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Hey, StarTalkians. I've got another Things You Thought You Knew coming your way. This time we're looking at twilight, clouds, and coastlines. But you've got to check it out to see how they connect and why. See you then. Welcome to StarTalk, your place in the universe where science and pop culture collide. StarTalk begins right now. Chuck, I'm going to tell you about the three Twilights. No, no, no, no. I'm sorry. I got to correct you on this one. There are four Twilights.
You got Twilight. Then you got New Moon. Then you got Eclipse. And then you got Breaking Dawn. I'm afraid the answer- That man can bite me any day. Okay. I'm afraid the answer is incorrect. What? Astronomically speaking. Oh. This is a science show. Oh, okay. Astronomical twilight is a thing. That is an actual thing. So Chuck, I don't know if you know this, but there's three different kinds of twilight.
Clearly, I did not. Okay. Oh, wait. Yes, I do know. So there's the one in the evening, and then there's the one in the morning, and then there's the one... Edward takes my heart. No, that's not correct. Okay. I'm sure. I'm pretty sure it was. But go ahead. What are the three? So, Twilight, in any given place on Earth, we rotate in such a way so that the sun... dips below your horizon. Unlike some movies and some court cases and some people who think that the instant the sun sets, it's dark.
Right. Okay. Nothing could be more false than that. They made this mistake in Back to the Future when Marty goes back to 1955 and he's driving out from the barn because he visited the farmer's barn in his DeLorean. And it is dark at the beginning of the driveway. And at the end of the driveway, you see sunrise and it's light. No. That's not how that works. All right. Okay. In John Wick 4, there's this scene that happens early morning hours. Yeah. And he ascends this staircase up to this plateau.
And then the sun rises and then it's light. Okay? No. No, these people just have never looked up. They think the sun alone, direct sunlight, is their only source of light. You know what else is lighting things up? The atmosphere. Okay. So the sun dips below the horizon. Light is still illuminating the atmosphere above your head. Right. It is still glowing from sunlight. That's called twilight.
We have a word for that. Twilight. Oh, it's beautiful. It's beautiful. It's gorgeous. It is beautiful. Yeah. By the way, if we had no atmosphere and the sun went below the horizon, dark. Dark. Dark. Oh, you know, they have that on the moon. Yes. Yes. That's why all of our astronauts landed in the daytime. Okay? That's a good, because otherwise the lights go out. That's it. Like that. Yeah. Okay.
So you can ask, the deeper below your horizon the sun goes, the higher and higher up the sunlight is hitting. So the lower atmosphere is more and more in darkness, okay? If it's really far around the other side, there's no light illuminating any part of the air above you. We call that nighttime, right? Nighttime. Very good. Just wanted to let you know I'm with you. All right. There are three kinds of Twilight. There is civil Twilight.
Quite frankly, I don't want to offend you in any way, if possible. I saw a comedy skit with civil engineers. Right. And they're sitting there offering each other tea. After you. Would you like some? Would you care for another pinafore? Oh, my good man. Please, I wouldn't dare. Civil engineers. Civil engineers.
If only civil wars could be that polite. Oh, wouldn't that be something? You know, I would kill you, but that would be rather unpleasant, wouldn't it? A civil war. It's a civil war. Let's just play checker. Exactly. is until the sun is six degrees below the horizon. Six degrees below the, so okay, it's a Kevin Bacon twilight. Gotcha. Oh, six degrees. Six degrees. Okay, okay. There's still some light in the upper atmosphere, still lighting. But for practical purposes, for ordinary people.
Nighttime begins when it's six degrees below. There you go. Okay. Civil twilight. Civil twilight. So people don't have much need for the sky. like other people do. So, civil twilight, six degrees. Let's keep going. There's another twilight called nautical twilight. Oh, okay. It's got to be darker than civil twilight for them to use their sextant and their navigate by the stars. That makes sense. It makes sense. So the sun's got to be... 12 degrees below the horizon. Look at that. Yeah.
And at that point, you start seeing many more stars. for you to navigate by. Okay. Where six degrees, not so much. Right, because there's still light in the atmosphere. There's still a lot of light in the atmosphere above you. The sky's still glowing. Right. The blue sky is light from the sun. Right. Scattered back to you. Right. On the moon, there is no scattered light.
