Things You Thought You Knew

There are topics you might think you understand, but, do you really? Neil deGrasse Tyson and comic co-host Chuck Nice investigate the differences between mass, weight, and density, why ice floats, and how much you would weigh in space.

Speaker names marked ? are inferred from speaking time and the show’s known hosts — they are not voice-verified.

• 0:01Neil deGrasse Tyson?

  Welcome to StarTalk. Your place in the universe where science and pop culture collide. StarTalk begins right now. Welcome to StarTalk. I'm Neil deGrasse Tyson, you're a personal astrophysicist, and this episode features compilations of things you thought you knew. Each segment, along with my co-host Chuck Nice, we dive into a topic that you might think you understand, but do you really? What's the difference between mass, weight, and density, for example? Well, let's find out. Chuck, good to see you again.

• 0:44Chuck Nice?

  Good to see you. What's happening? What do we got? What's going on? I can't wait to hear.

• 0:49Neil deGrasse Tyson?

  I'm still at it. You know, I lose sleep at night thinking, "I gotta tell this to Chuck." Just so you know, I'm thinking about you.

• 0:55Chuck Nice?

  I don't believe that for one second. But I'll take it. I will take it.

• 1:02Neil deGrasse Tyson?

  I just gotta straighten some things out. I think that they... Some people, not everybody, but some people, I think, have this all confused, and I want to straighten it out.

• 1:12Chuck Nice?

  All right.

• 1:13Neil deGrasse Tyson?

  It's the difference between mass, weight, and density.

• 1:16Chuck Nice?

  All right. Well, okay. Now, without a doubt, there is a lot of people that get that confused.

• 1:22Neil deGrasse Tyson?

  Okay, so generally, if you go on a diet, you want to lose weight, right?

• 1:27Chuck Nice?

  Absolutely.

• 1:28Neil deGrasse Tyson?

  So it's not what's actually happening. It is, but it's not the root of what's happening. What you're really doing is you're losing mass. You want there to be less of you tomorrow than there is today.

• 1:41Chuck Nice?

  If only I could keep the parts that I want.

• 1:45Neil deGrasse Tyson?

  If you consume fewer calories today than you burned calories today, you will lose weight. Okay? It's that simple.

• 1:58Chuck Nice?

  Okay.

• 1:59Neil deGrasse Tyson?

  And I joked about this. A weight-loss book written by a physicist would have one sentence. Consume calories at a slower rate than you burn them. That's the entire, that's it. But so if tomorrow you want less of you than there is today, you're losing mass.

• 2:17Chuck Nice?

  Okay.

• 2:17Neil deGrasse Tyson?

  The mass is the sum of all the particles that comprise Chuck.

• 2:22Chuck Nice?

  Okay.

• 2:23Neil deGrasse Tyson?

  That's your mass. I could take you and put you on the moon, you'll weigh less. But you still have all of your particles.

• 2:31Chuck Nice?

  Okay, then that is where I need to move. When can we do this?

• 2:35Neil deGrasse Tyson?

  So if you weigh 180 pounds, I don't know how much you weigh, but let's call you 180 pounds on Earth.

• 2:40Chuck Nice?

  Okay.

• 2:40Neil deGrasse Tyson?

  On the moon, you weigh one-sixth of that.

• 2:42Chuck Nice?

  Right.

• 2:42Neil deGrasse Tyson?

  So you weigh 30 pounds.

• 2:44Chuck Nice?

  Ah.

• 2:45Neil deGrasse Tyson?

  So Chuck, you want to lose 150 pounds? Your nutrition will say, "No, Chuck, you'll die." "No, I'm just gonna go to the moon for a day, weigh myself, I'm 150 pounds." So your weight is not itself the measure of how much mass you have.

• 2:59Chuck Nice?

  Okay.

• 3:00Neil deGrasse Tyson?

  All right, you also weigh a little less at the top of a mountain because you're farther away from the center of the Earth than you do in Death Valley, where you're at a low point relative to other places on Earth.

• 3:12Chuck Nice?

  So if you get on a scale at the top of Everest, you're gonna weigh less than you would on that same scale in Death Valley?

• 3:18Neil deGrasse Tyson?

  In Death Valley, correct.

• 3:19Chuck Nice?

  Okay.

• 3:20Neil deGrasse Tyson?

  People at the equator weigh a little less than they would if they're visiting Santa Claus.

• 3:27Chuck Nice?

  Oh, that's because there's a lot of sun down there and they gotta stay in bikini shape all year long.

• 3:32Neil deGrasse Tyson?

  That's why, right.

• 3:33Chuck Nice?

  That's really what it's about.

• 3:35Neil deGrasse Tyson?

  So, so the equator is, the speed at which you are moving is faster than at other latitudes. People on the equator are moving about 1,000 miles an hour. We here in New York, we're moving about 800 miles an hour. So that centrifugal force makes them lighter than we are.

• 3:51Chuck Nice?

  Got you.

• 3:52Neil deGrasse Tyson?

  So all of this is affecting your weight, but it's not affecting your mass.

• 3:55Chuck Nice?

  Mm-hmm.

• 3:56Neil deGrasse Tyson?

  Okay, so if you want to lose weight in any zone, then lose mass.

• 4:02Neil deGrasse Tyson?

  All right, just to be clear about that. All right. So weight loss programs are actually mass loss programs. Okay, and so weight then is about forces then. Correct. It's not about. It's the definition of weight. Weight is the force of gravity on you. Well, whose gravity are we talking about? Earth, or the sun, or Venus, or the moon? So you find out what are the conditions of that force of gravity on you in that place? Not only among planets, but even different places on Earth. And then you've got your weight. And that weight is related to how many molecules of chuck exist. But in the end of the day, if you want to weigh less, what you really mean is you want less mass.

• 4:46Neil deGrasse Tyson?

  You want less chuck tomorrow than you had today. So just want to put that out there. Something better, right. Everybody can agree on that. Less chuck tomorrow. Less chuck tomorrow.

• 4:57Neil deGrasse Tyson?

  It's like, we don't show you the mails we get. When will Chuck disappear?

• 5:05Neil deGrasse Tyson?

  We withhold those from you Chuck. Right. Okay, so now, we talk about how heavy something is. Okay? Okay. So when we think of something floating on water, generally the idea of it being heavy is not, that's not the same thought, correct? No, of course. If it's heavy, it sinks. Okay. So now, let's take, let's take,

• 5:31Neil deGrasse Tyson?

  you know, let's go to, who's the guy who splits wood sections into firewood? Lumberjack. Whatever that is, okay? Go take one of these. Paul Bunyan guys. Paul Bunyan cylinders of wood. Mm hmm. Okay, it's gonna be really heavy, we know this. Take it, clunk it down in a swimming pool. What happens to it? It floats. It floats! Even though it's super heavy. Okay, it is heavy, but it floats. Right. Okay, so how do you get around that? What do we, let's give more examples of that, okay? Um. Ivory soap. Nobody, what?

