explanation for why the climate is getting colder.

“That’s not really a properly controlled experiment,” said Twilight. “They really should have repeated it several times exchanging the containers used, and the cider could have a different viscosity to water due to the dissolved gas, and—”

“Twilight!”

The Fellows all smiled at this conclusion, but Luna and Celestia still looked a little confused.

“Canst thou explain thy scientific research such that a simple alicorn princess can understand?” asked Luna.

The Dean answered, “We have shown that colder liquid flows slightly slower than when it is warm. As it is the flow of water which sets the minute, this means the minute—and hence the length of a day and night—is longer during the cold of winter. Every year this has made winter slightly longer than it should be, which is making the weather colder, which, in turn, makes the water flow slower, so the effect keeps on.”

Luna and Celestia both paused for a moment to take in this information. Then Luna's face broke into a smile.

“You mean after all that stuff you said about windigos,” she said, dropping the Royal Canterlot Voice, “it turns out the real reason that it's so cold is that you can't keep time?”

The Abbess could have defended the work of the Order in many ways, but this was a time to show humility.

“Yes,” she said.

Celestia started to giggle as well. “So it's nothing to do with the sun. Or the moon. Or anything to do with us. It was your doing.”

The Abbess nodded slightly.

“All those silly ideas about the balance of the sun and moon,” said Luna with a broad smile, “and it turns out it was your balance that was off. The Order of the Time Turners is running a bit late.”

“A little out of order,” said Celestia.

“A temporary glitch no doubt,” said Luna.

“It will be put right in no time at all.”

The two sisters laughed so hard they had to support one another with their hooves. Eventually they calmed down and Luna looked her sister in the eye.

“I’m sorry I said that you weren’t keeping the sun hot,” she said.

Celestia smiled.

“That’s okay. I’m sorry that Philomena burnt your notebook. And I’m sorry about the moonfrogs.”

Once the Abbess was sure they were not looking at her, she permitted herself a small smile of her own, seen only by the Dean. All eyes in the hall were now turned to the two princesses who were looking at one another as reunited friends.

However just as the audience was waiting for the obligatory tearful happy hug, the magical atmosphere was shattered by the ringing of a bell. A porter, who had been assigned to check the time by the Minute, proclaimed the message:

“Three minutes until eleven o’clock!”

Author's Note

Verge and Foliot Mechanism

The verge escapement was the first step towards building a mechanical clock. The mechanism would advance a wheel by a fixed amount when pushed by an oscillatory process—this was provided by the foliot—a horizontal metal bar, with weights at either end which would swing back and forth. These appeared in European monasteries in the thirteenth century. They didn’t keep very good time, but they had the advantage of not freezing in winter.

Bungee Jumping

Time for quick excursion to the twentieth century. The modern sport of bungee jumping started in 1979 when members of the Dangerous Sports Club (an unofficially group of Oxford University students, with some similarities to the Cutie Mark Crusaders—cuteness not being one of them) leapt off Clifton Suspension Bridge in Bristol with elastic ropes tied to their feet. While the stupid behaviour of the British upper classes is not something I would ever support (Don’t try this at home), they were not completely reckless, as they were engineering and physics students who had calculated the forces involved and convinced themselves that it was safe. If done properly, bungee jumping is significantly safer than many other activities, such as pony riding.

Climate Change

The factors which have, and are, contributing to the long term changes in weather patterns in our world is a complicated subject.

The temperature of the Earth is primarily determined by the balance between the sunlight shining onto it, and that radiated away into space. The most significant cause of global warming in our world is the greenhouse effect—the earth, warmed by the sun, re-radiates this energy as infrared light. But the greenhouse gases in the atmosphere—most significantly carbon dioxide—absorb some of this. As the amount of carbon dioxide has shot up over the last hundred years due to burning fossil fuels, this has reduced the heat radiated into space, and led to a warming of the planet, set to get much worse.

But further factors come into play. Clouds have a cooling effect as they reflect some sunlight before it reaches the surface (or put more simply, on cloudy days we don’t see the sun). Some long term historic trends have been explained by changes the power output of the sun—although this is remarkably steady.

The tilt of the axis of the Earth is what determines the seasons, and so long term variations in this also influence the weather. The idea that the presence of our moon helps to stabilise the Earth’s tilt is an old idea, but recent studies do not believe this is significant (so Twilight is right to be sceptical).

Note that the Order of the Time Turners are only discussing the temperature at their abbey, and are not aware whether this is global or local effect.

Temperature dependence of water flow

The temperature dependence is the big thing limiting the accuracy of water clocks. From Wikipedia:

The rate at which a fluid passes through an orifice depends, other things being equal, on the viscosity of the fluid. Approximately, the flow rate is inversely proportional to the viscosity. The viscosity depends on the temperature. Liquids generally become less viscous as the temperature increases. The reverse is true of gases. In the case of water, the viscosity varies by a factor of about seven between zero and 100 degrees Celsius. Thus, a water clock would run about seven times faster at 100 °C than at 0 °C. Water is about 25 percent more viscous at 20 °C than at 30 °C, and a variation in temperature of one degree Celsius, in this "room temperature" range, produces a change of viscosity of about two percent. Therefore, a water clock that keeps good time at some given temperature would gain or lose about half an hour per day if it were one degree Celsius warmer or cooler.

The standard method to measure viscosity is by the time taken for water to drain through a hole in a standard container. I did try to reproduce this experiment in my kitchen, but the results were somewhat inconclusive, as it’s difficult to control all other factors, such as ensuring the head of water is equal for all tests. So, once again, Twilight is right to be sceptical.