So the sky, daytime sky is as dark as night. Black. Black. So nautical. Nautical. Civil nautical. They get some more stars to play with. Okay. But. the astronomers. We go deeper than what the eye can see. We bring out telescopes. I don't want twilight messing with my telescopic views of the night sky. So we go an extra six degrees lower than nautical twilight. Wow. 18 degrees. 18 degrees below the horizon. Okay. Only then.
is the end of Astronomical Twilight. Wow. Yeah. And what time would that be about? Well, no, so it depends. If you're near the equator, the angle that the sun sets... to the horizon is almost vertical. Right. So if you're going vertically down, you're booking into the darkness, okay? Twilight lights like 15 minutes. I mean, have you ever been in the Caribbean?
There is no culture of twilight in the Caribbean. That's true. Okay? Yeah. It's light and then it's dark. Not instantaneously at sunset, but the sun goes down fast. At most an hour. An hour. An hour later is 15 degrees below the horizon. You're done. You're done. You're done. Right. Okay? But the farther away from the equator you go, towards the poles, the sun's angle... to the horizon gets shallower and shallower. So here comes the sunset.
Well, it's ambling its way along a hypotenuse, okay? Along a slopey angle. So Twilight can last hours and hours. Right. Do you know all of England sits north? of the northernmost part of Maine. Wow. I did not know that. Of course not. Okay. Yeah. So. Why would I ever know that? So England has very long twilights. Very long twilights. Very long twilights. Oh, is that why, where is it? Where they have like. Oh, so if you keep going even farther north, okay.
There is no night. It's all twilight. It's just twilight. The sun never gets below your designated level. If it's astronomical twilight, it stays above 18 degrees. Right. Or above 12 for nautical, above 6. So then my wife is from Alaska. They just... The Fairbanks.
The midnight softball game on the solstice, the summer solstice. Right. Yeah, it's just twilight the whole time. It's just twilight the whole time. Yeah, so these are your twilights. I don't know how many people know about them. So recite them to me. What are they? So you got your civil, of course, and then your nautical, and then your astronomical, or as we're going to call that one, the neolite. Neolite.
No. You don't like that? No. Because it's got your name in it. No. No. So there you have it. Three Twilights. Nice. And when we go observing on Mountaintop. we are given the time of astronomical twilight. Right. So we can plan our observing schedule around that. Very cool. I'm Khyas from Bangladesh and I support StarTalk on Patreon. This is StarTalk with Neil Degras Tyson. Chuck, these don't stop. Okay, that's fine with me. Another explainer. Excellent. Okay, this one, unclass.
Have we done a clouds one before? Because you have better memory than I do. We have not done clouds. We have not done clouds. And, you know, I wouldn't think there was a lot to talk about with clouds. And maybe that's why we haven't done it. But have you looked at clouds from both sides now? Okay, you mean top and bottom? Joni Mitchell, forgive us. So, you ever wonder why clouds are just up there? I mean, I know. I mean, I haven't wondered. I mean, once.
I found out the clouds were basically water droplets. Yeah. Just basically vapor. Yeah. They became extremely uninteresting to me at that point. Okay. Let me get your interest back going for me. Okay. Okay. All right. Allow me to remind you that the sun does not heat the air. That I understand. The sun heats the ground. And the ground radiates. And that heats the air. And that heats the air. And it radiates in what band of light?
Infrared. Infrared. Right. And CO2 in the atmosphere actually traps infrared. Right. Oh, God, do I know. What a shame. So it's otherwise transparent to sunlight, ordinary visible light. But once the ground absorbs it. It re-radiates back infrared. There you get the trapping, what they call the greenhouse effect. Okay. Did you hear that, people? That's how simple it is. Did you see how simple that is? Okay. Comes in as visible light.
And passes through everything with no problem. Heats the ground. Ground sends it back as infrared gets trapped. Heats the earth. Climate change. So how do you know the atmosphere is transparent to visible light? How do we know? Yes. I don't know. Because you can see the sun? That makes sense. If it were not transparent. If it weren't transparent. You wouldn't be able to see the sun. You wouldn't be able to see the sun. There you have it. Okay. Right. Let me be more blunt.
