Announcers: You're listening to Radiolab from WNYC and NPR.
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. Today's Monday, tomorrow night so-
Robert: 50 hours. We have 50 hours left to 20-
Jad: No, less than that. 20-
Robert: Well, whatever. 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 going to 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: I'm a paleontologist, an evolutionary biologist at the University of Chicago. Just like a clamshell has an animal inside it so do corals.
Robert: A little fleshy wormy thing?
Neil: 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: Think about it this way. Let's just think about what happens to a creature as it lives its life in the water, which is what these things do. You know 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. 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: They are slapping on new skeleton if you will, a 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.
Robert: That's why Andy Mills and I called up our pal Emily Graslie whose job is-- what is it?
Emily: I am the chief curiosity correspondent of the Field Museum in Chicago.
Robert: That's your actual title?
Emily: The chief curiosity correspondent, yes. It is.
Robert: You brought some corals? Did you?
Emily: We have many corals. We have corals all over the studio desk right now.
Robert: All right.
Emily: All right. Let's cut it.
Robert: Because when you cut into these shells-
Emily: It's warm.
Andy: 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 grey strips.
Emily: They're all different variations of grey but some are really dark grey and some are tan.
Robert: They're like bands running either through or across the shell.
Emily: 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: When you hold it up close to your eye-
Robert: -if you look closer in between the strips you can see-
Emily: -wow, you can see the lines, wow.
Robert: -you can see that the spaces are filled with faint little lines.
Neil: That's where the piece of this story is just so fascinating.
Robert: Because in 1962, a paleontologist-
Neil: -Professor John Wells-
Robert: -was looking at some corals just like these.
Neil: He was just sitting there saying, "Okay, well what can we figure out from coral shells?" 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 to see?" He starts counting, there's 100, 200 lines, 300, about 310, 320 and every time he counted-
Neil: -he got a number-
Neil: -360, 365.
Jad: Wait a second.
Robert: Familiar number, no?
Neil: 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: They're not just making a grey mark after 365?
Jad: What are the grey 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,4 then it grows a lot the next summer. Again, that marks a year. Those big bands are like [sings] Happy New Year. [sings] Happy New Year. [sings] Happy New Year.
Neil: They're actually calendars and clocks inside each of these things. You just have to know how to read them.
Robert: This guy, Professor Wells-
Neil: -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: He was at Cornell University. Cornell University is surrounded by rocks around 370 or so million years old and he collected some nice corals. There are a lot of nice coral fossils known from there.
Robert: He opened up these ancient skeletons-
Neil: -and he did the count.
Robert: 100 days, 200 days-
Neil: He was expecting-
Robert: -300 days-
Neil: 360 to 365.
Neil: Lo and behold he found-
Neil: -between 400 and 410.
Neil: Yes, 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, 380 million years ago, there were more days in a year.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 got to be true for my animal, the clam." The oyster people said, "It's got to be true for oysters." Mussel folks said, "It's got to be true for mussels."
Neil: 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: 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.
Neil: 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 the year has declined from over 400 to what we have now which is 365.
Robert: We have lost 40 days since the--
Neil: Yes, since creatures first started to walk on land.
Robert: Now comes the obvious question, why? Why would there be more days then than there are now?
Jad: Wait a second. Wait a second. A year is a trip around the sun?
Robert: That's a trip.
Jad: Days are when we spin around into the-- we're going around the sun. 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: Then what is it?
Robert: Well Chris says the answer takes us back about 4 and a half billion years to a time when the Earth was very young.
Chris: There was this crazy period of time lasting about 50 million years.
Robert: Which they called The Great Bombardment period.
Chris: 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 a tacky magma. There was hail, brimstone, endless rain. A 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 parked right next to us.
Chris: It tugs us around in a hefty way.
Jad: Wait, I thought we tugged the Moon?
Chris: It works both ways. We tug the Moon and the Moon tugs us and the force is actually equal.
Jad: It's like a dance.
Chris: It's a dance.
Robert: I tug the Moon and the Moon tugs me.
Chris: Exactly. It's a celestial waltz.
The Stargazers: I see the Moon, the Moon sees me,
Out through the leaves of the old oak tree.
Robert: 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: 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. A total spin equals a day.
Robert: We all know that. Now, today we make 365 of these spins as we orbit the sun. That would be a year 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. Then along comes the Moon to join the dance and now here's the key according to Chris.
Chris: Earth is spinning faster than the Moonis orbiting it.
Robert: A dance part it takes a month to get them around us, we take 24 hours. 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 spin to slow down just a little bit, a teeny, teeny bit. As the spin has slowed, well, our days have gotten longer.
Chris: 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. The day before, that was 54 billionths of a second longer than the day before. The day before, that was 54 billionths of a second longer than the day before that, which was 54--
Neil: If you extrapolate that out over the millions of years, people like me think about-
Robert: That's Neil Shubin again, the paleontologist.
