Things You Thought You Knew – Is Everything Light?

How bright is the Earth from the moon? Neil deGrasse Tyson and Chuck Nice have fun with the sun’s reflectivity, discuss light pollution, and explore the electromagnetic light spectrum: how does sunscreen work?

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's Things You Thought You Knew. Three topics of immense interest to me, maybe even to you. We're going to talk about albedo, followed by light pollution, and ending with the electromagnetic spectrum. Be there.

• 0:22Neil deGrasse Tyson?

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

• 0:35Neil deGrasse Tyson?

  Chuck, I got one for you.

• 0:36Chuck Nice?

  Alrighty, I'm ready.

• 0:38Neil deGrasse Tyson?

  One of my favorite words.

• 0:40Chuck Nice?

  Okay.

• 0:41Neil deGrasse Tyson?

  Albedo.

• 0:42Chuck Nice?

  Alright, now what language is that?

• 0:46Neil deGrasse Tyson?

  The language of science.

• 0:49Chuck Nice?

  Really?

• 0:50Neil deGrasse Tyson?

  Albedo.

• 0:51Chuck Nice?

  Okay, first of all, it sounds like a scientist, not a scientist. Hey, how you doing? I'm Albedo. Perhaps you're familiar with my equations. But albedo, albedo.

• 1:03Neil deGrasse Tyson?

  Albedo. So, albedo is a very precise measurement of how reflective something is.

• 1:14Chuck Nice?

  Really?

• 1:14Neil deGrasse Tyson?

  At a given wavelength, but typically we're just at any wavelength. So, for example, if you have an albedo of... And albedo can range from 0 to 1, okay? So, think of it as a percentage, so 0% to 100%. So, an albedo of 0.5, that means half the light that hits it gets reflected.

• 1:38Chuck Nice?

  Gotcha.

• 1:39Neil deGrasse Tyson?

  So, what happens to the other half?

• 1:41Chuck Nice?

  Absorbed?

• 1:42Neil deGrasse Tyson?

  Absorbed, absorbed, okay. An albedo of 100% is?

• 1:48Chuck Nice?

  A mirror.

• 1:49Neil deGrasse Tyson?

  A mirror, precisely.

• 1:51Chuck Nice?

  Cool.

• 1:52Neil deGrasse Tyson?

  So, nothing gets absorbed, okay? And an albedo of 0 means 100% of the light energy gets absorbed and nothing gets reflected back.

• 2:03Chuck Nice?

  Wow.

• 2:04Neil deGrasse Tyson?

  Okay.

• 2:04Chuck Nice?

  Can that even exist?

• 2:06Neil deGrasse Tyson?

  Yeah, it's called a black hole, but...

• 2:10Neil deGrasse Tyson?

  No, but also, also, um, stars have basically zero albedo, but no one thinks about it that way because they're generating light of their own. Right, they're radiating light, so why would they be? Yeah, but that kind of makes sense. Yeah, so it turns out that these glowing stars out there, they absorb all energy that hits it and they manufacture their own energy to come back out. But it's the absorbed energy is not as They're just greedy little something. The absorbed energy is not as interesting to talk about when it is an energy generating source unto itself. Right. So let's see how albedo affects us. So, so if, if you didn't have anthropologists saying, "Let us divide the world into races", okay? Right.

• 2:55Neil deGrasse Tyson?

  If, if they really wanted to be sort of scientific about it, they could just have an albedo. You just get to have an albedo. Right, because, yeah. That's a full spectrum, right? I mean, that's so much, that's so much more specific. There's more information. Than the arbitrary designations that we give people based on their skin color and their culture. Yeah, right, because what we do is we say, "Everybody who has this rank, put them in this one bin and we'll describe them all that way." Exactly. And that way, but if, if you thought about albedo from the beginning, you'd realize that the human species fully populates the entire spectrum, uh, the entire range of albedos. Right. Okay, they're very highly reflective white people, they're very highly absorptive black people.

• 3:40Neil deGrasse Tyson?

  Right. And so, uh, dark-skinned people. Like, so like Jamin, like Jamin Hantu. The actor, the actor. The actor, he'd be like a point one. Yeah, way down there, very, way down there. Right. Okay, reflecting very little light that hits him. Right. And so, this tells you a lot of things, okay? Yeah, yeah. So, if you have very, if you're very fair-skinned, you're reflecting most of the sunlight that hits you. Right. Even so, fair-skinned people are susceptible to sunburn. Right. Even though they're reflecting most of the light that hits them, the little bit that gets through is sufficient to do skin damage. Right. If darker-colored skin, you're absorbing most of the light that hits you. Right.

• 4:23Neil deGrasse Tyson?

  So, the, the role of melanin is extraordinary in that regard. Okay? So, but let's keep going. Um, the, take a guess what the, what the albedo of the moon is, just take a guess.

• 4:38Neil deGrasse Tyson?

  You see it at night?

• 4:39Chuck Nice?

  I see it at night. Well, I gotta tell you, it's pretty bright, but it's nowhere near as bright as the sun, so I'm

• 4:45Neil deGrasse Tyson?

  Well, the sun gives off, it's, but the sun it radiates it, albedo is a reflectivity thing.

• 4:49Chuck Nice?

  Right, that's what I'm saying, so it's just, you know, it's not a mirror, because it would be as bright as the sun, so I'm gonna say, I'm gonna say five.

• 4:56Neil deGrasse Tyson?

  Point, point five?

• 4:57Chuck Nice?

  Yeah, point five.

• 4:57Neil deGrasse Tyson?

  Okay, so, no, no, the albedo of the moon is around point one.

• 5:02Chuck Nice?

  Wow.

• 5:03Neil deGrasse Tyson?

  The, the moon is almost as dark as the sidewall tires on a car.

• 5:09Chuck Nice?

  Wow.

• 5:11Neil deGrasse Tyson?

  Yep.

• 5:11Chuck Nice?

  That's just how bright the sun is.

• 5:14Neil deGrasse Tyson?

  Yes, yes.

• 5:15Chuck Nice?

  That's how bright the sun is.

• 5:18Neil deGrasse Tyson?

  Yes.

• 5:18Chuck Nice?