Windows are transparent to visible light. Right. Because I can see through them. You can see through them. Right. Walls. are not transparent to visible light. Because I'm not Superman. Okay, so Superman, back then, X-rays were like relatively new. X-rays were discovered in like, the first Nobel Prize in physics was given for the discovery of X-rays. Wow. Yeah, so it was late.
1890s, 1900 was the first time that was awarded. So first Superman comic was maybe 1930s. So x-rays are still kind of cool. Yeah, they're like, woo. All right. But radio waves go through walls also. Right. So he could have had radio wave vision. Then he'd have to tune in his eyes. Okay. So, but back then, x-ray was just metaphor for seeing through things. For seeing through things. Yeah, that's all it was. Yeah, exactly. So, infrared does not pass the window.
Not easily. Not easily? No. Okay. Do this experiment. If you're in a fireplace, right, and you have some distance from the side, get someone to walk in front of you with a plate glass window. In that instant, you don't feel any of the radiant heat from the fire. That's right. The heat is blocked. It blocked. OK? OK. That's cool. It blocks it. So if you had infrared vision.
A window is just the same thing as a wall to you. Just think about that. So some things are not just inherently transparent, they're only transparent to certain wavelengths of light. And none of that has anything to do with clouds. But that's the framing information here. Sunlight heats the ground, the ground heats the air. The farther away you are from the ground,
the less heat you're getting. That makes sense. Okay. Have you ever tracked the temperature in an airplane? Sometimes they do it on the track your plane thing. Right. Okay. What's the temperature up there? Cold. Thank you. That's the temperature. Is it exactly cold? Very, very cold. You measured it. Exactly. It's cold. It could be as low as 40 below. Right, yeah. 40 below zero. And Peggy Lee's Fever. Right. All right. And we all know that song. You're giving me fever. In the morning.
Right, right, right. So all the occasions where one gets fever. Right. Right. One of the stanzas toward the end is, now you've listened to my story. Here's the point that I have made Chicks are born to give you fever Be it Fahrenheit or centigrade. Ooh. Getting both temperature scales. Yes. In the song. In the most sexist way possible. And from a woman. That's how bad it was back then. That's how bad it was back then. Even the women were in Texas. Chicks were born to give you fever.
No, here's why I even went there. Go ahead. Well, first of all, I'm giving him a hall pass because... Fahrenheit is a human being's name. Right. We've actually invented the thermometer, the mercury thermometer. Also American. Thermometers. Centigrade, that's not somebody's name. Right. That's a scale. It's a scale. So what they should have said was Fahrenheit or Celsius. Right.
Well, then it wouldn't have rhymed. Then it wouldn't have rhymed. So that's why I got to give him a hall pass on that one. Right, right. Okay, ask me why I even went there. Why did you even go there? Because the Fahrenheit and Celsius scale cross at 40 degrees below zero. Interesting. 40 below zero, you don't even have to say. It's the same on both scales. It's just the same thing. The only temperature for which that is true.
40 below. Yes, it is. Yo, that's kind of that, right? I'm ready to stop the explainer right now. That is great information. The only temperature. That exists both Fahrenheit and centigrade at the same point. They cross at that temperature. 40 below zero. And it's within a degree of the temperature that Mercury freezes. Right. Which is especially relevant to Mercury thermometers. As you get higher, the temperature drops.
because you're getting farther away from Earth's surface where the sun is heating. This reverses in the thermosphere. where ultraviolet is absorbed by the ozone layer. What does it have to do with clouds? Because clouds are formed in warm, moist, unstable air. If you're unstable, it means you're not gonna stay where you are, you're gonna rise. Have a pocket of air at sea level. Or just near the ground. Oh, by the way, the official temperature that gets measured?
is at a predetermined height above the ground. Okay. Otherwise, you'd have different temperatures all over the place. Everywhere. You're up in a building, you get a different temperature there than if you're sleeping on a picnic blanket. So they have to standardize that for this reason. And it has some humidity level in it.