• 6:17Neil deGrasse Tyson?

  Yes, Ivory soap floats. Right. And as far as I know, it's the only soap that floats. I did an experiment when I was younger. Oh, really? Lately, but I did test this. Yeah, Ivory soap floats, all the others. Sink. Sink, okay. So, why that should be a selling point, I don't know. But in its day, it was a selling point. And then it was, it was eighty-eight one hundredths percent pure. Right. And it was like, pure what? Right, exactly. You know, I, I remember thinking that as a kid, but Ivory soap long predates me, but I remember thinking all of that. All right, so, heavy cream

• 6:55Neil deGrasse Tyson?

  is lighter than skim milk. Heavy cream is lighter than skim milk. And you know why? Because it floats on the skim milk. That's how you get skim milk. There you go. The cream floats to the top. Rises to the top, you skim it off, you got some heavy cream. So we say it's heavier, but we don't really mean heavier. Heavy, to me, is the absolute weight. How heavy is it? Can I pick it up? What we mean is thinner. With, with, no, it's not thinner. Well, it's more, it's not as viscous. Less dense. Okay, vis- viscosity is, no, I should have added that. We'll get to viscosity in a minute. Okay. Heavy cream is less dense than water, than, than skim milk. Right. If you are less dense than something else, you float.

• 7:40Neil deGrasse Tyson?

  There you go, there it is. Nothing else. Nothing else matters, right. Okay, you will float. So, heavy cream is, we would say it's lighter than skim milk, but that's a little deceptive. If you want to be precise, you say it's less dense than skim milk. Yeah, you do. Before it floats. Okay, so, this is the fight I, wasn't a fight, the encounter I had in a Pasadena coffee shop when I ordered hot chocolate with whipped cream, and the hot chocolate came, and there was no whipped cream anywhere to be found, and I said, um, server, where is the whipped cream? They said, oh, we put it on. I said, where is it? Oh, it must have sunk to the bottom. At which point I said, either you are lying,

• 8:25Neil deGrasse Tyson?

  or the laws of physics that apply to the rest of the universe do not apply in your coffee shop. And so he got all gruffy and indignant, and he went by and brought cream with him. Okay, and then plunked it down, and it took one bob and sort of, and it floated. I said, "Thank you for my whipped cream." Mm-hmm. Now, I don't know if that became like a story, you know, because I'm sure waitstaff tell stories. Right. But that's what happened. So he's thinking it's heavy, it probably fell to the bottom, and would choose to lie, rather lie about it, thinking that I didn't know what the hell I was talking about. And when you took it away, you looked at him and you went, "Science bitch."

• 9:08Neil deGrasse Tyson?

  You just got scienced. You just got scienced. Scienced. Um, so, a couple more things about weight, mass, and density. So, um, you realize that logs float, all right? Right. So if you're gonna say, "If I want it, but I don't float very well," all right? So if I want to float on the water, I'm gonna use a log. So why don't I get a big log and then hollow it out? Okay. These are the first canoes. Right. Okay, the canoes are made of wood, you know the canoe's gonna float. I'm gonna get in it, and we're good to go.

• 9:52Neil deGrasse Tyson?

  Well, why don't you make a boat out of steel? Well, I can't do that because the steel will sink. That's not a boat. That's not gonna work. No, let's be clever about it, okay? By the way, if you make a boat out of steel, it's then impervious to the weapons of other boats. Oh my gosh, what a military advance this would be. This in the 19th century, I think it was, where the first people figured out, "I can make a boat out of things that are impervious to cannonballs." Right. And so, whereas I'd make a boat out of wood, then it just busts through the wood. Right. So, what matters is not the density of the material. What matters is the density of everything that is sitting below water. Ah.

• 10:36Neil deGrasse Tyson?

  So, if I create a hull...

• 10:41Neil deGrasse Tyson?

  Only the outer edge of the hull is made of steel. What's everything else inside the hull made out of?

• 10:47Chuck Nice?

  Something else. No.

• 10:51Neil deGrasse Tyson?

  Air.

• 10:52Chuck Nice?

  Air.

• 10:53Neil deGrasse Tyson?

  Air.

• 10:54Chuck Nice?

  It's like a ballast.

• 10:56Neil deGrasse Tyson?

  Okay, no, no, ballast has a different purpose.

• 10:58Chuck Nice?

  Right.

• 10:58Neil deGrasse Tyson?

  Stabilize.

• 10:59Chuck Nice?

  Stabilize.

• 11:00Neil deGrasse Tyson?

  Okay, so you put some other, you put some heavy things just at the very bottom of the hull.

• 11:04Chuck Nice?

  And that keeps it in position.

• 11:05Neil deGrasse Tyson?

  And that keeps, that keeps, that keeps it in position. That'd be ballast.

• 11:08Chuck Nice?

  Okay.

• 11:09Neil deGrasse Tyson?

  And a lot of the cobblestone in Lower Manhattan that built the roads was ballast in ships that came from Europe. Okay, and then they offload that and build, build roads with it.

• 11:19Chuck Nice?

  Sweet.

• 11:20Neil deGrasse Tyson?

  Yeah, yeah, so, a lot of it, and other things as well, but. Point is, you, so now, the, the density is, what is the total mass? Divided by the total volume. Okay, so density is grams per cubic centimeter, or pounds per cubic inch. That's, that's, so those are the units of density. So let me get some units out there. So we've got the units of mass are grams and kilograms. And I'm not going to tell you the unit of mass for the English system. Okay. Um, and the unit, you're supposed to say, why not? Tell me.

• 11:58Chuck Nice?

  Why not?

• 12:01Chuck Nice?

  No, so seriously, what is, what, why wouldn't you give out the?

• 12:05Neil deGrasse Tyson?

  Okay, the unit of mass in the English system is slug.

• 12:10Chuck Nice?

  No.

• 12:11Neil deGrasse Tyson?

  Yes, that's why I told you, I told you not to ask me. So, so, so the mass, grams, kilograms, this sort of thing.

• 12:17Chuck Nice?

  That's it.

• 12:17Neil deGrasse Tyson?

  Volume is the cubic of some, of some length. So cubic inch, cubic centimeter, cubic meter, those are volumes. Density is the mass divided by the volume.

• 12:27Chuck Nice?

  Mass divided by volume.

• 12:28Neil deGrasse Tyson?

  Okay, so just see how that works. So if I have a certain amount of mass and I put it in a smaller and smaller volume.

• 12:33Chuck Nice?

  It becomes more and more dense.

• 12:34Neil deGrasse Tyson?

  Yeah, yeah, so what happens if, if the denominator gets smaller? Then the number gets bigger.

• 12:39Chuck Nice?

  It's bigger.

• 12:40Neil deGrasse Tyson?

  So we get a higher and higher density. Cause you're cramming all of this into a smaller volume.