  That it takes point one albedo and makes it look like

• 5:23Neil deGrasse Tyson?

  Look like, and you can read by the light of the moon at night, from earth, that's right.

• 5:28Chuck Nice?

  How romantic, I love it.

• 5:29Neil deGrasse Tyson?

  So, so point one, and so the moon is basically dark.

• 5:33Chuck Nice?

  Dark.

• 5:33Neil deGrasse Tyson?

  Now, so, so, when you measure the daytime temperature on the moon, that's kinda why it gets up to the hundreds of degrees.

• 5:42Chuck Nice?

  Right.

• 5:42Neil deGrasse Tyson?

  Okay, where's it getting this temperature, because it's absorbing all that sunlight?

• 5:46Chuck Nice?

  Wow.

• 5:47Neil deGrasse Tyson?

  If you're absorbing the energy, reflecting very little, this, the consequence is your temperature rises.

• 5:53Chuck Nice?

  That's cool.

• 5:53Neil deGrasse Tyson?

  Okay, so now.

• 5:54Chuck Nice?

  I mean, that's hot.

• 5:55Neil deGrasse Tyson?

  Okay.

• 5:58Neil deGrasse Tyson?

  That's good, that was good, that was good, alright, so now, let's look at the fashion industry. Summertime.

• 6:05Chuck Nice?

  Right.

• 6:06Neil deGrasse Tyson?

  Okay, are they rolling out their black shirts and black dresses and black blouses and black, no.

• 6:11Chuck Nice?

  Super light colors and white.

• 6:13Neil deGrasse Tyson?

  Colors lighten, so that in the summertime, where you want to stay cool, even when you're outdoors, here's this sunlight, and you wear white clothes, it reflects the sunlight, and if you wore dark clothes, not only are you hot because the air is hot, you'll get hot because you're actively absorbing sunlight.

• 6:33Chuck Nice?

  Right.

• 6:34Neil deGrasse Tyson?

  And so that's, it's, it's not just a fashion thing, it's a physics thing, that if you wanna stay cooler in the summer, then you wear lighter colored clothes, unless... It's the Arctic summer.

• 6:49Neil deGrasse Tyson?

  And it might warm up, and the Antarctic, it like, might warm up to 28 degrees, you know, in the, in the heat of the summer.

• 6:57Chuck Nice?

  Oh, that's a hot day in the summer, huh?

• 6:59Neil deGrasse Tyson?

  A hot day, so there you might wanna wear extra black to absorb as much sunlight as you can. And so-

• 7:05Chuck Nice?

  Or you're just from New York.

• 7:07Neil deGrasse Tyson?

  You just can be strategic about the color of the clothing that you wear. And then you put the fashion element on it. You can't wear white after Labor Day or whatever. Right. But still, I, I am strategic when I put on clothes, depending on the, how, whether this, forget the air temperature. Is the sun out? Do I want the sun's energy? Or do I not? And so, I will factor all this in before I step out the front door that day.

• 7:35Chuck Nice?

  Wow.

• 7:36Neil deGrasse Tyson?

  Okay, so now-

• 7:36Chuck Nice?

  Go ahead.

• 7:37Neil deGrasse Tyson?

  What do you think of the albedo the Earth is?

• 7:39Chuck Nice?

  Okay, so I'm looking at the Earth, it's mostly water. I'm gonna say that it's .3.

• 7:45Neil deGrasse Tyson?

  That's exactly .3.

• 7:47Chuck Nice?

  What?

• 7:47Neil deGrasse Tyson?

  So, so, well, it fluctuates. It depends. Chuck doing a happy dance.

• 7:57Neil deGrasse Tyson?

  So, so, so, the Earth is, is harder to, to give a single value to it, because if it happens to be cloudy on that side that's facing the sun, clouds are white and they're highly reflective. So, in that case, the albedo is higher than average. If there are no clouds and the oceans are pointing towards the sun, oceans do reflect a lot of sunlight, but they're basically dark. And so, you, the average comes out to about .3.

• 8:23Chuck Nice?

  Cool.

• 8:24Neil deGrasse Tyson?

  Okay. So that means 70% of the sun's energy that's hitting the Earth is absorbed.

• 8:32Chuck Nice?

  Right. Wow, and you know, wow, man, you just broke my heart when you said that, because, you know, the fact is that we're trapping heat, and then we got this heat coming in, and 70% is already absorbed, and then we're trapping what is being reflected. We're trapping what's being reflected. We're stupid as hell! What is wrong with us? What is wrong with us?

• 8:57Neil deGrasse Tyson?

  Chuck, I didn't mean for you to blow a gasket on that little bit of data there.

• 9:03Chuck Nice?

  It's like, why are we doing that?

• 9:05Neil deGrasse Tyson?

  Oh, exactly. So, so you've got, so that, so 70% gets absorbed and basically stays here unless it can re-radiate back. But that amount goes, gets to the earth's surface. That's the point. And gets absorbed.

• 9:19Chuck Nice?

  Look at that.

• 9:20Neil deGrasse Tyson?

  And what happens later is, is how much greenhouse gases are there.

• 9:23Chuck Nice?

  Yeah.

• 9:23Neil deGrasse Tyson?

  And this sort of thing.

• 9:24Chuck Nice?

  Yeah.

• 9:25Neil deGrasse Tyson?

  So, but, but wait, there's more.

• 9:27Chuck Nice?

  Oh, I love it.

• 9:28Neil deGrasse Tyson?

  So, Earth is about four times as wide as the moon is. Moon is about 2,000 miles across, Earth is 8,000 miles in diameter. So, it's about four times wider. If you do the math, Earth on the sky, seen from the moon, is 16 times larger than the moon in the sky as seen from Earth.

• 9:51Chuck Nice?

  That's...

• 9:52Neil deGrasse Tyson?

  If, if you do the math, okay?

• 9:54Chuck Nice?

  It must be so great to stand on the moon and...

• 9:56Neil deGrasse Tyson?

  So, watch, so, watch. So, full Earth on the moon is not only 16 times larger, it is also three times more reflective than the moon.

• 10:10Chuck Nice?

  Ugh.

• 10:11Neil deGrasse Tyson?

