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Stuff You Should Know

Keeping Time

20 Jan 2026

Transcription

Chapter 1: What is the history of timekeeping discussed in this episode?

0.031 - 6.172 Chuck Bryant

This is an iHeart Podcast. Guaranteed human. What if mind control is real?

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6.372 - 9.282 Josh Clark

If you could control the behavior of anybody around you, what kind of life would you have?

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9.346 - 12.69 Chuck Bryant

Can you hypnotically persuade someone to buy a car?

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12.87 - 16.954 Josh Clark

When you look at your car, you're going to become overwhelmed with such good feelings.

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17.054 - 19.557 Chuck Bryant

Can you hypnotize someone into sleeping with you?

19.577 - 22.901 Josh Clark

I gave her some suggestions to be sexually aroused.

23.121 - 43.812 Chuck Bryant

Can you get someone to join your cult? NLP was used on me to access my subconscious. Mind Games, a new podcast exploring NLP, aka neurolinguistic programming. Is it a self-help miracle, a shady hypnosis scam, or both? Listen to Mind Games on the iHeartRadio app, Apple Podcasts, or wherever you get your podcasts.

45.295 - 56.557 Spencer Graves

A man with Down syndrome tries the impossible, the grand slam in turkey hunting. Four 53 hits, we're legal shooting light. And he gives us this one last test.

56.577 - 56.717

Ow! Ow!

Chapter 2: How did ancient civilizations use shadows to keep time?

61.953 - 75.786 Spencer Graves

I said to the cameraman, do you have him? He said, shoot him. I said, Justin, shoot. You can download this episode and others from Lines and Tines with Spencer Graves on the iHeartRadio app, Apple Podcasts, or wherever you get your podcasts.

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76.357 - 84.405 Chelsea Handler

This season on Dear Chelsea with me, Chelsea Handler, we've got some incredible guests like Kumail Nanjiani. Let's start with your cat. How is she?

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85.085 - 87.127 Unknown

She is not with us.

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87.147 - 102.742 Chuck Bryant

Okay, great, great, great way to start. Maybe you will cry. Ross Matthews. You know what kids always say to me? Are you a boy or a girl? Oh my God. All the time. That's so funny. I know. So I try to butch it up for kids so they're not confused. Yeah, but you're butching it up. It's basically like Doris Day.

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Chapter 3: What innovations in timekeeping emerged in ancient China?

102.842 - 103.083 Spencer Graves

Right?

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103.143 - 104.524 Chuck Bryant

No, I turn into Bea Arthur.

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104.504 - 117.079 Unknown

Listen to these episodes of Dear Chelsea on the iHeart Radio app, Apple Podcasts, or wherever you get your podcasts. Welcome to Stuff You Should Know, a production of iHeart Radio.

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122.915 - 142.928 Josh Clark

Hey, and welcome to the podcast. I'm Josh, and there's Chuck, and Jerry's here too, and we're just hanging out. And we decided, hey, let's do some talking about timekeeping. So that's what we're doing today. Yeah, Livia helped us put this one together. I think the charge was, hey, how about something on the history of timekeeping?

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143.669 - 143.809

Mm-hmm.

143.789 - 166.126 Josh Clark

Without getting too in the weeds about how all of these things work, because that's a whole other thing, like if you want to really break down clocks and watches. But I think she did it just right. The Goldilocks zone, as they say. Oh, nice. Nice astronomical cosmological reference there. Well, I think that is a reference for a lot of things, right? Nope, just that. Okay.

168.329 - 169.291 Josh Clark

Where'd you get this idea?

Chapter 4: How did sundials evolve and what were their limitations?

169.311 - 188.93 Josh Clark

Because this was when you came up with. You know, man, I don't know. I think I was maybe thinking about a watch on my wrist. Okay. And then wondering, or no, maybe I saw someone had a, what do you call those things? A clock? An hourglass. Oh, okay. And I was wondering about just hourglasses.

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188.99 - 207.397 Josh Clark

And then I started thinking about, like, just, you know, the concept of time and when people started keeping time. And I was kind of had a hunch that I was right that, you know, the need to keep time didn't come around so much later. So, like, as we'll see, early timekeeping was more like seasonal or astrological.

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207.417 - 231.031 Josh Clark

And it didn't get to be a thing like, hey, I have an appointment at a certain minute until much, much later. Yeah, but earlier than you'd think, or earlier than I thought, at least. Yeah, agreed. So speaking of timekeeping, you really can kind of say the whole thing just started out with the sun. And one of the neat things about life on Earth is that you can cast a shadow.

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231.532 - 243.047 Josh Clark

Most things cast a shadow, with the exception of maybe like amoebae or something like that. But if you put like a stick in the ground... It's going to cast shadows that move throughout the day.

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Chapter 5: What role did water clocks play in early timekeeping?

243.087 - 268.995 Josh Clark

And if you really pay attention to this kind of stuff, you can actually use it to track time throughout the day. And that is almost certainly the earliest way that humans track time. And the stick they put in the ground is widely known as a gnomon, G-N-O-M-O-N. I think it means rod. In Greek, maybe? I also saw that it was slang in Greek for penis. Oh, really? Yeah.