Okay. Okay? Give me a percent. Let's say it's 50% humid. Okay. Not bad. New York City, that's very typical. Deserts, it's down in, like, single digits. Right. Rainforest, it's always up above 80s, 90s, 80s, 90s. All right. New York is 50%. That humidity that is reported is actually a relative humidity. Okay. Okay? What that means is that is...
It is 50% relative to how much it could carry at that temperature. As the blob of air gets heated and rises, the temperature drops. Colder air can hold less... humidity than warmer air. So the relative humidity goes up. It starts at 50 in this example, then it goes to 60, then to 70. to 80. So let's take 80. At 80%, you didn't add more water to it. No.
the capacity of the air to hold it dropped. Right. Okay? So never mind. So there it is. It is ascending. 80, 90. Bada-bing! You reach 100%. Right. 100% humidity. The humidity condenses out. as water droplets. Water vapor, basically. And boom, you have a cloud. That's why the cloud is up there and not down here. And now I know how clouds are born. That's how clouds are born. And all this time I thought you had a mommy cloud and a daddy cloud and they loved each other very much. A stork cloud.
That's kind of dope, though. And it's because of this temperature gradient from high temperature to low temperature from the ground on up. Right. Okay. There are two ways you won't get cloud. Okay. No matter your height. There's not enough. humidity here, where even if it rises, it can go 10, 20, 30, 50, 70, and it never hits 100 before it gets way up in the atmosphere. No cloud. No cloud. The other way is... The blob of air has autonomy and a right to choose.
It doesn't have to have a baby cloud if it doesn't want to. Is that where you were going with that? Okay. We were still on the baby making clouds. Sorry. Sorry. Okay. I had moved on from that. I couldn't. You couldn't. You were still. Yeah. The juvenile brain stayed with it. My childlike brain. All right. But that makes sense because it's really about the water that it's holding.
So, and the relative humidity as a capacity to hold, capacity to hold, to hold humidity. Right. Okay. So now, so one way is it starts out so low, even though it gets high up, it never hits a hundred percent. Right. No cloud gets formed. Right. Another way. is if you have descending air. Ooh. That can happen. So you can have, for example, cold air moving through the mountains. And cold air is, and then it comes into a valley.
and it descends, it comes down over the mountaintops, okay? If you have descending air, what's happening to the air? The air temperature. Well, it's getting warmer. It's getting warmer. So, and then condensation again. It can now keep holding more and more. You're not making clouds. Right.
So descending air does not make clouds because it keeps getting warmer. Right. Ascending air with not enough moisture will not make a cloud because it'll never get to 100%. Right. Okay. All right. So far, this is cool. Okay. You ready? Okay. So now, suppose there's no wind. and you got, like, let's say 70% humidity. All right. The sun sets, and the temperature drops. Gets to 100%. What happened? What just happened? We made a cloud. Where did we make the cloud?
Where the air is, I mean. Thank you, Chuck, for that brilliant answer. Right in front of me. Yeah, of course. It would be right here. Right here. Yeah. We have a new word for that kind of cloud. Do we really? Yes. What? Fog. You got me. It's fog. That's fog. And that's the cloud. That's why. When it's foggy, it's always a little cold. You ever notice that? Yeah, yeah. It's a little cold. A little chilly. And it's a little dank, a little chilly. So the fog...
is when you get this, you reach, it's called a dew point, to be precise. The dew point, and it's right at the ground level. Nice. And so it's interesting that in our language, you have a different word for a cloud above your head than for the same damn cloud right here, right in front of you. If the cloud formation is vigorous.
like the temperature dropped real fast, and it was really humid, and it comes up there, and it's still being unstable, and it's rising, and it's turning into water droplets. You get a cumulus cloud. Okay. Okay? If this is intense and it's unrelenting and it continues to build... That cumulus cloud, which is just white with sunlight moving through it, it becomes less white because the droplets are getting bigger and bigger. Oh. OK. And it starts getting gray. Nice. We have a gray cumulus cloud.
