Things You Thought You Knew – The Color of the Sun

0:00Hey everybody in the StarTalkiverse, 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. Welcome to StarTalk, your place in the universe where science and pop culture collide. StarTalk begins right now. Welcome to the Explainer Zone. Yes, the Explainer Zone. Yeah, yeah. Not the Twilight Zone. Not the Twilight Zone. We are confused at the end. Right. The explainer zone. Where you come out knowing more than you did when you went in. Knowing some stuff. Right. And so I think there's no end to this, just so you know.

0:48Good. I will be calling you forever. All right. So I want to talk about the sun, the color of the sun. Okay. All right. Well, you know me. I don't see color. You don't see color. Sorry. We're already done here. Um, 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? Um, well, I was a very depressed child. So black. Black. Okay. No, you knew about black holes. Yes, exactly. No. Oh, it's always a big yellow ball. It's always yellow. And this notion has been with us since childhood, that the sun is yellow.

1:34Yes. And that's not true. It's not even close to being true. Uh-oh. And so, yeah, I'm sorry. You know, I don't want to. Are there any kids watching? Please. 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. Okay. So here's the thing. The sun in broad daylight is too bright to look at. All right. Without risking damaging your eyes. So unless of course you have perfect eyes. Okay. So, so you don't do it. All right. So when is the time most people ever find themselves looking directly at the sun?

2:27When is that? Well, the only times I've ever done it is 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. Right. And it has a deep yellow color. Sometimes it's so deep it can be red, amber into red. Yeah. So, and we know the sun isn't red. Of course it's not red. We know that's an optical effect. Now, this isn't Krypton. It's not Krypton. Exactly. I had a red sun. So, you know intuitively it's not red, but somehow you don't know intuitively that it's also not yellow.

3:13Okay. what color is the sun it is white now now come on man why you gotta do that white see what what just like everything else all of a sudden chuck not everything we got a race commentary you know what seriously we gotta must we whitewash all of history including the sun really so yeah so it's not yellow okay 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 okay and you just need a little bit of trigonometry it's a simple calculation.

4:30And if it's low on the horizon, it goes through five, six, ten equivalent atmospheres 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 ten times that and more when it goes lower on the horizon. Okay. So let's see what the atmosphere is doing when the sun is overhead. 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 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 a violet side of the spectrum Those particles preferentially scatter the blue out of the sunlight.

5:32Preferentially 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. Look at that. Okay. 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 sky. That's why on cloudless days into sunset, the sun gets deeper and deeper and deeper blue.

6:15The bluest sky. That's why sky blue is light blue. Right. All right. You want to talk about serious right home to mama blue is the blue sky that surrounds the twilight curtain of a sunset. Now you're talking blue. Right. 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 going to get an amber sun. 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 now look at, oh, we have a yellow star.

7:04Look, it's yellow. No, the atmosphere made it yellow. Okay? Wow. It's lying to you. And 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 it's this is very very disturbing because the clouds themselves don't change the color of the sun it'll just it just dims it so you look at a slightly dimmer sun uh behind the thin clouds as they pass it's not yellow it's not yellow 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 address 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 they you do it's just the opposite and all right it's 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.

8:36Correct. 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. We kind of pinkish, but yeah. That's right. So it reflects all colors, but now it's only getting red. It's going to reflect the red. It reflects all colors. The page is red to 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, then snow would be yellow.

9:24yellow which by the way sometimes snow is yellow and it's not from the sun and whatever you do whatever you do stay away from that snow the fact that snow looks white right is evidence that it's being illuminated by white light wow that white light is either sunlight or a moonlight that's right which is also a reflection of sunlight it's just reflected sunlight there you go this is so disturbing so 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 ready to go up a notch on this i don't know if i'm ready to go up and i don't think you're ready okay so um white is the sun I hate where this is going already.

