Things You Thought You Knew – Force, Heat, & Speed

Do you feel the need… the need for speed?! Neil deGrasse Tyson and Chuck Nice break down things you thought you knew about force vs. pressure, heat vs. temperature, and speed vs. acceleration.

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

• 0:00Neil deGrasse Tyson?

  Coming up on StarTalk, it's another Things You Thought You Knew episode. This time, we dig into force versus pressure, heat versus temperature, and speed versus acceleration. Check it out.

• 0:16Neil deGrasse Tyson?

  Welcome to StarTalk, your place in the universe where science and pop culture collide. StarTalk begins right now.

• 0:29Neil deGrasse Tyson?

  I got more explaining to do. You got some explaining to do. Lucy, so here it is. Today, I want to talk about force and pressure. Gotcha. Okay, so I'm not talking about sort of emotional pressure. Okay. That's what I'm talking about. Right, right. You know, my job has gotten me under so much pressure that I'm talking about physics pressure and physics force, all right? By the way, another way we use those words in everyday life, we say, "How much force are you showing on the battlefield?" So that's another cultural usage of those two terms. Each of those words has a precise definition in physics. Not to mention space force.

• 1:16Neil deGrasse Tyson?

  Yes, that's in there too, okay? They don't call it space pressure, no, it's a space force. So a force is what you think it is, right? You push on something and you create a force that might set it into motion, okay? And if it's something that doesn't move, but it's still fragile, you put enough force on it, you might break it. Nice, yeah. Okay, so forces make things happen. And when we say happen, we mean something changes about the object. Typically, it's set into motion. And Isaac Newton first wrote down an equation about this, okay? He said, "Force equals the mass of the object times the acceleration it'll get

• 2:00Neil deGrasse Tyson?

  if you put that force on that object." Gotcha. Okay, so you use that formula. You say, "Well, here's an object, I'm going to put a certain amount of force, and it has to be like a net force." So in other words, if you put a force exactly opposite mine... Then the forces cancel and then there's no net forces, nothing accelerates.

• 2:20Chuck Nice?

  Right.

• 2:20Neil deGrasse Tyson?

  So if everything is in balance, you can have very high forces operating, but nothing's gonna happen.

• 2:26Chuck Nice?

  Right.

• 2:26Neil deGrasse Tyson?

  But if there's a slight imbalance,

• 2:28Chuck Nice?

  Mm-hmm.

• 2:29Neil deGrasse Tyson?

  Then there will be motion. And didn't long ago, we talked about this like at the gym? Why is it that the person spotting for someone else does not have to be as muscle bound as the person lifting the weights? Have you ever thought about that?

• 2:45Chuck Nice?

  Um, every time I go to the gym.

• 2:47Neil deGrasse Tyson?

  Okay.

• 2:48Chuck Nice?

  Because somebody will say, "Hey, man, give me a spot." And it's always a dude who's eight times bigger than I am. And he's lifting on a building. He's actually lifting a building.

• 3:01Neil deGrasse Tyson?

  And just stand there in case I drop it, right?

• 3:04Chuck Nice?

  And he goes, "Hey, buddy, can you give me a spot?" And I'm just like, "No." What am I supposed to do when you're lifting like?

• 3:13Neil deGrasse Tyson?

  And you're struggling. Not only struggling, if you're struggling and there's a point where you can't lift it anymore, you want me to come help you?

• 3:19Chuck Nice?

  Right, you want me to then take over.

• 3:21Neil deGrasse Tyson?

  Okay, here's why that works. Okay? Because if all forces are balanced, then any force will move it. No matter how small.

• 3:36Chuck Nice?

  Ooh.

• 3:37Neil deGrasse Tyson?

  So watch what happens. So I'm there, I'm on the bench, bench, just a bench press typically, right? Cause the weight is above the person's neck. Correct. This is dangerous. You don't need a spotter if you do a bent over sort of rowing lift.

• 3:49Chuck Nice?

  No, cause you could just drop the weight.

• 3:51Neil deGrasse Tyson?

  You just drop it. It's no big deal.

• 3:53Chuck Nice?

  When it's over your windpipe, it's like, "Hey Chuck, can you spot me?" And I'm like, "Hey, man, you wanna die, it's okay."

• 4:00Neil deGrasse Tyson?

  You get my skinny ass to prevent you from dying. So watch. So here I am, I'm lifting and that's getting harder and harder. All right? And now there's a point where I get it halfway and I can't get it any further. And I say, "Chuck, help me out here." In that moment, my upward force equals the downward force of those weights.

• 4:25Chuck Nice?

  Right.

• 4:26Neil deGrasse Tyson?

  And force on earth from gravity is called your weight. So the weight equals the force pushing up on it. If they're equal, now the thing has just stopped moving. Okay, it has stopped moving. So now you come along and say, here you go. And then you lift and you lift. You could probably use one hand to do this. You lift it back up onto the rack. Because the forces were balanced. Whereas previously, the person's force was greater than the weight of the weights. Right? And so if it's greater, I'm in control here and I can push the thing away from earth,

• 5:02Neil deGrasse Tyson?

  away from earth's urges to try to bring it back. When we're in balance, then you break that tie, basically, and put it over the hump. That's why that works.

