[RADIOLAB INTRO]

JAD ABUMRAD: Hey, I'm Jad Abumrad.

ROBERT KRULWICH: I'm Robert Krulwich.

JAD: This is Radiolab.

ROBERT: The podcast. It is almost New Year's, actually. We're recording this a few hours before New Year's Eve.

JAD: Well, it's not a few. I mean, today's Monday. Tomorrow night, so ...

ROBERT: 50 hours. We have 50 hours left of 20 ...

JAD: No, less than that. 20 ...

ROBERT: Well, whatever. I just—because it's that time of year, I want to tell you a story about a discovery I made. Not me, I just learned about it from other people, but it has made me completely reconsider what a year means and specifically how big a year really is.

JAD: How big a year? It—what?

ROBERT: How big a year really is.

JAD: I don't know—how is a year—how long a year is?

ROBERT: If you're confused now, I think I can confuse you even more. I'm gonna begin this investigation by introducing you to a little creature in the sea called a coral.

NEIL SHUBIN: Coral's a shelly animal. A little creature. There's ...

ROBERT: That's Neil Shubin.

NEIL SHUBIN: I'm a paleontologist, an evolutionary biologist at the University of Chicago. Just like a clam has an animal—clamshell has an animal inside it, so do corals.

ROBERT: A little fleshy wormy thing?

NEIL SHUBIN: Exactly. And it wears its skeleton on the outside. And because they sit in the same place for their whole life, they're really sensitive to local environmental changes.

ROBERT: Meaning what?

NEIL SHUBIN: Think about it this way. Let's just sort of think about what happens to a creature as it lives its life in the water, which is what these things do. Yeah, we live in a world of cycles of cycles on cycles, temperature rises and falls. Light rises and falls. The tides rise and fall several times in the course of a day. So you think about what that means for creatures living in water.

ROBERT: What it means for corals, says Neil, is that they're growing.

NEIL SHUBIN: They are slapping on new skeleton if you will, new shell.

ROBERT: In time with these cycles of rise and fall, of light and dark, hot and cold, and ...

ANDY MILLS: Hello, hello.

EMILY GRASLIE: Hi.

ROBERT: ... you can actually see these changes written onto their shells. Maybe into their shells.

ANDY: Emily!

EMILY GRASLIE: Andy!

ROBERT: That's why Andy Mills and I called up our pal Emily Graslie, whose job is—what is it?

EMILY GRASLIE: I am the chief curiosity correspondent of the Field Museum in Chicago.

ROBERT: That's your actual title?

EMILY GRASLIE: The chief curiosity correspondent, yes. It is.

ROBERT: You brought some corals, did you?

EMILY GRASLIE: We have many corals. We have corals all over the studio desk right now. [laughs]

ROBERT: All right.

EMILY GRASLIE: All right. Let's cut it.

[saw cutting]

ROBERT: Because when you cut into these shells ...

EMILY GRASLIE: Oh, it's warm.

ANDY: Here's a little bit of water. We can spritz it on there to cool it off.

ROBERT: ... right off you can see a pattern. You see these gray stripes.

EMILY GRASLIE: I mean, they're all different variations of gray but some are really dark gray and some are tan.

ROBERT: They're like bands running either through or across the shell.

EMILY GRASLIE: They radiate out like the bands of a tree.

ROBERT: Between the bands, there are spaces. You got a stripe, then a space, stripe then a space, stripe then a space. But ...

EMILY GRASLIE: When you hold it up close to your eye ...

ROBERT: ... if you look closer in between the stripes, you can see sort of ...

EMILY GRASLIE: Wow! You can see the lines. Wow!

ROBERT: ... you can see that the spaces are filled with faint little lines.

NEIL SHUBIN: And that's where the piece of this story is just so fascinating.

ROBERT: Because in 1962, a paleontologist ...

NEIL SHUBIN: Professor John Wells.

ROBERT: ... was looking at some corals just like these.

NEIL SHUBIN: He was just sitting there saying, "Okay, well what can we figure out from coral shells?" So what he did is he did something really simple. He says, "Well, golly gee ..."

ROBERT: "Why don't I count the number of little lines between these bands just—you know, just to see?" So he starts counting, gets to, you know 100, 200 lines, 300, about 310, 320. And every time he counted ...

