WEBVTT - Time to Talk About Clocks 0:00:04.040 --> 0:00:07.480 Again in text with technology with tech Stuff from stuff 0:00:07.520 --> 0:00:14.240 works dot com. Hey there, and welcome to tech Stuff. 0:00:14.280 --> 0:00:17.320 I am your host, Jonathan Strickland. I'm an executive producer 0:00:17.360 --> 0:00:20.520 here at how Stuff Works, and I love all things tech, 0:00:20.720 --> 0:00:24.640 and today I wanted to talk about something that I've 0:00:24.640 --> 0:00:29.639 always found interesting but also intimidating. A couple of years ago, 0:00:29.880 --> 0:00:32.640 I traveled to Berlin, Germany to give a talk at 0:00:32.640 --> 0:00:36.200 a conference. After my talk, a couple of really friendly 0:00:36.240 --> 0:00:38.839 locals offered to give me a walking tour of Berlin, 0:00:38.960 --> 0:00:40.839 and so we kind of set out to explore the 0:00:40.880 --> 0:00:44.120 city and at one point we ducked into a luxury 0:00:44.240 --> 0:00:48.120 clock shop and I got a nice explanation, half of 0:00:48.159 --> 0:00:50.760 it in German, of the inner workings of some of 0:00:50.800 --> 0:00:53.720 the more intricate clocks there. And it was really interesting 0:00:53.800 --> 0:00:58.160 and incredible to see the workmanship that went into creating 0:00:58.160 --> 0:01:02.120 these clocks. And I thought, well, it's about time to 0:01:02.160 --> 0:01:04.640 talk about time, or rather to talk about how we 0:01:04.680 --> 0:01:08.120 mark the passage of time. So today we're gonna talk 0:01:08.160 --> 0:01:11.000 about clocks. Now, most of this episode I'm going to 0:01:11.080 --> 0:01:14.280 focus on mechanical clocks, but you know me, I like 0:01:14.360 --> 0:01:17.480 to talk about precursors. And history leading up to the 0:01:17.480 --> 0:01:21.280 development of technology. And so we'll first take a quick 0:01:21.319 --> 0:01:24.760 look back at some of the earliest timekeeping technologies before 0:01:24.880 --> 0:01:28.240 the invention of the mechanical clock. So to count as 0:01:28.240 --> 0:01:32.240 a clock, you really need two elements. The first is 0:01:32.280 --> 0:01:37.200 some sort of consistent, regular action or process that gives 0:01:37.240 --> 0:01:40.680 you the ability to mark off equal increments of time. 0:01:41.240 --> 0:01:43.600 In theory, this could be something like the rate that 0:01:43.680 --> 0:01:46.240 water drips out of a container, which is the basis 0:01:46.280 --> 0:01:49.960 of many water clocks, or sands through an hourglass, so 0:01:50.080 --> 0:01:53.120 are the days of our lives. But we'll talk more 0:01:53.200 --> 0:01:56.840 about water clocks later. With mechanical clocks, it's the rate 0:01:56.920 --> 0:01:59.640 at which parts move within the clock itself. In order 0:01:59.680 --> 0:02:01.240 to keep time, you have to find a way to 0:02:01.360 --> 0:02:05.000 regulate that so that it is consistent. So that's element 0:02:05.080 --> 0:02:07.440 number one. The second element you need for a clock 0:02:07.560 --> 0:02:09.760 is some sort of way to keep track of the 0:02:09.760 --> 0:02:12.520 increments of time so that you know what time it is. 0:02:12.600 --> 0:02:14.919 You need a way to be able to read the time. 0:02:15.560 --> 0:02:19.799 So early clocks, some of the early mechanical clocks that 0:02:19.880 --> 0:02:23.160 came out of Europe didn't have a dial or a 0:02:23.200 --> 0:02:26.800 face or hands or anything like that. They were really 0:02:26.840 --> 0:02:30.160 automated systems to chime bells, so it was the chime 0:02:30.160 --> 0:02:32.080 of the bell that would indicate what the time was. 0:02:32.160 --> 0:02:35.280 That was the best you could do. But later on 0:02:35.360 --> 0:02:38.239 it would be a mechanical clock with a dial and 0:02:38.320 --> 0:02:41.679 a face with hands on it, and that would be 0:02:42.080 --> 0:02:44.640 the part that tells you what the time is. So 0:02:44.680 --> 0:02:46.640 it's not enough that the clock keeps time. It also 0:02:46.720 --> 0:02:50.600 has to communicate that or display it in some way. 0:02:50.840 --> 