Chapter 5: The First Second

“So that was how they came to realize the fundamental problem of using a water clock,” said Twilight. “Of course… As the flow rate is inversely proportional to the viscosity of the water and the viscosity falls as the temperature increases, this will limit its accuracy as a timepiece. With hindsight, it’s surprising it took them so long to realise this, but I suppose as they didn’t have any modern instruments, and they were using the water clock to set the official time…”

Scootaloo, Apple Bloom and Sweetie Belle all glared at Twilight.

“Can we hear the rest of the story?”

“Oh… Yes… Carry on Doctor.”

The porter’s announcement caused a momentary panic. Only three minutes until the most important celebration in five hundred years. Everypony had been so distracted by the experiment, the cider distribution, and the princesses, that they had forgotten the reason for the feast. They hurried back to their places. The Abbess remained calm and shouted instructions at the porters and Fellows.

“Put the barrels to the side. Now get to your places.”

Together with the other Fellows, she discretely exchanged places at the table to let Luna and Celestia remain side by side. Order was quickly re-established and in two minutes the ponies were in the proper places, standing silently as they did at the daily ceremonies. The Abbess looked around the hall. This moment was to celebrate the restoration of order to Equestria and the defeat of chaos. It was important that the hall should be perfectly arranged.

“Can you mop up that puddle?” she asked the Steward, pointing at a small pool of liquid where a careless novice had spilled some cider.

The Steward looked around for a mop or any sort of cloth, but saw nothing he could use. It was less than two minutes until the hour. No time to run to the stores for anything. With no other option, he removed his beautiful frock coat and laid it on the floor to absorb the spillage, before neatly folding it and stashing it under the table. The Abbess breathed a small sigh of relief. Everything was in order.

The events which unfolded in the following minute have been held up by many scholars of history as evidence that, at this point in time, the draconequus master of chaos was not completely immobilised and encased in stone, as was generally believed, but that some spirit of the demon was still present and up to his usual mischief, albeit not as dramatic as when he was at his full power.

Other scholars, who have studied the consecutive chronology in more detail, have concluded the opposite, saying that while it appeared to be the work of chaos, it was actually an ordered process, playing out in mysterious ways.

The Abbess always upheld that it was simply down to chance.

Outside the hall, in the dark night, a solitary nightjar was flying past the mountain. Focussed entirely on hunting moths, he paid no attention to the towers and terraces of the abbey, treating them simply as part of the cliffs and rocks that made up the terrain. Suddenly a gust of wind blew hard, throwing him off course and towards the walls, where he collided with a leaded window. Unfortunately the catch on the inside had not been properly fastened, and the crash pushed the hinged window inwards and the poor bird was thrown into the dining hall. Blinded by the light of all the candles, sensing that the wind had vanished and the air tasted different, but with no idea what had happened, he was thrown into a total panic. He squawked, flapping his wings wildly, and flew one way, then another, crashing into the upper walls, then flying through the candles in the chandelier and crying louder as the flames singed his feathers. All sorts of wild thoughts and fears appeared in his mind. Had he somehow flown through the gates of Tartarus?

Down on the floor of the hall, the ponies all looked up at the mad squawking avian visitor, unsure what to do. However the Dean kept her head. Throwing off her gown, she leapt up in the air and flew up to the top of the wall, opened another window, and gently coaxed the young bird out into the night air. Once outside in the dark cool air, he quickly calmed down and half a minute later had forgotten all about his brief existential crisis and was back happily hunting moths.

Inside, the Abbess and other ponies waited with bated breath. The Dean closed the window that she had just opened. This was on the opposite wall to where the nightjar had entered. With two windows open, a strong draft had blown across the upper space of the hall, setting the chandelier swinging. As this blocked her from flying across to the other wall, she called out to the crowd below, “Can somepony close that one?”

As she flew down to return to her place at the table, she assumed this task would be completed by one of the pegasus porters. However they were beaten to the task by a little filly. An eager-to-please young not-quite-novice, with an uncanny skill in running up walls.

Rap was not a pony to miss a chance to prove herself. Jumping up, she ran across the floor to the wall just below the open window, and hooking her hooves onto the moulding of the wooden panels covering the surface she shot upwards, flapping her wings madly to maintain balance, knocking aside a portrait of the ancient scholar Primum Mobile [1], and another of an unknown member of the Order [2]. On reaching the window ledge, she grasped the window—a metal structure supporting a grid of small squares of glass—and pushed it shut. Unfortunately fixing the catch with one hoof was beyond her skill, and when she reached to secure it with a second, she realised too late that there was nothing supporting her.

[1] Primum Mobile (345-397), an outstanding pony mathematician and philosopher who had made many important discoveries. After some early work studying the motion of stars, she was the first to show their movement was inherently random and unpredictable—a fact later attributed to the intense magical fields surrounding Equestria. She then advanced the theory that time could be regarded as a fourth dimension. Unfortunately in her later life she grew increasingly eccentric, and became convinced of a crazy notion that the universe had only two spatial dimensions, and any perception of depth was just a creative use of perspective. Declared mentally unstable, she died confined to the infirmary.

[2] It was a lovely portrait showing a happy earth pony stallion with a brown coat, and broad friendly smile. Unfortunately nopony could remember who he was, and the label had been lost when the painting was brought down for cleaning eighty years before.

Flapping her wings madly, she fell back, and grabbed at the only support in reach—a thin rope supporting the central chandelier. This ran from the horizontal wheel supporting the candles, up to the ceiling, where it went through a metal ring secured to a beam, then across to the eastern wall, and through another ring, just by the window, and down to the ground level where it was tied to a metal support.