• 5:12Chuck Nice?

  That's very cool. So we're teaming up on the weights, basically.

• 5:17Neil deGrasse Tyson?

  You're teaming up, right.

• 5:18Chuck Nice?

  And it doesn't make a difference how strong I am. I could take two fingers and just, whatever little bit I'm doing, now you're winning.

• 5:24Neil deGrasse Tyson?

  Provided, provided that he's not losing that battle. Okay, if the weight is on its way down, you're gonna need, it's not balanced. You have to counteract that.

• 5:36Chuck Nice?

  Right.

• 5:37Neil deGrasse Tyson?

  And then put in a little more to get the thing back up to the, to the stack.

• 5:41Chuck Nice?

  And that's when I stand over top of him and go, sorry, man, you're gonna die.

• 5:47Neil deGrasse Tyson?

  You sound like this has happened before.

• 5:50Neil deGrasse Tyson?

  All right, so just to get a sense of what forces are, okay? That's all. And, oh, so with regard to acceleration, if there's a net force, then the object's motion will continue to increase in speed. You have an acceleration. All right, so there you have it. One last thing, just in detail. If all forces are balanced.

• 6:13Neil deGrasse Tyson?

  It can still be in motion, it just won't be accelerating.

• 6:17Chuck Nice?

  Alright.

• 6:17Neil deGrasse Tyson?

  Okay, so you can have no motion or constant motion. If there's a net force, it will accelerate. That's the point that's going on here.

• 6:26Chuck Nice?

  Alright.

• 6:27Neil deGrasse Tyson?

  So, you're in your car and your foot is on the accelerator pedal and you're sticking to sixty miles an hour, fifty-five miles an hour. Well, what does it mean if your foot is on the accelerator pedal, but you're not increasing in speed? You're not accelerating. Oh, well, the force the accelerator pedal is trying to put in the car is exactly balanced by the friction of the tires on the road and the air resistance. All of that is balanced. And you're maintaining constant speed. If you want to take it out of balance, you press the pedal even harder to overcome that balance and now you can pass the car on the right. By accelerating up to seventy, you pass him and then you slow back down again.

• 7:11Chuck Nice?

  Alright.

• 7:11Neil deGrasse Tyson?

  So that's what's going on with force and you, everybody learns this in like Physics 101, the first ten days.

• 7:18Chuck Nice?

  Mm-hmm.

• 7:18Neil deGrasse Tyson?

  Okay, so now, what is pressure?

• 7:24Chuck Nice?

  Pressure is when you have been dating for four years and she goes, "What are we doing here?"

• 7:32Neil deGrasse Tyson?

  Okay, Chuck.

• 7:36Chuck Nice?

  Seriously, how many times can I take you home for Thanksgiving and explain to my parents that, you know, we're not ready yet? What's, I mean, what is happening?

• 7:46Neil deGrasse Tyson?

  That's pressure. You're telling me that's pressure?

• 7:51Neil deGrasse Tyson?

  Okay, that's not the kind of pressure I'm talking about here.

• 7:52Chuck Nice?

  Oh, okay, okay.

• 7:53Neil deGrasse Tyson?

  Okay, okay. That's dating pressure, how about that?

• 7:56Chuck Nice?

  Right.

• 7:56Neil deGrasse Tyson?

  So, we're talking about physics pressure. So, pressure intimately needs force to be what it is. But it's not the same thing.

• 8:06Chuck Nice?

  Uh-oh.

• 8:07Neil deGrasse Tyson?

  Okay?

• 8:08Chuck Nice?

  Okay.

• 8:08Neil deGrasse Tyson?

  It's not the same thing. So, if you want to find out what it is, you gotta look at the equation for pressure. Okay?

• 8:19Chuck Nice?

  Oh, okay.

• 8:20Neil deGrasse Tyson?

  Have you ever seen the equation for pressure?

• 8:22Chuck Nice?

  I don't think I have.

• 8:23Neil deGrasse Tyson?

  Alright, let me, before I get to that, let me tell you a few things that are affected by pressure. For example, uh, your knife set. How sharp are your knives? That is all about pressure. All about pressure. Okay. Uh, if you, are you gonna fall through the ice on that pond as you walk across it? That's all about pressure. And stupidity. That's stupidity. Right?

• 8:55Neil deGrasse Tyson?

  Alright, so let's talk about this. Here you go. Pressure is force divided by area. Oh, oh. Okay. And I didn't even know that equation, but that makes perfect sense! It makes perfect sense, so watch, so watch. So, if I'm walking out onto a frozen pond and I don't wanna fall through, if I have tiny itty bitty ass feet, then the area of the bottom of my feet is small, but what happens if you have a small number in the denominator of a fraction? The value of that goes higher. Right.

• 9:38Neil deGrasse Tyson?