0:02:52.400 So those are the two elements you need for it 0:02:52.440 --> 0:02:56.000 to be a clock. Now, since ancient times, people have 0:02:56.080 --> 0:03:00.520 found ways to mark the passing of time, everything from 0:03:00.600 --> 0:03:04.880 various versions of calendars to massive structures that could tell 0:03:04.919 --> 0:03:08.480 you all about when certain things are going to happen, 0:03:08.520 --> 0:03:10.920 like equal n ox Is. I mean, you've heard about 0:03:11.639 --> 0:03:15.400 structures like Stonehenge, But if you're talking about time, as 0:03:15.440 --> 0:03:18.359 in dividing up the increments of a day, you kind 0:03:18.360 --> 0:03:21.480 of have to look at the people's of Summer and 0:03:21.600 --> 0:03:25.880 ancient Egypt and their use of sun dials. The most 0:03:25.880 --> 0:03:28.840 primitive type of sun dial would be a stick stuck 0:03:28.840 --> 0:03:31.240 in the ground, and you can mark the passing of 0:03:31.280 --> 0:03:34.120 time by observing where the stick's shadow falls as the 0:03:34.120 --> 0:03:38.080 sun's position overhead changes throughout the day. Sun dials tend 0:03:38.160 --> 0:03:40.840 to be a bit more robust than a stick stuck 0:03:40.840 --> 0:03:43.360 in the ground. The sun dials of ancient summer were 0:03:43.400 --> 0:03:46.000 pretty much gone by the time historians got around to 0:03:46.080 --> 0:03:48.840 documenting these kinds of things, but there were still some 0:03:49.120 --> 0:03:52.880 that existed in Egypt. Now we know that the ones 0:03:52.920 --> 0:03:55.280 in Egypt were predated by the ones that were in 0:03:55.360 --> 0:03:58.480 sumer but we just don't have any examples of those 0:03:58.640 --> 0:04:02.160 so UH. In Egypt you could find things like obelisks. 0:04:02.840 --> 0:04:05.560 The obelisks dates to at least thirty d b c 0:04:05.800 --> 0:04:10.000 e before Common era. The shadows cast by those structures 0:04:10.200 --> 0:04:13.200 could help people mark the passing of time, and in fact, 0:04:13.280 --> 0:04:16.279 you might end up seeing one that has markings on 0:04:16.400 --> 0:04:20.240 the ground that indicates such. Now, both the Sumerians and 0:04:20.279 --> 0:04:23.720 the Egyptians created divisions for daytime, similar to the way 0:04:23.760 --> 0:04:28.160 we have ours. The Egyptians created ten segments of daytime 0:04:28.240 --> 0:04:31.640 between UH and between two and four for night time, 0:04:31.680 --> 0:04:34.039 but of course you couldn't track nighttime with a sun 0:04:34.080 --> 0:04:37.520 dial because for a sundal to work, you kind of 0:04:37.560 --> 0:04:41.040 need a sun and at nighttime that's in short supply. 0:04:41.880 --> 0:04:43.960 The same was true on any days with whether that 0:04:43.960 --> 0:04:46.880 would obscure the sun. Obviously, tracking time on those days 0:04:46.920 --> 0:04:50.560 would become difficult, but on clear days you could track 0:04:50.640 --> 0:04:54.640 the passing of time fairly well. The Egyptians would create 0:04:54.680 --> 0:04:57.000 markings on the ground that would indicate the time of day, 0:04:57.040 --> 0:04:59.279 so you'd see where the shadow falls. If it falls 0:04:59.520 --> 0:05:02.599 in atcular section, then you know it's time for lunch 0:05:02.760 --> 0:05:05.440 or I don't know. To listen to the New Bengals 0:05:05.720 --> 0:05:09.200 single if the Earth's axis didn't have a tilt to 0:05:09.320 --> 0:05:12.120 it relative to the position of the Sun, this would 0:05:12.120 --> 0:05:14.600 be a consistent way to track the time of day. 0:05:14.800 --> 0:05:18.000 But because of that tilt, during different parts of the year, 0:05:18.240 --> 0:05:20.800 the sun will occupy a slightly different part of the sky. 0:05:21.560 --> 0:05:24.600 This also depends upon where north or south of the 0:05:24.640 --> 0:05:26.880 equator you are. If you're right, if you're very close 0:05:26.920 --> 0:05:31.080 to the equator, the variation is slight, but the further 0:05:31.120 --> 0:05:33.440 way you are from the equator, the greater the variation is. 0:05:33.680 --> 0:05:35.640 And because of that tilt, during different parts of the year, 0:05:35.680 --> 0:05:38.400 the sun will occupy those different areas of the sky, 0:05:38.520 --> 0:05:42.000 meaning the shadow that it casts on the ground from 0:05:42.040 --> 0:05:44.000 any object is going to be different at one time 0:05:44.040 --> 0:05:46.560 of year than at a different time of year. The 0:05:46.560 --> 0:05:49.760 Egyptians had all this sussed out, and they would include 0:05:49.760 --> 0:05:53.280 indicators for the time of year so that timekeeping could 0:05:53.279 --> 0:05:56.440 remain fairly accurate. And it was easy to see which 0:05:56.480 --> 0:05:58.760 days were the longest and the shortest, because on the 0:05:58.800 --> 0:06:02.359 longest day, the obelisk would cast a longer shadow because 0:06:02.360 --> 0:06:04.839 the sun would appear lowest in the sky as it 0:06:04.880 --> 0:06:08.159 crossed overhead. On the shortest day, the shadow would be 0:06:08.240 --> 0:06:11.920 short as the Sun would pass closer to directly overhead. 0:06:12.080 --> 0:06:14.839 So little indicators there that can tell you more about 0:06:14.880 --> 0:06:16.880 the time of year. Now, the fact that the Earth 0:06:16.960 --> 0:06:20.719 is round, sorry flat earther's it also meant that you 0:06:20.720 --> 0:06:23.560 couldn't just design a universal sun dial that's going to 0:06:23.600 --> 0:06:26.839 be accurate wherever you go all year round. As you 0:06:26.880 --> 0:06:28.960 travel north or south, the angle of the Sun's light 0:06:29.040 --> 0:06:31.680 hitting your sun dial changes, and so you have to 0:06:31.720 --> 0:06:34.600 take that into account. A sun dial must be designed 0:06:34.600 --> 0:06:37.280 for the specific location if you want the time markings 0:06:37.279 --> 0:06:40.520 to be accurate throughout the year. The sun dial made 0:06:40.520 --> 0:06:44.080 its way to Greece and from there pretty much everywhere else. 0:06:44.360 --> 0:06:48.280 The Greeks created some pretty cool sun dials, including hemispherical 0:06:48.400 --> 0:06:51.559 sun dials. Now, as this name suggests. These sun dials 0:06:51.640 --> 0:06:56.720 used a hemispherical surface upon which shadows would fall. Typically 0:06:56.760 --> 0:06:59.240 the surface kind of like a bowl that have been 0:06:59.279 --> 0:07:02.120 cut in half or even quartered. So you had this 0:07:02.120 --> 0:07:06.000 this little bowl shaped area, but not a not a 0:07:06.040 --> 0:07:09.760 full bowl with lines on the inside to mark time segments. 0:07:10.600 --> 0:07:13.760 And the object that was to cast a shadow would 0:07:13.800 --> 0:07:17.160 be an appropriate distance from the sides of that bowl, 0:07:17.560 --> 0:07:21.480 and it's orientation would be such that no matter which 0:07:21.480 --> 0:07:23.800 way it's facing, it's facing away where the sun is 0:07:23.800 --> 0:07:26.520 always going to cast a shadow against the bowl. So 0:07:26.600 --> 0:07:29.400 you want to make sure that it's facing the right direction, 0:07:29.480 --> 0:07:31.800 otherwise you get a part of the day where the 0:07:31.840 --> 0:07:34.600 shadow would be outside the bowl and you would say 0:07:34.640 --> 0:07:38.040 it is the end of times and cause a panic. Now. 0:07:38.080 --> 0:07:41.960 I learned more about Sundale construction by visiting a website 0:07:41.960 --> 0:07:45.480 called sun dials dot org. It's a site dedicated to 0:07:45.520 --> 0:07:48.480 the art and science of sun dials, which is pretty 0:07:48.520 --> 0:07:52.679 fascinating stuff, even to a liberal arts major such as myself. 