• 12:43Chuck Nice?

  Right.

• 12:44Neil deGrasse Tyson?

  The volume gets bigger and bigger and bigger for the same amount of mass.

• 12:47Chuck Nice?

  Right.

• 12:47Neil deGrasse Tyson?

  Then the density gets lower and lower and lower. You get beach balls and other things.

• 12:51Chuck Nice?

  Right, you're spreading it out.

• 12:52Neil deGrasse Tyson?

  Spreading out. So what I've done with the steel is I've put air in between the two steel sides of the boat. So now the density, the effective density is the mass of the steel plus the mass of the air divided by the volume. And when I do that, I get something that's less dense than water.

• 13:11Chuck Nice?

  Right.

• 13:11Neil deGrasse Tyson?

  The whole thing floats.

• 13:12Chuck Nice?

  So then it go, it will only go down a certain amount in the water.

• 13:15Neil deGrasse Tyson?

  A certain amount.

• 13:16Chuck Nice?

  That's it.

• 13:16Neil deGrasse Tyson?

  That's it. And it, but it will float.

• 13:19Chuck Nice?

  Wow.

• 13:19Neil deGrasse Tyson?

  So that's how you make boats out of steel and that's how military ships were first put together.

• 13:25Chuck Nice?

  I mean, cool.

• 13:25Neil deGrasse Tyson?

  The, the, the indestructible type. Right. So then you needed a weapon that can destroy the steel and then you have the, the eternal contest of warring.

• 13:33Chuck Nice?

  Arms raised.

• 13:34Neil deGrasse Tyson?

  Arms raised.

• 13:35Chuck Nice?

  Yeah.

• 13:36Neil deGrasse Tyson?

  Exactly. So, so there, there you have it, Chuck. So, so we have mass density. So anything that floats on water is simply less dense than water.

• 13:46Chuck Nice?

  Right.

• 13:46Neil deGrasse Tyson?

  It doesn't matter how much it weighs.

• 13:47Chuck Nice?

  Or what it is. It just has to be less dense than water.

• 13:51Neil deGrasse Tyson?

  Does, nothing else matters.

• 13:53Chuck Nice?

  Wow, that's cool.

• 13:54Neil deGrasse Tyson?

  And it could weigh a zillion pounds and it'll just, it'll still float.

• 13:57Chuck Nice?

  Which is why my Uncle Edward floats.

• 14:04Chuck Nice?

  That's a big man. That's a fat brother, I'm telling you right now.

• 14:07Neil deGrasse Tyson?

  Oh, he's a big and fat buddy float. Well, so, so fat is less dense than, than water and bones and muscle is more dense. So if you float every time, you just have way more fat than muscle and bone.

• 14:18Chuck Nice?

  Well, there you have it. Good for you, Uncle Eddie.

• 14:23Neil deGrasse Tyson?

  That's why it's no accident that, that marine mammals have a lot of fat.

• 14:29Chuck Nice?

  Right.

• 14:29Neil deGrasse Tyson?

  Okay, the blubber, like as they call it, right?

• 14:32Chuck Nice?

  Yes, huh?

• 14:32Neil deGrasse Tyson?

  So there's a lot of fat there and that gives them buoyancy in the water.

• 14:36Chuck Nice?

  Yes.

• 14:37Neil deGrasse Tyson?

  All right. Oh, by the way, what's an ice cube made out of?

• 14:40Chuck Nice?

  Water.

• 14:41Neil deGrasse Tyson?

  But why do they float?

• 14:43Chuck Nice?

  Because they have air inside of them. I don't know.

• 14:45Neil deGrasse Tyson?

  No. Well, sometimes they do, but that's not.

• 14:47Chuck Nice?

  Oh, no. They expand.

• 14:49Neil deGrasse Tyson?

  They expand. It's less dense than water.

• 14:50Chuck Nice?

  Right. So it's less dense than water.

• 14:52Neil deGrasse Tyson?

  The water it used to be now takes up more volume.

• 14:54Chuck Nice?

  Right.

• 14:55Neil deGrasse Tyson?

  So bigger volume makes it less dense. So ice floats.

• 14:57Chuck Nice?

  There you go.

• 14:58Neil deGrasse Tyson?

  You know, we should do an explainer on ice expanding. We should do that.

• 15:01Chuck Nice?

  All right. Well, looking forward to ice expanding then.

• 15:04Neil deGrasse Tyson?

  Okay. Thanks for doing this with me, Chuck.

• 15:06Chuck Nice?

  Of course. Always a pleasure.

• 15:08Neil deGrasse Tyson?

  We got to take a quick break, but when we come back, we're going to talk about, you guessed it, ice expanding, why ice floats on StarTalk. It's Things You Thought You Knew Edition. We'll see you in a moment.

• 15:37Speaker 02

  I'm Joel Cherico, and I make pottery. You can see my pottery on my website, cosmicmugs.com. Cosmic Mugs, art that lets you taste the universe every day. And I support StarTalk on Patreon. This is StarTalk with Neil deGrasse Tyson.

• 16:03Neil deGrasse Tyson?

  Chuck, we're back.

• 16:04Chuck Nice?

  Yes, we are.

• 16:06Neil deGrasse Tyson?

  And this was interesting. There are certain things that we just experience in our lives and never even think to question it.

• 16:13Chuck Nice?

  True.

• 16:13Neil deGrasse Tyson?

  Because it's in our everyday life.

• 16:16Chuck Nice?

  And, and, and, and some things you don't want to know the answer.

• 16:19Neil deGrasse Tyson?

  You don't want to know the answer. That's different.

• 16:21Chuck Nice?

  Some things you just like.

• 16:23Neil deGrasse Tyson?

  Best left unexplained, unknown.

• 16:24Chuck Nice?

  No, I'm not, I'm not going to mess with this.

• 16:26Neil deGrasse Tyson?

  Not going to go there. No, no. This one, you ask a simple question. Why does ice float?

• 16:32Chuck Nice?

  Right.

• 16:32Neil deGrasse Tyson?

  Have you ever asked that?

• 16:35Chuck Nice?

  I have.

• 16:36Neil deGrasse Tyson?

  You have? Okay.

• 16:37Chuck Nice?

  I have. Yeah. I mean, because when you think about it, it's water, but you're putting it in water.

• 16:43Neil deGrasse Tyson?

  Yeah.

• 16:43Chuck Nice?

  It's liquid.

• 16:43Neil deGrasse Tyson?

  It's water in water. Right.

• 16:45Chuck Nice?

  It's water in water. So.

• 16:46Neil deGrasse Tyson?

  And usually when you cool something down, it shrinks. Okay? It becomes more dense.

• 16:53Chuck Nice?

  Tell me about it.

• 16:57Neil deGrasse Tyson?

  So it becomes more dense. And so you would think that a cooler version of some liquid would be, you know, if you shrink the same mass down to a smaller volume, it's more dense, then all ice cubes would sink to the bottom of your glass.

