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Chapter 1: How bright is the Earth from the moon?
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. Welcome to StarTalk, your place in the universe where science and pop culture collide. StarTalk begins right now. All right, Chuck, I got one for you. All righty.
I'm ready. One of my favorite words. Okay. Albedo. All right. Now, what language is that? The language of science. Really? Albedo. Okay, first of all, it sounds like a scientist. Not a science intern. Oh, Albedo? Hey, how you doing? I'm Albedo. Perhaps you're familiar with my equations. But Albedo, Albedo.
Albedo. So Albedo is a very precise measurement of how reflective something is. At a given wavelength, but typically we're just at any wavelength. So, so for example, if you have an albedo of, by the way, an albedo can range from zero to one. Okay. So think of it as a percentage. So 0% to a hundred percent. So an albedo of 0.5, that means half the light that hits it gets reflected. Got you.
So what happens to the other half? It's absorbed. Absorbed. Absorbed. Absorbed. Okay. An albedo of 100% is? A mirror. A mirror. Precisely. Cool. So nothing gets absorbed. Okay. And an albedo of zero means 100% of the light energy gets absorbed and nothing gets reflected back.
Wow.
Okay.
Can that even exist?
Yeah, it's called a black hole, but it's fine. No, but also stars have basically zero albedo, but no one thinks about it that way because they are generating light of their own.
They're radiating light, so why would they be?
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Chapter 2: What is albedo and why is it important?
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 you thought about albedo from the beginning, you'd realize that the human species fully populates the entire spectrum, the entire range of albedos. Right. They're very highly reflective white people.
They're very highly absorptive black people. Right. And so dark-skinned people. Like, so, like, Jamin Honsu.
The actor. The actor.
He'd be, like, a point one. Yeah, way down there. Very way down there. OK? Reflecting very little light that hits him. And so this tells you a lot of things, OK? Yeah, yeah. So 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. So the role of melanin is extraordinary in that regard. Okay. So, but let's keep going. Take a guess what the albedo of the moon is. Just take a guess. You see it at night.
I see it at night. Well, I got to tell you, it's pretty bright, but it's nowhere near as bright as the sun. Well, the sun gives off, the sun radiates it. Albino is a reflectivity thing. 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 going to say five.
0.5. Yeah, 0.5. OK. So no, no. The albedo of the moon is around 0.1. Wow. The moon is almost as dark as the sidewall tires on a car.
Wow. Yep. That's just how bright the sun is. Yes, yes. That's how bright the sun is.
Yes.
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Chapter 3: How do different colors of clothing affect heat absorption?
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 on your retina or even 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 Dark Sky Association.
Okay, they sound like a group of super villains. That's all I'm saying.
That's all I can tell you about them.
Yes, exactly. We've called this meeting of the International Dark Sky Association to finalize our plans to permanently block out the sun. That is true. Dark skies for everyone 24 hours a day. Like, that's so funny. I've never heard of that. And how much will it cost? It will cost a million dollars. Sir, just want to let you know that's not a lot of money these days. Okay. Five million?
What's the inflation rate? How much should we ask for? Should we ask for something more? Did he ask? Was that whole conversation in the movie? I think so. I don't know how it went, to be honest, but it was something like that. Just like, oh, and how much now is it?
What?
So they, that organization has gotten more and more powerful and more 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.
Right.
At night from your airplane.
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Chapter 4: What is Earthshine and how does it relate to light?
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 gamma rays, these just continue forever. And we don't have more words for it.
Right. Which is why we have so many different broadcasts. Or are those just frequencies?
But the frequency is the wave. They call them wavelengths. Right. But it's our habit to call them frequencies. Right. Right. So each frequency, when you're tuning, in the old days, you'd have an AM or an FM radio. When you're turning the dial, you are changing the frequency of your detector to receive a signal sent through that zone. Wow. There you have it.
That's great.
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 it a little sharper. I don't know if you knew that, okay? 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, if you drew all of these things and you ask, well, how much of this whole electromagnetic spectrum can we see? Right.
And we see this tiny slice. this tiny slice among all these broad zones in the electromagnetic spectrum, we are practically blind. And we didn't even know that until William Herschel discovered infrared light.
Right.
Look at that. And I think I said in another explainer how he discovered it. I'll do it real quick now.
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