0:07:52.680 --> 0:07:54.960 For one thing, I learned that the two parts of 0:07:54.960 --> 0:07:57.480 your basic sun dial, like the kind you might see 0:07:57.520 --> 0:08:00.400 in a park or a garden, are the dial plate 0:08:00.880 --> 0:08:04.440 and the nomon g n O m o n The 0:08:04.520 --> 0:08:07.600 gnomon is the thing that casts a shadow onto the 0:08:07.640 --> 0:08:10.160 dial plate. And you've probably seen sun dials that have 0:08:10.160 --> 0:08:13.920 a common nomon that has set an angle respective to 0:08:14.080 --> 0:08:16.440 the dial plate, so it comes up almost like a 0:08:16.520 --> 0:08:20.440 triangle sticking up out of this circular dial. I learned 0:08:20.440 --> 0:08:23.920 from sundals dot org that that angle should equal the 0:08:24.000 --> 0:08:28.120 location's latitude. The markings on the dial plate also depend 0:08:28.240 --> 0:08:31.520 upon the latitude of the location. Only by pairing these 0:08:31.560 --> 0:08:33.599 two will you get a reliable way to mark the 0:08:33.640 --> 0:08:36.640 passage of time throughout the year at that location, and 0:08:36.720 --> 0:08:40.800 of course only on sunny days. Sun dials would continue 0:08:40.840 --> 0:08:44.760 to be an important method of timekeeping for thousands of years. 0:08:44.760 --> 0:08:48.120 It was only with the development and refinement of mechanical 0:08:48.200 --> 0:08:50.840 clocks that sun dials even fell out of use in 0:08:50.920 --> 0:08:54.120 naval ships in the seventeen hundreds. But sun dials were 0:08:54.160 --> 0:08:57.040 just one method of keeping time in those early days. 0:08:57.360 --> 0:09:00.800 Another method was to use a water clock. Now, a 0:09:00.840 --> 0:09:03.720 basic water clock is sort of like an hour glass, 0:09:03.880 --> 0:09:06.280 which of course is another form of ancient timekeeping, but 0:09:06.360 --> 0:09:10.120 we'll set that aside. So you have two containers, typically 0:09:10.200 --> 0:09:13.360 in a very simple water clock, connected by a tube 0:09:13.480 --> 0:09:16.400 or a channel of some sort. One container is set 0:09:16.520 --> 0:09:18.920 higher than the other, and it has water in it, 0:09:19.040 --> 0:09:23.280 and gravity pulls that water, so it flows down into 0:09:23.520 --> 0:09:27.000 the lower container through the tube or the channel in 0:09:27.040 --> 0:09:30.199 a more or less controlled way. The lower container has 0:09:30.240 --> 0:09:33.080 markings on the inside of it indicating how much time 0:09:33.080 --> 0:09:35.360 has passed based upon the amount of water in the 0:09:35.400 --> 0:09:38.960 second container. Occasionally you have to dump out the water 0:09:39.080 --> 0:09:41.480 in the lower container and refill the water in the 0:09:41.559 --> 0:09:45.319 upper container. Otherwise the clock just runs out of water. 0:09:45.559 --> 0:09:47.120 You can't tell the time anymore. It's kind of like 0:09:47.160 --> 0:09:50.280 if a a watch that has a spring in it, 0:09:50.440 --> 0:09:53.280 once it unwinds all the way, it won't keep time anymore. 0:09:53.320 --> 0:09:56.319 Same sort of thing here. Now. The method had one 0:09:56.400 --> 0:09:59.800 major advantage over sun dials, because it would work what 0:10:00.000 --> 0:10:02.680 there the sun was out or not. But it wasn't 0:10:02.720 --> 0:10:07.400 necessarily always consistent. Even a well designed water clock couldn't 0:10:07.440 --> 0:10:10.920 regulate the flow of water precisely enough to keep excellent time. 0:10:11.240 --> 0:10:14.400 But it worked well enough for most folks. It wasn't 0:10:14.480 --> 0:10:17.240 like you had a whole bunch of people saying, uh, 0:10:17.280 --> 0:10:19.680 you know, over here in the fiefdom, I've gotta go 0:10:19.760 --> 0:10:24.280 meet my lord for talking about how much corn. I've 0:10:25.040 --> 0:10:28.280 harvested um, and I've got a three fifteen meeting, so 0:10:28.360 --> 0:10:30.640 i really need this water clock to be precise. Now, 0:10:30.679 --> 0:10:33.680 that just didn't happen in those days. Now, water clocks 0:10:33.800 --> 0:10:36.800 date as far back as fifteen hundred b c. E. 0:10:37.120 --> 0:10:41.200 The Greeks would call their water clocks clipsid draws. Now 0:10:41.440 --> 0:10:44.959 that actually means water thieves, as the word comes from 0:10:45.080 --> 0:10:48.280 clip time, meaning to steal. You might have heard the 0:10:48.400 --> 0:10:52.480 term kleptomaniac that's someone who has a compulsion to steal things, 0:10:52.559 --> 0:10:56.680 and high door, which means water. They started using