Pod Insights StarTalk Podcast Things You Thought You Knew – The Color of the Sun About this episode What’s the true color of the sun? Neil deGrasse Tyson and comic co-host Chuck Nice discuss things you thought you knew about the color of the Sun, the sound of weather, and why friction is our friend.
Transcript Speaker names marked ? are inferred from speaking time and the show’s known hosts — they are not voice-verified.
0:00 Neil deGrasse Tyson? Hey everybody in the Startalkverse. We've got yet another Things You Thought You Knew episode. This time Chuck and I get into the color of the sun, weather acoustics, and friction. Check it out.
0:16 Neil deGrasse Tyson? Welcome to Startalk, your place in the universe where science and pop culture collide. Startalk begins right now.
0:30 Neil deGrasse Tyson? Welcome to the explainer zone.
0:32 Chuck Nice? Yes, the explainer zone.
0:34 Neil deGrasse Tyson? Yeah, yeah, not the Twilight Zone.
0:37 Chuck Nice? That's Twilight Zone.
0:37 Neil deGrasse Tyson? We're confused at the end.
0:39 Chuck Nice? Right.
0:39 Neil deGrasse Tyson? The explainer zone.
0:40 Chuck Nice? Where you come out knowing more than you did when you went.
0:43 Neil deGrasse Tyson? Some stuff, right. And so I think there's no end to this, just so you know.
0:48 Chuck Nice? Good.
0:49 Neil deGrasse Tyson? I will be calling you forever.
0:53 Neil deGrasse Tyson? All right. So I want to talk about the sun, the color of the sun.
0:56 Chuck Nice? Okay, all right. Well, you know me, I don't see color.
1:00 Neil deGrasse Tyson? You don't see color?
1:01 Chuck Nice? Sorry, we're already done here.
1:05 Neil deGrasse Tyson? So, so, so here's the thing. If you're a school child and you to draw a scene, and you want to put the sun in the sky, what crayon do you reach for?
1:16 Chuck Nice? Um, well, I was a very depressed child, so black.
1:20 Neil deGrasse Tyson? Black. Okay, no, you knew about black holes, baby.
1:23 Chuck Nice? Yes, exactly. No, it's always a big yellow ball.
1:26 Neil deGrasse Tyson? It's always yellow. And this is, this notion has been with us since childhood, that the sun is yellow.
1:35 Chuck Nice? Yes.
1:35 Neil deGrasse Tyson? And that's not true. It's not even close to being true.
1:41 Chuck Nice? Uh oh.
1:42 Neil deGrasse Tyson? And so, yeah, I'm sorry, you know, I don't want to, are you sad about this?
1:47 Chuck Nice? Are there any kids watching, please?
1:51 Chuck Nice? You might want to leave the room right now because we're not sure if there's a Crayola available for you to draw your little scenes with the house and the grass and the little tulip.
2:03 Neil deGrasse Tyson? Here's the thing, the sun in broad daylight is too bright to look at. All right, without risking damaging your eyes. So no.
2:11 Chuck Nice? Unless, of course, you have perfect eyes.
2:18 Neil deGrasse Tyson? So, so you don't do it, alright? So, when is the time most people ever find themselves looking directly at the sun? When is that?
2:27 Chuck Nice? Well, the only times I've ever done it is sunset and sunrise.
2:31 Neil deGrasse Tyson? Sunset and sunrise. Exactly, exactly. So, not only do we have the yellow crayon in our crayon box from childhood, anytime we actually ever find ourselves looking at the sun, either on purpose or by accident, it's low on the horizon. The sun is rising or setting, and it has a deep yellow color. Sometimes it's so deep, it can be red, amber into red.
2:56 Chuck Nice? Yeah.
2:56 Neil deGrasse Tyson? So, and we know the sun isn't red. Of course, it's not red. We know that's an optical effect.
3:01 Chuck Nice? This isn't Krypton.
3:02 Neil deGrasse Tyson? It's not Krypton. Exactly, with a red, had a red sun. So, you, you know intuitively it's not red, but somehow you don't know intuitively that it's also not yellow. Okay? What color is the sun? It is white.
3:16 Chuck Nice? Now, now, come on, man. Why you gotta do that?
3:19 Neil deGrasse Tyson? White.
3:20 Chuck Nice? See?
3:21 Neil deGrasse Tyson? What?
3:23 Chuck Nice? Just like everything else, all of a sudden.
3:26 Neil deGrasse Tyson? Chuck, not everything.
3:28 Chuck Nice? We gotta white. You know what? Seriously, we gotta, must we whitewash all of history, including the sun? Really?
3:39 Neil deGrasse Tyson? So, yeah, so it's not yellow.
3:42 Chuck Nice? Okay.
3:42 Neil deGrasse Tyson? It's not yellow. Now, I can give you evidence of this, if you need evidence, but I'm simply saying that as the sun gets, let's look at Earth, and, and there's the atmosphere wrapped around the Earth. If the sun is directly overhead, or anywhere near directly overhead, it goes to sort of, let's call that one thickness of atmosphere. Okay? Top to bottom. As the sun gets lower and lower in the sky, the path of light through the atmosphere is longer. Okay? Because now you got, there's that angle through it. And the lower the sun gets on the sky, the more and more atmosphere it has to pass through. And in fact, you can calculate how many equivalent atmospheres it went through.