• 17:14Chuck Nice?

  As a matter of fact, in certain parts of the oceans, I'm gonna, where you have what they call, um, oh, God, now I forget the name of it. It just, it was just on the tip of my tongue. But the coldest water stays at the bottom of the ocean.

• 17:33Neil deGrasse Tyson?

  Yeah, we're not there yet.

• 17:35Chuck Nice?

  Oh, we're actually gonna talk about that?

• 17:37Neil deGrasse Tyson?

  Yes.

• 17:38Chuck Nice?

  Oh, we are?

• 17:39Neil deGrasse Tyson?

  No, yeah.

• 17:40Chuck Nice?

  Oh, sweet.

• 17:41Neil deGrasse Tyson?

  Oh, my gosh, we're totally going there. Okay.

• 17:43Chuck Nice?

  Forget about that. Okay, all right.

• 17:45Neil deGrasse Tyson?

  All right, so, so a peculiar thing happens to water when it changes state. Okay, a change of state means you go from liquid to solid, solid to gas. So we have water, and there it is. When it freezes, the water molecule, in order to freeze, takes up more volume than does the water molecule in a liquid state. So the water expands by about 10%.

• 18:13Chuck Nice?

  Nice.

• 18:14Neil deGrasse Tyson?

  Okay, and roughly you can think about that as if you are, if you expand 10% and you go back into your liquid, you will bob with about 10% of your volume above the water.

• 18:26Chuck Nice?

  Okay.

• 18:27Neil deGrasse Tyson?

  And 90% below. So just put, put an ice cube in your glass. It's easier to see this if it's in a cube shape rather than in those crescent shapes or other things. But if you take a cube and put it in there, 10% will be above the water and 90% will be below.

• 18:41Chuck Nice?

  All right, hold on. I just happen to have a glass of water here.

• 18:45Neil deGrasse Tyson?

  Oh, you do? And are your, is your ice in it? Are they cubes?

• 18:48Chuck Nice?

  Oh, my goodness, look at that. That's awesome. Yes, this is a cube.

• 18:51Neil deGrasse Tyson?

  Okay.

• 18:52Chuck Nice?

  And you're, and you just see it's got like a little surface. You can't see it, but it's got a little surface because the top part is clear. I don't know why. But it's just like you said.

• 19:02Neil deGrasse Tyson?

  It's like, it's bobbing up. Yeah, it's.

• 19:04Chuck Nice?

  Bobbing, but most of it is below.

• 19:07Neil deGrasse Tyson?

  Yeah, so Chuck.

• 19:07Chuck Nice?

  A little bit above.

• 19:08Neil deGrasse Tyson?

  It's not happening because I said so. It's happening because this is how the universe works.

• 19:13Chuck Nice?

  No, it's, no, you're a wizard.

• 19:16Neil deGrasse Tyson?

  Stop lying!

• 19:19Neil deGrasse Tyson?

  Now, here's an interesting fact. If you take that same glass of water with that one ice cube in it and fill it as much as you possibly can, so that not another drop can go in it without spilling over the edge. Right. If you do that, okay, the ice will be sitting above that level, above the lip of the glass. Right. And you might be worried, "Oh, my gosh, I better get a coaster, because when this melts, it's gonna overflow."

• 19:49Neil deGrasse Tyson?

  But no, when it melts, it's gonna take up the volume that it's already displacing in the water itself, and it's not gonna get any higher than it currently is. Right. This is why the Arctic ice sheets, in the Arctic, so where Santa Claus is. Right. It is ice that is floating on the water.

• 20:12Neil deGrasse Tyson?

  In the future, where global warming melts the entire northern cap, when that happens, it will not, that alone will not increase the sea levels of the world, because the ice is already floating in the bathtub of that water. That's correct. So, the ice you need to worry about is the ice that's on land. Oh, that runoff. The runoff, okay, that ice. You melt that, you're directly adding water content that's on Greenland and primarily Greenland and Antarctica. So that then starts flooding the oceans and raising, raising the sea levels. Okay, so now... By, by the way, 232 feet if that were to happen. Oh, thank you for that number.

• 20:55Neil deGrasse Tyson?

  Yeah, I think I tweeted once that if you, if you do that, then the water level will go up to the left elbow of the Statue of Liberty. Yeah. The one that's holding, I think it's the Declaration of Independence, just in her arm. And, yeah, and that, basically, you lose Manhattan and basically every other coastal city of which, where you find most of the great cities of the world are on the water's edge. So, anyhow, so, so, so that's why ice floats, but there's more going on here. You could delay the freezing of the ice. It freezes at 32 degrees or 0 degrees Celsius. You can make it freeze at like 1 degree below 0 if you put it under pressure. Okay, yeah. So it gets colder and it says, "I wanna freeze, I have to get bigger, I have to get bigger, I'm not letting you."

• 21:37Neil deGrasse Tyson?

  So then it doesn't, it doesn't change the state, okay? But if you keep taking the temperature lower and lower... Under pressure, the ice says, the ice says, "Bleep it." Okay? And I will expand no matter what you're doing, and boom! Pipes break. Yeah. Okay, so- I don't know why I'm ha- I don't know why I'm so happy about that. I'm a homeowner. What am I talking about? That's disastrous! You're happy that you now understand the full dynamics of that? So it would be very hard for ice at 32 degrees to break a pipe. Because the pipes are made of typically, they're made of copper or some strong metal. And so it'll keep it squeezed down. And it say, "No, you're not freezing at 32."

• 22:20Neil deGrasse Tyson?

  "No, I'm not gonna let you freeze at 30 degrees." "No, not at 29." "Oh, 25 degrees, pow." And it is stronger than the pipes. And you just break the pipes. And, by the way, at that moment, all the pipes are frozen. There's no leakage. When do you have leakage? When the temperature goes up again, and then the ice melts out of the path, and then the water flies. Ugh. So the act of broken pipes, in most cases, is not the moment where you get the leak. Because the ice is there. The ice is there plugging the pipes. It's later on when the ice moves out of the way. So, so this is the power of freezing ice.

• 23:04Neil deGrasse Tyson?

  Now, last point I wanna make is, well, how about the density of water just as water? Does it change density? Yes, it does. Okay? As you cool water, it takes up slightly less and less volume. Hardly noticeable if you're just swimming in it, or just looking. And if you heat water, it takes up slightly more volume. And a lot of the increased sea level rise in the future of global warming is simply because the oceans are warmer. And they're warmer, they take up, you know, let's say it's 1% more depth. Right. But you come, but what is 1% more depth in the middle of the ocean where it's 3 miles deep? Okay? If it's 1% more depth, by the time you get to the shoreline, you have flooding. Right.

• 23:49Neil deGrasse Tyson?

  So, let's cool the water. It gets colder and colder and colder, it begins to shrink. Well, at some point, that has to turn around, because eventually, it's gonna become ice. Where it's bigger. There is a point where ice is at its densest. And it's 3 degrees Celsius.