water 0:10:56.720 --> 0:11:00.560 clocks around three b C. And then since than everyone 0:11:00.640 --> 0:11:04.160 uses clepsydras to be the term for water clocks. And 0:11:04.200 --> 0:11:07.839 there are several variations. I described the simple one just 0:11:07.880 --> 0:11:10.560 a second ago, but others might involve one vessel dipping 0:11:10.559 --> 0:11:13.640 water out of a small hole into a second vessel 0:11:13.720 --> 0:11:17.120 which has markings on this inside identicate the passing of time. 0:11:17.200 --> 0:11:19.200 Or you could have a single vessel with markings on 0:11:19.200 --> 0:11:22.080 the inside that are revealed as the water level decreases 0:11:22.400 --> 0:11:24.360 when water drips out of it. So, in other words, 0:11:24.400 --> 0:11:28.200 you create a small hole in a vessel, you fill 0:11:28.280 --> 0:11:31.520 the vessel with water, and it's sort of a reverse 0:11:31.559 --> 0:11:35.120 of what I was talking about. Before the more water 0:11:35.760 --> 0:11:39.959 leaks out of the container, you see more markers telling 0:11:40.000 --> 0:11:43.920 you what hour it is. In North Africa, people would 0:11:43.960 --> 0:11:46.960 mark time by placing a metal bowl with a hole 0:11:47.120 --> 0:11:50.920 in it inside a larger container of water, and they 0:11:50.920 --> 0:11:53.880 marked the passing of time by the sinking of that 0:11:53.920 --> 0:11:56.760 metal bowl. It would sink within a certain amount of time, 0:11:56.760 --> 0:11:58.600 and that method was used in some parts of Africa 0:11:58.640 --> 0:12:02.120 as late as the twentieth cent well. Many water clocks 0:12:02.120 --> 0:12:07.000 were simple, some were devilishly complicated. For example, the water 0:12:07.120 --> 0:12:10.960 clock tower built by Sue Song in the eleventh century CE. 0:12:11.200 --> 0:12:14.880 Historians descriptions of Sue Song put him in that rare 0:12:15.080 --> 0:12:18.480 category of humans that includes other amazing polly maths like 0:12:18.600 --> 0:12:22.400 Leonardo da Vinci. He was a cartographer, he was a mathematician, 0:12:22.520 --> 0:12:25.160 he was a physician, and he was a horologist. Now 0:12:25.200 --> 0:12:28.400 that last one essentially means he was a clockmaker. Sue 0:12:28.440 --> 0:12:31.160 Song and a team of mathematicians came up with the 0:12:31.240 --> 0:12:34.960 idea for the mechanics that would make the clock tower possible. 0:12:35.360 --> 0:12:39.840 The tower was pretty tall, uh. It had inside of 0:12:39.880 --> 0:12:43.040 it several levels, like it was three stories tall. The 0:12:43.120 --> 0:12:46.760 top level had a model of the universe on it. 0:12:46.880 --> 0:12:49.960 The middle one had kind of a a globe to 0:12:50.000 --> 0:12:53.360 show you what constellations would be where at what point 0:12:53.480 --> 0:12:56.600 point of the year, so sort of an astronomical slash 0:12:56.640 --> 0:13:01.160 astrological clock. And then the base level had the actual 0:13:01.320 --> 0:13:06.040 time piece itself. Uh. There was a vertically aligned water 0:13:06.120 --> 0:13:10.000 wheel which was eleven feet in diameter, So think of 0:13:10.000 --> 0:13:13.720 a wheel on its side. It's it's you know, vertically aligned, 0:13:13.720 --> 0:13:17.760 it's got scoops on the outer edge of it. Water 0:13:17.800 --> 0:13:20.960 would flow from a giant container through a narrow slit 0:13:21.000 --> 0:13:24.240 at the container's base, and that water would then fill 0:13:24.480 --> 0:13:27.920 whichever of the thirty six scoops mounted on the outside 0:13:27.920 --> 0:13:32.040 of the wheel was level with that that drainage spot. 0:13:32.960 --> 0:13:35.600 So water flows out of the container and it starts 0:13:35.640 --> 0:13:39.040 to fill up that that scoop. Once the scoop got 0:13:39.080 --> 0:13:42.520 heavy enough, the wheel would rotate, which in turn would 0:13:42.520 --> 0:13:45.280 power all the other gears in the tower and help 0:13:45.360 --> 0:13:49.720 keep time. Now, a series of horizontally aligned gears on 0:13:50.040 --> 0:13:53.559 this tower had small figurines mounted to the outer edges. 