As Rap fell down, she pulled the rope down with her, which in turn caused the chandelier to shoot upwards and crash into the ceiling, sending the burning candles and molten wax falling down onto the central table. Waving her legs and wings, she desperately tried to swing herself over to the wall, but only succeeded in wrapping the rope around her hoof. Tugged by the extra force, the knot securing the rope at floor level suddenly gave way. The loose end shot upwards, and Rap fell down, but still linked to the ceiling, she was swung across the width of the hall. At the lowest point, she sailed just above the heads of her friends. Her momentum carried her onwards, and up, almost touching the opposite wall. From this zenith, she swung back towards the eastern wall.

At that moment, the bell of the clock tower struck marking the eleventh hour. The Steward raised his hoof across his eyes unable to watch any more. The Dean stared at the hall, littered with half burnt candles, and upturned food, as the young filly swung back and forth. She had no idea what to do and simply looked across at the Abbess for guidance. Celestia and Luna both burst into a fit of giggles, but the rest of the hall was shocked into silence.

The Abbess took a deep a breath, then stood up and addressed the hall.

“My friends, members of the Order, novices, Fellows and princesses. We are assembled tonight to mark the five hundredth anniversary of the defeat of Discord, the evil Master of chaos, who turned our world upside down, and covered it with sour cream and chocolate sprinkles. Thanks to the bravery of Celestia and Luna, our gracious and noble protectors, he was vanquished. And thanks to the Order—to you and your predecessors, we have lived in ordered harmony since then, and counted the years, days, hours and minutes ever since. Two hundred and sixty-two million, nine hundred and eighty thousand minutes, to be precise. While this day has not gone quite to plan, it is perhaps not inappropriate that we should be reminded that we do not always get it right. No timepiece is perfect. But together we have kept sufficient order to let Equestria prosper, and together, we will do better in the future. So let us drink to good times.”

With that she raised a tankard of cider into the air beside her and all the other ponies followed. The Steward kindly levitated a mug towards Rap, still swinging back and forth, who caught it and drank with the rest of the Order, without spilling a drop—quite an impressive feat given her inverted perspective.

The hall of ponies let out a loud cheer. A group of musicians took up their lyres, flutes and horns and started playing a lively jig and soon a large crowd were dancing between the tables or clapping their hooves together with the beat. Luna and Celestia leaped over the main table and joined them. This was not part of the scheduled ceremony, but the Abbess could only smile as she watched the princesses hopping among the novices. Above them, Rap continued to swing back and forth.

“I suppose we should release her,” said the Abbess.

As Rap swung towards her side of the table, the Dean flew up in the air and caught the young filly with her hooves. She held her steady as the abbess focussed her magic on the rope wrapped around her hooves to untie the knot.

“What will the next five hundred years bring?” the Dean said to the Abbess.

“Whatever it brings,” replied the head of the Order. “We will need an improved timepiece to measure it.”

“How will we do that? The atomic clock?” The Dean released Rap from the rope and let her fall to the floor. The little filly landed on four hooves and grinned at the two Fellows.

“I know what to do,” she said.

Four weeks later, every pony in the abbey was crowded into the Eastern Hall. Row after row of fillies, colts, mares and stallions were standing on the polished wooden floor, packed so close together that they could feel each others hearts beating with anticipation. They were all silent. If they had listened very carefully, they could have just heard the faint snores of Strombol the Dragon, resting on the treasure of the abbey in the undercroft beneath the floor they were standing on. But everypony's attention was focussed on something else.

At the front of the hall, in a narrow space kept clear of ponies stood the Abbess. Princess Celestia and Princess Luna stood in the front row of the audience. High above the Abbess, a large metal hook was mounted on a girder running across the wall. From this a long metal chain ran down to the floor, held away from its equilibrium position by Rap, standing atop of a wooden crate.

With all eyes watching her, the Abbess turned towards the pegasus filly and nodded her head, at which Rap jumped off her support, gripping the chain between her hooves, and swung across the room. She sped past the Abbess at maximum speed and swung up to the height she had started at, but on the other side of the hall, where her speed dropped to zero, before she swung back in the opposite direction.

Behind the Abbess was a similar mechanism built to a smaller scale, with a pendulum as tall as a pony connected to a clock mechanism. The Abbess pushed this rod to one side, and when Rap had swung back to her starting extremity, she released this so that the two pendula fell down together. But the smaller version fell faster, such that by the time Rap had completed a full cycle and swung back to her origin, it had completed three such periods. With each passage, to the left or right, a cog-wheel on the clock was advanced by a peg and a clear 'tock' sound resonated around the hall.

For a while the Abbess waited as Rap swung back and forth in front of her, in phase with the pendulum clock. The repetitive motion and tocking sound had cast a spell of sorts on the audience so that they said nothing, but simply watched and listened to the pattern.

The Abbess walked over to the two princesses to explain the new ceremony, addressing the alicorn sisters, but loud enough for everypony in the room to hear.

“It turns out that a simple pendulum, nothing more than a weight attached to a chain or the end of metal rod, is the most isochronous measure—the best way to keep time—that we have found to date. Provided it is only swinging back and forth by a few degrees, then the time it takes depends only on the length from the pivot to the weight. The chain which young Rappel is riding is nine times the length of my standard pendulum here. It takes precisely three times as long to swing back and forth—the square root of nine.

We have tested this new clock against our best hourglasses and every other time measuring device known to ponykind. It is at least as accurate as every one of them. And by comparing two separate pendulum clocks, and seeing how long it took them to get out of sync with each other, we conclude that it is accurate to a small fraction of a minute per day.

Hence we propose to retire the Minute as the standard clock of Equestria, and replace it with a new clock. We propose a new unit of time, equal to the period it takes this pendulum—with a length equal to the height of an adult pony—to swing from one side to the other. This shall be called The Second. The Minute shall now be defined as equal to sixty seconds. The hour shall remain sixty minutes, and the day twenty-four hours, as before.”