  So if pressure is force divided by area, and that area gets smaller and smaller, the pressure gets higher, and you punch through that ice and you die. You need clown shoes! You need clown shoes!

• 9:55Neil deGrasse Tyson?

  Get the biggest ass shoes you can find. So that force is spread over the largest area possible. Right. So when you have a big area, the force divided by a big area makes a low pressure. And so with low pressure, now you can get across the ice without sinking through. It improves your chances of, of, of, of not breaking the ice. This is what snow shoes are. What, what are snow shoes? They're like the, the, the, the, you know, the mountain man's snow equivalent of clown shoes. Alright? Because the, the snow shoe is this big... It's a, uh, it's like a big net.

• 10:38Neil deGrasse Tyson?

  And it attaches to the bottom of your feet, and when you walk on it, your body weight is now spread over a larger area, and you don't plunge down through deep snow. Mmm. You still sink a little bit, but not as much as you would have, and then you can actually walk. Have you ever seen the width of the paws of a polar bear?

• 11:02Neil deGrasse Tyson?

  They're huge. Oh my God, it's like, oh my God, cuz there's some big mofo's and they don't wanna sink through the snow, okay, they spend a lot of their time on ice, but this matters, okay? And so, what about your knives? When you go to cut something, you apply a force. How do you make that force as effective as possible to cut? You want the lowest possible area over which you're applying that force, so that you have the highest possible pressure, okay? You get pressure for free. So when you, so what, what, what is a dull knife?

• 11:47Neil deGrasse Tyson?

  You look at it under a microscope, it's, it's a, it's all chewed up, it's flat, it's thick, so your pressure, let's say you put 10 pounds of pressure on it, is spread over this long area over the length of the blade, and you try to cut something with it, with it, and you mangle the food, you have to press even harder to get it through? A perfectly sharpened blade, what's the area of a blade edge? Tell me that. The area of a, of a sharpened blade edge, it is so tiny, that even the mildest force of that knife will cut through the food. And that's why chefs are always sharpening their knives, cuz they wanna increase the

• 12:27Neil deGrasse Tyson?

  pressure on their food, because they don't wanna have to increase their force to get the pressure they want. They're reducing the area to get the pressure they want. Sweet. So, this is, this is force versus pressure. And, uh, I don't know how many people internalize this, feel it, think about it, but this distinction between force and pressure manifests everywhere, everywhere. And by the way, it's why a tornado can explode your house.

• 13:06Neil deGrasse Tyson?

  Wow, okay. You say, oh, because the wind is high. Here's what's happening, alright? It's very low pressure in the middle of a tornado, okay? Really, really low pressure. And inside your house, you have slightly higher pressure than that tornado. Now suppose that pressure difference is like one pound per square inch difference, let's say. Okay, it might be a little high for this example. A tenth of a pound per square inch. I don't care. A tenth of a pound, okay? So, inside the house, the air has not equilibrated with the outside of the house yet. The tornado comes, it sits on your house.

• 13:45Neil deGrasse Tyson?

  Oh my gosh, every square inch of your wall is feeling a tenth of a pound pressing outward. So 10 square inches feels how much? 100. No, 10th, it's a tenth of a pound. So 10 square inches is a pound, okay? 100 square inches is just 10 inches by 10 inches. That's 10 pounds. Right. Your wall is probably bigger than 10 inches by 10 inches square. You keep adding this up. And that pressure builds on top of it. You get a thousand pounds of pressure. Oh my god, that's more than the Kool-Aid guy actually exerts to get through a wall to say, oh yeah! So, what I didn't, I didn't say it right.

• 14:27Neil deGrasse Tyson?

  So, the, the, it's thousands of pounds of total force. Right. Spread across that wall, but the whole wall is only built to handle you leaning on it, or, or, or to hold up the house. It's not enough to prevent the tornado from exploding your house. And all the walls blow out. Take a look at video footage of homes. They don't collapse. No, they're, they're turned into mat sticks. They're mat sticks and they explode outwards. That is pressure at its most deadly.

• 15:01Chuck Nice?

  Wow.

• 15:02Neil deGrasse Tyson?

  And so, you know, there you have it.

• 15:04Chuck Nice?

  Now see, this is what I'm talking about when I say plot twist. No one would ever think that you just talk about force and pressure and we end up right here.

• 15:12Neil deGrasse Tyson?

  Right, and by the way, it's how bombs work. What is a bomb? It sets a pressure wave, high temperature expansion of the air. Cause there's some, like an explosion is a very high temperature abrupt device, right? But it happens, has to happen rapidly so that it's like, like a bullet firing. It's a rapid expansion of gas which shoves the bullet out. But if it's a bomb, there's no bullet, it's just the expanding air.

• 15:36Chuck Nice?

  Right.

• 15:37Neil deGrasse Tyson?

  Sometimes you can put in shrapnel, but air will do this. And the expanding air comes out and now you have air pressure too high on one side of the wall versus the other and that'll blow the wall inward rather than outward. Or if the bomb is inside the house, it'll blow the house up instead of it. Right, so this is pressure on the wall spread over the area. And by the way, if all of that force were in one spot, it would just puncture a hole through the wall.