10:20Relative to incandescent bulbs. Right. Okay. Your kids will have no memory of incandescent bulbs, 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. It was a bulb with a little piece of wire in it. Okay. That wire used to light up. You hear me? That sounds like a Ken Burns special. The guy on the porch. 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 and we pulled the switch we pulled the switch and it gave off light now first it looked like magic

11:07okay we gotta put you on the list of the next Ken Burns special the origin of the light bulb so alright So where was it? I forgot. Okay. He's saying incandescent bulbs. 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 or 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.

11:47Okay? So if you bring out film that needs the full complement of blue, and you take a picture under incandescent lights, everything is going to be red. That film, if it needed the blue, is called daylight film. This is why there was a difference. Again, I'm only talking old timers here. There was indoor film and 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, it's getting all the blue it ever wanted.

12:29If 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 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 going to 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.

13:10If 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. Red and orange. Okay, so emotionally, we think of blue as cold and red as hot. Photographers will tell you we need to reduce the temperature of the light, which means make it colder emotionally. functionally. 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.

14:04So 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. Wow. And that language is still embedded in that entire profession. Yep. That is true. 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.

14:39I'm Ali Khan Hemraj. And I support StarTalk on Patreon. This is StarTalk with Neil deGrasse Tyson.

14:57so i got one for you how about acoustic effects in climactic phenomenon really yeah yeah i i just thought just thought about that okay it sounds um like something that But if somebody said to me at a cocktail party, I'd be like, I got to get a drink. I'll be right back. But they will come back because it's intriguing enough, but they got to get prepped. First, they got to get prepped. They're chemically prepped for it. Exactly. 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 the cloud, never goes in a straight line.

15:39because 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. It's thousands of degrees. But what matters is that the air is some other temperature, and then it is instantaneously made extremely hot. This creates an expanding shockwave that we hear as thunder. Okay.

16:27Now, because the path of the lightning is not straight, Right. There are kinks in the root. So each segment of that kinky lightning has its own generated shockwave. Okay. Right. So now you have multiple kinks generating their shockwaves and you can have constructive and destructive interference of competing shockwaves. 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 50 000 degrees 50 000 degrees fahrenheit yes okay that that's hot okay all right i'll send it 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 the 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.

17:30So the sound will hit you at different times. But it's one generated event. Right. So that's why the lightning can go, snap, quackle, pop. Okay? That's why it's not just one acoustic experience. It is a highly... I love your thunder. Okay. You like my thunder? We have to isolate. No. What just happened? If I see that on a meme, I'm going to kick you. Oh, my God. I am so. I'm going to kick. That is so going to be a meme. 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 one of my favorite things in the world is to hear lightning, to hear thunder.

18:25but not the rumbling thunder the thunder that sounds as if it is tearing the sky 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.

19:08So 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.

19:28that's the rhythm section of the beat well what do they call the beat the the the beat boppers what do they call the beat batzers yes yeah yeah yeah but if i heard lightning starting to do that it was like whoa There is a God. God is a DJ. So here's what happens. The lightning sound is a huge cacophony of frequencies 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, lose its energy relative to the energy that it started with. And if high frequency sound loses its energy, it becomes lower frequency sounds.

20:21So the farther away you are from a lightning strike, the lower is the total cacophony of frequencies that reach you. uh-huh so lightning on the horizon is all right okay if you have a pet dog they'll they hear that and they notice that and 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 where that sounds of like it's ripping the fabric of the space-time continuum. It meant it hits your house.

21:08All 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 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? 600 divided by 60. That's how far? I don't know. You've just set up the verbal math problem in my computer. No, that's not allowed. I don't know, 120 miles. So if it's 600 miles an hour and you divide by 60 minutes, okay? Then sound will move 10 miles in a minute.