  Because it has an albedo of .3 instead of .1.

• 10:14Chuck Nice?

  .1.

• 10:15Neil deGrasse Tyson?

  So, that means, full Earth seen from the moon is three times 16, so is nearly 50 times brighter.

• 10:28Chuck Nice?

  Brighter.

• 10:29Neil deGrasse Tyson?

  On the moon than full moon is on Earth.

• 10:32Chuck Nice?

  Ugh. God, the moon has it so much better than we do. It's like, you could sit there, I mean, to watch an Earth rise on the moon is just like so much better than what we get.

• 10:42Neil deGrasse Tyson?

  Yeah, yeah, so you, so you talk about, uh, uh, people, lunar, lunar beings.

• 10:48Chuck Nice?

  Yeah, lunar beings.

• 10:49Neil deGrasse Tyson?

  Have it real good.

• 10:50Chuck Nice?

  Moon men.

• 10:51Neil deGrasse Tyson?

  Moon people. Yes, so, yes, and so they could easily read by the light of the Earth if they needed to do so. Now, the Earth is so bright... That the crescent moon,

• 11:04Chuck Nice?

  Right.

• 11:04Neil deGrasse Tyson?

  The crescent moon, uh, if you do the geometry on this, if you see the crescent moon in the sky, you're looking towards where the sun is, and the entire side of the earth that's lit by the sun is facing that crescent moon.

• 11:19Chuck Nice?

  Okay.

• 11:19Neil deGrasse Tyson?

  Okay, so, what that means is, if you're in the darkened area of the moon, not the crescent, so there's the crescent and the rest of the moon, stand where it's not crescent. The earth is this bright orb in the sky. Okay, so now watch. The sunlight goes from the sun to the earth, goes to you on the moon, and you're impressed that we're 50 times brighter, and it is so bright on that darkened area of the moon, that it reflects back to earth.

• 11:46Chuck Nice?

  Ah.

• 11:47Neil deGrasse Tyson?

  That's why you can see the outline of the rest of the moon from the crescent. Have you, have you seen this?

• 11:54Chuck Nice?

  Yes, I was just about to say! That happened!

• 11:58Neil deGrasse Tyson?

  You can't, you, the sun isn't illuminating that, there's no reason at all in this universe for that to be visible to you, except that it's double reflecting earth light.

• 12:08Chuck Nice?

  Oh, that's amazing. That is really cool. I mean, that is just, that's amazing.

• 12:13Neil deGrasse Tyson?

  And it's called earth shine.

• 12:15Chuck Nice?

  Earth, oh!

• 12:16Neil deGrasse Tyson?

  And I think it really should have been called moonshine, if you ask me, that's just me. That's just me, but it's the sun illuminating full earth, illuminating the darkened moon, coming back to earth, and that's why that's visible.

• 12:30Chuck Nice?

  That's, that's, yo, that's great.

• 12:32Neil deGrasse Tyson?

  And it's all about the albedo.

• 12:34Chuck Nice?

  It's all about, mm, you know what? I'mma, I'mma make some moonshine and call it albedo.

• 12:44Chuck Nice?

  Albedo moonshine, baby. When you, when you wanna shine twice as bright.

• 12:49Neil deGrasse Tyson?

  Count me in on that. I wanna be an early investor on your moonshine albedo. Uh, and one last thing before we, we land this plane here. Uh, for the longest while, people assumed that the moon was the source of its own light.

• 13:04Chuck Nice?

  Right.

• 13:04Neil deGrasse Tyson?

  Okay, then you had to come up with explanations for why it would go through phases, which was hard, but that was just assumed. And it's basically, that's traceable back to biblical genesis. You know, God created the moon to light the night and the sun to light the day, and no one understood the geometry of what was going on. And it was just widely assumed that that meant the moon was making its own light. So, earth shine was unexplained until Leonardo da Vinci.

• 13:29Chuck Nice?

  My man.

• 13:30Neil deGrasse Tyson?

  And in his notebooks, which are all, he's left-handed and he writes backwards and he illustrates what he's talking about and he's a brilliant artist. So, he figures out, because he saw where the sun is, where earth is, what must be illuminated, what must not. He has a picture, I think it's in this codex like, like, just, codex like, which is these, these opuses of his writings. And in it, you, he draws this, a ray of sunlight coming to the earth, going back to the moon, then coming back to earth.

• 14:00Chuck Nice?

  Wow.

• 14:01Neil deGrasse Tyson?

  And so, he first figured it out, 15th century.

• 14:03Chuck Nice?

  Guy's a genius.

• 14:04Neil deGrasse Tyson?

  We got it.

• 14:04Chuck Nice?

  I saw the rest of it, that's amazing.

• 14:06Neil deGrasse Tyson?

  There it is. So, that's Albedo, and you see why I like the word. It's fun to say, it's fun to think about, and it applies to so many things in this world.

• 14:13Chuck Nice?

  Uh, including earthshine, which is my new thing. I love it.

• 14:17Neil deGrasse Tyson?

  All right, Chuck.

• 14:18Chuck Nice?

  That was great, man. That was, Albedo. Yes.

• 14:23Neil deGrasse Tyson?

  I, I got an applause for that one. Oh, thank you.

• 14:25Chuck Nice?

  That was, that, I'm telling you, that was really cool, man. I'm gonna name my next son, Al.

• 14:30Neil deGrasse Tyson?

  Okay.

• 14:31Chuck Nice?

  All right.

• 14:32Neil deGrasse Tyson?

  And, and if you have a daughter, you're gonna name her Clairvoyant, right?

• 14:40Chuck Nice?

  Right.

• 14:41Neil deGrasse Tyson?

  And people, then, that's when, um, uh, child services comes to your house.

• 14:49Chuck Nice?

  Right.

• 14:50Neil deGrasse Tyson?

  They say.

• 14:51Chuck Nice?

  Yeah, we're here to pick up Albedo and Clairvoyant, uh, because you certainly are in no mental state to take care of these kids.

• 15:15Neil deGrasse Tyson?