4:26 Neil deGrasse Tyson? Okay, and you just need a little bit of trigonometry. It's a simple calculation. And if it's low on the horizon, it goes through five, six, 10 equivalent atmospheres. Gotcha. When it's low on the horizon. So whatever the atmosphere is doing to the sun when it's high up overhead, it's doing it 10 times that and more when it goes lower on the horizon. Okay. Okay. So let's see what the atmosphere is doing when the sun is overhead. Um, in comes white light. Okay. And white light is composed of colors, as Isaac Newton demonstrated. All the colors of the rainbow, red, orange, yellow, green, blue, indigo, if you must, violet. Violet.
5:10 Neil deGrasse Tyson? Okay. So in it comes, particles in Earth's atmosphere that happen to be the same size as the wavelength of light of the blue side of the spectrum, the blue, indigo, purple, violet side of the spectrum. Those particles preferentially scatter the blue out of the sunlight, preferentially scatters it. So it subtracts away a little bit, just a little bit. All right. The rest of the light makes it all the way to Earth's surface. But some of the blue gets scattered, and that's why we have a blue sky. Nice. The blue sky is stolen sunlight that would have otherwise passed straight through.
5:52 Neil deGrasse Tyson? Look at that. Right. Because the sky is really clear, right? Okay, so now watch. How beautiful is that? Now, let's have the sun get a little lower in the sky. Well, there'll be more of this going on. Okay, more of the scatter. That's why on cloudless days into sunset, the sun gets deeper and deeper and deeper blue. The bluest sky, that's why sky blue is light blue. Right. All right. You want to talk about serious ride home to mama blue is the blue sky that surrounds the twilight curtain of a sunset. Now you're talking blue. Right.
6:33 Neil deGrasse Tyson? Okay, so, so much blue is taken out that we now, Roy G. Biv, red, orange, yellow, green, blue, and he took out blue, indigo, violet. What's left? Red, orange, yellow, green. Okay. If you add those colors together, you're gonna get an amber sun.
6:53 Neil deGrasse Tyson? And depending on how many particles there are, you'll get a red sun or you'll get a simple yellow sun on the horizon. And so you'd now look and say, oh, we have a yellow star. Look, it's yellow. No, it's the atmosphere made it yellow. Okay? It's lying to you. And if you, so here's what you do. Broad daylight, if there's thin cirrus clouds, okay? So it's safer to look up to the sun. Look up to the sun in the middle of the day. Is it yellow? No, no. It is white. This is very disturbing. This is very, very disturbing. Because the clouds themselves don't change the color of the sun. It'll just, it just dims it.
7:37 Neil deGrasse Tyson? So you look at a slightly dimmer sun behind the thin clouds as they pass. It's not yellow. Nice. Not only that, consider the following. All right? Now, this takes a little extra thinking. Put your thinking cap on. Okay. And we, in another explainer, we addressed this, but now there's a different reason for it. If I have a sheet of paper and it's white, that means light reflected of it, from it, is an even mixture, an equal mixture of red, orange, yellow, green, blue, violet. All those colors together in optics makes white. Don't tell this to an artist. Right. It doesn't, doesn't work on the easy. No, it's, you do, it's just the opposite in art.
8:22 Neil deGrasse Tyson? It's the opposite. Just the opposite. You don't get black, but you'll get like sludge. You'll get sludge, right. All right. So the fact that the page is white means all of those colors of light are hitting that page. So that when they reflect up, you see white. Okay. So a white light illuminating a white piece of paper shows up to you as a white piece of paper. There you go. Okay? Now, white reflects all colors. Let me put a red gel in front of the light. Now look at the paper. What color is it? It's red. It's red. Kind of pinkish, but yeah. Yeah, that's right. So it reflects all colors, but now it's only getting red. It's going to reflect the red.
9:07 Neil deGrasse Tyson? It reflects all colors. The page is red. Turn your eye. Let's put a blue gel. What happens to the page? The page is blue. Same thing, yeah. Okay? So if the sun were yellow.
9:21 Neil deGrasse Tyson? Then, snow.
9:23 Chuck Nice? Would be yellow. Which, by the way, sometimes, snow is yellow and it's not from the sun. And whatever you do, whatever you do.
9:35 Neil deGrasse Tyson? Don't eat the yellow snow.
9:36 Chuck Nice? Stay away from that snow.
9:38 Neil deGrasse Tyson? The fact that snow looks white.
9:41 Chuck Nice? Right.
9:42 Neil deGrasse Tyson? Is evidence that it's being illuminated by white light.
9:46 Chuck Nice? Wow.
9:47 Neil deGrasse Tyson? That white light is either sunlight or a moonlight.
9:50 Chuck Nice? That's right, which is also a reflection of sunlight.
9:52 Neil deGrasse Tyson? It's just reflected sunlight. There you go.
9:54 Chuck Nice? This is so disturbing. So disturbing.
9:57 Neil deGrasse Tyson? So, so I'm just trying to be honest. I'm just trying to put it out there. And just, and by the way, let me take, you want to go up a notch? Are you, are you ready to go up a notch on this?
10:08 Chuck Nice? I don't know if I'm ready to go up a notch.
10:10 Neil deGrasse Tyson? I don't think you're ready. Okay. So, um, white is the sun.