• 16:01Chuck Nice?

  Right, that's so cool. Oh my God, so why can't we find a way? Everybody's always trying to figure out a way to predict where a tornado will go, which is almost impossible. Why not just have like a tornado airbag? Well, you would die.

• 16:18Neil deGrasse Tyson?

  No, I was gonna say. Wait Chuck, Chuck, wait Chuck, you don't need tools to tell you where the fricking tornado is. Just look.

• 16:30Chuck Nice?

  That's true.

• 16:31Neil deGrasse Tyson?

  You're trying to see airbags exploding. Oh, there must be a tornado somewhere here.

• 16:35Chuck Nice?

  Right.

• 16:38Chuck Nice?

  Yeah, exactly.

• 16:41Chuck Nice?

  I'm overthinking.

• 16:42Neil deGrasse Tyson?

  You're overthinking that one totally Chuck.

• 16:43Chuck Nice?

  Overthinking, yeah.

• 16:45Neil deGrasse Tyson?

  Okay Chuck, we're done there. That's pressure versus force.

• 16:48Chuck Nice?

  That's very cool. Not to mention, very, very cool song. Under Pressure.

• 16:53Neil deGrasse Tyson?

  Oh yeah, yeah, the Queen, yeah, very good, very good.

• 17:09Chuck Nice?

  Hey, this is Kevin the Sommelier, and I support StarTalk on Patreon. You're listening to StarTalk with Neil deGrasse Tyson.

• 17:27Neil deGrasse Tyson?

  It's a source of no end of misconception in our world, in civilization.

• 17:33Chuck Nice?

  Oh, okay.

• 17:34Neil deGrasse Tyson?

  Yeah, yeah, so it's a big one, okay?

• 17:36Chuck Nice?

  All right.

• 17:37Neil deGrasse Tyson?

  And it's the difference between heat and temperature. They are not the same thing.

• 17:44Chuck Nice?

  Okay, so you have already, you're right, because if you say that this is a source of misunderstanding, then I am the source. Because guess what? Heat and temperature, I mean-

• 18:02Neil deGrasse Tyson?

  It's the same damn thing.

• 18:04Chuck Nice?

  That's the same thing to me.

• 18:05Neil deGrasse Tyson?

  I will start off, I hate starting off this way, but I will. I'll start off defining them from the point of view of a physicist, okay?

• 18:13Chuck Nice?

  All right.

• 18:13Neil deGrasse Tyson?

  All right, so the temperature of a thing is the average kinetic energy of its vibrating molecules.

• 18:25Chuck Nice?

  Okay.

• 18:26Neil deGrasse Tyson?

  All right, so you have a thing that is of a temperature. You go, you look in close, all the molecules, or if they're atoms, it could be atomic, they're all vibrating. Are they vibrating fast? Are they vibrating slowly? Okay? You put a thermometer in there, that vibration gets communicated to the thermometer. The thermometer reads a temperature. It is the average kinetic energy, the average energy of motion of the vibrating particles. The average, which means a single particle has no temperature.

• 18:57Chuck Nice?

  Okay.

• 18:58Neil deGrasse Tyson?

  Okay.

• 18:59Chuck Nice?

  Wait a minute, a single.

• 19:00Neil deGrasse Tyson?

  A single particle, that's right. There's no, it doesn't meet, right. So, temperature is a macroscopic thing that you obtain from a, from a, from a liquid, a solid, a gas, it doesn't matter. Okay? That's temperature.

• 19:15Chuck Nice?

  Okay.

• 19:16Neil deGrasse Tyson?

  Okay? So, you heat it up some more, you get higher temperature. Oh, by the way, there's a range of which they vibrate. Some vibrate slowly, some vibrate quickly. It's the average that's the temperature.

• 19:27Chuck Nice?

  Uh.

• 19:28Neil deGrasse Tyson?

  Let me say that another way. At a given temperature, uh, there's like, uh, uh, uh, the average, which is where most of them are kind of vibrating, and then there's some off at the tail. Some are vibrating slowly, some are vibrating quickly. Okay?

• 19:41Chuck Nice?

  Okay.

• 19:42Neil deGrasse Tyson?

  Here's an example. Okay? Let's get water at, let's stick to Fahrenheit. Let's say we are 200 degrees. Water, no, room, room temperature water, 75 to 70 degrees. Okay? Here you go. Some of those water molecules are vibrating very fast, others very slowly. Okay?

• 20:04Chuck Nice?

  Right.

• 20:05Neil deGrasse Tyson?

  Some of them are vibrating fast enough to escape.

• 20:10Chuck Nice?

  Right, yes.

• 20:12Neil deGrasse Tyson?

  Okay? But it's just those only at the, at the edge, they escape.

• 20:16Chuck Nice?

  They're at the very top.

• 20:17Neil deGrasse Tyson?

  At the very top. They'll escape, the rest are stuck.

• 20:20Chuck Nice?

  Stuck, right.