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269.015 - 298.155 Josh Clark

And that just... Like, hey, check out the gnomon on that guy? Yeah, almost exactly that. If not that, but just said in ancient Greek. Oh, okay, gotcha. In Hellenic. Yeah. But just tracking the shadow that the gnomon cast, hopefully just to stick in the ground. Yeah. That was early timekeeping. Oh, man. I have a thousand jokes I'm just going to walk right past. At this point.

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Chapter 6: How did the pendulum clock change timekeeping accuracy?

298.175 - 308.865 Josh Clark

Good for you, buddy. You're a pro. I know. I'm growing up here at 54. So that was, yeah, that's what people use for the longest time. And that eventually, as we'll see, would carry over to things like sundials.

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308.965 - 333.469 Josh Clark

But it's no surprise that China was way ahead of the game as far as timekeeping goes, because the oldest surviving sort of actual thing that we have comes from northern China from an archaeological site that they found dated back to 2300 B.C. And again, as you'll see, this is a recurring theme like I mentioned. It wasn't necessarily like, hey, we got to keep the time from day to day.

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333.509 - 355.475 Josh Clark

It's more like let's calculate the seasons or, you know, the things happening up in the sky. Right. Because it was snowing in the middle of China and somebody said, what season is it? And somebody else said, let's find out with this gnomon. And the other person was like, no, no, pull that out. And they're like, no, I mean the stick. Right. They said you can get canceled for that.

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356.161 - 363.908 Josh Clark

So if you're like, well, that sounds a lot like a sundial, you're right. The thing that sticks up for the sundial is a gnomon.

Chapter 7: What advancements led to the development of mechanical clocks?

364.288 - 386.168 Josh Clark

There's another version of it that's even earlier than the sundial, it seems, from ancient Egypt called the shadow clock. Yeah. It's actually really hard to describe. It's much easier to just go look up. But imagine a capital T laying flat on its back on the ground, and it's raised its head and neck up to look at its feet. That's essentially... That's kind of perfect, actually. Thank you.

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386.148 - 407.32 Josh Clark

I really thought about that one for a while, I have to admit. But the shadow that that crossbar, the top of the T, casts on the rest of the T over the day is demarcated. So you can track six hours a day as the sun is rising in the east, and then you turn it around at noon, and then you track the next six hours as the sun is setting in the west.

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407.941 - 413.169 Josh Clark

Pretty spectacular considering that's close to 3,000 years old.

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413.924 - 430.649 Josh Clark

Yeah, for sure. Uh, for that descriptor, did it help you that you were laying flat on your back, uh, with your neck raised up looking at your feet? Yeah. Sadly, I have to admit that I, I had to go lay down and figure it out myself. Okay. That's good. But yes, I was. Yeah.

Chapter 8: How did watches evolve from mechanical clocks to modern timepieces?

431.17 - 452.681 Josh Clark

Nice work. Uh, finally to the sundial, the first round sundial that we kind of know as a sundial, um, seems like it was created by a Greek philosopher named, uh, Anaximander, very cool name, not Alexander, but Anaximander, of Miletus. This was 6th century B.C., but again, probably still tracking seasons at this point.

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454.002 - 470.669 Josh Clark

The first sundials out of Greece that actually marked hours, like when people started keeping track of the hourly time, and as we'll see, it just gets more specific until eventually, much later, we'll get to minutes, but the hourly timekeeping started in 350 B.C.E. Yeah.

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470.87 - 492.945 Josh Clark

And then very quickly after that, around 280 BCE, they came up with the hemicycle, which is imagine like a cube block of stone with a basin, a bowl carved out of the middle. And then they managed to cut it perfectly in half. So that you just have half of a bowl. That's a hemicycle. Because it turns out all you need is half a bowl to make a sundial like that.

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493.466 - 517.017 Josh Clark

And I really do wonder if somebody built them like that. Like they'd make one, split it in two, and then all of a sudden they had two hemicycles to sell. I bet. You're getting really good at describing things at this juncture in your career. It took me long enough. We're almost to year 18. It's dismaying to try to explain something and just make it even more confusing than it was initially.

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517.378 - 523.512 Josh Clark

I finally got dismayed enough that I decided to do something about it. And what I did was lay down naked and think it over.

523.532 - 523.632

Yeah.

524.54 - 557.147 Josh Clark

By the way, quick correction, because a listener just wrote in about this. We're about to be at year 19 and completed year 18, technically. No, really? Yeah, because year 19 and year 20 are the two next years. Does that make sense? It does, but I feel like it's wrong because we started in April 2008 and going to April of 2026, that's 18 years. Completed. I see. Yeah, I should have known.

557.287 - 571.806 Josh Clark

Right when somebody busted out math, I should have just been like, yeah, that's right. The cool thing about the Hemi cycle, besides the fact that people back then probably said, is that thing a Hemi when they walked by? You know, I couldn't resist that one.

571.826 - 593.157 Josh Clark

But they knew at that point, it's a pretty smart thing, that the sun's position changes over the course of the year, over the course of those seasons. Obviously, shorter winter hours, which we're going to get to. But they they accounted for that. They had sundials that would show the time using multiple arcs carved into the hemisphere to account for that sun changing over the course of the year.

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