You got cumulonimbus. Okay. That stuff will hurt you. So the cumulonimbus, now the water droplets, it is so laden with water, it cannot contain the humidity, even at 100%. And so the humidity nucleates. It finds dust in the air, things. It says, and other bits of water vapor collect to it. And it's held there for a while because you have updrafts because that's how you made the cloud in the first place. Right. But then it gets so big it drops out.
So the more vigorous the cloud is, the heavier the raindrops are. Because it was holding them up. Right. Okay? The very fast-moving air is holding it up until it can't hold it up anymore, and that big fat-ass drop falls out of the sky, and you get the big drop, thunderstorms. Nice. Okay? Let's say it's even more vigorous than that. Uh oh. Okay. We went from cumulus nimbus to cumulus negro. That's when the clouds get black. Black clouds. They get black. Okay. So.
So the updrafts are so severe. Right. Okay. Oh, I forgot to tell you. Often the rain forms as snow. As water crystals. Because it's high up. Right, right. Okay? Right. Very cold. And you can keep those pretty buoyant, but then as it begins to fall, it gets to a warmer air temperature and it just melts into rain. Right. Okay? So, all right. Now. Imagine updrafts so strong that not even the raindrops can fall out. And it just stays up there.
And gets bigger and bigger. And then one day I say, I can't hold you anymore. I got to let you go. And now it's too big to melt. Oh, my God. And what do you get? You got hail. Hail. That's terrible. You got hail. That's updraft. That's an insurance cloud. So the conclusion here is the bigger the hail. That means the bigger the hail pellets. Pellets, spheres.
the more severe the storm was. Right. Because it meant the updrafts were just so significant. It was so catastrophic, turning just moist air into- Giant balls of ice. Giant balls of ice. That's right. Yeah. Go on. By the way, with these puffy clouds, it's why they're more frequent in the tropics. because you still have the ground heating, but you start out with such higher humidity air that when it rises, of course, you're going to puff up a cloud, like right there. Now.
If you pop off a cloud here and not over there, then it could be raining over there and not over here. Right, yeah. Okay? And this is the conditions, almost all the conditions you need for a rainbow. Okay. Okay? So to have a rainbow, you know it's very specific. I don't know if you knew this. Okay? Right. So, it's gotta be... raining in front of you and has to be late enough in the day for the sun to be low enough in the sky for the sun to be behind you. That makes sense.
Okay. So it can create the... It would be a late afternoon thunderstorm. Right. That's over there. Right. The sun is behind you. And the sun is behind you. Right. Okay? That's why you never see a rainbow in the middle of the day. Because the sun is directly overhead. Right. And it's not raining under your knees. Right. You would if in a sprinkler. Right. A lawn sprinkler. What if you're in a plane looking down? Yes. If you're a plane looking down, you got full view. Awesome. Yeah, you got it.
So, these are the configurations here. And there are other kinds of clouds, like I said. Cirrus clouds are... They can be transparent, but they mess with our viewing of the night sky. Little wispy, thin clouds. Right, right. And these are clouds that just hang out up there, and they're just, they're very stable. serious clouds, and then you have weather fronts that come in where there's a change in temperature. You never heard of a warm front.
Right. That's not how that works. It's always a cold front. Because if things get warmer, you're going to hold more moisture. More moisture. It's when the cold front comes in. Right. The cold front comes in. Messing up everything. And you had warm air that had moisture. Right. And they meet at the boundary.
It turns your moisture into rain, into storms, into clouds. And so it's always the cold front you got to watch out for. It's the drunk uncle at the cookout. The cold front. It's messing things up. All right. So. Just one other interesting thing, I think. These are especially visible in airplanes. You see these long, I'll call them columns, but they're horizontal. columns of clouds. Yeah. One after another.
Yes. These are called cloud streets. Cloud streets? Streets. Okay. Cloud streets. Okay, because- the clouds that I just described, the air goes up. But wait a minute, if air is going up, what's replacing that air? Got to be more air. Thank you, Chuck. Brilliant answer. Okay. So for every bit of air that goes up, there's air that drops and comes in to fill the gap. So these are convective cells. Okay, that's what's happening here. But in a cloud street, the convective cell is cylindrical.