0:13:53.600 --> 0:13:57.320 So these gears are are all horizontal, not vertical, so 0:13:57.320 --> 0:14:00.960 they're at a nine degree angle relative to the water wheel. 0:14:01.480 --> 0:14:03.640 The figurines were positioned in such a way to be 0:14:03.679 --> 0:14:06.800 easily seen through windows of the tower, So if you 0:14:06.840 --> 0:14:09.280 looked at the tower from the outside, you'd see these 0:14:09.320 --> 0:14:13.040 little figures in various windows along that side, like three 0:14:13.120 --> 0:14:18.520 levels of them, with one window showing certain figures that 0:14:18.640 --> 0:14:21.800 indicate a certain increment of time. The figures all carried 0:14:21.880 --> 0:14:26.080 signs that represent numbers. That means they were effectively digit counters, 0:14:26.880 --> 0:14:29.000 so you look at the figures and you could suss 0:14:29.040 --> 0:14:31.520 out what time it is. But Sue Song had to 0:14:31.560 --> 0:14:33.920 come up with a way to make this a steady, 0:14:34.240 --> 0:14:37.680 regular series of events. If you left this on its own, 0:14:37.720 --> 0:14:40.560 if you just had a big water wheel and you 0:14:40.600 --> 0:14:43.400 were having water flow into these scoops, the water wheel 0:14:43.400 --> 0:14:46.400 would eventually just start turning continuously as long as there 0:14:46.480 --> 0:14:49.200 was water to push it, which means all the figures 0:14:49.200 --> 0:14:51.720 would constantly be in motion, and that could be tricky 0:14:51.760 --> 0:14:55.080 to read the time, especially between minutes. So you know, 0:14:55.200 --> 0:14:56.960 you could have a figure that's half in view and 0:14:57.000 --> 0:14:59.120 half out of you you're not really sure what time 0:14:59.120 --> 0:15:01.280 it is. So Song need a way to keep a 0:15:01.320 --> 0:15:05.680 gear in position for a certain interval a given amount 0:15:05.720 --> 0:15:08.440 of time, such as a minute, and so he and 0:15:08.480 --> 0:15:10.240 his team had to come up with a way of 0:15:10.280 --> 0:15:13.400 stopping gears, but only temporarily, so that the passage of 0:15:13.400 --> 0:15:16.800 time could be more regularly communicated. So he and his 0:15:16.880 --> 0:15:19.280 team created a clever gadget that would end up being 0:15:19.280 --> 0:15:24.480 an important part of clocks for centuries. It's called an escapement. 0:15:25.200 --> 0:15:28.440 So what is an escapement. We'll go into that in 0:15:28.520 --> 0:15:31.600 just a bit, but first let's take a quick break 0:15:31.840 --> 0:15:43.360 to thank our sponsor. Okay, So, an escapement, what isn't 0:15:43.840 --> 0:15:46.760 well in clocks is an element within a device that 0:15:46.920 --> 0:15:50.120 regulates the turning of other gears. You can think of 0:15:50.120 --> 0:15:53.760 it as a lock that unlocks itself at consistent intervals 0:15:53.760 --> 0:15:56.640 to allow gears to turn before locking back in place. 0:15:57.080 --> 0:16:00.240 And if you've ever seen a pendulum clock, that the 0:16:00.360 --> 0:16:03.000 purpose for that pendulum. But we'll get into that a 0:16:03.000 --> 0:16:06.360 little bit later. Sue Song created an escapement to lock 0:16:06.520 --> 0:16:09.040 the gears in place in his water tower until there 0:16:09.080 --> 0:16:10.840 was a need for them to shift to the next 0:16:10.920 --> 0:16:14.400 increment of time. Sue Song's approach was using a balance 0:16:14.480 --> 0:16:18.360 called a steel yard. It's all one word. Steel yards 0:16:18.400 --> 0:16:21.320 are pretty cool applications of one of the simplest machines 0:16:21.480 --> 0:16:24.120 the lever. If you have a lever with a pivot 0:16:24.160 --> 0:16:27.440 point in the exact center of its length, assuming the 0:16:27.480 --> 0:16:30.680 mass is equal on both sides, the lever will balance 0:16:30.720 --> 0:16:34.160 out if you put two equal weights, two equal masses 0:16:34.200 --> 0:16:37.840 really on either end, and it remains balanced. Well. It 0:16:37.920 --> 0:16:40.320 does so because of this very nature