10:17 Chuck Nice? Hate where this is going already.
10:19 Neil deGrasse Tyson? Relative to incandescent bulbs.
10:22 Chuck Nice? Right.
10:23 Neil deGrasse Tyson? Okay. Your kids will have no memory of incandescent bulb, but old timers, if you're over 25, you're an old timer, you remember bulbs that would get hot when you put them in.
10:32 Speaker 02 It was a bulb with a little piece of wire in it.
10:36 Speaker 02 That wire used to light up.
10:40 Neil deGrasse Tyson? That's, that's, that's sounds like a Ken Burns special. Big other guy on the porch.
10:45 Speaker 02 Right. I remember the days when it had a bulb with a little piece of wire. Now that wire would light up and get hot.
10:53 Neil deGrasse Tyson? And we, but we pulled a switch.
10:55 Speaker 02 We pulled a switch and it gave off light. Now first, it looked like magic.
11:07 Neil deGrasse Tyson? Okay, we gotta put you on the list of the next Ken Burns special, the origin of the light bulb. Um, so, all right, so where was I? I forgot what, okay.
11:16 Chuck Nice? He's saying incandescent bulb.
11:18 Neil deGrasse Tyson? Okay, incandescent bulbs. Incandescent bulbs, when you turn them on, the temperature of the filament is not as high as the temperature of the surface of the sun. And so, the higher the temperature, the more full that spectrum becomes. So if you looked at the spectrum of a bulb in your house, okay, an incandescent bulb, it's very weak in the blue section. There's some blue there, which is why blue still looks blue under that light, but the blue is very weak under an incandescent light bulb. Okay, so if you bring out film that needs the full complement of blue and you take a picture under incandescent lights, everything is gonna be red.
12:02 Neil deGrasse Tyson? That film, if it needed the blue, is called daylight film. This is why there was a difference. Again, I'm only talking to old timers here. There was indoor film And outdoor film. tungsten film and outdoor film. And the outdoor film was color balanced to get the entire spectrum of the sunlight. If you took indoor film and put it outside, that indoor film is too sensitive to blue because it's making up for the feeble blue coming out of a bulb and it goes out and it's getting all the blue it ever wanted. If you have indoor film took a picture outside, everything looks blue. Because it was hypersensitive to blue. And the sun has plenty of it. Okay, so to a photographer, sunlight is blue.
12:46 Neil deGrasse Tyson? It's highly blue. And they have to correct for that if they're going from indoors to outdoors. They have to redo the color balance on a white sheet of paper to account for the difference between indoor lighting and outdoor lighting. Now, here's where they all got it wrong. But they're not gonna change it because they're deep into it. You ready? Now we have the blending of science and technology with art. You ready? Here it is. If an artist draws an Arctic scene, what color is prevalent? White. And what color? Blue. Blue. Right. If an artist draws Dante's Hell, what color is prevalent? Red and orange.
13:28 Neil deGrasse Tyson? Red and orange. Okay, so emotionally, we think of blue as cold and red is hot.
13:37 Neil deGrasse Tyson? Photographers will tell you we need to reduce the temperature of the light.
13:46 Neil deGrasse Tyson? Which means make it colder emotionally. But the only way to do that is to get more blue in it, which means upping the temperature of the tungsten that they have shining on you, or to put more blue into it. And in the old days, that meant a hotter light bulb. So they said, we need a cooler scene, they had to have a hotter bulb. We need a warmer scene, they had to have a colder bulb to do that.
14:11 Chuck Nice? Wow.
14:12 Neil deGrasse Tyson? And that language is still embedded in that entire profession.
14:15 Chuck Nice? Yep. That is true.
14:18 Neil deGrasse Tyson? The opposites, and they meet in the middle and they deal with it. The opposites of art and technology and science and the physics of light.
14:39 Speaker 03 I'm Ali Khan Hemraj, and I support StarTalk on Patreon. This is StarTalk with Neil deGrasse Tyson.
14:58 Neil deGrasse Tyson? So I got one for you. How about acoustic effects in climatic phenomenon?
15:04 Chuck Nice? Really?
15:05 Neil deGrasse Tyson? Yeah, yeah, I just thought about that.
15:08 Chuck Nice? Okay, it sounds like something that if somebody said to me at a cocktail party, I'd be like, I gotta get a drink, I'll be right back.
15:19 Neil deGrasse Tyson? But they will come back because it's intriguing enough, but they gotta get, they gotta prep.
15:23 Chuck Nice? First, they gotta get prepped.
15:24 Neil deGrasse Tyson? They're chemically prepped for it.
15:26 Chuck Nice? Exactly.
15:27 Neil deGrasse Tyson? All right, so let's start out with thunder and lightning, for example. So lightning, in its path between the ground and the clouds, or between a cloud and a cloud, never goes in a straight line because it's finding the path of least resistance the entire time, unknown to you, this is what it's doing. And then when you see the lightning strike, it is already a predetermined path between one point and another. All right. Now, it turns out the sound of lightning is simply the shock wave of rapidly heated air. By the bolt of electricity moving through the air, which is extremely hot. Right. Okay, it's thousands of degrees.