Interesting. Okay. So imagine a horizontal cylinder that's rotating. Oh, nice. On the side that's rotating up, you get cloud formation. And on the side that's rotating down, no clouds form. Because it's downward air. We've been through that. But wait a minute, how about the other cylinder? it has to be turning the opposite way. Otherwise, they would cancel. You can have up air and down air simultaneously in the same place.
So these cloud streets have cylinders rolling with sides that match each other, both going down or both going up. So the next time you're in an airplane, look for this, it's beautiful. And it can go on for miles and miles. So again, depending on how the terrain is heated, where the moisture is, is there a lake, is there an ocean, is there a...
Is there asphalt, which heats hotter than other beaches? So all of this makes for the beautiful diversity of clouds we see and love in the sky. That's very cool. And to think that all we ever do is look at them and see bunny rabbits and... And George Washington. Right. Always George Washington. No other president. He's got the, you know, he's got the do for it. That's true. Yeah. So, Chuck. Yes. Ask me about Coastline.
What's going on with Coastlines, Neil? I thought you'd never ask. Well, we're in my office here, so nothing is ever farther than an arm's reach for whatever I got to use. Okay. So I'm just reaching right here. Okay. Look at that. I got the whole world in his hands. Did anyone sing that anymore? I bet they don't.
No, because that was so kumbaya. United Nations. It was like bring it all together. Hippie love. Hippie love. Not anymore. Days are gone. All right. Anyhow, so here's the earth. When we think of earth. We say to ourselves, there are bodies of water, oceans are the largest. and there's land. And we see this and we think about it as though it's a fundamental feature.
of our planet. That's Africa, because it has that shape. Here's Asia with this coastline, and Japan is an island. We have this understanding of the world. Brought to you by settlers and explorers and politicians. With a few wars thrown in here and there. You always gotta have a good war to bring about changes in geography. Also color-coded, right? Which I came to realize in my cynical adulthood.
are ways so that you can learn early on who your friends are and who your enemies are. Because none of this is visible from space. No, it isn't. No, it's just land. It's just land. Okay. Right. All right. So, when you take a look at a coastline, there's the urge to think there's something fundamental about it. But there isn't. Well, really? That's just the coastline today.
That makes sense. Okay. Have you seen maps where you can look through the water? In North America, for example, here we go. Have you ever seen maps where you can... that the continent extends a little further out underwater. Have you ever noticed that? You know what they call it? No. The continental shelf. Right. Yeah. I've seen that. You've seen that? Yes. And so it kind of follows our contour. Right. But it's way out there. Exactly. And in fact.
a lot of trash dumping activity. In the old days, now you process the trash. The old days, they were put on a barge. and go beyond the continental shelf. Dump. Dump it there so it goes way down to the bottom. Right. Rather than possibly ever washing back up. Back up, right. Okay, and I remember looking at it as a kid and I said, why does the shape of- our continent continue underwater.
I didn't understand that. Ooh. Because it's intriguing to me that that, okay. Do you know what that other edge is underwater? That's the coastline of North America when the ocean had less water in it. Right. When the oceans were drained. Yeah. Get used to that, people. Get used to that. Wait, hold on. When the oceans were drained. All these coastlines looked different. Right. They were bigger. They were bigger. They were bigger. And so, well, when were the oceans drained? During the Ice Age.
You know how ice ages work? You still have your oceans. And you still have evaporation. Because where does- water come from that falls out of the sky. It used to be in the ocean. It didn't come from land. No, of course not. It came from oceans and other bodies of water. All right, so the water evaporates up, but Earth is really, really, really cold. So it goes into the cloud.
And it doesn't rain, it snows. And deposits that water as snowflakes. Okay? So the snow is there. Does the snow ever make it back to the ocean? There we go. It stays there. It stays there. And then another snowfall comes. All right. And layers on top. And the feet and the yards. Right. And in some cases, miles. Right. By the way, this is a great opportunity to take the time and explain to people.