of levers. So 0:16:40.440 --> 0:16:42.760 are you with me so far? Now imagine that we 0:16:42.800 --> 0:16:45.960 move that pivot point more toward the right side of 0:16:46.000 --> 0:16:48.560 the lever. That would mean that more of the lever's 0:16:48.640 --> 0:16:51.680 mass is on the left side. The right side is 0:16:51.720 --> 0:16:53.840 shorter than the left side because we've moved the pivot 0:16:53.880 --> 0:16:56.400 point closer to the right end. So if you just 0:16:56.440 --> 0:16:58.360 step back the left side, the lever will be on 0:16:58.400 --> 0:17:00.720 the ground. It's gonna tilt downward it until it's either 0:17:00.800 --> 0:17:02.960 on the ground, or if you haven't suspended in the air, 0:17:03.360 --> 0:17:07.640 it's gonna be dangling vertically with the short end at 0:17:07.640 --> 0:17:10.199 the top, you know, the bit that's closer to the pivot. 0:17:10.720 --> 0:17:13.800 So to balance it out, you would have to put 0:17:13.840 --> 0:17:16.200 more weight on the right side. You would have to 0:17:16.240 --> 0:17:19.479 have more mass to equal out the mass that's on 0:17:19.520 --> 0:17:21.920 the left and balance it all out. This is how 0:17:21.920 --> 0:17:24.720 a steel yard works, and you may have used one 0:17:24.720 --> 0:17:27.399 of these with weight scales. If you've ever stepped on 0:17:27.440 --> 0:17:30.199 a scale that requires you to move a counterweight along 0:17:30.200 --> 0:17:33.080 an arm, you've used a steel yard. The trick is 0:17:33.080 --> 0:17:35.919 to get the counterweight adjust the right spot on the 0:17:36.000 --> 0:17:39.040 lever to make the arm balance out. If the counterweight 0:17:39.119 --> 0:17:41.320 is too close to the pivot point, the arm will 0:17:41.520 --> 0:17:43.240 be up in the air. It will say no, you 0:17:43.359 --> 0:17:46.720 weigh more than that. You need to push that counterweight 0:17:46.760 --> 0:17:49.440 further towards the end of the arm. If it's too 0:17:49.480 --> 0:17:51.600 close to the end of the arm, it's gonna go 0:17:51.720 --> 0:17:53.800 down as far as it can go. Like in a scale, 0:17:53.800 --> 0:17:56.840 there's typically a little stop point and it'll just sink 0:17:56.880 --> 0:17:58.760 to the bottom. So getting the counterweight in the right 0:17:58.800 --> 0:18:01.000 position makes the arm ba elens in the middle, and 0:18:01.040 --> 0:18:03.600 the position of the counterweight will tell you how much 0:18:03.760 --> 0:18:07.040 you way. There will be some marking. They're saying, congratulations, 0:18:07.080 --> 0:18:10.240 away a hundred fifty pounds. Sue Song's tower used a 0:18:10.280 --> 0:18:12.359 steel lyard kind of like this. Now, I want you 0:18:12.400 --> 0:18:15.680 to imagine a vertical wheel made of spoons. All right, 0:18:16.040 --> 0:18:18.920 All the spoons are facing in the same direction, and 0:18:19.040 --> 0:18:21.840 all the scoop parts of the spoon are faced in 0:18:21.880 --> 0:18:25.560 such a way where they're you know, they're just if 0:18:25.600 --> 0:18:26.960 you were to stack them in a stack, they would 0:18:27.000 --> 0:18:29.720 all be stacked together perfectly, but you've fanned them out 0:18:29.760 --> 0:18:34.160 into this circle. It's a vertical circle. Uh. And imagine 0:18:34.160 --> 0:18:36.280 we're looking at this wheel from the side, so we're 0:18:36.280 --> 0:18:39.640 looking at the profile of the wheel, not dead on position. 0:18:39.680 --> 0:18:42.320 Halfway up the wheel to one side is a chamber 0:18:42.359 --> 0:18:45.959 of water that can flow out into the empty spoon 0:18:46.520 --> 0:18:49.520 that is next to it. The one that's closest to it. 0:18:49.560 --> 0:18:52.639 Will say that this this spoon is parallel to the ground, 0:18:53.119 --> 0:18:56.000 So this is the one that is at the three 0:18:56.040 --> 0:18:59.200 o'clock position for those of you who still know how 0:18:59.280 --> 0:19:02.240 to read analog clocks. On the other side of the wheel, 0:19:02.280 --> 0:19:05.440 over at the nine o'clock position is a weighted arm, 0:19:05.800 --> 0:19:09.040 and it rests on the back of the spoon opposite 0:19:09.080 --> 0:19:12.360 to the one getting filled. And the weighted arm, it 0:19:12.400 --> 0:19:16.919 can't reverse the direction of the wheel. It just holds 0:19:16.960 --> 0:19:19.480 it in place. The weight of that arm just keeps 0:19:19.520 --> 0:19:22.439 it locked there. But the weighted arm is on a pivot, 0:19:22.800 --> 0:19:26.560 so it can be lifted if enough force is applied. Now, 0:19:26.600 --> 0:19:29.920 as soon as the spoon fills with water, it gets heavier. 