While she was reciting this speech she looked at the two princesses and was pleased to see them gently rubbing their necks together as the best of friends. She glanced at the rest of the audience and saw that they were not watching her, but just staring at the swaying pendula.

“Does the Order vote to support this motion?”

While there was no precedent for agreeing such a move. The Abbess felt that such a major decision of changing the very definition of time required the unanimous or near unanimous support of the full Order. Hence the decision to summon everypony and the princesses for a full demonstration, and to seek their approval.

The day after the historic feast, after the chandelier in the main hall had been repaired, she had spent hours adjusting its height and measuring how the time it took to swing from side to side varied with the length of rope supporting it. She had then spent several weeks at work with Rap and the clockwork mechanics in the workshops, testing pendula of all lengths. The Practical Scholar had made numerous suggestions, and the Dean and other Fellows, as well as Patina and Ginger Root had also joined in the project. Eventually they had constructed a new sort of clock in which the timekeeping element was a swinging pendulum. The power to sustain the swinging was provided by a weight, connected to a chain wound around a spindle, such that as it fell, it turned the spindle, providing a kick to the swinging rod. Provided the weight was lifted each day to 'wind up' the clock, then it would keep going forever—or at least until some gear or lever wore out.

Relying on a pony to wind the clock each day troubled the Abbess—what if the pony assigned to do so overslept? Therefore she had designed a mechanism to do this automatically, driven by a lever arm connected to a water wheel in a similar fashion to the Minute.

The Abbess waited for a response from the audience but they were all silent. She realised that they were no longer listening, but had fallen into a hypnotic trance induced by the motion of the swinging pendulum. For a moment she was unsure what to do. But then a decision was made for her by Rap. The little filly grew tired of riding the swing and let go, sailing through the air and landing on the floor on four hooves.

“Everypony stomp your hooves for The Second!” she shouted.

The action woke up the crowd, and they promptly hammered their hooves on the floor in agreement. Rap gave a big grin. “Okay, now let's go for dinner!”

Although it was not the usual procedure for a novice to order the entire abbey community, all the ponies of the order obeyed without hesitation and filed out of the Eastern Hall, across the courtyard, and into the dining room in the Western Hall.

We just said 'a novice' but if you remember back to chapter two, we said that Rap was still not even a novice, as she had not yet demonstrated her special talent and gained her cutie mark. You have no doubt guessed the new detail which we have not mentioned until now. For as Rap walked out of the hall, together with the Abbess, the princesses, and her best friends, every pony could admire the image of a simple pendulum on her flank.

“She did it! She did it! She got her cutie mark!” The crusaders jumped around the Doctor thrilled to have finally reached the climax of the story.

“Could we get our cutie marks in inventing a pendulum clock?” said Apple Bloom.

Sweetie Belle looked sceptical. “You can only invent something once. I don’t know if you can get a cutie mark for reinventing something.”

Scootaloo was more enthusiastic. “We could try. It might be quite fun anyway.”

The ponies of the Order entered the Western Hall where the kitchen ponies had set out a huge feast. The Abbess, other Fellows and the princesses sat at the plush cushions at the high table. Rap, of course, as a novice, sat at the lower benches among her friends. Following the custom, the Abbess turned the hourglass over and banged the gavel to signal the start of the meal. In this particular case, the hourglass merely timed the duration of each course. The feast would continue late into the night.

And it was a banquet appropriate for the grand occasion. Pastries and pies stuffed with vegetables, potatoes, carrots, swedes, turnips, cauliflower, rich cheese sauces, bread rolls, huge bowls of rice, beans, lentils and salads of every composition and flavour. The food was accompanied glasses of wine and mugs of ale and cider. There was laughter throughout the hall.

At the high table Celestia and Luna sat side by side, thrusting their snouts into bowl after bowl to sample the delicacies on offer, then chatting and laughing together as if their fifty-year quarrel was of not the slightest importance. Opposite them, the Abbess sat watching them with a contented smile.

“Now I think about it,” said Luna, while munching a mouthful of salad, “your predecessor—what’s his name—Fanonical Flowers?”

“Canonical Hours,” said the Abbess.

“That’s him. He said that the water clock wouldn’t last.”

“That’s true,” said Celestia. “When it was inaugurated, he said that it was a temporary measure until you could find something better.”

“He was right,” said the Abbess.

“I just wonder why it took so long?”

“Because the Order has its priorities,” said Celestia, taking a bite of a caramelised onion, garlic and olive tart. “If they had focussed too much on telling the time, who would have developed these wonderful recipes?”

Eventually—after the vegetable and salad courses had been followed by cake, chocolate pudding, sweet pastries, cheeses, further salad, then more cake—the Abbess banged her gavel to signal the end of the formal dinner. The novices and younger members would stay partying in the hall for another few hours. Luna and Celestia had decided to have a sleepover at the abbey, and were escorted to a suitably regal guest bedroom. But as soon as the Fellows had departed, they returned to the hall to continue the party with the young foals. (The Dean would ensure that they were sent back to bed by midnight—nopony wanted to risk that they would not be in a fit state to perform their duties the following morning).

While the younger ponies were laughing, screaming, and singing songs, the Abbess and Dean slipped quietly through the door, taking a bottle of port with them, and climbed the spiral staircase to the Abbess's room. Where, following their usual custom, they settled down on cushions for an evening chat.

“Well...” said the Dean, pulling the stopper out of the port bottle with her teeth and positioning a glass with her hooves. “It's great the way everything turned out clockwork. Climate change is under control. A new clock. A new initiated novice—who seems to have rather more brains than some of those much older than she is. It's the start of a new era for the Order. And best of all, it's lovely to see the princesses as friends again.”

“Yes,” said the Abbess softly, levitating the port bottle towards her and filling her glass.