16:11 Neil deGrasse Tyson? But what matters is that it is, the air is some other temperature and then it is instantaneously made extremely hot. This creates an expanding shock wave that we hear as thunder. Okay. Now, because the, because the path of the lightning is not straight. There are kinks in the root. So each segment of that kinky lightning has its own generated shock wave. Okay? Right. So now you have multiple kinks generating their shock waves and you can have constructive
16:54 Neil deGrasse Tyson? and destructive interference of competing shock waves. That makes so much sense. Which is, oh, go ahead. Okay, okay. Oh, this is good. Okay, so our researchers just found the, the lightning, fifty thousand degrees. Fifty thousand degrees Fahrenheit? Yeah, okay. That, that's hot. Okay, all right. So now, so now watch. So with these different segments, that's why a single lightning bolt, and by the way, the lightning bolt is not all the same distance from you. Okay? There are parts that are a little closer that are on the ground. If it's cloud to cloud, the part directly above you is closer than farther away. So the sound will hit you at different times. But it's one generated event. Right.
17:38 Neil deGrasse Tyson? So, so that's why the lightning can go. Snap, quackle, pop.
17:45 Neil deGrasse Tyson? Okay? That's why it's not just one acoustic experience. It is a, it is a highly. I love your thunder. I, okay, you like my thunder? We have to isolate. No. What just happened? You, if I see that on a meme, I will. Oh, my God, I am so. I'm gonna kick. That is so gonna be a meme.
18:08 Neil deGrasse Tyson? So, so here's the lightning and it's because of the acoustical configuration of the lightning bolt itself. That is wonderful. I'm serious. That is so great because.
18:21 Chuck Nice? One of my favorite things in the world is to hear lightning, um, to hear thunder. But not the rumbling thunder. The thunder that sounds as if it is tearing the sky.
18:34 Neil deGrasse Tyson? Yeah, because that it's okay, I'm getting there. That's my next point. Okay, so, so that, so I'm just simply accounting for, oh, by the way, constructive and destructive interference, if you're not familiar with that. So, so sound travels in waves. So it crests and troughs, and that's, this is a pressure wave through the air. It hits your eardrum, your eardrum vibrates. We interpret that as sound. So does your body too. By the way, there's certain frequencies of sound that are longer, sorry, there's certain wavelengths of sound that are longer than what will fit in your eardrum.
19:09 Neil deGrasse Tyson? So your eardrum will have a hard time communicating it to your brain. But the length of the wavelength is about the size of your chest cavity. That's the low frequency, long wavelength. And so there are some sounds that you feel more than you hear. Ooh, ooh, ooh, ooh.
19:28 Neil deGrasse Tyson? That's the, that's the rhythm section of
19:33 Neil deGrasse Tyson? the beat, well, what do they call the beat, the, the, the beat boppers? What, what do they call the?
19:37 Chuck Nice? Beat boppers, yes.
19:38 Neil deGrasse Tyson? Yeah, yeah, yeah.
19:41 Neil deGrasse Tyson? But if I heard lightning starting to do that, it was like, whoa, there is a god.
19:47 Neil deGrasse Tyson? A god is a DJ. Uh, so here's what happens. The, the lightning sound is a huge cacophony of frequencies of, of sound energy. Okay, high frequency, low frequency. But here's the problem. High frequency doesn't travel very far. It's easily disrupted. It's easily, uh, it can easily lose its energy relative to the energy that it started with. And if high frequency sound loses its energy, it becomes lower frequency sounds. So the farther away you are from a lightning strike.
20:27 Neil deGrasse Tyson? The lower is the total cacophony of frequencies that reach you. Uh huh. So, lightning on the horizon is
20:40 Neil deGrasse Tyson? Okay, if you have a pet dog, they'll, they'll, they hear that and they notice that. And they, they might start trembling and you don't even know why, because that frequency is below what you can hear, the dogs hear it. All right. As the storm gets closer and closer, the higher frequencies become more and more part of what you, what you hear. And if you hear a lightning strike, would that sound like it's ripping the fabric of the space-time continuum? It meant it hit your house.
21:08 Neil deGrasse Tyson? All right. So, so that's what's, that's what's going on there. Sound moves through air at about 700 miles an hour, plus or minus, depends on the, the density of the air. But I like easy math, so let's just declare that the sound is moving at 600 miles an hour. Okay, 600 miles an hour is the speed of sound in air. How far does sound go in a minute? Uh, 600 divided by 60. That's how far? I don't know.
21:40 Neil deGrasse Tyson? You just set up the verbal math problem, then I computed? No, that's not allowed.
21:47 Neil deGrasse Tyson? I don't know, 120 miles.
21:51 Neil deGrasse Tyson? So if it's 600 miles an hour and you divide by 60 minutes. Right. Then sound will move 10 miles in a 10 miles in a 10 miles in a minute. In a minute. Okay. So if sound moves 10 miles in a minute, how many seconds does it take the sound to move one mile? Um, 10 seconds. Or 6, 6 Seconds, right? 6 seconds. So it moves a mile every 6 seconds, so that after a minute, it moves, it moves 10 miles. And after an hour, it moves 600 miles. Right. So, so basically, if you want to know how far away the rain is from you.