• 24:07Chuck Nice?

  Really?

• 24:08Neil deGrasse Tyson?

  Okay, so you cool water at the surface. It's denser than the water below it, and so that cool water drops and it goes to the bottom. Okay? And it stays there. You keep trying to cool water at the top and it goes down to the bottom. But what happens now you're cooling water, now the water is two degrees Celsius or one degree Celsius. It begins to stay on top. Then it hits zero degrees Celsius. It freezes on top.

• 24:37Chuck Nice?

  On top.

• 24:38Neil deGrasse Tyson?

  Keeping the three degree water at the bottom.

• 24:41Chuck Nice?

  Right.

• 24:43Neil deGrasse Tyson?

  Preserving all aquatic life over the winter time.

• 24:49Chuck Nice?

  That's why you don't have bird's eye frozen fish once the, uh, once the lake freezes.

• 24:55Neil deGrasse Tyson?

  Just think about it, if ice sank. Oh my gosh, you would freeze lakes from the bottom up. You'd freeze the top layer, we'd go to the bottom and slowly but surely all the fish would be swimming in an ever thinner layer of water. Until you just go and scoop them all up and that's the last fish that would ever exist in that lake.

• 25:14Chuck Nice?

  Oh, what a, what a bear's dream.

• 25:15Neil deGrasse Tyson?

  So, no, they're hibernating, they're missing this.

• 25:19Chuck Nice?

  That's true, yes.

• 25:20Neil deGrasse Tyson?

  So, so this feature of water protects life over the winter, aquatic life over the winter.

• 25:30Chuck Nice?

  Wow.

• 25:31Neil deGrasse Tyson?

  And once you form the ice layer on the top, it actually insulates the bottom. You get really cold on top, but that does that, how long will that take to transmit through a thick layer of ice? It takes a long time by then, it's daytime compared to night where spring has come. And so you rarely, if ever, do you end up freezing an entire lake. And it's because of this property of water that ice floats. The ice is less dense than water.

• 25:55Chuck Nice?

  That is amazing and it's, it's pretty cool that this, this becomes like its own little closed ecosystem where the ice freezes on top, insulates the water beneath it so that all the life is protected.

• 26:10Neil deGrasse Tyson?

  It's protected.

• 26:11Chuck Nice?

  That's amazing.

• 26:12Neil deGrasse Tyson?

  It's, it's basically, so this is a feature of this fact about water, the water molecule. One other thing, it's what enables you to ice skate. Okay, because the reverse is true. So I, if I have an ice cube and it's sitting at, let's say 30 degrees. Okay?

• 26:27Chuck Nice?

  Right.

• 26:27Neil deGrasse Tyson?

  And it's frozen, so minus one, let's say Celsius. If I squeeze it, if I squeeze it. Under pressure, I'm trying to put it into a smaller volume.

• 26:37Chuck Nice?

  Mm-hmm.

• 26:37Neil deGrasse Tyson?

  Ice won't let you do that.

• 26:39Chuck Nice?

  Right.

• 26:40Neil deGrasse Tyson?

  But if I press it really hard, what's the only way the ice can respond to you to go into a smaller volume?

• 26:47Chuck Nice?

  It's gotta become water.

• 26:48Neil deGrasse Tyson?

  It's gotta become water. So you can squeeze melt something even at sub-freezing.

• 26:53Chuck Nice?

  Oh my god! That's... That's how you get the great ice cube... no, no, ice spheres for drinking scotch. What you just said, they take a copper press and... I'm too excited about this, I'm sorry.

• 27:07Neil deGrasse Tyson?

  Is this bar information that you're sharing?

• 27:11Chuck Nice?

  I know, I know. Now we're talking about scotch and drinking. I'm like, oh my god!

• 27:16Neil deGrasse Tyson?

  And you don't even have your scotch voice today.

• 27:18Chuck Nice?

  I know, exactly, yeah, exactly.

• 27:22Neil deGrasse Tyson?

  You want to know this guy?

• 27:22Chuck Nice?

  Definitely need a little scotch, that's what I'm saying.

• 27:27Neil deGrasse Tyson?

  Wait, wait, let me just finish this point.

• 27:30Chuck Nice?

  Go ahead.

• 27:31Neil deGrasse Tyson?

  So, um, when you're skating on ice, okay, the blade is the way it's sharpened is... It has very sharp edge on one side and on the other. On the left and on the right-hand side. So you go on an edge and skaters know about this, on the inside edge or on the outside edge, that is a lot of pressure. That pressure is so high that it actually melts the ice in place. And the skate glides on a bead of water.

• 27:56Chuck Nice?

  Wow, that's great.

• 27:57Neil deGrasse Tyson?

  That's why ice is slippery on ice skates.

• 28:00Chuck Nice?

  Um, yeah. So, so, yeah, I mean, that same premise you just demonstrated. When you get a... they make spheres of ice for drinking scotch.

• 28:10Neil deGrasse Tyson?

  Ice spheres, yeah.

• 28:11Chuck Nice?

  Ice spheres. And they use, for some reason, copper, I don't know why, but they use copper or brass, one or the other. And they just put the ice in the sphere and they let the brass... it's a big weight. It's a brass weight or a copper weight and it just... presses down on the ice and then the ice melts into a ball. That is so cool.

• 28:33Neil deGrasse Tyson?

  Oh, okay. So they take, okay, so shaping the sphere from the pressure on a shape that's not a sphere.

• 28:41Chuck Nice?

  That's right.

• 28:41Neil deGrasse Tyson?

  Okay, yeah, so under pressure, yes, it will melt, under pressure.

• 28:44Chuck Nice?

  It melts.

• 28:44Neil deGrasse Tyson?

  Yet, yet, when you relieve the pressure, it freezes instantly.

• 28:47Chuck Nice?

  It freezes right back.

• 28:48Neil deGrasse Tyson?

  Because it's the, it's the below freezing temperature that you started with.

• 28:52Chuck Nice?

  Exactly. And then you just have a big, a literal ball of ice.

• 28:55Neil deGrasse Tyson?

  Okay, Chuck, I don't go to many bars. I've never seen this. I trust that in your bar hopping, this is something feature.

• 29:02Chuck Nice?

  I'm gonna have to, I'm gonna have to get you out, man.

• 29:04Neil deGrasse Tyson?

  I gotta get out more often.

• 29:06Chuck Nice?

  I'm gonna have to get you out of the house.

• 29:08Neil deGrasse Tyson?

  All right, so that's, that's it, Chuck. That's, ice is less dense than water.

• 29:13Chuck Nice?

  Nice. I'm always fascinated how we end up in these great places from something so seemingly mundane as a cube of ice or ice melting.

• 29:26Neil deGrasse Tyson?

  The next time we do this, we gotta do this with one of your spheres of ice. And I want to do a whole video with you and your Scotch voice.