• 20:20Neil deGrasse Tyson?

  Okay? So now, they escape. This is evaporation.

• 20:24Chuck Nice?

  Correct.

• 20:24Neil deGrasse Tyson?

  And you don't have to be boiling water to evaporate the water, because the fastest moving molecules are always escaping. Okay? That's my point. Okay?

• 20:32Chuck Nice?

  That makes sense.

• 20:32Neil deGrasse Tyson?

  Also, just while we're there, if you are a low mass atom, or low mass molecule, relative to high mass molecules, your low mass ones are vibrating even faster, on average. You can split them up. The heavy ones are moving slowly, the light ones are moving quickly. The average of all of them, that's the temperature.

• 20:50Chuck Nice?

  So funny how even atoms work kind of the way, uh, even molecules work the way we do. You know, the, the heavy ones kind of slow.

• 21:01Neil deGrasse Tyson?

  We're just kind of chill.

• 21:04Chuck Nice?

  Oh, God. Oh, damn, I got, I gotta get about this chair.

• 21:09Neil deGrasse Tyson?

  I gotta get out the chair.

• 21:11Chuck Nice?

  Oh, give me a second.

• 21:14Neil deGrasse Tyson?

  And you never left the room.

• 21:15Chuck Nice?

  Right. And the lighter ones are, so.

• 21:19Neil deGrasse Tyson?

  All right. So for example, our atmosphere has both oxygen and nitrogen in it. And the oxygen molecule weighs slightly more than the nitrogen molecule.

• 21:28Chuck Nice?

  Okay.

• 21:29Neil deGrasse Tyson?

  So on average, if you separated out the oxygen, it would be at a lower temperature than the nitrogen. But mix them together, you only get one temperature because it's a mixture. That's all I'm saying about temperature. Okay.

• 21:42Chuck Nice?

  Okay.

• 21:42Neil deGrasse Tyson?

  So heat, let's go to that individual vibrating molecule and say, how much energy you got? Write down that number. Let's go to the next one. How much energy you got? Write down that number and just keep doing it for every molecule.

• 21:59Chuck Nice?

  For every molecule.

• 22:00Neil deGrasse Tyson?

  Every molecule in your soup.

• 22:02Chuck Nice?

  So it's not, okay, got you.

• 22:04Neil deGrasse Tyson?

  So, so the sum of all the kinetic energies of all the vibrating molecules? That's how much heat is in the thing.

• 22:13Chuck Nice?

  Gotcha.

• 22:14Neil deGrasse Tyson?

  Okay.

• 22:15Chuck Nice?

  So one is an average, the other is the, the actual number, the sum of all the.

• 22:21Neil deGrasse Tyson?

  So your cup of coffee in the morning at 210 degrees Fahrenheit.

• 22:28Chuck Nice?

  Right.

• 22:29Neil deGrasse Tyson?

  Is hotter than the ocean, but the ocean has more heat.

• 22:37Chuck Nice?

  Oh, snap.

• 22:41Chuck Nice?

  It's hotter than the ocean, but the ocean, because the ocean has more molecules and you're going to add up the sum. You add up the sum of all the molecules.

• 22:53Neil deGrasse Tyson?

  Total molecules, okay?

• 22:56Chuck Nice?

  So even.

• 22:56Neil deGrasse Tyson?

  That's why your coffee cup, your coffee cup is not going to start a hurricane.

• 23:01Chuck Nice?

  Right.

• 23:01Neil deGrasse Tyson?

  It doesn't have enough energy in the coffee cup to make that happen.

• 23:05Chuck Nice?

  And that, and that heat is, is the, all the energy in the ocean.

• 23:10Neil deGrasse Tyson?

  Oh, my gosh.

• 23:12Chuck Nice?

  And that's why the ocean can start a hurricane, but your coffee can only make your morning very bad because it spilled in your lap.

• 23:21Neil deGrasse Tyson?

  Or it can speed up your digestive tract and you're stuck in the car when you gotta go to.

• 23:28Neil deGrasse Tyson?

  Coffee has other consequences to your life. About that part. Oh, so that's the last time I drink coffee and get stuck in traffic. Oh. So that is amazing. Important. So now watch what happens. So, so now we have climate change where the, the world is heating. Right. And you can say, okay, um, how much did the, of the air, we don't want the air to go up by two degrees Celsius, whatever, because that could trigger other changes. Well, let's check the ocean. How much did the ocean go up? The ocean went up a fourth of a degree or like a half a degree. And you're saying to yourself, that's not much. Do you know how much total energy that is? Oh my gosh.

• 24:14Neil deGrasse Tyson?

  That is. Oh my gosh. That's. Okay. So Chuck, that's why when you're trying to create the energy budget of a climate system, right? There's sunlight coming in and it warms the air. Was that where all the energy goes? No, no, all the whole, there's energy that goes into the ocean and it can hang out there lurking. All right. So you could, you could reduce your carbon footprint and reduce the warming of the atmosphere. Then the ocean says, I got heat. I can dump into the atmosphere and I can keep doing this even after you have corrected your behavior to protect future generations.