NEIL SHUBIN: He got a number ...

ROBERT: ... around ...

NEIL SHUBIN: ... around 360, 365.

JAD: Wait a second.

ROBERT: [laughs] Familiar number, no?

NEIL SHUBIN: Doesn't take a lot of inference that hey, maybe those individual rings represent a daily pattern.

ROBERT: Meaning each of these little lines actually equaled a day.

JAD: And why—they're not just making a gray mark after 365?

ROBERT: No.

JAD: What are the gray lines?

ROBERT: Well, the thicker lines are the times of the year when the coral grows a lot. But if you've got a summer coral, then it grows a lot in one summer then it goes quiet, then it grows a lot the next summer. So that's again, that marks a year. Those big bands are like [singing] Happy New Year! [singing] Happy New Year! [singing] Happy New Year!

NEIL SHUBIN: There are actually calendars and clocks inside each of these things. You just have to know how to read them.

ROBERT: So this guy, Professor Wells ...

NEIL SHUBIN: What he did was then—this is the really dull bit I thought, which is he then said, "Well okay, that's a living coral. Let's look at some fossils."

ROBERT: He was, after all, a paleontologist.

NEIL SHUBIN: So he was at Cornell University, and Cornell University is surrounded by rocks around, you know, 370 or so million years old. And he collected some nice corals, and there are a lot of nice coral fossils known from there.

ROBERT: And he opened up these ancient skeletons ...

NEIL SHUBIN: And he did the count.

ROBERT: 100 days, 200 days ...

NEIL SHUBIN: He was expecting ...

ROBERT: ... 300 days ...

NEIL SHUBIN: 360 to 365.

ROBERT: 368.

NEIL SHUBIN: Then lo and behold, he found ...

ROBERT: 400?

NEIL SHUBIN: ... between 400 and 410.

JAD: Really?

NEIL SHUBIN: Yeah! And he looked at lots of specimens.

ROBERT: That number, the 400 number kept showing up.

JAD: What does that mean?

ROBERT: Well, that means that it's now reasonable to think that back in the day, you know, 380 million years ago, there were more days in a year. And he published a paper saying more or less that, and right away, clam scientists said, "Well, if that's true for corals then it's gotta be true for my animal, the clam." And the oyster people said, "Well, it's gotta be true for oysters." And mussel folks said, "It's gotta be true for mussels."

NEIL SHUBIN: This paper set off a bit of a cottage industry of folks applying this technique to other species. In looking at these other species, they found the general trend is absolutely correct.

ROBERT: That when you compare modern animals to ancient animals, you will find they record—the old ones—more days in a year.

NEIL SHUBIN: So you go back to a time period called the Ordovician, which is about 450 million years ago, a typical year had about 415-410 days in it.

ROBERT: Really?

NEIL SHUBIN: If you go to the time period I work on, in the Devonian, about 360 million years, probably about 400 or so. What you see is the number of days in a year has declined from over 400 to what we have now, which is 365.

ROBERT: That's really—we have lost 40 days since the ...

NEIL SHUBIN: Yeah, since creatures first started to walk on land.

ROBERT: So now comes the obvious question: why? Why would there be more days then than there are now?

JAD: Okay, wait a second. Wait a second. Wait a second. So a year is a trip around the sun?

ROBERT: That's a trip—that's right.

JAD: And days, days are when we spin around—we're going around the sun. Okay, so maybe if you want to squeeze more days into a year, maybe it just means the trip around the sun took longer back then?

ROBERT: Well, if you ask astronomers about that—I asked Chis Impey at the University of Arizona, and he says ...

CHRIS IMPEY: There's no sense that the length of time it takes the Earth to orbit the sun is changing.

ROBERT: Because the Earth's orbit around the sun is basic physics, and it hasn't really changed significantly. He's pretty sure of that.

JAD: So then what is it?

ROBERT: Well, Chris says the answer takes us back about four and a half billion years to a time when the Earth was very young.

CHRIS IMPEY: So there was this crazy period of time lasting about 50 million years.

ROBERT: Which they called The Great Bombardment Period.