22:35 Neil deGrasse Tyson? Time, get the time difference between when you see a lightning strike and when you hear it. So you see the flash and then you count 1001. Mississippi 2003. So if it's five seconds, let's say, that's almost six seconds. So the storm is about a mile away. Mile away. Yeah, about a mile away. And so, and the real number is 700 miles an hour. So it's, you know, you make a small adjustment, but you get the basic idea. Okay? Sound moves a mile every six seconds. And so just for your habits, and if you hear the thunder and it never gets closer than that, the rain is not headed towards you. Don't worry about it. Go home, go back to sleep. Nice. If that time delay keeps getting shorter and shorter and shorter. Watch out. Watch out.
23:20 Neil deGrasse Tyson? Yeah, we're gonna lose your house. Hit you, you're about to lose your house. Yeah, Dorothy, you're not in Kansas anymore. There you go. Nice. So a couple of other acoustic things. So for example, a snowflake is very, is highly variegated, right? It's got six sides. It's got a lot of texture. And if you have snow that's descending and it's just softly landing on blankets on a surface. Okay? Now you have sound. Generally, when you hear someone from a distance, you are relying on the fact that the sound is bouncing off the pavement, off the walls. We don't think often about this, but reflected sound is a big part of how we interact with our world around us. Mm-hmm.
24:05 Neil deGrasse Tyson? All right. If you have snow everywhere, the surface of the snow is not rigid. It's not highly reflective. In fact, it's highly absorbent. So particularly for city people know this, if all of a sudden the city gets quiet and you don't hear anything, look out the window, chances are it's snowing. Nice. Because the sound of the cars, when all the normal sounds that reach you by reflecting off of steel and glass and concrete and cement is no longer reflecting, it's all muffled. Yeah. And so, so the song, the Christmas song Silent Night, Holy Night, whatever other reasons you want to think of it as a silent night, if it has just snowed,
24:49 Neil deGrasse Tyson? guaranteed to be more silent than it otherwise would have ever been. Snow is nature's soundproofing. And they are soundproofing. Now. When you're walking on snow, okay?
25:02 Chuck Nice? As opposed to walking on sunshine.
25:04 Neil deGrasse Tyson? Okay, so it's just snowed and you're walking on it, okay? And that will normally be a silent exercise, okay, because you're just pressing down snowflakes because they landed softly and now you're just sort of compressing them, fine. If it's colder, I forgot the temperatures, if it's colder than like twenty five degrees, twenty, low twenties. If it's definitely if it's in the teens or lower. If you then step on the snow, okay, the snow says, I will not yield under your boot print. I'm going to hold my shape because it is cold enough that we are all solid and rigid. And what happens?
25:49 Chuck Nice? The snow crunches. Yeah.
25:52 Neil deGrasse Tyson? Then you crunch on snow. So if you're filming a movie or if you're observing a scene and you hear people crunching on the snow, guaranteed the temperature in the low twenties or in the teens.
26:02 Chuck Nice? Or there's a guy in a booth with some cornflakes and he's just matching the sound to the people walking.
26:08 Neil deGrasse Tyson? The sound studios have all those, the sound effects in there. Right, so, so that's why snow crunches at cold temperatures and does not crunch at warmer temperatures. By the way, at the warmer temperatures, your pressure is enough to melt the snow. Okay, to bring it immediately below the freezing point. That's a whole other StarTalk explainers that we've done. What, what ice will do under pressure.
26:30 Chuck Nice? Under pressure.
26:31 Neil deGrasse Tyson? Yeah, so these are some interesting sort of sound things to look out for when this happens. Now, it has been rumored that aurora, that you can hear aurora. And, and I don't, I'm not convinced of that.
26:47 Chuck Nice? Really?
26:48 Neil deGrasse Tyson? Yeah, yeah, because it happens, you know, it's, it happens fifty thousand feet up. You know, and ten miles away and farther up in the atmosphere where the atmosphere is really thin. It is electrical. So it could be that it's it's creating other electrical phenomenon in your environment. But to say that you heard sound that comes from that higher, I'm not convinced of that. I don't believe, but people say it, so it's worth.
27:14 Chuck Nice? Yeah, that's it. It sings. Yeah.
27:16 Neil deGrasse Tyson? Yeah. Yeah. It's worth investigating.
27:19 Chuck Nice? I think so.
27:20 Neil deGrasse Tyson? Yeah. Yeah. And so let me think. Any other sounds you heard in weather that you wonder about?
27:25 Chuck Nice? I mean, you know, aside from the fact that my uncle used to like to make his own sounds and then blame it on me.
27:34 Chuck Nice? While we were walking in the cold, other than that.
27:39 Neil deGrasse Tyson? Now, and here's another one. Um, you know, the sound of hail hitting, right? These are basically, these are like marbles falling out of the sky.
27:47 Chuck Nice? I know what that sound is. That is the sound of a call to the insurance adjuster.
27:56 Neil deGrasse Tyson? So people think, you know, you know, when do you get hailed most? You get it in the summertime. Right? That's weird. Ice falling out of the sky in the summertime. Well, it's a reminder that the sun is not heating the air. The air is transparent to sunlight. That's why you can see the sun from Earth's surface through the air.
28:16 Chuck Nice? Except in Los Angeles.
28:19 Neil deGrasse Tyson? Los Angeles and Beijing and Mexico City. Right. So those are inversion layers that so they're climatically susceptible to trapping smog. Both of those three areas, you notice they're all in basins. All Santiago, Chile as well. So here's what happens. The sun heats the ground, the ground heats the air. All right. But if you go high above the ground, it gets very, very cold, very, very quickly, no matter the time of year. All right. But in the summertime, you have the most ground heating. And so you have the most unstable air columns. So the biggest, thickest, juiciest cumulonimbus clouds, which we all learned about in elementary school.