Neil: -that becomes quite significant.
Andy: You're telling me that today is the shortest day of the rest of my life?
Robert: Andy worries about these things.
Neil: Well, you're not going to live longer because of this. I'm sorry to say.
Robert: Now, so this Moon dance does not affect the ticking of time, it just affects what we choose to call a day. By the way, one of the consequences of this dance is,4 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. 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: -a couple of inches.
Robert: According to Chris.
Chris: The length of a warm.
Robert: Really, so the Moon is getting a worm's distance further away from us every year.
Robert: He says, if you go back about four billion years-
Chris: -the Moon was originally about 10 times closer than it is now.
Robert: 10 times closer.
Chris: Imagine a Moon looking 10 times bigger than it does now that would have been crazy. Also, the days would have been six hours long.
Jad: Six hours long?
Neil: To me, what this says is that everything that we take for granted as normal, in our world, and 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.
When I'm sitting in a hole in the middle of the Arctic, digging at a fish fossil, every now and then, I pinch myself and say, here I am in the Arctic, digging a fish that lived in an ancient subtropical environment. The juxtaposition between present and past sometimes is utterly mind blowing. It's very informative about our own age, and 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 to 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 them, Emily, we said, "Find us a paleontologist and the saw," and she did.
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 going to 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: Yes, 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. Here's him and I talking about holding on to time. It's a little goofy, but here it is, just for the fun of it.
Robert: 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 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. If you started walking on the equator, depending on which direction you walk, your day will either last longer or shorter. 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 a day, a 27-hour a day. There's a speed with which you can walk on the equator in the Earth going west, where your day lasts forever. That is the rotation rate of the Earth. You would have compensated-- [crosstalk]
Robert: That would be a gerbil.
Tyson: A gerbil running on a beach ball or rotating beach ball. That would be on the top of a beach ball. That speed for the equator is about 1,000 miles an hour. The equator moves 1,000 miles an hour. That gives us the 24 hour day. If you want to go 1,000 miles an hour to the opposite direction, you will stop the day. The sun will never move in the sky and your day will last.
Robert: Superman did that once when he had this thing with [unintelligible 00:15:34].
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.
Tyson: He would have scrambled all, anything not bolted to the Earth would have been--
Robert: Wait, it would have flown off?
Tyson: Yes. Depending on your latitude and equatorial residence, if you stop the Earth, they will go in at 1,000 miles an hour with the Earth. If you stop the Earth and you're not seatbelt it to the Earth, you will fall over and roll due east 1,000 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. Stop the Earth, we will roll 800 miles an hour due east and crash into buildings and other things that are attached to it.
Robert: Going back to Venus now.
Tyson: Well, you want to go to Venus? Isn't this enough for you?
Robert: No, I want to-- That whole point was to go to Venus, because it's so different there.
Tyson: Yes, on every way.
Tyson: No, it's about the same size and about the same surface gravity. That's it. It's 900 degrees Fahrenheit, it's a runaway greenhouse effect. It is heavy volcanic activity that repaves the surface periodically. The very few craters on Venus
Robert: Just unpleasant in general.
Tyson: Unpleasant, rotates very slowly.
Robert: That's why I want to stop. How slowly does it rotate?
Tyson: I don't remember the exact number--
Robert: Its like 4 miles an hour or something like that.
Tyson: 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: If you're that guy from Jamaica, what's his name?
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?
Tyson: 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 sunrise in the opposite side of the sky than it normally would. Venus is rotating slowly enough that you wouldn't have to be Usain Bolt. I'd have to check my numbers.
Robert: I don't think you would. Maybe in order to have the sun actually seem to go backwards-- That's what you're saying, that the sun goes backwards?
Tyson: Yes, yes.
Robert: You'd be having lunch, you're Usain Bolt, and you're going to say, "Now I'm going to run, " and the sun's going backwards towards the mornings in the horizon.
Tyson: You can reverse the sun. That's correct.
Robert: In fact, that is a really good reason to sprint, I think.
Tyson: Well, but who cares about the sun anymore?
Robert: Me. If I were Usain Bolt--
Tyson: Is the sun telling you when to eat lunch? I don't think so. 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. Now you can legally have lunch." No.
Robert: You're not buying my poetic premise at all today.
Tyson: This is the 21st century, Jack. 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-
Tyson: I'm not going to 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: All right, but let's suppose you are a rooster and you like to crow at dawn, just a deep feeling.
Tyson: You could totally mess with a rooster in this.
Robert: Yes, that's what I want to do.
Tyson: Usain Bolt carrying a rooster.
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.
Tyson: Because he ran backwards to the sunrise rather than to--
Robert: Well, he ran forward but the sun went backwards.
Tyson: Yes, he ran the other way to reverse the sun back to sunrise. The rooster will need therapy.
Robert: I think it's time for us to definitely go now.
Jad: We should definitely go. I'm Jad.
Robert: I’m Robert. Thanks for listening.
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