• 29:31Chuck Nice?

  Okay. Oh, absolutely. Not a problem. Not, I'll start on it right now.

• 29:38Neil deGrasse Tyson?

  Right now. We got this.

• 29:47Neil deGrasse Tyson?

  Okay, okay. Next on StarTalk's Things You Thought You Knew Edition, we're gonna talk about the concept of weight in space. We'll see you in a bit.

• 30:10Chuck Nice?

  It's time to give a Patreon shout out to the following Patreon patrons. Christopher Sukanena, Dmitri Pukachevich, and Ingenio Barrera. Thank you so much, guys, for your support. Without you, you know, we couldn't do this show. And for those of you listening who would like your very own Patreon shout out, please go to patreon.com/starTalkRadio and support us.

• 30:43Chuck Nice?

  Okay Neil, here's one for you.

• 30:45Neil deGrasse Tyson?

  Okay, okay.

• 30:46Chuck Nice?

  Okay, alright. In space, how much does an astronaut weigh?

• 30:54Neil deGrasse Tyson?

  You see, weight is not what you think it is. You remember when we talked about mass versus weight? Do you remember that?

• 31:01Chuck Nice?

  Right.

• 31:02Neil deGrasse Tyson?

  We talked about that. And I said, "You wanna weigh less? Go to the top of a mountain." You'll burn calories getting up there, so you'll get... You'll lose a little bit of weight for that, but at the top of a mountain, you're farther away from Earth's center. And you run the math, you weigh a little bit less. An ounce, nothing significant, nothing large, but a measurable amount.

• 31:23Chuck Nice?

  Right. It's not gonna replace your P90X workout.

• 31:27Neil deGrasse Tyson?

  Exactly, thank you.

• 31:31Neil deGrasse Tyson?

  Not only that, you don't weigh as much in air as you would in a vacuum. Okay? Because air has a buoyant force that makes you weigh a little less than you would if there was no air around you. We don't even think about that. That doesn't even... But a helium balloon knows everything about that.

• 31:50Chuck Nice?

  Right, that's so funny, yeah.

• 31:52Neil deGrasse Tyson?

  You remember that, right? A helium balloon cares what the buoyant force of the air is on it, because it wants to float at the top of the air. Okay. So I ask you, you know, what do you weigh when you're in the water? If I say, "Chuck, what do you weigh?", and you'll probably give me your weight on dry land.

• 32:09Chuck Nice?

  Right.

• 32:09Neil deGrasse Tyson?

  But your weight in the water, since you're about the density of water, your weight is basically zero.

• 32:15Chuck Nice?

  Really?

• 32:16Neil deGrasse Tyson?

  Some people float, some people sink, and on average, people just sort of bob there. That means you weigh nothing. You're weightless in the water. In fact, NASA trains astronauts in a huge swimming pool to simulate what it'd be like to be weightless in space. Do you realize there's a swimming pool big enough to submerge an entire mock-up of the Hubble Space Telescope? And to put in astronauts in there with tools to work on it.

• 32:44Chuck Nice?

  Okay, that's the pool I want. I want to swim in.

• 32:46Neil deGrasse Tyson?

  That's a badass pool. I think it's the biggest swimming pool in the world, actually.

• 32:50Chuck Nice?

  Yeah, that that pool is dope, okay?

• 32:52Neil deGrasse Tyson?

  Yeah.

• 32:53Chuck Nice?

  And it's, and I'm sure it's more than three feet, because...

• 32:57Neil deGrasse Tyson?

  But there's no diving board.

• 32:58Chuck Nice?

  Right, yeah. Only there was a diving board, that pool would be amazing.

• 33:02Neil deGrasse Tyson?

  Let me dive down the tube of the Hubble telescope.

• 33:05Chuck Nice?

  And if they had a water slide too, oh my god.

• 33:09Neil deGrasse Tyson?

  So, here's the thing. When we think of the blue whale, for example, the largest animal there ever was. By the way, point of pride, blue whale is a mammal, okay? So mammals have the record. They're bigger than dinosaurs ever were. We can say, well, how much does it weigh? And you look it up and you Google it, it'll give you a weight for that whale, a full grown whale. But no, excuse me, that's if you took it out of the water, put it on land and put it on a scale.

• 33:39Chuck Nice?

  Right.

• 33:39Neil deGrasse Tyson?

  But that's not where it lives. That's not its environment. No.

• 33:43Chuck Nice?

  I'd like to see that scale.

• 33:45Neil deGrasse Tyson?

  You'd have to... You have to weigh it in the water, and when you do that, it weighs zero.

• 33:52Neil deGrasse Tyson?

  That's why whales can just hang there.

• 33:54Chuck Nice?

  Yeah, it's such a beautiful thing to see.

• 33:57Neil deGrasse Tyson?

  Okay, if they had weight in the water, they would sink.

• 33:59Chuck Nice?

  Right.

• 34:00Neil deGrasse Tyson?

  So they're just there. They're very close to zero. So they still have all the mass. So I'm saying, we don't really think of the word "weight" the way we ought to in a sort of physically significant way. That's, I just want to put that out there.

• 34:14Chuck Nice?

  Okay.

• 34:15Neil deGrasse Tyson?

  Whales weigh nothing in the water. And they don't hang out on land, so their weight on land is kind of irrelevant to us and to them. Okay? So really, we should find a way to think about how much mass they contain, rather than simply how much they weigh. And usually, that's what people mean when they say that.

• 34:31Chuck Nice?

  Right.

• 34:32Neil deGrasse Tyson?

  But I just want to try to be clear about that, physically clear about that.

• 34:36Chuck Nice?

  And whales are a lot of blubber, so, you know, muscle weighs more than fat, so probably not a lot of mass there.

• 34:43Neil deGrasse Tyson?

  No, no, it's a lot. No, there's still a lot of mass.

• 34:47Chuck Nice?

  There's still a lot of mass, I know. I'm just trying to, I'm just trying to not body shame the whale. I don't want to body shame the whale.

• 34:55Neil deGrasse Tyson?

  You're the one that said they got blubber. You started it.

• 35:00Neil deGrasse Tyson?

  All right, so now, astronauts in orbit weigh precisely zero.

• 35:10Neil deGrasse Tyson?

  Precise zero. Okay? And it's not because they're far away from Earth. As I've said in other, others of these, how far away is the astronaut from Earth in, in, they visit the space station? Three eighths of an inch above the, a schoolroom globe, if you shrunk it all down to that, be three eighths of an inch away. Right. That's close. It's a fingernail. Right, so, uh, finger, yeah, the width of your finger, uh, less even. Yes, less than, yeah. Yeah, yeah, so, so that's the distance. Right. So you can't tell me, oh, they're in space, they've left gravity. No, no, if you've left gravity by being in orbit, then what the hell is holding the moon in orbit? Okay? Right. What do you think the moon is orbiting? Of course, the moon feels Earth's gravity.