29:02 Neil deGrasse Tyson? The big puffy ones, though you find those in the summertime. And you look at them and you think the cloud is just sitting there, but if you look for long enough, you will see that it is roiling. And in the roiling, there is very highly unstable air rising within it. The more unstable the air is in the upwardly rising cones, the harder it is for whatever is hanging out in there to fall out of the cloud. Because it's kept buoyant by these upwardly moving air columns. Right. So, so you, so you first nucleate a little droplet of, of, of ice.
29:44 Neil deGrasse Tyson? It wants to fall. I say, no, you're not. And it comes back out and it nucleates with more moisture. Cause what is a cloud? It's a big pocket of moisture. Okay, droplets. Droplets, water drops. So it gathers more moisture and ah, no, you're not. And it keeps doing this. It keeps doing this until the frozen ball says, you ain't holding me this time.
30:05 Neil deGrasse Tyson? And that's why all of hail is about the same size because they had to, it had to get to that size to overcome the highly unstable air columns that were supporting, supporting it. And so, so, so the, the more turbulent is the air, the, the louder they will be when they hit the ground. And then there it is. And, and we always reference the size of hail to some other object, which I find interesting. No, it's softball sized hail. It was baseball sized hail. I've never seen anybody talk about hail sized golf balls. Right.
30:42 Neil deGrasse Tyson? Maybe it's obvious why, but I don't know. But anyhow, so Chuck, that's a little bit of the, the sound of weather. I love it. So, so very cool. Oh, and one other thing, one last thing. You ever been driving a car and it's raining and it's raining, you know, the whole time you're driving and then you come under an overpass and it's silent. Yes. Okay. Just silent. That's an interesting phenomenon because what your brain had done was create the sound of rain as the normal, so that when you go under the underpass, it's the absence of rain that you take notice of. See, and that happens in my everyday life where the normal sound is a house full of noise.
31:27 Neil deGrasse Tyson? Children running around. And when you, when you step out the house, you say, what was that?
31:34 Neil deGrasse Tyson? When you step out into silence, you wonder, you look around. So silent out here. What's relevant? What happened? And oh my God, did we move to the country?
31:45 Neil deGrasse Tyson? So there's a word I've seen and it hasn't caught on, but I think it should. It's the sound of the absence of rain.
31:53 Neil deGrasse Tyson? Under an overpass, okay? And it's called a down pause. Oh, instead of a down pour. Yeah. Down pause. Down pause. Oh, that's lovely. I will leave you with that.
32:28 Neil deGrasse Tyson? Friction. Oh, my goodness. Yes. Friction. Friction. Now, friction, usually when people talk about friction, it's bad. All right? You could bring out the WD-40. It's squeaking, it's friction. And friction burn. Friction burn, right? Right, right. But let me tell you.
32:49 Neil deGrasse Tyson? Without friction, life as we know it would not be possible. Hmm. Friction is your friend. See, I have lots of missing skin on my knees. Would that differ? So, so friction, I mean, just think about it. If you just sort of put your elbow on the table. Right. And you just rest it there. Yes. And then you want to listen to me. If there was no friction, you would just slide off the table. There'd be, there'd be nothing keeping your elbow there. That's why I stopped wearing silk shirts.
33:30 Neil deGrasse Tyson? So, so, and let's say you wanted to drive your car. You need the friction between your tires and the road so that you will move forward. If there were zero friction between your car and the road, the wheels would just spin. And nothing would happen. Okay. You would go nowhere. You wouldn't be able to start the car, to move the car, slow down the car, stop the car, or even steer the car. All of that requires friction. To walk.
34:03 Neil deGrasse Tyson? To walk, you put a foot down. There is friction there. You press back and you your next foot moves forward in advance of it. That required friction. This is why on slippery ice where there is no friction. You can't walk, you can't run and you say, and you say, this is bad. Put me back on regular ground. What you're really pleading for is give me some friction. Right. You don't say that because friction has a bad name. And what do you do when it's cold out and you're not wearing gloves? What do you do?
34:36 Neil deGrasse Tyson? Hands get hot. I just realized it's cold in my house.
34:42 Neil deGrasse Tyson? So you do that, okay? Friction is your friend. Oh, that's nice. So so we'll do a whole other thing on friction becoming heat. That's a whole other explainer. That needs its own time for that. Oh. But friction can help get you warm. All right. So the only thing that really does not use friction. Is rockets. All other transportation requires friction. Oh. Bicycles, trains. Okay. Uh, uh, planes in order to take off. Okay? Oh, my goodness. That's right. All of this requires friction. To take, the planes needed to take off. Ah. So with a rocket, however.
35:27 Neil deGrasse Tyson? By the way, it's why rockets work in space. Where there's no air, there's no nothing rubbing against anything else. It sends material out the back. And it recoils forward. Right. So all rockets that are accelerating are losing mass in order to do it in a recoil. Whereas you don't have to lose mass to do it. You just have to press against the earth. Right. Well, Newton told us for every action is an equal and opposite reaction. So if you are stand still and you start moving forward. Actually, something has to start moving backwards. Hmm. And it's communicated that way through friction. So what happens? You move forward with a certain momentum. What are you pushing against?