The Dean turned to face her friend. “You don't seem quite as happy as I would have expected. Is something wrong?”

“No... Well... It's just something I was thinking during dinner. While listening to Luna and Celestia telling all those jokes about us...”

“They didn't mean any offence, it was all just good humour.”

“I know... But... It's just clear that they see us in another way now. I guess they've grown up a bit. They used to respect the Order absolutely. But now that they've seen that timekeeping isn't quite as absolute as all that...”

“They still respect us.”

“Yes... For now... But maybe not forever. Now they can see that we sometimes get things wrong, they will question what we do. Heaven forbid that immortal alicorns should think that they have the right to question the authority of mortal ponies.”

“Surely they wouldn't dare?”

“I guess not... But... What would we do if one day Luna were to refuse to lower the moon?”

The Dean paused for a moment to contemplate the thought before shaking her head and looking back at the Abbess.

“Pass the port.”

Author's Note

The Bird in the Night

It’s time to include a reference to a real member of a monastic order. Saint Bede the Venerable (673-735) was a scholar at the monastery of Jarrow in North East England. His many contributions to scholarship include On the Reckoning of Time which describes how the motion of the Sun and Moon explain the seasons, the phases of the moon and the tides, and a polemic controversy of his time: how to calculate the date of Easter. His most famous work, however, is An Ecclesiastical History of the English People, in which he recounts how the King of Northumbria was converted to Christianity by the following parable:

When we compare the present life of man on earth with that time of which we have no knowledge, it seems to me like the swift flight of a single sparrow through the banqueting hall where you are sitting at dinner on a winter's day with your thegns and counselors. In the midst there is a comforting fire to warm the hall; outside, the storms of winter rain or snow are raging. This sparrow flies swiftly in through one door of the hall, and out through another. While he is inside, he is safe from the winter storms; but after a few moments of comfort, he vanishes from sight into the wintry world from which he came. Even so, man appears on earth for a little while; but of what went before this life or of what follows, we know nothing. Therefore, if this new teaching has brought any more certain knowledge, it seems only right that we should follow it.

This argument convinced the king of the superiority of the new religion, and he and his kingdom enthusiastically embraced the Christian faith. It is possible that the economic benefits of trading with Christian kingdoms may have also influenced his judgement.

Pendulum Clocks

Simple though it is, the invention of the pendulum clock was the breakthrough in timekeeping which marked the transition from the old world of medieval monks, whose world view was based on ideas from ancient Greece, to the new era of the Renaissance and experimental science.

Galileo Galilei, whose contributions to mathematics, physics and astronomy were matched only by his ability to get into trouble with the church (although he was officially pardoned in 1992), is credited with first recognising the isochronous nature of a swinging pendulum. According to one story he noted this while watching a lamp swinging from the roof of Pisa cathedral, and timed its period with his pulse. But it was left to Christian Huygens to build the first working clock in 1656.

The verge and foliot mechanisms were soon replaced by pendula and such timepieces were then the standard for many years to come, well into the twentieth century. Their accuracy was such that it was considered at one point defining the metre as the length of a pendulum with a half-period of one second.

Chapter 6: A Brief History of Equestrian Time

Tock... Tock... Tock... Tock... Tock... Tock... Tock... Tock... Tock... Tock... Tock... Tock...

The Cutie Mark Crusaders stood in front of the swinging pendulum, turning first left, then right, to track its motion with their eyes. Doctor Hooves, Twilight and the three fillies had moved into the Eastern Hall of the abbey, where the clock continued to mark time, as it had thirteen hundred years ago. The steady pattern had again hypnotized the foals into silence.

“So this was the pendulum clock that marked time from that day on?” asked Twilight.

“Yes, indeed,” replied Hooves. It became known as The Second, being the second attempt to build a universal time standard, as it were, and thus set a new unit of time equal to one sixtieth of a minute. And this clock was used to mark time for many centuries. There were some modifications made. After fifty years it was found that it had the opposite problem to the minute—it ran just a little slower in summer and a little faster in winter, as the pendulum would expand with heat, increasing its length. Fortunately this was realised before the longer-than-scheduled summer days had much effect on the Equestrian climate. They made a new pendulum with two different types of metal, which expand at different rates, such that the effects cancel out and keep it the right length. Very ingenious.

“Over the years the scientists of the Order developed other timepieces. They soon found ways of making a weight attached to a spring oscillate back and forth with the same regularity. This worked as well as a pendulum, and had the advantage of being much easier to transport. So the watchmakers of the tenth century constructed a series of portable timepieces, each better than the previous one. The pinnacle of this achievement was the Canterlot Chronometer, so called because it was taken to Canterlot to keep accurate time within the city itself, and brought back to the abbey every three weeks to adjust it to match The Second. With the invention of chronometers Celestia and Luna no longer had to fly to the abbey twice a day, as they had their own portable timepieces.”

“Told you she had a fancy pony princess watch,” said Scootaloo.

“And the Princesses went back to live in the Castle of the Pony Sisters?” asked Twilight.

“Yes,” continued Hooves, “where they lived happily together, and fought many a prank war, for another century. But unfortunately, as we know, dark times would come again, and when they did they were darker than ever before. For as the Abbess had predicted following the water clock's demise, the princesses no longer viewed the Order with quite the same veneration as they had in those early days. Time was something that anypony could measure, if he or she had a good enough clock, and was no longer dictated by an elite group. So when Luna was overcome by jealousy of her sister, she no longer saw the need to let the Order dictate when she should lower the moon. If the Order had got it wrong before, who was to say that they were right now? Why should she let Celestia, the Order, or anypony else dictate the length of the night? Why could the night not last forever? Tragically once this thought had settled in her mind, it grew like a tumour, until the spirit of Nightmare Moon had taken control of her.”

