In the early 1330s, a young King  Edward III visited the abbey in St Albans, a town about 30  kilometers outside of London.

He found the building in disrepair,  and its abbot gravely ill. And this abbot, Richard of Wallingford, was spending a lot of time, effort, and money on a very fancy clock.

It’s said that Edward asked him, "Ought you not to get on with  the building of your Church?" To which Wallingford replied, "Sire, there are plenty who can build a church. If I die, there is none who can finish my clock". Now, this didn’t quite turn out to be true.

Wallingford died in 1336, before  he could complete his clock. And there were many other clockmakers in Europe tinkering with new clock technologies. But thanks to blueprints uncovered in the 1960s, we now know it was a true marvel of its time.

You might even say Wallingford’s  clock was so advanced, it helped reinvent the concept of time itself. [♪INTRO] Let’s roll back the proverbial  clock to before modern, mechanical clocks existed. How  did humans conceptualize time? Well, for one thing, there was the  daily observation of it being light, then dark, then light again, and so on.

And those periods of darkness were  generally a less productive time, so it was at least worth  distinguishing them from day. If you were living in, say,  Ancient Egypt around 1200 BCE, you would divide both your day and night separately into 12 equal parts. And during the summer, when you got more sunshine, one hour in the day would be  longer than one hour of night.

And vice versa. This philosophy of timekeeping  persisted around the globe into the middle ages, and became  known as unequal hours. So the exact “time” was  intrinsically linked to the Sun.

But rather than always  referring to the nearest sundial to know what time it was, many humans were simply concerned with how long it would  be until some future event. Like, I’m a baker and I  need to pull these loaves of bread out of the oven at just the right moment. Or, I’m a monk and I need to pray a certain length of time after sunset.

So in addition to marking the position of the Sun, there was one other type of timekeeping that really mattered before modern  clocks: setting a timer. And one particularly popular  timer was the water-clock. At its simplest, a water-clock is just a vessel with a hole near the bottom.

You’d fill the vessel to a specific height, and the water would drain out  the hole at a predictable rate. Then, by checking the water level  against markings inside the vessel, you could tell how much time  had passed since you filled it. Over the centuries, humanity improved both of these timekeeping technologies.

But the philosophy of time measurement remained the same from antiquity through the Middle Ages. We can see this in the word “clock” itself. It comes from the Latin word for “bell”, because a timer-type clock was usually rigged to ring a bell at specific intervals.

So measuring time was super closely linked to a device that we would today  describe as an “alarm”. Now, by the end of the 13th  Century, water-clocks had become the pinnacle of timekeeping  technology around the world. In fact, diplomatic envoys would often gift water-clocks as a great way to humble brag!

Elaborate systems of pipes and tanks produced smooth and reproducible water flow. And little floats inside could move  boards or dials as the water level dropped to drive not just an actual  clock face, but astronomical models! A lot of these fancy clocks  would end up at monasteries, because they were both important  political hubs and because the monks had to adhere to a  very strict prayer schedule.

But even the best water-clocks  had one major problem: they had to be refilled… by a human… who might occasionally forget  to fill the vessel before the water ran out, or not fill it  up to precisely the right line. Meanwhile, academics had gotten interested in measuring things as precisely as possible. Both secular and religious  scholars were obsessed with computing ridiculously long  strings of numbers, or creating incredibly detailed tables  of astronomical measurements.

And since astronomical events occur so regularly, an accurate clock could double as  an accurate model of the heavens. So this obsession with precision measurement was naturally extrapolated  to time, and it additionally sparked debates regarding the nature of time: Is it a physical entity or something that only exists in our experience of it? Is it discrete, or continuous?

How can it describe the motion of the heavens, and what does that mean for the human soul? If you were a monk who was into both astronomy and precision measurements of prayer times, you’d probably be obsessed with the  idea of building a perfect clock. You’d want to invent something that needed as little human intervention as possible.

And that would require a mechanism that changes at a predictable pace, plus a power source that reliably drives that mechanism. The first place you could look to  for inspiration was grain mills, which now featured gears that could make your clock-slash-astronomical model  move with greater accuracy. And for the power source, you might  consider adding an oscillator… a component that takes advantage of gravity to reliably move to and fro.