36:12 Neil deGrasse Tyson? The ground. The ground. The ground has to move backwards. And it does. So, the entire Earth is responding to the fact that you moved in one direction. Okay? Oh, man. Could we all get together, every human being, just in one group, and start running in one direction? Would we speed up the Earth? Yes. Or slow it down, depending on which direction. And it has to be due east or due west. Correct. Due to eastward. Yes. What? So, if you...
36:41 Neil deGrasse Tyson? So, if everyone lined up, okay? And started running due east. Okay? So, that will sort of spin, but which way we turn it? Returning this way. So, you have to run and run due west. And if everybody does that with their scurrying feet, you will speed up the rotation of the Earth. What? That is the response of the Earth to you propelling yourself forward by way of friction connecting you to the Earth itself. It's true with cars, it's true with everything. Now, I once did a calculation, and I said, "Let's get our most powerful rocket engines, bench mount them at the equator where you have sort of maximum torque on the Earth,
37:24 Neil deGrasse Tyson? and can we use that to either speed up or slow down the Earth?" And I did the math on that, and it's hopeless.
37:31 Neil deGrasse Tyson? Okay. It's like a gnat flying full speed into the side of an elephant, and believing the elephant even took notice.
37:43 Neil deGrasse Tyson? So, very confident gnat. Very confident. It's a very confident gnat. In fact, it's less than that. So, but, but... Take that, dumbbo. What I'm saying is, the momentum that we all gave each other by putting ourselves into motion, you can write down that number. Momentum is your mass times your velocity that you gave yourself. Okay? Earth's rotation increase or decrease will have changed by exactly that same amount of momentum, so that they both cancel. Because you started out both not moving relative to each other. So, if one thing starts moving, the other thing has to recoil the other way, so that they balance out.
38:23 Neil deGrasse Tyson? That's physics 101. So if you go forward, Earth goes backwards by the exact same total momentum. But Earth has so much mass relative to all the mass of the humans that your momentum, which is mass times velocity, that's the only quantity that has to be the same. All right. So all we humans run forward and add up all our mass and get our velocities, add it all up, and we got this honking Earth with this really large mass and it gets a teeny nitty bitty velocity to balance us out. So if you don't notice it, but you can calculate what that effect is and it is real.
39:01 Chuck Nice? It is real. Wow. Excellent.
39:03 Neil deGrasse Tyson? And it's friction. It's all friction. So I just want you to think of friction as a good thing. It's more good than bad. One thing friction does is it slows down things that were put into motion. And Aristotle, not really understanding friction, Aristotle got most of his physics wrong, by the way. He's not a champ. He's no hero in physics and astrophysics.
39:28 Chuck Nice? Thank God he had philosophy.
39:30 Neil deGrasse Tyson? Philosophers like him. And he did important things, but there's stuff he could have really checked and he didn't. And so it's before experimental philosophy kicked in as a version of thinking philosophy. And so the experimental philosophers, Bacon had a whole book just on experiments that he said he conducted, but there's like a thousand experiments in it and that's what all he'd be doing every day for the rest of his life. So I don't think he did them all, but it's a book. He collected them. And so he and Galileo, do the experiment if you have an idea. Okay.
40:05 Chuck Nice? So Because otherwise, and no disrespect Aristotle, you're just bullshitting.
40:11 Neil deGrasse Tyson? You're just, you're just thinking stuff up that you think should be true because it makes sense to you.
40:17 Chuck Nice? We can all do that.
40:19 Neil deGrasse Tyson? In the armchair. So he said, things in motion tend to come to rest. Okay. So
40:27 Neil deGrasse Tyson? that's true, right? All right. But Galileo said, wait a minute. If I wax the track, you know, I have a thing, I roll it down the hill and it stops like here. Now I make it smoother. It stops a little farther away. Make it even smoother. It starts even farther away. And he said, wait a minute. What would happen if there was no friction on this track? Where will it stop? And he concluded that things in motion will tend to stay in. He fed Newton's, things in motion tend to stay in motion. It's the opposite of Aristotle, unless acted on by an outside force.
41:08 Chuck Nice? Ah, look at that.
41:09 Neil deGrasse Tyson? And so Galileo was the bridge between Aristotle and Newton. And doing the experiments by waxing the track, making it ever more smooth. Reducing the friction coming, that enabled him to establish a fundamental truth about nature. Going beyond just what your life experience is.
41:29 Chuck Nice? Look at that, Galileo, the Mr. Miyagi of physics. Who knew?
41:37 Neil deGrasse Tyson? Wax on, wax off. So I just want you to appreciate friction.
41:47 Chuck Nice? You know, I, I, I will, I will not, I, no. I still can't get my head around liking friction. But, but it is necessary.
41:58 Neil deGrasse Tyson? Without, without friction, everything would just be floating, would be gliding.
42:02 Chuck Nice? Sliding around.
42:03 Neil deGrasse Tyson? Sliding around. You sit on a couch, the couch would just slide back. By the way, you could push very heavy things. If there's a freight train, I don't care what it weighed. If it's on frictionless tracks, let's say it's a maglev frictionless track and you have a little, a little, a little handle. Just take it and start pulling. So you could put a force on it and yes, it's way more mass than you are. So the velocity will be small, but it'll have some velocity. So you can just start pushing it. And this is why those strong men in competitions, okay, where they pull with it in the old days. They pull the train with their teeth. Okay.