That's how we know that climate change is real and that the amount of CO2 in the atmosphere is greater today than it was back then for all you people who say, oh, it's just cyclical. It's not a big deal. That's how we know from what Neil just described, because in each one of those layers, we can count the carbon dioxide. A public service message was brought to you. So stop it. It's real. OK, anyway, go ahead.
What happens is, once the oceans evaporate out and it snows on land, by the way, it'll also snow in the ocean, and then, okay, it'll just turn into water again. It just turns back into water. Water, all right, so that's just fine, but... for every snowflake that goes to land and never melts. You have systematically drained water from the oceans. And if this goes on for thousands of years, you then build these layers of snow to make a new form of ice, which is glacial ice.
It's not snow and it's not ice in your freezer. It's a different form of matter for the water molecule, glacial ice. It's basically compactified snow. All right, it just stays there. All right? So you're draining the ocean. And as you drain the ocean, oh my gosh, what happened? Oh, back here, where Alaska and Asia meet.
With the Bering Strait. Our ancestors walked over. Oh, they didn't take a boat. What? They didn't fly. What you doing Tuesday? Let's take a walk. Take over a walk. So there they were in Asia. And there was a land and settlements there, we've come to learn. They crossed into North America after having risen up. out of Africa, risen up in terms of latitude here, up out of Africa into Europe. Others went into Asia. Some stayed low. Others went high. They get to that boundary. They cross over.
and they settle North America, Central America, and South America. Then the Ice Age ends. Right. Okay. Oh, my God. We're so trapped. What happened to the land bridge? Well, no, that's long forgotten. Yeah. Okay. It happens kind of slow. Right. And then it covers over. All right. Many generations. All right. So, yes, but you are correct. with the water levels rising, changing all the coastlines, has now stranded a branch.
has now stranded a branch of the human species into North, Central, and South America. So we strand. a branch of the human species into North and South America, and the water levels begin to rise. But at that time, the coastline of the Americas was that continental shelf. Now imagine if people started building cities on that continental shelf. They'd all be gone today. What a shame. Okay, so what happens is the Ice Age ends. And the end of the ice age is a mixture of warmth
And cold. Where the cold has retained glaciers. for tens of thousands of years up here in Greenland. And of course, down here. Antarctica. Antarctica. And so that period is relatively stable. Yes, we have some storms and things, yes. But we have sustained one of the most... climactically peaceful periods. 10,000 years of relatively stable climate. Ice Age. And when you're relatively stable, you say, oh, well, where is the coastline? Here is the coastline. Let's put New York there.
or New Amsterdam. Why? Because it's on a river. You can have irrigation. You have transportation. You have, what else do you use? Commerce. Commerce. Okay, business. All right. So the coastline of all the world's nations today reflects 10,000 years of stable climate. The glaciers stayed glaciers in the cold parts, and other glaciers that had melted had filled up the oceans. It's been stasis, relative stasis.
we are now warming Earth beyond that period of time. And so the glaciers- that are still there, that were in kind of equilibrium with us as we built civilization. And by the way, where are all major cities in the world? They're on the water's edge. On the coastline. Practically, except for Denver, right? Practically every major city in the world. Right.
famous historical city is on some kind of water line. That's right, yep. Okay, so now we are warming the Earth. The glacial ice on Greenland, let's find Greenland right there. and the glacial ice on Antarctica, you say, well, Greenland's not all that big and Antarctica's not. Well, what are you worried about? If we lose all the glacial ice in Greenland. Right.
It'll melt and go into what? The ocean. The ocean. We melt it on Antarctica? Ocean. Goes into the ocean. That's right. Raising the sea level. Rising sea level. Okay. If we lose all that glacial ice. Now, the Statue of Liberty is actually on a huge pedestal. I don't know if you knew that. It's huge. Almost as big as the bottom of the Statue of Liberty. Yeah, no, that's what she sits on. That's what raises up out of the bed. Exactly. So the water levels will rise so high.
Her left elbow. That's crazy. That means there will be no. No more Manhattan. Yeah, yeah, yeah. You lose New York. You lose New York. You lose all of North Jersey. Not that anybody cares. Let's be honest. He said no one ever. We lose New York and we lose North Jersey too. He said no one ever in the history of climate conversation. Who invited this guy? The dude from Jersey.