• 35:54Neil deGrasse Tyson?

  And, and it could also be, you know, the moon is kind of sweet on the earth, but so.

• 36:01Neil deGrasse Tyson?

  So, uh, and there was a, a, a, a, a well-known, uh, uh, news announcer back in the 1960s, who, when the Apollo astronauts were headed to the moon for the first time, they said, the Apollo astronauts, as of eight thirty this morning, like, whatever time it was, have officially left the gravitational pull of the Earth. It's like, no. They actually said that on, on this? Yes, yes, yes, yes. You can't leave the gravitational pull of the Earth en route to the moon if the moon is orbiting Earth. Right. Okay, so I don't think they thought that through. And in fact, in the equations, Earth's gravitational field gets less and less and less as you go out in space, but it never actually hits zero until you get to infinity. Okay?

• 36:46Neil deGrasse Tyson?

  So, you tell me when you get to infinity, call me and we'll talk.

• 36:52Neil deGrasse Tyson?

  So, uh, the reason why they're weightless has nothing to do with their distance from Earth. Uh, it has to do with the fact that they were falling towards Earth. Wow. Free fall. So I put you in an elevator shaft in a tall building and I cut, cut the cable. Right. Okay, no, I put you in the elevator, you're just standing there, right? So here we go, and you're standing on a scale that has a spring. So you're squeezing the spring and it shows your weight. But let's just be, use round numbers, say you're 200 pounds, okay? So there you are, the scale registers 200 pounds because you're squeezing the scale. Okay, gravity's pulling on you to squeeze the spring to indicate the, the measure. Okay, now, now I, now I cut the elevator cable.

• 37:30Neil deGrasse Tyson?

  Okay, so what now happens? The elevator drops. Right. The scale drops. Right. You drop. Right. All three of you are now falling at exactly the same rate. Right. So there is no net force of you on the spring. Right, there's, right. So while you are falling, you weigh zero. And the scale will say zero because it will not- The scale will say zero. Because there will be no compression to measure. Correct, and here's another measure of that. You ready? Let's say you're in an elevator and it's just standing there and you're holding, you know, from my professor angle, I say you're holding a piece of chalk, but no one holds chalk. So what are you holding?

• 38:15Neil deGrasse Tyson?

  Find a, you're holding a ball, okay? Okay. There you go. If you let go of the ball, it drops to the ground, right? Okay? Right. In fact, in fact, drop it is synonymous with let go. Because gravity does that work, right? The phrase drop it, you just let go. You could just say let go and it means drop it, all right? Because we live in a gravitational field, that- That doesn't work in a cop movie, though. It just sounds off. Sorry. Let go of the gun! Let, let go of the gun!

• 38:50Neil deGrasse Tyson?

  They do say drop it, though. They do say it. Yeah. All right. Unless you're black, in which case they just- That's a whole other thing, all right. Okay, let's go. So, so now what happened? Now I cut the elevator cable. Now you begin to fall. Now you're standing there, holding the ball. Now let go of the ball. Right. Well, you're falling. The ball is falling at exactly the same rate you are. So it'll appear to float in front of your face. Right, but really you're both- But it's not floating. Your boat is falling. Everybody's falling. But from your point of view, you're saying to yourself, wow, it's floating. I'm floating. I'm, you do this until you die, when the elevator hits the bottom. Right, exactly. It's a beautiful experiment until you're a pile of goo when the elevator hits the bottom. Yeah, and the ball survives, of course.

• 39:36Neil deGrasse Tyson?

  The ball bounces, yes. Right, you know. All right, so, so here's the deal, okay? I'm telling you the astronauts in orbit around the Earth are falling towards Earth. Right. In free fall, just like you in the elevator cable that I just cut. Right. All right, now the, now the reason why they don't hit Earth, because they have really fast sideways motion. So watch what happens, okay? Watch what happens. Here you are in an elevator, and you know you're gonna hit the ground and you're gonna die, okay? But I'm gonna say, alright, let's take this elevator and move it sideways really fast. Right. Well, how fast should it go? Let's move it sideways so fast, so by the time it drops a foot, let's say,

• 40:21Neil deGrasse Tyson?

  Earth has curved a foot away from it.

• 40:25Neil deGrasse Tyson?

  You drop five feet, Earth has curved five feet away from it. So whatever distance you have fallen, the curvature of Earth, because you're traveling so fast downrange, the curvature of the Earth Cancels it out. cancels it out. Wow. Precisely. That's perfect. And there's one speed for which that is true. And that is if you go sideways, five miles per second. Wow. On Earth. So you go sideways, five miles per second. At that speed, you will free fall to Earth at exactly the same rate Earth curves away from you. You will never hit Earth, and we have another word for this, because if you never hit Earth, this will just keep going.

• 41:10Neil deGrasse Tyson?

  Right, you just go right. You come back where you started and you keep going. We have a word for that. It's called orbit.

• 41:17Neil deGrasse Tyson?

  So orbit is free fall with high sideways velocity around the Earth. And that's why people say, oh, we launched the rocket into space today. What you really did was, have you ever watched a rocket more than just a couple of minutes after the launch pad? Yeah. Okay, what does it do? It's downrange. It starts to careen off, like. Most of the energy that's launching that rocket is not to get it into space. No, it's to give it that sideways motion at five miles per second so that it can sustain an orbit around the Earth. That's pretty dope. It's totally dope. And you know who first figured this out? My man. No, don't even say it. I- Isaac Newton?

• 42:00Neil deGrasse Tyson?

  My- my man, Isaac Newton. Okay? He drew a picture. He had Earth, okay, and he drew a little mountain, and he had a little, was it a cannon or something at the top of the mountain? He said, "What happens if you shoot the cannon out sideways, okay, and it just hits the ground? Suppose you give it more speed, it'll go farther before it hits the ground." Let's giving it more and more speed, and as you follow this diagram, the cannonball continues around the Earth but still hits Earth. Is there a speed where it goes all the way around the Earth, does not hit Earth, and it hits you in the back and ahead? But you duck, and the cannonball continues. Is there a speed for that? Yes. And he figured out what that speed is, and that's the speed of orbit around the Earth. And like I said, that's five miles per second. Wow.

• 42:44Neil deGrasse Tyson?

  Isaac Newton invented orbits with that simple diagram. And in so doing, he- he merged our understanding of falling objects with the orbit of the moon around the Earth. This was his revelation when he watched the apple fall. He didn't hit him on the head, by the way, that's the- he watched the apple fall straight down, and he sees the moon in orbit around the Earth. And he said, "This is exactly the same phenomenon." Wow. Except the moon is going sideways so that it doesn't hit the Earth. So the moon in Earth's gravity is weightless, because it's in free fall around the Earth. There you go. Wow, that's- that's amazing. Okay, so now, I just gotta- I gotta put this out there. The movie Ad Astra, okay? Yes, with, uh, Matt Damon. No, not Matt.