42:42 Neil deGrasse Tyson? It's because trains are on steel, rolling wheels on steel tracks, which has very low friction. Okay. If you took it off the tracks and let it sit there in the mud and then have them try to tug the train, that ain't happening.
43:00 Chuck Nice? That's, that's kind of funny though.
43:02 Neil deGrasse Tyson? You could pull things that have wheels on them because wheels have very low friction in the transmission of the movement of that object to the ground because you're not dragging it on the ground.
43:14 Chuck Nice? Right.
43:14 Neil deGrasse Tyson? But the wheel itself still needs a little bit of friction in order to not spin, spin out. That's all.
43:21 Chuck Nice? That's so cool. Oh, you know, I, I have to say, I, I, I will never think of friction in the same way.
43:31 Neil deGrasse Tyson? One last thing.
43:33 Chuck Nice? Okay.
43:33 Neil deGrasse Tyson? One last thing.
43:36 Neil deGrasse Tyson? When astronauts re-enter the atmosphere and they have that, you know, the, the burning phase, you know?
43:41 Chuck Nice? Yes.
43:42 Neil deGrasse Tyson? The flames and the thing, alright. We say, oh my gosh, will they survive? This is bad. How could, no, you need that.
43:51 Neil deGrasse Tyson? The astronauts coming out of orbit are going 17,000 miles an hour and they didn't bring fuel to break.
43:58 Chuck Nice? Oh.
43:59 Neil deGrasse Tyson? Okay, because all they would have to do, all they would have to, we don't do this, but what they could do is bring enough fuel, wh- while you're in orbit at 17,000 miles an hour, because that's orbital speed, turn their ship around and fire it backwards.
44:12 Chuck Nice? Right.
44:13 Neil deGrasse Tyson? That will slow you down. And you keep doing that until you like have zero velocity and then you just drop out of the sky. If you drop out of the sky, you're not going to be burning up. Because what's burning up is the kinetic energy of having gone 17,000 miles an hour in the first place.
44:33 Neil deGrasse Tyson? I saw a movie, I think it was, it was one of these Mars movies, uh, one of the earlier ones that came and went, where there, there's something happening on a platform and the guy falls off the platform, but it's a stable platform up there, uh, above the ground. And as he falls, you see him just burn up. It's like, no, no. The act of falling through the atmosphere alone is not what burns you up. It's the fact that you were going from 17,000 miles an hour to zero and where does all the kinetic energy go? There is friction between you and the air molecules passing across your surface. There's also shock waves that communicate as you're going faster than the speed of sound.
45:15 Neil deGrasse Tyson? Shock waves take all this energy that you have and convert it into heat and then the heat dissipates. And then you fall down out of the sky alive because you have special heat shields that protect you.
45:29 Chuck Nice? Uh huh. There you go.
45:31 Neil deGrasse Tyson? And before we perfected the tiles that we used on the shuttle.
45:35 Chuck Nice? We had the heat shield.
45:36 Neil deGrasse Tyson? Astronauts. They weren't really shields. A shield is something that protects you. We call them shields, but that's not what they were. You know what they were? They were like onion layers of burnable material.
45:48 Chuck Nice? Oh, so they just burned off.
45:50 Neil deGrasse Tyson? Exactly.
45:51 Chuck Nice? But you had to go through enough of them to get to the crispy center.
45:59 Neil deGrasse Tyson? Where the astronauts are.
46:00 Chuck Nice? Where the astronauts are.
46:02 Neil deGrasse Tyson? So, so it turns out coming out of orbit, you need more of these layers than when you come back from the moon. So coming back from the moon, they just make that layer thicker. And then it ablates and it heats, it burns off and goes out. It takes the heat away and eats as these layers go. So it was a very blunt, effective heat shield. But it's really a shield that dissolves away in the heat. All of that, the friction, the shock waves, and that allows you to not have to take fuel in order to slow down using fuel because you're basically aero braking.
46:35 Chuck Nice? Sweet.
46:37 Neil deGrasse Tyson? That's what reentry is. It's a form of aero braking.
46:40 Chuck Nice? That is fascinating.
46:41 Neil deGrasse Tyson? Friction is your friend. That's all I'm trying to tell you, Chuck.
46:44 Chuck Nice? Every astronaut loves friction. Otherwise, they can't come home.
46:47 Neil deGrasse Tyson? Can't come home. Or you need fuel to slow down. That's all I'm saying. You want to exploit, exploit what you got. And so you should say, great, they're burning up their heat shields. That's a good thing.
46:59 Chuck Nice? Sweet. All right.
47:01 Neil deGrasse Tyson? All right.
47:01 Chuck Nice? I'm liking it.
47:02 Neil deGrasse Tyson? Chuck, friction is your friend.
47:05 Chuck Nice? All right. I got a new friend today. That makes one.
47:10 Neil deGrasse Tyson? Makes one, one, one friend. Chuck and his one friend.
47:13 Chuck Nice? I got my one friend.
47:17 Neil deGrasse Tyson? All right. Neil deGrasse Tyson here, your personal astrophysicist. Keep looking up.
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