“And the rest is history,” said Twilight.

“Yes, but a history which also decided the fate of the abbey, for in the violent struggle between Nightmare Moon and Celestia which followed on that fateful night, many a blast of magic was thrown by each pony into the sky and onto the ground. The fight began in their castle in the Everfree forest, but the two alicorns flew far and wide in the course of the battle. Canterlot Mountain itself was hit, triggering a landslide. Falling rock rained down onto the abbey roof, and the courtyard plaza was shattered and covered by falling masonry. The members of the Order fled into tunnels into the mountain. But when they returned, once Celestia had banished Luna and lifted the sun, they found the abbey buried under piles of rock. They were forced to abandon their home, and moved to Canterlot. They took what books and other belongings they could, but it was a hasty removal. The mountain had been thoroughly cracked and many paths were blocked. Pegasi tried to assist from the air, but it was difficult to alight onto the sharp fallen rocks, which would just tumble down once they set a hoof on the rubble. Eventually when everypony was safe in Canterlot, the Order re-established itself within the city. The Canterlot Chronometer became the new standard timepiece which counted the days and nights for the next few centuries. The Order built a splendid new building, just outside the castle walls, which would one day become Princess Celestia's School for Gifted Unicorns.”

“But they came back to restore the abbey one day?” said Twilight.

“All in good time,” continued the Doctor. “The Order resided in the city for three hundred and twenty-eight years. During this time Celestia took charge of both the sun and moon and raised and lowered them at the times measured by the chronometer. Those were austere times, and the number of ponies in the Order fell to just twenty-four at one point. But they took great pride in continuing the tradition, maintaining full records, and keeping the chronometer wound, oiled and adjusted. They kept this up for over three centuries. Until one fateful day...”

“What happened?” asked Apple Bloom.

“Celestia was having a difficult morning. Attempting to make up lost time and keep to her schedule, she was trying to raise the sun, levitating the chronometer in front of her to check the time, while at the same moment, reading a report from the Royal Guard and also eating her breakfast. This multitasking effort proved too much, as at that point her pet phoenix, standing on a perch on the opposite side of the table suddenly burst into flames. This of course did no harm at all to the phoenix, being all part of its natural life cycle, but Celestia's attention was momentarily distracted, and she let the chronometer drop into a large pot of strawberry jam.”

“Oh no!” said Twilight.

“It was an embarrassing moment for Celestia, but a much darker day for the Order. They cleaned up the mechanics as best they could, but being immersed in jam does tend to damage even the best watches. The chronometer never ran properly again. Of course they had other timepieces, and in a practical sense, it was not a serious problem, they just replaced Chronometer One with Chronometer Two. But they had counted every second since the first pendulum had swung. And now they thought they had lost that connection, and the clock they had brought from the old abbey had been lost. Everypony felt as wretched as they had broken a priceless heirloom.”

“So what happened then?”

“They wanted to remake the chronometer. But none of the Order at the time had the skill to accomplish the task, so they set out to relearn it. They read all the ancient books they had salvaged from the abbey, and made a few new chronometers, but none of these were as good as the old No. 1. Then the Fellowship of the day decided to launch an expedition to return to the old abbey and see if they could find some more books, or other information to help them. This was a major undertaking. It took several months for them to rebuild the old paths and bridges and excavate the rubble filled tunnels. Meanwhile the pegasi started to clear the fallen rocks by air, until they could safely land on the old plaza. Eventually in summer 1328, they finally removed the rocks blocking the doorway to the eastern hall.”

“And did they find the books they needed?” asked Twilight.

“Yes, and they also found something else.”

“What? What did they find?” asked Sweetie Belle, Apple Bloom and Scootaloo in unison.

“Strombol the Dragon. Who everypony had forgotten about. It had been assumed that he had flown off into the Foal Mountains during the chaos following Luna's exile. But they were wrong. He had stood by his place in the abbey, guarding the treasure. And when he found the rest of the Order had fled, he took charge of maintaining the Second, following his duty as a Fellow of the Order, lifting the weights each day, oiling the gears and ensuring everything ran smoothly. He also noted the times of sunrise and sunset each day, and kept full records. For three hundred and twenty-eight years he kept his place in the abbey. He did not know the fate of the rest of the Order. When they asked why he had not flown down to Canterlot, he replied that he did not like to leave the Second unattended. He always knew they would return one day.

“It was a joyous occasion for all. To return home to the abbey and find that they had not lost track of time after all. Strombol was hailed as a hero of the Order. They soon renovated the old buildings, and the abbey returned to the life it had known before they left. Strombol lived for another hundred and seventy years before he died peacefully at the age of eight hundred and seventy-four. There is a monument to him on the south slope of the mountain. The most long-lived, loyal and devoted Fellow ever to serve the Order.”

“I must tell Spike about him,” said Twilight.

“Since then the Order has continued to keep time. As before the exile, Celestia kept the Chronometer in Canterlot and came to synchronise it to the Second once a week. The Second kept time for another five hundred and sixty years. However it was eventually replaced when new timepiece technology was developed. In 1877, a former rock farmer, Piezo Electric, built a clock based on a quartz crystal, which, when an electric potential was applied, resonated at a very regular frequency. Even better than the best mechanical chronometers.

“Then in 1956, the descendants of the Practical Scholar Spin Precession, who had founded a satellite abbey to the west, finally achieved the dream of producing a cloud of cold atoms. By shining a laser system in such a cloud, they could see the atoms precessing, just as predicted, like spinning tops, and thus they made Equestria's first atomic clock. Such an instrument was installed in the abbey here, and is the most accurate timepiece ever made, which we use to this day to keep Equestria running to time. The second is now defined as nine billion one hundred and ninety-two million six hundred and thirty-one thousand seven hundred and seventy oscillations of a caesium atom. Our clocks can keep time so accurately that they gain or lose less than a second over a hundred million years.”