  Why do UFO sightings persist? Are at least some of them figments of our imagination? Or are we missing something? In my latest book, Take Me To Your Leader, I separate science from speculation. I actually explore what's possible in this universe, given the universal laws of physics. Because if the aliens are out there, the laws of physics will dictate how they find us. I also narrated the audiobook, so I'm duly informed that the audiobook and the print version are available now, wherever books are sold.

• 15:59Neil deGrasse Tyson?

  So Chuck, how often do you think about pollution?

• 16:02Chuck Nice?

  Quite a bit, honestly. I mean...

• 16:04Neil deGrasse Tyson?

  Yeah, okay.

• 16:05Chuck Nice?

  I absolutely...

• 16:06Neil deGrasse Tyson?

  You're a green guy.

• 16:07Chuck Nice?

  I am a green guy. I think about it quite a bit and the deleterious effect that it is having on our existence.

• 16:17Neil deGrasse Tyson?

  Our ecosystem. So not all pollution is made of plastic. So, very early on, the astronomers of the world have complained about light pollution. When you have the electrification of the cities, all of a sudden, the night sky was competing with lights that were shedding photons up into the atmosphere. And I grew up in a city, so I had no understanding of the night sky. Until my first visit to the Hayden Planetarium at age nine.

• 16:50Chuck Nice?

  Nice.

• 16:50Neil deGrasse Tyson?

  And I know, it was nice. And I looked up, and the lights dimmed, and the stars came out. I said this before, I'll say it again, I thought it was a hoax. Way too many stars.

• 16:59Chuck Nice?

  Wait a minute, all that is up there?

• 17:02Neil deGrasse Tyson?

  I don't know what this is. I'll go along with it for now, but stop trying to pull my leg. Next time I come back, show it how it really is.

• 17:09Chuck Nice?

  Fake news, fake news.

• 17:12Neil deGrasse Tyson?

  It was totally fake news.

• 17:13Chuck Nice?

  Right.

• 17:14Neil deGrasse Tyson?

  And to this day, from mountaintops, when I've gone to high-level mountaintops with eye-level telescopes, I look up at the night sky and I say, "It reminds me of the Hayden Planetarium."

• 17:25Chuck Nice?

  Wow.

• 17:26Neil deGrasse Tyson?

  That's an urban...

• 17:29Chuck Nice?

  Yeah, urban frame of reference.

• 17:31Neil deGrasse Tyson?

  Urban frame of reference, that was. So, plus, I'm old enough to remember what not only was there light pollution, as there still is, but back then, there was also air pollution. And today, we think of polluting the atmosphere with carbon dioxide. Carbon dioxide is transparent, so that's not what I was thinking at the time. I was thinking auto-exhaust and this sort of thing. So, not only did lights, but auto-exhaust disrupt your ability to see all objects in the night sky, especially the dimmest objects. And we should do a whole explainer on noise of all kinds, so remind me to do this.

• 18:08Chuck Nice?

  Yes.

• 18:09Neil deGrasse Tyson?

  But let me just say, if you're in a perfect dark night, and you can just barely see a very dim star... And then other light gets added to this. The first things to go are the dimmest stars. So you start hacking away at the dimmest things available to you simply because other light is competing with it. And it no longer shows up in on your retina or even in a in a camera. So these are problems. And so we've been living with this like our whole lives. In fact, there's something called the IDA, International ID International, International Dark Sky Association.

• 18:49Chuck Nice?

  Okay, they sound like a group of supervillains. The IDA. All I'm saying.

• 18:57Neil deGrasse Tyson?

  That's all I can tell you about them.

• 18:58Chuck Nice?

  Yes, exactly. So we've called this meeting of the International Dark Sky Association to finalize our plans to permanently block out the sun.

• 19:09Neil deGrasse Tyson?

  That is true.

• 19:10Chuck Nice?

  Dark skies for everyone 24 hours a day. Like, that's so funny. I've never heard of that.

• 19:18Neil deGrasse Tyson?

  And how much will it cost? It will cost a million dollars.

• 19:22Chuck Nice?

  Uh, sir, just want to let you know that's not a lot of money these days. Okay. Five million dollars. What's the inflation rate? How how much should we ask for? Should we ask for something more?

• 19:36Neil deGrasse Tyson?

  Did he have with that whole conversation in the movie?

• 19:38Chuck Nice?

  I think so. I don't know how it went, to be honest, but it was something like that, just like. And how much now is it?

• 19:46Neil deGrasse Tyson?

  So they that organization has gotten more and more powerful and more it power not in a let's override you, but there's a lot of interesting, sensible things to do. For example, let's say you're in an airplane and you're flying over a city and you look down and you see the suburbs and you see the streetlights illuminating the streets.

• 20:08Chuck Nice?

  Right.

• 20:08Neil deGrasse Tyson?

  At night from your airplane.

• 20:10Chuck Nice?

  Right.

• 20:10Neil deGrasse Tyson?

  Do you know why you can see the streetlight?

• 20:13Chuck Nice?

  Uh, because it's bright. I don't know.

• 20:19Neil deGrasse Tyson?

  Because somebody in that town is paying for electricity to go into this lamp to generate photons that are going up into the, through the window of my airplane.

• 20:30Chuck Nice?

  I got you. So I got you. Like a lantern. The light's going everywhere.

• 20:35Neil deGrasse Tyson?

  Everywhere.

• 20:36Chuck Nice?

  It's not directed.

• 20:37Neil deGrasse Tyson?

  You don't need the light everywhere, do you?

• 20:40Chuck Nice?

  You only need it on the street.

• 20:41Neil deGrasse Tyson?

  If I see your light, it means you are paying to illuminate my airplane flying overhead.

• 20:46Chuck Nice?

  That's.

• 20:47Neil deGrasse Tyson?

  If you can see any light at all, directly from its source, somebody's paying to illuminate the sky.

• 20:53Chuck Nice?

  Right.

• 20:54Neil deGrasse Tyson?

  So the idea simply makes the economic argument. Do you want to save money? Okay, so you put a little hat on each lamp.

• 21:03Chuck Nice?

  Oh, that's adorable.

• 21:04Neil deGrasse Tyson?

  Now, wait a minute, and make it reflective. So, hey, that light that used to be going upwards is now coming downwards, and I don't need that much light. I was wasting half of it.

• 21:16Chuck Nice?