• 24:58Neil deGrasse Tyson?

  And the balance, it's actually in imbalance at this moment, the, the relationship between the, the heat that the land retains and the atmosphere and the ocean, the ocean wins every time. Right. Because of it's, it's this tremendous heat reservoir. So I just wanted to distinguish the difference between heat and, um, temperature. And there's one little thing you might not know. Okay. Okay.

• 25:25Neil deGrasse Tyson?

  Do you know air conditioners, right? It's like, it's hot outside and it makes you cool on the inside.

• 25:32Chuck Nice?

  Yes.

• 25:33Neil deGrasse Tyson?

  Okay. All right. Do you ever ask how it accomplishes this?

• 25:38Chuck Nice?

  Um, not really.

• 25:39Neil deGrasse Tyson?

  You just turn it on.

• 25:41Chuck Nice?

  I just turn it on and it works. And from the time I was a kid, I know that you don't leave the door open because we're not trying to cool the whole neighborhood.

• 25:53Chuck Nice?

  What the hell? You think we're trying to cool the whole neighborhood? Shut the door!

• 25:57Neil deGrasse Tyson?

  Chuck, I thought you had finished your therapy on your childhood experiences, but apparently some sessions remain. So, so what's happening there is, okay? There is heat inside of your room. No matter what temperature your room is, as long as it's above absolute zero, there is heat there. There's a pump that takes that heat, removes it from your air and sticks it outside. That's why, no matter the temperature outside, if you feel the air conditioner, it's hotter at the air conditioner. Why is it hotter? Because it just pulled that heat from your 72-degree room that you're trying to keep cool. It pulled it out and it can reverse that. Okay?

• 26:42Neil deGrasse Tyson?

  So, let's reverse it. It's called reverse, it's a heat pump, a reverse heat pump. In your winter, okay? You want it to be warmer in your room than the outside. Once you switch the heat pump, your air conditioner says, "Okay, let me take heat from this cold air out there. It's 40, 50 degrees, I don't care. Let's take heat from that cold air and put it in your room and make your room hotter, even hotter than it would otherwise be compared to the outside." It can do that because there is heat there no matter what the temperature is as long as it's above that. As long as it's above absolute zero.

• 27:23Chuck Nice?

  That is, okay.

• 27:25Neil deGrasse Tyson?

  It's clever engineering, just think.

• 27:27Chuck Nice?

  Brilliant.

• 27:28Neil deGrasse Tyson?

  Go hug hug your favorite engineer. This is where this comes from.

• 27:31Chuck Nice?

  Brilliant. Okay, so I'm gonna admit that when we started this, I was like, this guy has really dug a hole for himself this time. No way. No way this is gonna be interesting.

• 27:48Chuck Nice?

  But I gotta admit, this is great.

• 27:50Neil deGrasse Tyson?

  Next time you sip a cup of coffee looking out at the ocean.

• 27:53Chuck Nice?

  Yeah.

• 27:54Neil deGrasse Tyson?

  Just, just think to yourself.

• 27:56Chuck Nice?

  Know that that ocean has more heat than this hot scalding cup of coffee.

• 28:01Neil deGrasse Tyson?

  You could burn yourself with the coffee, but the hurricane won't, it won't matter to the hurricane.

• 28:06Chuck Nice?

  That's right. Wow, that is so cool, man. That is cool.

• 28:09Neil deGrasse Tyson?

  All right, that's a quick one.

• 28:33Neil deGrasse Tyson?

  Speed versus acceleration.

• 28:36Chuck Nice?

  I knew one day we were gonna have to have this talk.

• 28:43Neil deGrasse Tyson?

  Sit down Chuck.

• 28:45Chuck Nice?

  Chuck, I need to, I need a word with you. Son, I've been meaning to talk to you about speed versus acceleration.

• 28:52Neil deGrasse Tyson?

  You're of age now where this is the time.

• 28:56Chuck Nice?

  Don't worry, there's nothing to be embarrassed about.

• 29:02Neil deGrasse Tyson?

  So, there's a nice scene, nice, there's a rememberable scene in the movie Top Gun. Where they just came out of their, out of their planes and they're holding their helmet. And what, what does one of them say to the other as they high five each other? I've got the need for speed. Okay. I thought it was. Thanks. I feel, I feel the need for speed and I wanna push back on that, if I may. Uh. Okay. You wanna push back on the need for speed? Yes, I am. Oh, no.

• 29:39Neil deGrasse Tyson?

  Cause I claim that their speed is almost irrelevant to what it is their, their, it's triggering their emotions. Really? Yeah, yeah. Uh, because for example, right now, uh, at our latitude on earth, the rotation of earth is carrying us due east at 800 miles an hour. Do, are you saying, I feel the need for speed and this is great? No. Well, that may explain why I keep throwing up every time I, every time I stand up. It could be a reason why I vomit.

• 30:20Neil deGrasse Tyson?