CHRIS IMPEY: There was still a lot of debris left over from the formation of the solar system, so the meteor impact rate was thousands of times higher. The Earth was still like a tacky magma. And so there was hail, brimstone, endless rain. I mean, a kind of crazy time, really. And a bit of that mayhem, of course, we think gave birth to the Moon.

ROBERT: There was a huge collision, and a rock about the size of Mars banged into us, flung a hunk of Earth shrapnel into orbit, and those pieces coalesced and became our Moon, which is now sort of parked right next to us.

CHRIS IMPEY: And so it sort of tugs us around in a kind of hefty way.

JAD: Wait, I thought we tugged the Moon?

CHRIS IMPEY: Oh, it works both ways, you know? We tug the Moon and the Moon tugs us, and the force is actually equal.

JAD: So it's kind of like a dance.

CHRIS IMPEY: It's a dance.

ROBERT: [singing] I tug the Moon and the Moon tugs me.

CHRIS IMPEY: [laughs] Exactly. It's a celestial waltz.

[ARCHIVE CLIP, Dickie Valentine: [singing] I see the Moon, the Moon sees me, out through the leaves of the old oak tree.]

ROBERT: And it's that dance, that waltz, that explains why the Earth used to have 450 days in a year, then 400 days in a year and now only 365.

JAD: Well, I don't see how this explains anything.

ROBERT: Well first of all, let's just remember what a day is. A day is a full spin of the planet, from the sun coming up in the morning then going down and coming up the next morning. So one spin, a total spin equals a day.

JAD: Yes.

ROBERT: We all know that. Now today we make 365 of these spins as we orbit the sun. That would be a year.

JAD: Right.

ROBERT: But back when the Earth was born, when it was all by itself dancing alone, in those days it spun faster. It was making more of these spins as it went around the sun, so a year had more days in it. But then along comes the Moon to join the dance, and now here's the key according to Chris.

CHRIS IMPEY: Earth is spinning faster than the Moon is orbiting it.

ROBERT: A dance partner takes a month to come around us. We take—feoom!—24 hours. Feoom! And you know how it is when you're dancing with a partner who's slower than you are, then you have to tug them along, which is what has happened here gravitationally. We are constantly tugging the Moon along, it is constantly dragging us down. There's a transfer of energy here that over billions of years has caused the Earth's spin to slow down just a little bit, a teeny, teeny bit. And as the spin has slowed, well, our days have gotten longer.

CHRIS IMPEY: And if you do the math, you calculate that the day is getting longer by 1.7 milliseconds each century.

JAD: 1.7 milliseconds each century!

ROBERT: What this means on a daily basis is that today was 54 billionths of a second longer than yesterday. And the day before that was 54 billionths of a second longer than the day before. And the day before that was 54 billionths of a second longer than the day before that, which was 54 ...

NEIL SHUBIN: And if you extrapolate that out over the, you know, millions of years people like me think about ...

ROBERT: That's Neil Shubin again, the paleontologist.

NEIL SHUBIN: ... that becomes quite significant.

ANDY: So you're telling me—you're that today is the shortest day of the rest of my life?

NEIL SHUBIN: Yes.

ROBERT: Andy worries about these things.

NEIL SHUBIN: Well, you're not gonna live longer because of this. I'm sorry to say.

ROBERT: No, so this Moon dance does not affect the ticking of time, it just affects what we choose to call a day. And by the way, one of the consequences of this dance is is we lose a little energy to our Moon every year, and the Moon picks up a little energy from us, because these things are always equal. Think about, like, when you throw a ball, the more energy you use, the further the ball is away from you.

JAD: Mm-hmm.

ROBERT: Well, as we add a little more energy to the Moon, the Moon very slyly moves a little further away from us. Every year, it's about ...

CHRIS IMPEY: A couple of inches.

ROBERT: According to Chris.

CHRIS IMPEY: The length of a worm.

ROBERT: Really? So the Moon is getting a worm's distance further away from us every year.

CHRIS IMPEY: Yeah.

ROBERT: And he says if you go back about four billion years ...

CHRIS IMPEY: The Moon was originally about 10 times closer than it is now.

ROBERT: Ten times closer!

CHRIS IMPEY: Imagine the Moon looking 10 times bigger than it does now. That would have been crazy.