0:19:30.680 --> 0:19:32.800 When it gets heavy enough to counteract the weighted arm 0:19:32.800 --> 0:19:35.879 on the other side, the weighted arm pivots up. This 0:19:35.960 --> 0:19:40.000 allows the wheel of spoons to turn in one increment. 0:19:40.520 --> 0:19:43.320 It turns so that the next spoon is moved into place. 0:19:43.520 --> 0:19:46.359 The weighted arms slips off the back of the spoon 0:19:46.480 --> 0:19:48.720 it had been on and comes down to prevent the 0:19:48.760 --> 0:19:51.960 next one from moving upward, locks it into place. That 0:19:52.040 --> 0:19:55.720 whole process repeats, and that's basically how siouxs Song's escapement worked. 0:19:55.760 --> 0:19:59.000 As long as there was water steadily flowing into the tower, 0:19:59.440 --> 0:20:03.080 the clock would keep accurate time. Now I wish I 0:20:03.119 --> 0:20:05.479 could tell you that you could go and visit this 0:20:05.560 --> 0:20:09.879 amazing clock tower in Kaifeng, but sadly you can't. The 0:20:09.960 --> 0:20:13.240 tower was finished in ten ninety four. Sue Song himself 0:20:13.280 --> 0:20:16.360 died in eleven oh one, which means he didn't live 0:20:16.400 --> 0:20:20.040 to see his amazing creation disassembled by soldiers. After the 0:20:20.040 --> 0:20:24.680 Manchurian Army invaded Kaifeng, they took the clocks pieces back 0:20:24.720 --> 0:20:28.880 to their capital, which is today's modern Beijing. They attempted 0:20:28.920 --> 0:20:31.879 to reassemble it, but the complex nature of the clock 0:20:32.000 --> 0:20:35.920 confounded them and it never worked again. There is, however, 0:20:36.440 --> 0:20:40.480 a working replica of the tower in the Gishido Suwako 0:20:40.800 --> 0:20:44.240 Watch and Clock Museum in the Nagano Prefecture in Japan. 0:20:44.960 --> 0:20:47.520 I've seen photos of it and it is gorgeous. I 0:20:47.560 --> 0:20:50.600 hope one day to see it in person. This particular 0:20:50.800 --> 0:20:54.639 replica was built based upon the best understanding of sus 0:20:54.640 --> 0:20:58.760 Song's designs. Many of those designs survived all of that 0:20:59.520 --> 0:21:04.200 invade Jian issue, but there were little details left out, 0:21:04.280 --> 0:21:08.159 so people the modern replica makers had to kind of 0:21:08.160 --> 0:21:10.680 fudge things here and there to make it work properly. 0:21:10.760 --> 0:21:14.560 So it may not be one to one a replica, 0:21:14.720 --> 0:21:17.439 but it's really close and it looks amazing in the 0:21:17.440 --> 0:21:20.320 pictures I've seen. This escapement would prove to be a 0:21:20.440 --> 0:21:23.160 very important component of clocks and watches as the art 0:21:23.160 --> 0:21:27.080 and science of clockmaking evolved. As for purely mechanical clocks 0:21:27.119 --> 0:21:30.800 that did not depend upon water, their origin is somewhat 0:21:30.840 --> 0:21:35.000 lost to time, which is not an irony but seems fitting. 0:21:35.320 --> 0:21:40.159 Monasteries were building clock towers called turret clocks as early 0:21:40.359 --> 0:21:43.600 as the fourteenth century, at least maybe earlier. These were 0:21:43.720 --> 0:21:47.080 massive towers that passed marked the passing of time by 0:21:47.119 --> 0:21:50.480 tolling a bell, so there were no dials or hands 0:21:50.560 --> 0:21:53.080 or other indications of what time it is. The machinery 0:21:53.200 --> 0:21:57.040 was large and relied upon weights and gears. Now, the 0:21:57.040 --> 0:21:59.919 weight is a very important part of these early make 0:22:00.040 --> 0:22:03.399