  So, no, but see, I'm about to say that what we think of as motion sickness is not motion sickness, it's acceleration sickness. Okay. Okay, so earth is in orbit around the sun 18 miles per second. That, all of these speeds are way faster than anything they're doing in their airplane. This is true. So it's not really after speed. Wow, 18 miles in a second. In a second, one second. From my house, I would overshoot the Bronx. I mean, no, I would overshoot Brooklyn from where I am right now. You'd end up in Long Island Sound. I would, I, oh wow, in one second.

• 30:58Neil deGrasse Tyson?

  Okay, so you, you live in Jersey. You, you cross the Hudson River, the width of Manhattan, all of Brooklyn, and then you come out, come out the other side. Oh my God, that's amazing. So here's the thing, when you are moving at constant speed.

• 31:15Neil deGrasse Tyson?

  Your body has no idea you're moving at any speed at all.

• 31:21Neil deGrasse Tyson?

  Okay. It's only when your speed changes that you get some sense of motion. And by definition, when your speed changes, it's an acceleration. Now, in physics, an acceleration can be positive or negative. In the English language, we have another word for when it's negative acceleration. It's just called what? Deceleration. Deceleration, okay. So I might say acceleration in my next few minutes. I mean, increasing or decreasing, it doesn't matter. It's either positive or negative. Acceleration, okay. When that happens, you feel it, and that's what you're reacting to. All right?

• 32:06Neil deGrasse Tyson?

  By the way, think of velocity, okay? So a velocity, a change of velocity is an acceleration. But a velocity has a direction. Right. But suppose you're banking a turn. Your direction is constantly changing.

• 32:20Neil deGrasse Tyson?

  Well, if velocity has to have one direction, now I'm changing the direction. That's also an acceleration.

• 32:27Neil deGrasse Tyson?

  So here's my point. When you're in a moving object, no matter its speed, if the direction or the speed changes, you are accelerating. And when you feel an acceleration, your body is going to respond. If you accelerate forward, your body will be thrown backwards. If you decelerate quickly, your body goes forward. If you bank a turn, you lean against the door or against the person next to you in the front seat. So that's how you know you're accelerating, because your body is responding in this way. So these folks said, "I feel the need for speed."

• 33:08Neil deGrasse Tyson?

  It's because they're doing barrel rolls in their plane and upside down and all the stuff they're doing, that's what they're feeling. But if they were going perfectly at Mach 1, 2, 3, 4, or 30, they wouldn't be saying, "I feel the need for speed." Because that's not anything they would notice. This was been the complaint about the Lexus car. When it first came out, the Lexus was a, you know, a luxury car, and that ride was smooth. I read one commentary and it said, "It's like sitting on your living room couch while you're driving your car."

• 33:45Chuck Nice?

  Hmm, that sounds lovely.

• 33:48Neil deGrasse Tyson?

  So, nobody who feels the need for speed is buying a Lexus. They want a car that can bank turns and go from 0 to 60 in whatever how many seconds you're talking about. That's an acceleration.

• 34:01Chuck Nice?

  Yeah, but it doesn't sound good to say, "I feel the need for acceleration." "It's a celebration of acceleration." Now I just sound like Jesse Jackson. That's what I'm saying.

• 34:19Neil deGrasse Tyson?

  My man rhymes anything that comes out of his mouth.

• 34:21Chuck Nice?

  Celebration of acceleration. Keep hope alive.

• 34:31Neil deGrasse Tyson?

  So, so that's all I'm trying to tell you. So that's why, they will give top speed when you're buying a car. They will give a top speed. But they will also give 0 to 60 or 0 to 50 in a certain amount of time. So, that is the change in velocity over a certain amount of time. And so, if you change velocity in less, in less amount of time, your acceleration is higher and higher and higher. That's why they keep trying to drop the acceleration time. Then it's more head, it's more head snapping.

• 35:04Chuck Nice?

  Right, yeah.

• 35:05Neil deGrasse Tyson?

  Now.

• 35:07Chuck Nice?

  That's why everybody loves Tesla.

• 35:09Neil deGrasse Tyson?

  Oh, because it's high, it'd be true for any well-made electric car will have very high acceleration.

• 35:15Chuck Nice?

  Yeah.

• 35:15Neil deGrasse Tyson?

  Even at low speeds, right. Teslas can accelerate 0 to 60 in 3, 4 seconds.

• 35:20Chuck Nice?

  Yeah, it's great.

• 35:21Neil deGrasse Tyson?

  And I've been in it and you can feel it. It's like, "Mmm." Okay, okay, so now, watch. Let's kick it up a notch. You ready? I don't think you're ready. Are you seated?

• 35:29Chuck Nice?

  All right, I'm seated.

• 35:30Neil deGrasse Tyson?

  Okay. There is

• 35:33Chuck Nice?

  Hold on, because I don't want to accelerate too fast. I better strap it.

• 35:39Neil deGrasse Tyson?

  Okay, so if acceleration is the rate of change of your velocity. Okay, so if that, if your rate changes quickly, you have high acceleration, you will feel this response all the more. Okay, all right. If acceleration is the rate and change in your velocity, what happens when you have a rate of change of your acceleration?