ROBERT: Whoa!

CHRIS IMPEY: Also, the days would have been six hours long.

JAD: Six hours long?

NEIL SHUBIN: To me, what this says is that everything that we take for granted as normal in our world—ice at the poles, seas in certain places, continents configured the way they are, the number of days in a year, all that is subject to change. And all that has changed. All that has dramatically changed over the course of the history of our planet, and that includes how we measure time itself. So, you know, when I'm sitting in a hole in the middle of the Arctic digging out a fish fossil, every now and then I pinch myself and say, "Here I am in the Arctic, digging out a fish fossil that lived in an ancient, subtropical environment. You know, the juxtaposition between present and past sometimes is utterly mind blowing. It's very informative about our own age in that we think things are eternal, they're not. Everything is subject to change. Changes is the way of the world.

ROBERT: Special thanks to Neil Shubin, University of Chicago. His new book is called The Universe Within, and it describes how you and I are linked in oh so many ways, through our bones, our chemistry, ourselves. Also to Chris Impey, University of Arizona. His newest is called Shadow World. And to Emily Graslie and Paul Mayer of the Field Museum in Chicago. We called Emily. We said, "Find us a paleontologist and a saw," and she did. And before we go, because it's the end of the year, and who wants to leave when you've had a good year, and who knows what's gonna happen next year? I just want to play you a little bit of—can we do this? Can we just add an end to the end?

JAD: Yeah, sure.

ROBERT: I was talking to Neil deGrasse Tyson, who's an astrophysicist and who thinks about spin, which we just thought about, thinks about the inner solar system, which we've just thought about. So here's him and I talking about holding onto time.

JAD: [laughs]

ROBERT: It's a little goofy, but here it is, just for the fun of it.

ROBERT: So if you're on Earth, and you're walking around Quito on the equator, if you're walking at four miles an hour, your day will go sort of the normal way. The sun will rise behind you, go overhead and then go down on the other side.

NEIL DEGRASSE TYSON: Well, if you're stationary, it will be the 24 hour day, yes.

ROBERT: Yeah.

NEIL DEGRASSE TYSON: If you started walking on the equator, depending on which direction you walked, your day will either last longer or shorter, okay? So if you walk west, the faster you walk, the longer your day will become. You could walk at a pace—we have a 25-hour day, a 27-hour day. There's a speed with which you can walk on the equator in the Earth going west, where your day lasts forever. And that is the rotation rate of the Earth. You would have compensated ...

ROBERT: Roughly what type—that would be a gerbil.

NEIL DEGRASSE TYSON: A gerbil running on a beach ball, a rotating beach ball. So that would—on the top of a beach ball. So that speed for the equator is about a thousand miles an hour. So the equator moves a thousand miles an hour, and that gives us the 24 hour day. If you want to go a thousand miles an hour the opposite direction, you will stop the day. The sun will never move in the sky and you'll have a—and your day will last.

ROBERT: Superman did that once, I think, when he had his thing with Lois.

NEIL DEGRASSE TYSON: Superman would have so messed up everybody on Earth for having stopped the rotation of the Earth, reversed it, and then set it forward again.

ROBERT: Yes, he did that.

NEIL DEGRASSE TYSON: He would have scrambled all—anything not bolted to the Earth would have been ...

ROBERT: Wait, it would have flown off?

NEIL DEGRASSE TYSON: Yeah, yeah. So depending on your latitude and equatorial residence, if you stop the Earth, they were going at a thousand miles an hour with the Earth. If you stop the Earth and you're not seatbelted to the Earth, you will fall over and roll due east a thousand miles an hour. In our mid-latitudes—we're in New York, you can do the math—we're moving about 800 miles an hour due east. And stop the Earth, we will roll 800 miles an hour due east and crash into buildings and other things that are attached to it. All right?

ROBERT: That are attached to it. But let's—going back to Venus now.

NEIL DEGRASSE TYSON: Oh, you want to go to Venus? Isn't this enough for you?

ROBERT: No, I want to—the whole point was to go to Venus, because it's so different there.