• 43:27Neil deGrasse Tyson?

  I'm sorry, sorry. Wait, don't tell me, don't tell me. Because that's the Martian. Get your leading man straight. Yeah, um, that's Brad Pitt going, looking for his dad, who was Tommy Lee Jones. Correct, correct. Okay, so, in that movie, um, they knew correctly that you don't have to wait three days to get to the moon. That's- that's like a, sort of a, a minimum energy transfer to the moon. Where you fire your rockets until you have enough to sort of get into the moon's pull, and then the moon pulls you down, so you use minimal fuel. But if you want to get there, you can get there in a few hours, you just use a lot of rocket fuel, okay? If your rockets are burning on your ship, you have weight on that ship.

• 44:14Neil deGrasse Tyson?

  Because it's accelerating towards you.

• 44:18Neil deGrasse Tyson?

  Right. Okay, that is no different from you having weight standing here on Earth. Because Earth, the force of gravity is that same phenomenon. Right. Okay, so if I go in a ship and I don't care where I am in the universe, if I'm accelerating the ship at 9.8 meters per second per second, that's the acceleration of gravity on Earth. If I accelerate the ship at that speed in any direction, I can stand up at the bottom of the ship and it is though I'm standing on Earth. And what I'm telling you is that in that movie, they showed people jetting around the solar system because it's the future and the rockets are always ignited and everyone is floating in the ship. No. No. No. Didn't, it wouldn't have worked like that.

• 45:03Neil deGrasse Tyson?

  They got that totally wrong, okay? So what would have happened is they would have been pinned up against. Pinned up against the thing if it's strong acceleration. That's right, because what's happening is at any given moment, the whole system is going at a certain speed, okay? But if it's accelerating, then the ship is accelerating towards you. Right. And so it's going to come up against you and put a scale between there. You're going to have an equivalent weight on that ship. Wow. So space is not inherently a weightless place, unless you are free falling towards one place or another. And to make that happen, you can't have rockets firing.

• 45:40Neil deGrasse Tyson?

  Just got to have a sideways motion going on. Around the Earth. Around the Earth. Or you launch from, from the Earth and you reach up and you turn off your rockets and then you free fall towards the moon. Right. Then you're weightless that whole way. But the moment you turn on the rockets, you, you're going to pin to the side, the back, the front. And so in fact, there are long-term plans to go to Mars. If you don't want to lose bone mass and all this and you don't want to rotate the ship, you accelerate halfway there, okay?

• 46:09Neil deGrasse Tyson?

  And then you have to decelerate, otherwise you'll miss Mars. So what they do is, then they turn the rocket around.

• 46:15Chuck Nice?

  Right.

• 46:16Neil deGrasse Tyson?

  Okay, then you decelerate, but in either case, you can have equivalent of one G.

• 46:21Chuck Nice?

  One G.

• 46:22Neil deGrasse Tyson?

  You can have earth gravity the whole way.

• 46:24Chuck Nice?

  Wow, look at that.

• 46:25Neil deGrasse Tyson?

  And you'll get there like in weeks, a couple of weeks.

• 46:28Chuck Nice?

  That's cool.

• 46:28Neil deGrasse Tyson?

  I think maybe even faster, rather than the nine, 10 months that it normally takes.

• 46:32Chuck Nice?

  Yeah, that's the premise behind The Expanse, the movie The Expanse.

• 46:37Neil deGrasse Tyson?

  Okay, no.

• 46:37Chuck Nice?

  I mean, not the movie, the series.

• 46:39Neil deGrasse Tyson?

  The series, that's next on my binge list.

• 46:42Chuck Nice?

  Yeah, definitely.

• 46:43Neil deGrasse Tyson?

  One very last thing, because we're out of time.

• 46:45Chuck Nice?

  Okay.

• 46:46Neil deGrasse Tyson?

  So just to be clear, there are three ways to simulate gravity. One of them is just be on earth, and let's call that real gravity.

• 46:53Chuck Nice?

  Okay.

• 46:53Neil deGrasse Tyson?

  Another way is to accelerate something at the acceleration of gravity.

• 46:57Chuck Nice?

  Right.

• 46:57Neil deGrasse Tyson?

  And a third way is you can rotate something, and then the centrifugal force that wants to fling you outwards, that you'll read that as a gravitational force. And so that's where you'd have a ring. So if you did rotate a ring, you'd walk around on the outer rim, as they shown famously in the movie 2001.

• 47:14Chuck Nice?

  Right.

• 47:15Neil deGrasse Tyson?

  The Space Odyssey. So there you have it. Going into space does not automatically make you weightless. Only a free fall towards an object will.

• 47:24Chuck Nice?

  Very cool. And the thing that I took away from this talk most is, if you shoot a cannon off the side of a mountain at five miles per second, you should duck.

• 47:35Neil deGrasse Tyson?

  Duck, duck 88 minutes later.

• 47:37Chuck Nice?

  Yeah.

• 47:38Neil deGrasse Tyson?

  That's how long it'll take.

• 47:39Chuck Nice?

  That's cool.

• 47:41Neil deGrasse Tyson?

  Oh, by the way, that calculation, we're not going to get into it here, but I'll just tell you. If you dig a hole through the earth, going through the center and coming out the other side, and then you drop something through, it'll fall towards the center, overshoot the center, come out the other side, and if nobody grabs it, it'll then bob back down and come back into your hand. That round trip also takes 88 minutes.

• 48:04Chuck Nice?

  Nice.

• 48:05Neil deGrasse Tyson?

  Yes. Yes. Oh, man. Well, I'm gonna start, I'm gonna start digging now, cuz I wanna- Wait, I got one more, one more. You ready? Just while we're on the subject. Uh, Earth's equator feels a little bit of centrifugal force. So you weigh a little bit less on the equator than you do at other latitudes. So if I speed up Earth, you'll weigh less and less and less and less. Sweet. There's a speed with which I can spin Earth where you weigh so much less that you weigh zero. Okay, I'm all about it. You know what speed that is? At the equator, you know what speed that is? Seventy-eight RPM?

• 48:45Neil deGrasse Tyson?

  Chuck, how old are you? No, so that's speed. So if you, if, so if the equator makes one full spin in eighty-eight minutes? Right. You're weightless. There you go. You'll just hover over the ground. And so basically, at that point, you're in orbit around the Earth. It's all the same number. Right. That's what's cool about it. That is cool. The Earth rotates once every eighty-eight minutes, everyone on the equator is weightless. Sweet. Gotta end it there, Chuck. All right, that was cool. I'm going to Ecuador.

• 49:18Neil deGrasse Tyson?

  What a coincidence, the name Ecuador and they're on the equator. Who would've thought?

• 49:24Neil deGrasse Tyson?

  All right, Chuck, always good to have you. Always a pleasure. Neil deGrasse Tyson here.