  Right.

• 21:17Neil deGrasse Tyson?

  So now I can cut the wattage in half, or by whatever fraction.

• 21:21Chuck Nice?

  Right.

• 21:21Neil deGrasse Tyson?

  Use less light, and now I'm not illuminating the airplanes flying overhead. It's that simple.

• 21:27Chuck Nice?

  And that's why we don't do it. Because it's that.

• 21:31Neil deGrasse Tyson?

  It's simple.

• 21:31Chuck Nice?

  And anything that's simple, we just can't do.

• 21:34Neil deGrasse Tyson?

  Which can't wrap our head. So the town of Tucson, Arizona, which is proximal to Kid Peak Mountain, which has Kid Peak Observatory, which is one of the major observatories of the nation's astronomers, long ago came into an agreement with the municipal leaders to say, "Look, if your, if your place keeps getting brighter, we can't do our science. We gotta move our base, because the home base is in town, where all the scientists hang out before they go to the mountain." And so, but they like this distinction, plus Arizona is beautiful and it's got deserts and, you know, so why not preserve it all? And so they got together, and there are ordinances, city ordinances that control how bright the lights can be,

• 22:17Neil deGrasse Tyson?

  how, what, what kind of hat should be on them, when you should turn them off, all of this. And so, that was successful. That became a model for other towns to emulate. And so that's the light pollution and and like they said, the air pollution is essentially gone relative to when I was growing up. When I was growing up, I'd come home from school, from elementary school, you could brush the ash off your shoulders.

• 22:39Chuck Nice?

  Okay.

• 22:40Neil deGrasse Tyson?

  From incinerated garbage that had gone into the sky and descended back to earth.

• 22:44Chuck Nice?

  That is just crazy. It was snowing garbage?

• 22:47Neil deGrasse Tyson?

  Snowing ash, correct.

• 22:49Chuck Nice?

  That's.

• 22:50Neil deGrasse Tyson?

  Every, every day.

• 22:51Chuck Nice?

  That's, that's amazing.

• 22:53Neil deGrasse Tyson?

  Yeah, yeah, yeah. So now, so that's that. But we have more pollution than that.

• 22:57Chuck Nice?

  Right. Wait, let me just say this about the light pollution that I just thought about right now because of what you just said.

• 23:04Neil deGrasse Tyson?

  Mm hmm.

• 23:04Chuck Nice?

  Uh, when they were building the big hotels in Atlantic City, of course, I'm from Philly, so Atlantic City, they were building these giant hotels, um, and, uh, the conservationists uh, in the area, the scientists that, you know, care for animals and sea life and birds, they basically realized that you're killing all the birds because they never know that it's nighttime.

• 23:32Neil deGrasse Tyson?

  Oh.

• 23:33Chuck Nice?

  Yeah, and people.

• 23:34Neil deGrasse Tyson?

  Okay, so at least I didn't lose my, at least I didn't lose my life over this.

• 23:39Neil deGrasse Tyson?

  Yeah. Wow. So the bird is just completely disrupting all of their.

• 23:43Chuck Nice?

  Just all, everything. They, they had no more circadian rhythm and they were flying until the, and they were dying of exhaustion and all kinds of crazy stuff. It was, it was a weird little study that they did, but, uh, and I don't know what they did about it because they haven't changed anything. But I think the consensus from the public was, they're seagulls. Who gives a crap?

• 24:04Neil deGrasse Tyson?

  Oh.

• 24:07Neil deGrasse Tyson?

  Seagulls and pigeons, right?

• 24:08Chuck Nice?

  Seagulls and pigeons?

• 24:10Neil deGrasse Tyson?

  Plenty more of them where they came from.

• 24:12Chuck Nice?

  You want us to care about that? There's, I mean, first of all, we could see if they were chickens. They're delicious. But, you know, it was terrible. It was terrible.

• 24:20Neil deGrasse Tyson?

  So Chuck, it's not only light pollution that worries astronomers. When we think of light, you think of like visible light, right? But we don't only use visible light to communicate with the universe or to receive the universe. We also have radio waves, huge radio telescopes, okay? Well, wait a minute, we have TV, right, you know, AM, FM, satellite, microwave, all those are in the radio parts of the spectrum. So not only is there light pollution with visible light that interferes your eyes from seeing dim objects, there's radio wave pollution.

• 24:57Neil deGrasse Tyson?

  That prevents our radio telescopes from seeing dim objects.

• 25:01Chuck Nice?

  Right.

• 25:02Neil deGrasse Tyson?

  So other bands of the electromagnetic spectrum are also polluted. And so our best radio telescopes have to be put in places where there's like a radio free zone around it. All right, just so that we don't get noise, radio noise coming in disrupting our observations of radio galaxies, the microwave background of the formation of the universe and all of this.

• 25:27Chuck Nice?

  Well, there you go, people. Cool it on the Hot Pockets.

• 25:31Neil deGrasse Tyson?

  Microwave.

• 25:32Chuck Nice?

  Take it easy on the Hot Pockets, people.

• 25:35Neil deGrasse Tyson?

  And you know what else? The remote fobs for cars.

• 25:38Chuck Nice?

  Right.

• 25:38Neil deGrasse Tyson?

  Also creates a background noise of radio waves. Uh, to a radio telescope that is extremely sensitive. So, uh, leaving the realm of light in that sense, there's also a new kind of pollution called satellite pollution. Oh my gosh. And so what happens here is the effect of this is the satellite is moving across your field of view and it's reflecting sunlight. So you get a streak.

• 26:06Neil deGrasse Tyson?

  So other parts of your photo might be okay, but suppose that streak goes to the one object you're trying to look at.

• 26:10Chuck Nice?

  Right.

• 26:11Neil deGrasse Tyson?

  So you need a way to sort of subtract it out from the process. We have people working on software to accomplish that right now. We don't know how this is all going to shake out in the coming years. So we're, we're preloading our, uh, our data reduction utilities just to try to subtract them out. Uh, I'm, I'm told, I just attended a, a workshop on, on satellite pollution. Where there was an agreement with Elon Musk for some of his satellites to use a, a sun shade.

• 26:39Chuck Nice?

  Okay.