“Enough of the science stuff,” said Scootaloo. “Tell us what happened to Rap and the other novices.”

“That is another story. Once they had grown older, they were appointed Fellows of the Order, and lived their lives in the abbey for many years, maintaining the Second, eating many big dinners, and doing their best to discipline the novices which came after them. Patina and Ginger Root were both appointed Abbess for a period. It is likely that Rap would have also taken the role, except she got distracted by a passion for mountain climbing. Her wings never did lift her far off the ground, as does happen to to some pegasus ponies, but she was determined to scale as many peaks as she could in the Unicorn and Foal ranges. She spent most summers off on peak-bagging expeditions, but always returned to the abbey to see her friends each autumn.”

“She was really cool,” said Scootaloo. “It was great how she got her cutie mark in the end.”

“She would have been a crusader,” said Apple Bloom. “Except they didn't have crusaders in the olden days.”

The three fillies ran off around the museum hall which housed all the historic clocks used by the Order during the previous six centuries. The huge pendulum of the Second, the beautiful brass and gold mechanics of the Canterlot Chronometer Nos. 1,2,3 and 4. (No. 1 had been painstakingly cleaned of the jam residue and restored as a museum piece). The digital displays of the first quartz and atomic clocks were rather less visually impressive. Twilight and the Doctor continued chatting, until eventually they all grew tired of the hall and they walked together out onto the courtyard. By now it was early evening and the Western Hall cast a long shadow across the flagstones of the plaza, cutting the meridian line, through which the water flowed steadily.

Once outside, they were surprised by the sight of a group of stallions of the Royal Guard standing to attention. The reason for their presence was revealed once they turned to the side.

“Princess Celestia! Princess Luna!”

Twilight smiled at the unexpected arrival of the two sisters. The Doctor bowed his head politely. The Cutie Mark Crusaders bounced up and down too excited to remember the formal etiquette for how to greet the princesses of the sun and moon.

“Good evening Twilight,” said Celestia.

“What brings you here?”

“It is approaching the time of day when it is my duty to lower the sun, and allow Luna to lift the moon into view. While we could, of course, do this from Canterlot, and still get the time right thanks to the clock display the Order kindly fitted in my bedroom, connected by optical fibre directly to the Atomic Timepiece No. 4 here in the abbey. But it is nice, sometimes to fly up here and see the old buildings and old friends. So when we heard that you were visiting this afternoon, Luna and I decided it was time.”

“The Doctor's just been telling us a cool story,” said Scootaloo. “About you and Luna and the Abbess and Rap and the ponies who lived here in the old days.”

“And don't forget Strombol the Dragon,” added Apple Bloom.

“We remember them all well,” said Luna. “We were good friends.”

“Will you join us for dinner?” asked Twilight.

“We'd love to,” replied Celestia. “But first, we must perform our duty.” She glanced up at the face of the clock on the tower built into the cliff. “It is nearly time.”

“Of course.”

“And since we are here,” continued Celestia. “Why don't we act out the traditional rite, as it was done in that bygone era. “It will be the first time I have performed it together with Luna in over a thousand years.”

Everypony agreed with this proposal.

“We need somepony to preside over the ceremony,” continued Celestia. “Could you do it Twilight?”

“I could,” said Twilight. “But as I am not a member of the Order. I think I should defer to the Doctor.”

Dr Hooves nodded his head to agree. Then the ponies moved into their position. Celestia and Luna facing one another on either side of the meridian. The Doctor stood on the podium straddling the zero longitude water channel, facing the clock. Twilight and the young girls stood to one side to watch, together with the other tourists, guard ponies, and the members of the Order who had come out to watch the proceedings.

The clock showed 7:19, and sunset was scheduled for 7:21. For two minutes the crowd waited in silent anticipation. Then as the minute hand of the clock moved into position, the Doctor sang out the opening line of the liturgy with perfect pitch.

“By the authority vested in me as a member of the Order of the Time Turners I hereby ask Her Royal Highness Princess Celestia to lower the sun—”

Celestia spread her wings and stood on her hind hooves, her horn aglow. As she focussed her magic, the audience stared to the west watching the sun fall beneath the horizon. The sky fell dark and the twinkling stars appeared above the mountains. The crowd of ponies now turned their heads to the east to face Princess Luna as the Doctor began the next verse.

“Now that the day has finished and the night is begun I hereby ask Her Royal Highness Princess Luna to lift the moon—”

With her eyes closed, Luna gently flapped her wings, rising slightly above the ground as a white aura appeared around her horn, silently coaxing the moon above the horizon. The ponies watched the gleaming white disk rise into the sky, shining moonbeams onto the plaza, and casting shadows across the courtyard.

“We thank you the Royal Pony Sisters in the name of the Unicorns and the Pegasi and the Earth Ponies. Amen.”

The Doctor finished the ceremony, and walked towards the centre of the plaza. Luna and Celestia did the same at a steady pace. With a series of whoops and cheers the Cutie Mark Crusaders rushed forwards to join them, followed by Twilight. The other ponies present all stomped their hooves on the flagstones to applaud the show.

The day complete, and all ceremonies done. The princesses, fillies and the Doctor all went into the Western Hall where dinner was waiting to be served. As guests of honour they were invited to sit at the high table. Scootaloo and Sweetie Belle both insisted on sitting next to Princess Luna. Celestia, Apple Bloom, Twilight and the Doctor all settled on cushions on the opposite side of the table. Once the dishes were brought in, the fillies and the two alicorn sisters forgot about their companions and enthusiastically attacked their food. Twilight watched them with affection before catching the Doctor's eye.