But my mama lives in North Jersey. So you lose all of that. Yeah. And it's a different coastline. It is. It's a coastline. Once again. Without Florida. There you go. Oh. So there's one good thing to climate change. Would you stop? No, stop. Stop. Stop. We got to protect all our 50 states. So the average elevation of Florida is six feet. Oh, forget it. Say goodbye, Florida. You know, Florida has the lowest
highest elevation of all 50 states. Wow. Right. Can you follow that sentence? That makes sense because New Orleans is like below sea level. Florida has the lowest, highest elevation. No, no, but in Louisiana. their highest elevation is way higher than the highest elevation of Florida. Right. That's what I'm saying. No, you can have places with low elevation. I'm talking about the average. The average. Okay.
so well six feet would do it six feet if you start with six feet you ain't got nothing exactly it's like yeah so basically uh your elevation is chuck plus an inch You in a lot of trouble, man. If you fly over, there's some satellite shots over Florida and with the sun in the right angle. at the correct angle, you see these reflections off of these bodies of water.
throughout Florida. So of course there's the Okeechobee Lake, which is the big one right there in the middle. But you look around, it's like body of water, body of water, body of water. So it's like the water. is already ready to take over. Yeah, it's like we're waiting. One day we will all join with one another. Bide your time, fellas. Our time is at hand. We have invited the oceans to join us. The oceans are on board. All we need now is time.
And they're resolved not to do anything. They're human stupidity. So that's a whole other coastline. Look at that. So that's a whole other coastline of the future. And so now you're going to look down on Earth and... There's nothing inherent about the existence of Florida on Earth's surface. That's my point. There you go. And there are other parts. We'll lose a lot of, in northern Canada, there's a lot of sort of low-lying lands. Almost all of the south Pacific Island nations.
are gone. They also have very low elevations. Get your vacations in now. Florida, as we said, we lose Florida. The Florida Keys, in fact, have even a lower elevation than Florida itself. So they're gone, and Ken is gone. We're gonna lose Ken. I think he hung out at the Florida Keys. Yeah, exactly. So anyhow, I just want to impress upon you that when we think of Earth, There's nothing inherent about the existence of land poking up above the existence of water.
Right. The water levels have changed over time, and they're changing now, and they're gonna redraw the map once again. Cool and not cool. Like it's a great novel thing to know and consider, but it's also terrifying that we, the difference is that was a natural. engineering of coastlines that you explained before that's a natural engineering of coastlines what we have now is a anthropomorphic engineering right and in fact
Like I said, we grew civilization on a stable climate and a stable coastline. And that took thousands of years before that to get to that point and stabilize out. And now on a timescale of decades. We're looking at maybe changing all of that. All of that. There you have it. All right. So Chuck, I don't mean to bum you out like that. I'm just saying. I'm so sad right now. I'm so sad. In fact, one last thing. It's neither here nor there. When we talk about how much water is on a body.
The way geologists refer to it is, how deep is the water if the water was the same depth everywhere on its surface? It's just a way to think about how much water is there. So if you take the water and spread it smoothly, And so, no, it's not filling in the low parts or trickling off the high parts. Just have it go everywhere. How much would it be? So you can say, well, how much water did Mars have? If you give an answer, it'll be in those terms.
It would have 50 feet of water or 1,000 feet of water or 10 feet of water. You'll just do this. conduct this exercise. When you do it, you learn things like Europa, one of Jupiter's moons, which is frozen on the outside and liquid underneath. You add up that liquid, it's more liquid than all the oceans on Earth.
Wow. And since all our evidence tells us life began in the oceans, that's why we can't wait to get our hands on that ocean to see if there's any life forms on Europa, which we would have to then call them. europeans europeans right because that's what you want to or we can just call them you know space white people What? They're Europeans. Oh, if they're Europeans. Don't. They're jokes. They're jokes, people. Stop it. So that's it. Chuck, that's yet another StarTalk explainer.
delivered to you from the Cosmic Crib. At the American Museum of Natural History, Hayden Planetarium. Neil deGrasse Tyson here, as always. Keep looking up.