If you could put all these pieces together, you’d have a fully mechanical clock. Around 1276, someone got awfully close using liquid mercury instead of water. It featured a dial that could make  one full rotation every 24 hours, and was powered by a weight  wrapped around a spinnable drum.

The mercury was put inside that drum to slosh around and act as a counterbalance, dictating when the weight was  actually allowed to turn the drum. But it wasn’t a perfect setup,  and there was no oscillator. So ultimately, the dial couldn’t  rotate at a totally reliable rate.

There’s no surviving record of who  managed to invent the first proper mechanical clock, but it was  likely around this point in time. Between 1273 and 1321, several  clocks around England underwent maintenance that involved some  kind of new clock component. None of these clocks still exist, nor do any detailed descriptions of them.

So some of this work may have  been upgrades to water-clocks, instead of making the jump  to purely mechanical ones. But historians literally have the receipts, so we know something important  was happening around this time. And we also know that by  1327, Richard of Wallingford had finally started the plans  for his extraordinary clock.

But before we get into that,  we have to keep the lights on. So here’s an ad: This SciShow video is supported by KiwiCo. With five different clubs to choose from, KiwiCo makes hands-on learning  fun for every age and interest.

The activities grow with kids,  introducing new challenges that keep them engaged, from  their first sensory explorations with the KiwiCo Panda Crate to learning how to engineer their own robots with KiwiCo Labs. KiwiCo Labs, in particular, transforms science and engineering into a hands-on  adventure, with projects designed by real educators, engineers, and rocket scientists,  tested and approved by kids. We got to play with the delivery bot, which is a radio-controlled robot that I can use to deliver this tiny duck to the production  coordinator over there.

Building this robot was a  good mental break to my day and now we have a new mascot  around the Complexly office! The instructions are super easy to follow. The end product is adorable.

And a bunch of adults are having fun driving this guy around the studio. You can make your own at  kiwico.com/SciShow, and if you use code SciShow, you’ll get 50% off  your first monthly club crate! Wallingford’s clock combined three  key innovations: an escapement, an hour-striking mechanism,  and an oval-shaped gear.

He probably didn’t invent any of these components, but the precision of his designs… and the innovative way he combined them… was an absolute feat of engineering. An escapement is a mechanism that slows down the driving force of a clock. The mercury counterbalance from earlier is an example of a rudimentary escapement.

One of the first types of oscillating,  and therefore more reliable escapements, was probably  the verge and foliot style. They featured a rod that twists to allow a big, toothed gear to advance at periodic intervals. Meanwhile, Wallingford’s escapement  came to be called a “strob”.

It had a wheel studded with pins like a porcupine. And in this setup, a rotating  rod rolled between the pins, smoothly advancing the mechanism  and tracking the passage of time. Next up: hour-striking.

These days, we take it for granted  that a clock will chime once when it’s one o’clock, twice  when it’s two o’clock, and so on. But this was actually a pretty  tricky engineering problem to solve. Just striking a bell at the top  of the hour, or even playing a little musical tune, wasn’t a  novelty in Wallingford’s time.

But he managed to design a barrel  of pegs that, as it rotated, counted the hours of the day and triggered the corresponding number of bell chimes. In his blueprints, he laid  out a table with the precise positions of all 300 pegs studding the barrel. He even arranged them in a spiral pattern, to make them easier to manufacture!

Finally, Wallingford’s greatest achievement was an oval-shaped gear,  which he made to precisely track the movement of the Sun across the sky. See, the speed that the Sun crosses the sky is different depending on the time of year. Scholars in the 14th century  didn’t know the real reason why.

After all, they still thought  everything orbited the Earth. But they had a fancy equation to keep track of it. That equation didn’t translate  well to clocks, though.

A clock that could accurately tell  you where the Sun was at a given hour during summer would be  woefully off-target come winter. Until Wallingford came along, that is. Because instead of using  the typical circular gears, he carefully constructed an oval gear from the arcs of four different circles.