• 26:40Neil deGrasse Tyson?

  Right. So even though they're up there, they will, the, the sun, the sun will not reflect off of it down to us. And it did improve the seeing conditions.

• 26:48Chuck Nice?

  Gotcha.

• 26:49Neil deGrasse Tyson?

  It did improve it, but I think that whatever might be a long-term solution to this has not yet arrived. So that, that's what we're in the middle of now.

• 26:57Chuck Nice?

  That is kinda crazy.

• 27:00Neil deGrasse Tyson?

  And the current most powerful telescope on earth.

• 27:03Chuck Nice?

  Okay.

• 27:03Neil deGrasse Tyson?

  Is called the Vera Rubin Telescope and it is designed to take movies of the night sky every single night.

• 27:11Chuck Nice?

  That is pretty dope.

• 27:13Neil deGrasse Tyson?

  Okay, because think about it, up till now, we've been taking just snapshot, okay? So if the thing did something different an hour later, after you're on the way back to the computer.

• 27:19Chuck Nice?

  Ah, tough talks.

• 27:21Neil deGrasse Tyson?

  You missed it.

• 27:22Chuck Nice?

  Tough talk.

• 27:24Neil deGrasse Tyson?

  You missed it, missed out, okay? So it's taking a movie so that, it's called, um, there's an entire branch of my field that concerns itself with things that change over time.

• 27:38Chuck Nice?

  Right.

• 27:39Neil deGrasse Tyson?

  Because most images you're seeing is just a static picture or something, right? So the people who care about stuff that changes in the universe, uh, this will be a delight for them. And, but now that we're taking movies, we basically have movies of all these satellites crossing our field of view. And we have to distinguish between that and what might be a killer asteroid moving across the field of view, because this has an asteroid alert system built in.

• 28:03Chuck Nice?

  Wow, so, without, I mean, this sounds more important than it might appear. Because this ain't just looking at a telescope and going, what is that? Oh, that's some old Elon Musk junk, don't worry about it. And then it ends up being a killer asteroid.

• 28:21Neil deGrasse Tyson?

  Yeah, what is that? Oh, that's a killer asteroid that we almost mistook for an Elon Musk satellite.

• 28:25Chuck Nice?

  Right, right, yeah.

• 28:26Neil deGrasse Tyson?

  Right. So, yeah, that's what we're confronting with right now. The buckets of pollution that influence the modern astrophysicist knows no bounds.

• 28:35Chuck Nice?

  Wow.

• 28:36Neil deGrasse Tyson?

  And none of it has anything to do with plastic or carbon dioxide. What do you think of that?

• 28:39Chuck Nice?

  Well, what we should have is an astrophysicist standing next to a rocket with a single tear rolling down their face.

• 28:59Neil deGrasse Tyson?

  That'll be a public service announcement, alright?

• 29:01Chuck Nice?

  Right.

• 29:02Neil deGrasse Tyson?

  Well, I'll volunteer, I'll be the tearing astrophysicist for that.

• 29:05Chuck Nice?

  Ah, that'd be great.

• 29:06Neil deGrasse Tyson?

  Space pollution, only you can stop.

• 29:09Chuck Nice?

  Only you can stop space pollution.

• 29:25Chuck Nice?

  This is Ken the Nerd Neck Zabera from Michigan and I support StarTalk on Patreon. This is StarTalk Radio with Neil deGrasse Tyson.

• 29:40Neil deGrasse Tyson?

  Tell you a story from a childhood.

• 29:42Chuck Nice?

  Oh, okay.

• 29:43Neil deGrasse Tyson?

  So, yeah, yeah. So, I, as a kid or even as adult, who doesn't love potato chips, right? Okay, so I had potato chips. And then, you know, you go to a fast food restaurant and then I ordered french fries. Okay, that's kind of cool. And then, you know, for turkey dinner, there's mashed potatoes, right? And then, in the breakfast brunch, you know, diner, you can get hash browns.

• 30:10Chuck Nice?

  Yes.

• 30:11Neil deGrasse Tyson?

  Okay, I think I was 11, maybe 10, before I figured out that all of those were the same food.

• 30:22Chuck Nice?

  Right.

• 30:23Neil deGrasse Tyson?

  A potato.

• 30:24Chuck Nice?

  It's nothing to think about when you're 11 or 12.

• 30:27Neil deGrasse Tyson?

  It's just food.

• 30:27Chuck Nice?

  It's just food and it's delicious.

• 30:29Neil deGrasse Tyson?

  And only one of them, two of them have the word potato in it.

• 30:32Chuck Nice?

  That's right.

• 30:33Neil deGrasse Tyson?

  Mashed potatoes and potato chips, but they are completely different from each other.

• 30:37Chuck Nice?

  Oh, without a doubt.

• 30:37Neil deGrasse Tyson?

  And french fries, no one says potato, and hash browns, they don't say potato. So, I realized-

• 30:43Chuck Nice?

  And my kids grew up on Freedom Fries, so they don't even know what french fries-

• 30:47Neil deGrasse Tyson?

  Freedom fries, okay. So, so it was a revelatory moment for me to realize that one food could be made so different, and so interestingly different, to have its own place within our culinary offerings. Each one of those could do that, right? Oh, another one I liked were the potato sticks. Do you remember those?

• 31:09Chuck Nice?

  Oh, God, yes.

• 31:10Neil deGrasse Tyson?

  Man.

• 31:10Chuck Nice?

  Do you remember the potato sticks that, um, uh, oh, well, yeah, they're the same thing. Never mind. So, they had, they were like french fries. They had the big potato sticks, and then they had the tiny little matchsticks potato sticks.

• 31:23Neil deGrasse Tyson?

  The matchstick, those were the best, because it was like a lot of salt in it. Okay, so the point is-

• 31:27Chuck Nice?

  Okay, I am starving. I'll be back, I'll be right back.

• 31:31Neil deGrasse Tyson?

  So, they were all different, yet they were the same.

• 31:34Chuck Nice?

  Right, right.

• 31:36Neil deGrasse Tyson?

  And so too was my-

• 31:39Neil deGrasse Tyson?