22:0010 miles in a minute. In a minute. Right. Okay. So if sound moves 10 miles in a minute, how many seconds does it take the sound to move one mile? 10 seconds. Or six. Six seconds, right? Six seconds. So it moves a mile every six seconds so that after a minute, it moves 10 miles. Right. 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

22:37time 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 one down 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 lose a mile every six seconds. And so just for your habits, if, 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.

23:13Go home, go back to sleep. Nice. If that time delay keeps getting shorter and shorter and shorter, watch out, watch out. Yep. Yeah. I'm going 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.

23:57We don't think often about this, but reflected sound is a big part of how we interact with our world around us. 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 and 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 the song, the Christmas song, Silent Night, Holy Night, um whatever other reasons you want to think of it as a silent night if it has just snowed guaranteed to be more silent than it otherwise would have ever been snow is nature soundproofing and they are soundproofing now when you're walking on snow okay as opposed to walking on sunshine okay if it's just snowed and you're walking on it okay and that will normally be a silent exercise, okay?

25:16Because 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 25 degrees, low 20s, 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? The snow crunches. Yeah. 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, guarantee the temperatures in the low twenties are in the teens or or there's a guy in a booth with some cornflakes and he's just matching the sound to the people walking is the sound studios have all those sweat the sound effects in them 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 star talk explainers that we've done, what ice will do under pressure.

26:30Under pressure. 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 I'm not convinced of that. Really? Yeah. Yeah. Because it happens, it, you know, it's, it happens 50 ,000 feet up, you know, 10 miles away and farther up in the atmosphere where the atmosphere is really thin, right? It is electrical. So it could be that it's creating other electrical phenomenon in your environment. But to say that you heard sound that comes from that high, I'm not convinced of that. I don't believe, but people say it.

27:14So it's worth the essays it sings yeah yeah yeah it's worth investigating i think so yeah yeah and so let me think any other sounds you've heard in weather that you wonder about i mean you know aside from the fact that uh my uncle used to like to make his own sounds and then blame it on me while we were walking in the cold other than that now and here's another one um you know the sound of hail hitting right these are basically these These are like marbles falling out of the sky. I know what that sound is. That is the sound of a call to the insurance adjustment.

27:56So people say, you know, when do you get hailed most? You get it in the summertime. All 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. So the septum of Los Angeles. The septum of Los Angeles and Beijing and Mexico City. Right. So those are inversion layers. So they're climactically susceptible to trapping smog. Both those three areas. You notice they're all in basins. Oh, yeah. Santiago de Chile as well. So here's what happens.

28:38The sun heats the ground. The ground heats the air. But if you go high above the ground, it gets very, very cold very, very quickly, no matter the time of year. 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, the big puffy ones, 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.

29:19The more unstable the air is in the upwardly rising columns, the harder it is for whatever is hanging out in there to fall out of the cloud. Wow. Because it's kept buoyant by these upwardly moving air columns. Right. So you first nucleate a little droplet of ice. It wants to fall. I say, no, you're not. And it comes back out and it nucleates with more moisture. Because what is a cloud? It's a big pocket of moisture. Droplets. Droplets. Water drops. So it gathers more moisture. And, uh-huh, 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.

30:05And that's why all of hail is about the same size. Because it had to get to that size to overcome the highly unstable air columns that were supporting it. And so the more turbulent is the air, the louder they will be when they hit the ground. And then there it is. And we always reference the size of hail to some other object, which I find interesting. It was softball-sized hail. It was baseball-sized hail. I've never seen anybody talk about hail-sized golf balls. Right. Maybe it's obvious why, but I don't know. But anyhow, so Chuck, that's a little bit of the sound of weather. I love it. So, so very cool.

30:51Oh, 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 annoying children running around. And when you step out the house, you say, what was that? I was surprised.

31:34When you step out, it's a silence. You wonder, you look around. So silent out here. What's relevant? What happened? And I'm like, God, did we move to the country? 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 under an overpass okay and it's called a down pause oh instead of a downpour yes down pause down pause there oh that's lovely i'm gonna leave you with