NEIL DEGRASSE TYSON: Yeah, on every way. [laughs]

ROBERT: [laughs]

NEIL DEGRASSE TYSON: No, it's about the same size and about the same surface gravity. But that's it. It's 900 degrees Fahrenheit, it's a runaway greenhouse effect. It is heavy volcanic activity that repaves the surface periodically, so there are very few craters on Venus

ROBERT: Just unpleasant in general.

NEIL DEGRASSE TYSON: Unpleasant. Rotates very slowly.

ROBERT: Well, that's why I want to stop. So how slowly does it rotate?

NEIL DEGRASSE TYSON: You know, I don't remember the exact number ...

ROBERT: Like four miles an hour or something like that.

NEIL DEGRASSE TYSON: Yeah, it's some very slow rate at its equator, slow enough so that you don't need airplanes to stop the sun. You don't need special speed devices. You could probably trot and stop the sun on the horizon, or wherever the sun is in the sky.

ROBERT: So if you're that guy from Jamaica, what's his name?

NEIL DEGRASSE TYSON: Usain Bolt.

ROBERT: Usain Bolt. And you happen to be on Venus for a little while, and you decide to go for a run. What happens to Usain during the run?

NEIL DEGRASSE TYSON: Okay, so normally, the sun would rise in one direction and set in the other. Depending on which direction you chose to run in, you could reverse your day and have the sun rise in the opposite side of the sky than it normally would. And—but I think Venus is rotating slowly enough that you wouldn't have to be Usain Bolt. I'd have to check my numbers on this.

ROBERT: Oh, I don't think you would. Maybe in order to have the sun actually sort of seem to go backwards—that's what you're saying, is the sun would go backwards?

NEIL DEGRASSE TYSON: Yeah. Yeah.

ROBERT: So you'd be having lunch. You're Usain Bolt, and you say, "Now I'm gonna run," and the sun's going backwards towards the mornings in the horizon.

NEIL DEGRASSE TYSON: Yes, you can reverse the sun. That's correct. In fact ...

ROBERT: That is a really good reason to sprint, I think.

NEIL DEGRASSE TYSON: Well, but who cares about the sun anymore?

ROBERT: Me. If I were Usain Bolt ...

NEIL DEGRASSE TYSON: Is the sun telling you when to eat lunch? I don't think so.

ROBERT: [laughs]

NEIL DEGRASSE TYSON: Your stomach is telling you when to eat lunch. You're saying, "Okay, Usain, you eat breakfast, but you want to have lunch real soon? Run so that the sun is now at the top of the sky, so now you can legally have lunch." No!

ROBERT: You're not buying my poetic premise at all today.

NEIL DEGRASSE TYSON: This is the 21st century, Jack. The sun is—we wake by alarm clocks not by roosters and sunlight. I'm sorry.

ROBERT: I wish I could help you out by thinking, let's suppose ...

NEIL DEGRASSE TYSON: I'm not gonna depend on running on Venus to get the sun in the middle of the sky at my command so that I can have lunch.

ROBERT: Okay. All right, but let's suppose you are a rooster and you like to crow at dawn, just a deep feeling.

NEIL DEGRASSE TYSON: You could totally mess with a rooster this way.

ROBERT: Yes, that's what I want to do.

NEIL DEGRASSE TYSON: Usain Bolt carrying a rooster. [laughs]

ROBERT: Usain Bolt carries a rooster on Venus. He does a remarkably fast sprint. The rooster, having started the run in the middle of the day, well past the crowing period, feels a strange compulsion to crow two hours into the run.

NEIL DEGRASSE TYSON: Because he ran backwards to the sunrise rather than to ...

ROBERT: Well, he ran forwards but the sun went backwards.

NEIL DEGRASSE TYSON: Yes, he ran the other way to reverse the sun back to sunrise. Yeah, the rooster is gonna—will need therapy. [laughs]

ROBERT: [laughs]

JAD: Well ...

ROBERT: I think it's time for us to definitely go now.

JAD: Yeah, we should definitely go. I'm Jad.

ROBERT: I’m Robert. Thanks for listening.

[LISTENER: This is Christine Stone from Maplewood, New Jersey. Radiolab is supported in part by the National Science Foundation and by the Alfred P. Sloan Foundation, enhancing public understanding of science and technology in the modern world. More information about Sloan at www.sloan.org.]

 

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