  Revelation, middle school, early middle school. It was probably, probably sixth grade now, where, because I was an early geek, but realizing that, okay, you've heard of these things called microwaves. You've heard of radio waves, you've heard of infrared, ultraviolet, you've seen rainbows, visible light, you've heard of X-rays, you've heard of gamma rays. It's all the same thing.

• 32:05Chuck Nice?

  Right.

• 32:06Neil deGrasse Tyson?

  It is, it is just different ways of preparing your light. Okay, to use my potato analogy.

• 32:14Chuck Nice?

  And so you're basically 11 years old and you're making this discovery for yourself.

• 32:19Neil deGrasse Tyson?

  After I realized about the potatoes, yes.

• 32:22Chuck Nice?

  Okay, because I was 37.

• 32:26Neil deGrasse Tyson?

  So, so I said, my gosh, it's all light. It all travels at the speed of light. And this word light, where you're talking about what the human retina can see, that's very limiting for, if you want to talk about the universe. Because, so what's the, our favorite light colors, red, orange, yellow, green, blue, violet?

• 32:48Chuck Nice?

  White, tea, blue.

• 32:49Neil deGrasse Tyson?

  Okay, continue there, you go to the other side of violet, you get ultraviolet. You go beyond violet, that's how it got its name. It's beyond violet and we abbreviate it UV, but I like fleshing it ultraviolet. Give me, give me all the syllables that it's got. Okay, and this is the-

• 33:07Chuck Nice?

  Sounds far more har- harmful.

• 33:09Neil deGrasse Tyson?

  Oh, but, but, in fact, it is, because this, in this direction, we are reducing the wavelength of light that's coming to us. And when you reduce the wavelength of light, more energy is packed into one pulse of that light, and so the energy goes up.

• 33:27Chuck Nice?

  Okay.

• 33:27Neil deGrasse Tyson?

  Okay, so the higher the frequency, it's how many crests go by per second, the higher is the energy of that light. So- The red, orange, yellow, green, blue, violet is all sort of pretty harmless. You get into ultraviolet light, it has enough energy to break apart biological molecules. Uh oh. And this will give you sunburn and skin cancer. Right. Okay, so I heard a DJ talk about when he just learned that the temperature on Venus was 900 degrees. He said, "Well, you better bring sunblock a million for that." So he's wrong. He's thinking that you're protecting from the heat. That you can block that. Right, no, right, you're not blocking heat. Right.

• 34:10Neil deGrasse Tyson?

  The point of the sunblock is to block just the UV. Just the UV. Okay, right, so. So you're still getting dark and crispy no matter what you want to do. Yeah, you'll get toasted, you're toasted. No matter what. No matter what. So then you go beyond the ultraviolet and that's when you get the X-rays. Right. X-rays is a part, it is continuous with the ultraviolet, right? We put a line there just because of our convenience of words and machines built on it. But ultraviolet smoothly transitions to X-rays. Interesting. Okay, and you know X-rays are bad for you because when you go in the X-ray room, what does the X-ray tech do? Um, they go to a bomb shelter.

• 34:54Neil deGrasse Tyson?

  They leave the room.

• 34:58Neil deGrasse Tyson?

  They say, "Are you okay? Are you comfortable?" Yeah, okay, boom, door closes. Exactly.

• 35:05Neil deGrasse Tyson?

  And they look through a lead glass and then they, okay. So X-rays can actually penetrate your skin unlike ultraviolet. And in doing so, it can actually harm your organs. All right, and so you get organ failure from it. And organ cancers are triggered by this. Now, once again, it's a continuum of a change of wavelength of light. And then you get to beyond X-rays, you get to gamma rays.

• 35:33Chuck Nice?

  Right.

• 35:34Neil deGrasse Tyson?

  And by the way, gamma rays just keep getting higher and higher energetic, but we don't have more words for it. It's just the last word we've got. But you could have divided that up even more. We just don't. Okay. And so gamma rays.

• 35:47Chuck Nice?

  Get omega rays or something like that.

• 35:50Neil deGrasse Tyson?

  Ooh.

• 35:51Chuck Nice?

  Yeah. I wonder what superhero would be made from omega rays.

• 35:57Neil deGrasse Tyson?

  Well, gamma rays are, um, in the early days before we fully understood what the sources of energy were, there were alpha particles, beta particles, and gamma particles. Alpha, beta, gamma. And the alpha particle is a helium nucleus. The beta particle is an electron. And the gamma ray is a photon. But they all had energies that we could measure. So we're measuring the energies, not knowing what the thing was that caused it at the time. But that all splits out. So we have, um, like I said, ultraviolet, X-rays, gamma rays. There you have it. All right. Go the other direction. Wavelengths are getting longer. The energy is dropping. So you go below the red. You get infrared. Below the red.

• 36:41Neil deGrasse Tyson?

  All right. By the way, you can't see infrared. You can't see ultraviolet. If you buy, I want an ultraviolet bulb. We used to call them black light bulb. I want an ultraviolet bulb and you turn it on. And you see it. You say, I can see the ultraviolet. No, you're not. You're seeing the violet.

• 36:55Chuck Nice?

  Right.

• 36:56Neil deGrasse Tyson?

  Okay, there's a little bit of violet spilling out. The actual ultraviolet, you don't see at all. Same with the infrared lamps. You buy an infrared lamp. If that was pure infrared, you turn it on, you wouldn't see a damn thing. Okay.

• 37:08Chuck Nice?

  Right. You're not a predator.

• 37:10Neil deGrasse Tyson?

  Exactly. So a little bit spills into the red part. So you see the red emitted by the infrared lamp. All right. We can detect infrared, not by our eyes, but by our skin.

• 37:22Neil deGrasse Tyson?

  You, you detect infrared as warmth.

• 37:24Chuck Nice?

  Right.

• 37:26Neil deGrasse Tyson?

  All right. It's a detector. Think of it that way. All right. A warmth detector. So there's the infrared and then you go beyond infrared, below infrared. The, what used to just all be called radio waves. And then they said, well, there's a section of the radio waves that have special utility for us for communicating. It's just the shortest of the radio waves and they call them microwaves.

• 37:50Chuck Nice?

  Sweet.

• 37:51Neil deGrasse Tyson?