This gear featured exactly 331  teeth, meticulously machined, so that a smaller gear with  8 teeth could traverse them. The exact shape of the oval, and  the ratio of teeth in each gear, replicated the Sun’s variable  speed all year round! It’s not an innovation you’d  find in a modern clock, but remember: at this point in history, knowing where the Sun was still  a crucial part of timekeeping.

So Wallingford’s clock kept  track of a lot of information, and it was super accurate. It was so accurate, it could distinguish the difference between a 24-hour solar day… based on measuring how long it takes the Sun to reappear at the same point in the sky… and a sidereal day which is based on how long it takes the stars to reappear at the same point. A sidereal day is about four  minutes shorter than a solar day, because the Earth is both rotating on its axis and revolving around the Sun at the same time.

And over the course of one  month, Wallingford’s clock would only be off on that sidereal  measurement by one second. Based on all these fancy, automatic calculations, this clock could also track  when it was high or low tide, the phases of the Moon, and even lunar eclipses! A clock this intricate required  a lot of time and money to build.

Unfortunately, Richard of  Wallingford succumbed to what may have been leprosy before he  could see his clock completed. We aren’t sure exactly when it was  finished, but the abbey’s records made sure to specify that  the project went over budget. And for a long time, records like  those were all we had to go on.

Because part of this clock’s magic  is that it was nearly lost to time. Just like many other clocks  built around that time, it doesn’t exist any more. There’s a good chance it was  broken down for spare parts or raw materials after good ol’  Henry “I want a divorce” VIII dissolved the St Albans monastery in 1546.

The final eye-witness account was written by a librarian in 1534… nearly 200 years after the clock was constructed. And yet, he described it as “a marvel still without equal in all of Europe”,  and jotted down descriptions of the astronomical details  the clock could display. That was the last anyone heard of  the St Albans clock until 1965.

John North, an astronomy historian at Oxford, was browsing through a book that had been donated to the university sometime in the 17th century. And much to his surprise, it contained detailed instructions for building  a very sophisticated clock. And yes, he did use them to make a reconstruction.

The book that North uncovered  appears to be a copy of the abbot’s own notes, created shortly after he died, probably by a monk who had been  tasked with caring for the clock. It’s the world’s oldest and  most complete description of a mechanical clock ever  discovered, marking the 1330s as a definitive transition to  mechanical clocks in Europe. Because shortly after Richard of Wallingford died, mechanical clocks rapidly spread to nearly 80 cities across the continent.

That includes clocks installed not in monasteries, but in town centers. For  the first time in history, standardized time was  publicly accessible knowledge. And while clocks were originally  designed to bring glory to God through their impressive astronomical predictions, their practical limitations created  a new rhythm for daily life.

It was way easier to make mechanical clocks that only had to keep track of 24 equal hours. So rather quickly, both industry and commerce shifted away from the daylight-based unequal hours that civilizations had  relied on since antiquity. Because of mechanical clocks tracking equal hours, time was no longer a measure of a  thing, but a thing in-and-of itself.

That had resounding implications on society. Time was now a thing to be managed and controlled. The usage of time began to have moral weight, and timeliness picked up brand  new moral and social connotations.

Many of which persist to this day. Clockmakers added more hands to measure smaller and smaller units of time, and subtracted the motions of the astronomical bodies. Probably because they couldn’t fit all of that information on newer, smaller, clock faces.

Then, in the 19th century, cultures around the world adopted “mean time”. This was convenient for setting train schedules, but meant that in most places, noon was no longer the moment when the Sun was at its highest point in the sky. And in 1967, we severed time  from the cosmos entirely.

Scientists redefined the  length of one second to be based on a subatomic property  of the metallic element cesium. Which sounds a bit random, but they  do use cesium in atomic clocks, the most accurate timekeepers we have right now Humanity invented the mechanical clock to help track our Earth-based view of the heavens. Even if that’s all Richard  of Wallingford’s clock did, it would be quite an achievement.

But because of people like Wallingford, you could say we also invented time. Which is also an achievement. Although as a person who  stresses out way too much about being late to things, I wouldn’t  necessarily say it’s a greater one. [♪OUTRO]