“Thank you so much for showing them around the abbey and for telling such a great story. You really are an outstanding storyteller. You make the whole place come alive with the way you talked about the ponies who lived here so many years ago. It's as if you've actually met them.”

The Doctor smiled.

Author's Note

Chronometers

No history of horology would be complete without a mention of John Harrison, master clock builder, and his battles with the Longitude Board.

In 1714 the British government announced the Longitude Prize – a promised reward of £20,000 for the development of a practical method of determining longitude at sea. The longitude problem was perhaps the biggest technological challenge of the day. Sailors could easily fix their latitude (degrees North or South) from the position of the sun or stars, but the position east of west was more difficult. As the local time (determined from the position of the sun) shifts by 4 minutes for each degree east or west, this could be done if only you knew the time at Zero Longitude (Greenwich). The trouble was even the best pendulum clocks were disrupted by the motion of a ship at sea.

Harrison set out to build a suitable timepiece—a marine chronometer—which could keep time to a precision of better than second a day, even in the rough environment of the high seas. Like many obsessive instrument builders, he changed his designs as he learnt more, in the end constructing a series of chronometers, now known as H1 to H4 (on display at the National Maritime Museum, Greenwich). H1 to H3 used double-ended pendula, while H4 was essentially a large pocket watch ticking at five times a second.

But claiming his reward was a more difficult challenge. A competing method was the Lunar Distance Method – fixing the time by measuring the angle between the moon and certain stars, and comparing this to a published table. Both Harrison’s chronometers and the lunar distance method had their own pros and cons, and both would be used to find longitude at sea in the years that followed. But the Longitude Board had a bias against Harrison, being made up of astronomers led by the unpleasant Nevil Maskelyne, proponent of the lunar distance method, who looked down on the master instrument builder as a mere clockmaker.

Harrison never did received the longitude prize, but was eventually rewarded an equivalent sum after he appealed to King George III. In the years that followed the building of marine chronometers grew into an industry and allowed the growth of world trade and let Britannia rule the waves for the next two centuries.

In Equestria such marine chronometers would only be useful for navigation as long as you could trust Celestia to raise the sun on time. Every morning the princess of the sun must go about her work with the knowledge that slipping up could misdirect a ship on the other side of the world into the rocks. Unless ponies have deployed a network of GPS satellites.

Piezoelectric Quartz Resonators

The first clocks to reach a better precision than pendula were based of crystals of quartz. In an electric field, these tiny pieces of rock will vibrate at a resonant frequency determined by the dimensions of the sample. The very best crystals, kept in a constant temperature oven, can reach a stability of better than 0.1 parts per million. Sounds good, but that’s only accurate to a few seconds over a year. Atomic clocks are stable to one second in a hundred million years. Still, quartz crystals are cheap, and easy to integrate with electronics, and allow a $3 digital watch to beat the precision of Harrison’s best.

Atomic Clocks

I’ve left atomic clocks until the end—for chronological reasons of course—but also because this is the trickiest bit to explain. The principle of using an atomic frequency to measure time was realised a long time ago, but it was many years until a working clock was built. Atomic clocks are based on the idea of using the frequency of microwave radiation which is emitted or absorbed by a particular process in a particular atom as a time regulator. Specifically the transition between two levels in a caesium-133 atom.

Atoms consists of a nucleus (made from protons and neutrons) surrounded by clouds of electrons. Using quantum mechanics, we can show that the electrons are in fixed energy levels. When we blast an atom with microwaves, it can move the electrons from one energy level to another. The frequency of the microwave radiation is set by the energy difference between the levels.

In one sort of atomic clock we make a cloud of atoms (by heating a sample in a vacuum). Set them up in the lower energy state, then send them through a tube where they are microwaved. At the other end of the tube, there’s a detector to count the number in the higher energy state. We can tweak the frequency of the microwave gun up and down, and set up a feedback loop so we push it one way or the other to give the maximum count rate on the detector when we are right-on the atomic transition.

Here’s another way to picture it, as preferred by the Practical Scholar Spin Precession, but which Twilight would point out is not entirely accurate:

The two different energy states of the atom correspond to the outermost electrons being either polarized spin-up (in the direction of the magnetic field), or spin-down (the other way). They start off spin-down. A blast of microwaves then rotates them by 90 degrees. They are then neither spin-up, nor spin-down, but in an in-between state where the spin precesses round and round just like a spinning top tilted to the side. If our microwave gun is precisely tuned to the same frequency at which the electrons are precessing, then if we wait a fixed number of cycles then before giving another blast, it will rotate all the electrons to spin up. But it there is a difference between the two frequencies, then the microwaves are out of phase with the atoms, so some end up spin-up, and some spin-down. We adjust the frequency to get the maximum count.

This was the principle behind the first atomic clocks. The idea was developed by Isidor Rabi in the US, but the first atomic clock to beat quartz was built by Louis Essen at the National Physical Laboratory (NPL) in London. Since then there have been improvements. The latest caesium fountain clocks use a set of lasers to produce a cloud of ultra-cold atoms, these are launched upward, into a microwave beam, and then fall back down.

Atomic instruments were the first clocks to measure time to a greater precision than the movement of astronomical bodies, allowing us to measure the rate at which the spin of the Earth is changing. Therefore in 1967 the second was redefined as 9,192,631,770 cycles of radiation in a particular transition in the caesium atom. A network of atomic clocks in now used to define Universal Time in our world as in Equestria.

Which brings me back to where I started. I visited NPL in November 2013. Afterwards, on the train home, I started to think about how an atomic time standard would work in Equestria. Which led to this story.

Thanks to everyone who has read this far. I hope you found this interesting. Thanks also to twoSteamPonies for comments on the first draft.