  Short radio waves, microwaves. So that that gets that got a labeled right there between infrared and radio waves. And beyond microwaves, we have radio waves, but and now we're getting physically, realizably sized wavelengths of light. So microwaves are about a centimeter long. We can actually show that between a millimeter up through a few centimeters. And then we get into the meter zone, yards and things. Those are radio waves. And once again, like like gamma rays, these just continue forever. And we don't have more words for it.

• 38:22Chuck Nice?

  Right. Which is why we have so many different broadcast. Or is those just frequencies?

• 38:28Neil deGrasse Tyson?

  But the

• 38:28Chuck Nice?

  Yeah, the frequencies Is the wave.

• 38:31Neil deGrasse Tyson?

  It you can call they call it call them wavelengths.

• 38:33Chuck Nice?

  Right.

• 38:33Neil deGrasse Tyson?

  But it's our habit to call them frequencies.

• 38:35Chuck Nice?

  Right.

• 38:35Neil deGrasse Tyson?

  Right. So each frequency, when you're tuning.

• 38:38Chuck Nice?

  Right.

• 38:39Neil deGrasse Tyson?

  On a up in the old days, you'd have an AM or an FM radio. When you're turning the dial, you're changing the frequency of your detector to receive a signal sent through that zone.

• 38:49Chuck Nice?

  Wow.

• 38:51Neil deGrasse Tyson?

  There you have it.

• 38:51Chuck Nice?

  That is, that's great.

• 38:53Neil deGrasse Tyson?

  And in the old days, when you turn, old timers, you turn the knob to change the channel on the TV. You're actually changing the frequency detector inside the television. And there's that secondary knob that you could tune a little sharper. I don't know if you knew that. Okay. That that got you honed in on that one frequency. Was it channel seven, channel eight? We just numbered them. We didn't give you the frequency because that's why, when you can just number them, which is what we did in the day. So anyway, all of these move at the speed of light. It is all light. Most of it is invisible to you. In fact, if you put this on a scale,

• 39:32Neil deGrasse Tyson?

  on on a on a on a, if you drew all of these things and you ask, well, how much of this whole electromagnetic spectrum can we see?

• 39:40Chuck Nice?

  Right.

• 39:41Neil deGrasse Tyson?

  And we see this tiny slice. This tiny slice among all these broad zones in the electromagnetic spectrum, we are practically blind.

• 39:53Chuck Nice?

  Oh.

• 39:54Neil deGrasse Tyson?

  And we didn't even know that until William Herschel discovered infrared light.

• 40:01Chuck Nice?

  Right. Look at that. That is-

• 40:04Neil deGrasse Tyson?

  And I think I said in another explainer how he discovered it. I'll do it real quick now.

• 40:07Chuck Nice?

  Yeah, I love this. I love this. Yeah, I do remember.

• 40:10Neil deGrasse Tyson?

  Okay, Herschel, Herschel's a big fan of Newton. Newton has a spectrum. He shows sunlight is composed of colors. And you, you put a sort of slit in the curtains so that a beam of light comes through your prism. So that it's dark elsewhere except where the prism light goes. And Herschel said, I wonder what the temperatures are of each of these different colors. To even think to ask that.

• 40:32Chuck Nice?

  Yeah.

• 40:33Neil deGrasse Tyson?

  All right. So he's got a thermometer and he puts it in the blue and then he puts, and by the way, it's an experiment. So you need a control thermometer. So you put the control thermometer somewhere where, somewhere where the colors are not. All right. On the same table, but just put it outside the colors, which is what he did. And he checked the temperature of the blue and the violet and the green and the orange and the red. And he wrote down all of these temperatures. And what he noticed is that the temperature sitting outside of the visible spectrum read the highest temperature of them all.

• 41:05Chuck Nice?

  Right. And now, why didn't he just say, oh, it must be hot in this room?

• 41:12Chuck Nice?

  I didn't realize how hot it was in here.

• 41:16Chuck Nice?

  Maybe there's something wrong with me. I can't, I can't feel heat anymore.

• 41:20Neil deGrasse Tyson?

  So, so there it was. And because he didn't put the thermometer somewhere else, he put it next to the other-

• 41:26Chuck Nice?

  Right next to it.

• 41:27Neil deGrasse Tyson?

  Right next to it because at the same environment as there. And he said, oh my gosh, there must be a form of light, quote, unfit for vision.

• 41:36Chuck Nice?

  That's a, I love the terminology.

• 41:38Neil deGrasse Tyson?

  Unfit for vision.

• 41:40Chuck Nice?

  Light that is unfit for vision.

• 41:42Neil deGrasse Tyson?

  And had that thermometer been on the other side of the violet, it's not clear that ultraviolet would have warmed the thermometer in this way. But he happened to have it on the side where the red was and he discovered infrared light with that experiment. And so, so, so when I, when I look at my microwave oven and I look at a radio transmitter, I look at my cellphone and I look at the, my lamp on my table, it is one happy family of electromagnetic spectrum coming to us.

• 42:11Chuck Nice?

  That's, that's so cool.

• 42:13Neil deGrasse Tyson?

  That, yeah. It's dope. And it's called electromagnetic because it, it's a wave that simultaneously moves between being an electrical wave and a magnetic wave and it's self-propagating through space. So it's a wave that can move through the vacuum of space without having needed a medium through which, that will, to vibrate to send it through like sound does.

• 42:34Chuck Nice?

  Right.

• 42:35Neil deGrasse Tyson?

  So all those movies, Star Wars, they'd all be silent movie because no explosions are in space. But light has no problem moving through space even though it's a wave because it's a very different kind of wave. It's, it's a self-propagating electrical and magnetic wave. That's why we call it the electromagnetic spectrum. There you have it Chuck.

• 42:52Chuck Nice?

  That's great.

• 42:54Neil deGrasse Tyson?

  And it all started with my potatoes.

• 42:58Neil deGrasse Tyson?

  Just saying.

• 43:00Chuck Nice?

  And what wavelength are they on? The delicious wave.

• 43:04Neil deGrasse Tyson?

  The, the, delicious. We keep them warm with infrared. It all comes full circle.

• 43:09Chuck Nice?

  That's so true.