• 36:03Chuck Nice?

  Oh, my goodness. Let me guess. Your head explodes.

• 36:08Neil deGrasse Tyson?

  Yes, well, okay, so if you have a rate of change of acceleration, that has a term in physics, it's called the jerk. Okay.

• 36:19Neil deGrasse Tyson?

  So.

• 36:22Chuck Nice?

  Oh, man, that's great.

• 36:23Neil deGrasse Tyson?

  Okay, so watch what happens. You ready?

• 36:25Chuck Nice?

  Go ahead.

• 36:26Neil deGrasse Tyson?

  Um, so I'm headed towards a brick wall. I'm trying to come up with these examples on the spot. Headed towards a brick wall. And so I should put on my brakes. So you put on your brakes. Okay, and while you put on your brakes, you feel yourself, you're leaning into the shoulder strap. Okay? When you hit the wall, your body jerks forward. Because you had a steady slowing down of your speed until your speed went to zero instantly. So that is a rate of change of your acceleration, and then you feel a jerk.

• 37:03Chuck Nice?

  Okay, but why, why did we run into a wall?

• 37:08Neil deGrasse Tyson?

  Okay, so the jerk is what actually does sort of musculoskeletal damage in an accident.

• 37:16Chuck Nice?

  Oh, okay.

• 37:17Neil deGrasse Tyson?

  Okay, because we can sustain an acceleration, but when they say I have 1G, 2G, those are pure constant accelerations. But if you go from 1G to 6Gs in an instant, your whole body snaps.

• 37:30Chuck Nice?

  Right.

• 37:31Neil deGrasse Tyson?

  That's this, and so.

• 37:33Chuck Nice?

  And the same thing in reverse.

• 37:35Neil deGrasse Tyson?

  And the same thing in reverse, correct.

• 37:36Chuck Nice?

  That's, so what you're basically saying is jumping out of a 20-story window doesn't kill you.

• 37:42Neil deGrasse Tyson?

  That's correct.

• 37:44Chuck Nice?

  It's, it's the ground.

• 37:49Chuck Nice?

  It's the ground.

• 37:53Neil deGrasse Tyson?

  If there were no ground.

• 37:55Chuck Nice?

  Right.

• 37:55Neil deGrasse Tyson?

  You'd be fine.

• 37:58Chuck Nice?

  Oh, man.

• 38:01Neil deGrasse Tyson?

  So, so that's velocity, acceleration, and jerk. So, almost every, and, and there's some cars, they say, in this car, you can feel the road. If you ever test drive like a sports car, they tell you that, right? Well, what does it mean to feel the road? Well, if the, if the road were perfectly smooth, you wouldn't feel anything. So, the fact that the road has certain bumps? The Lexus wouldn't feel those bumps because the tires are adjusting to it. But your sports car, which has, quote, rigid suspension, it is rigid enough so that you're feeling that. Alright, so you and the road and the bumps and wiggles and the turns and twists on the road, you're feeling it all.

• 38:42Chuck Nice?

  Nice.

• 38:43Neil deGrasse Tyson?

  You feeling it. And so you, so this is what you like, this is what you seek. This is what the sports enthusiast is actually after, even if they're not self-conscious of it. Cause if they only want at high speeds, you can just get on a, you know, get on a high-speed train. And then you don't feel it because they're smooth. No, you wanna, you wanna bank the turns and feel it.

• 39:05Chuck Nice?

  That reminds me of a, a guy on the, I was on the turnpike and a guy comes by on a motorcycle. And he's already, I'm doing 80, so he had to be doing a little faster than 80 because he came by me. And then he pulls back on the throttle and pops a wheelie at 80 miles an hour.

• 39:23Neil deGrasse Tyson?

  Oh.

• 39:24Chuck Nice?

  And pulls off.

• 39:25Neil deGrasse Tyson?

  Okay.

• 39:26Chuck Nice?

  So...

• 39:29Chuck Nice?

  And, and I, and I'm pretty sure he was like, I feel the need for acceleration.

• 39:37Neil deGrasse Tyson?

  And with the high-accelerating cars, of course, a constant acceleration is a, is a one-time thing. By the way, you either press yourself back or forward or lean one way or another. And any abrupt change in that creates this, this jolt. But, but even if you, if you're, if you're going at zero and you floor it, there is the initial head snap. Okay? That's a very high moment of acceleration, but then you stays that way. Until you like hit the brick wall and then you're snapping another way. So anyhow, I just put, I'm just putting all this out there. In case you didn't know.

• 40:12Chuck Nice?

  So, all I can say is, please take Neil's word for everything he just said. Let's not try the brick wall experiment for ourselves. Okay? We're not responsible for anybody

• 40:27Chuck Nice?

  who crashes their car into a wall. All right? Just take his word for it.

• 40:32Neil deGrasse Tyson?

  All right. There it is once again. Chuck, you heard it here. And I'm Neil deGrasse Tyson, as always. Keep looking out.