StarTalk Radio - Things You Thought You Knew – Is Everything Light?

Episode Date: May 12, 2026

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? NOTE: StarTalk+ Patrons can listen to this entire episode commercial-free here:  https://startalkmedia.com/show/things-you-thought-you-knew-is-everything-light/ Thanks to our Patrons Nicholas Santiago, Bill Mccollough, Mizarare, Marcus Lanigan, Hrvoje Medarac, Geoff Skinner, Scooter, Odf12, Michele H, Thecasualtease, Alna Hofmeyr, Bev, Mitc…Nicholas Santiago, Bill Mccollough, Mizarare, Marcus Lanigan, Hrvoje Medarac, Geoff Skinner, Scooter, Odf12, Michele H, Thecasualtease, Alna Hofmeyr, Bev, Mitchell Abbott, Hades 1000, Allysia Wright, A Smith, Patrick Miller, Brian Parch, McBeardy, Blue, TamTam, Brendan Santangelo, Jonathan Collins, Nick Obrien, David Everett, Beautiful Universe, Vlad Condoroș, William T. Drummond III, Vision Novaa, Adam Martin, Courtney Lopotosky, Christopher Pickett, Tormonty, Abby Roberts, Claire Ture, Diego Kunke, Anatolii Okhotnikov, Tom Grissom, Korrey Allen, Simon, D Biswas, Sidlywinks, Gabriel Snell, Sonja Gardiner, John B, Mike Rivera, Duane Wolfe, Eva Carleton, Dan Hadaway, William Benedict, Zachary E, Muhammad Jawad Bashir, Jonathan Greenberg, Robert Hollis, Quinn McSperryn, Ross Kennedy, Kyle Brummet, Chadders, Erick Valdez, Jamie Haley, William Tyree, Sternritter, Yung Alien, Cosmicmoss, Kristopher Kapeel, David Bunting, Scotti Hinds, David Lott, JD Morales, Dan, DaleMorgansLife, Kelsey LeVert, Ethan Free, Johnathan Letcher, Misha Art, Tarsha Wynn, Periloux Peay, Jeremiah B Luther, Dee Programmer, Luis Santiago, Claude Jones Jr, Michael Rose, Robert Pennell, C.B. Winterton, Javier Alvarado, Toygar Ermin, John Cucetta, Uqbar, Alisha, Charles Loflin, Bobby Sue, Colton Upchurch, Michele Bollo, Michael Baker, William Crew, Charlie Mahoney, Seth Stinson, Brent Wiese, Vallous, Linda in Alameda, and Bzd for supporting us this week. Subscribe to SiriusXM Podcasts+ to listen to new episodes of StarTalk Radio ad-free and a whole week early.Start a free trial now on Apple Podcasts or by visiting siriusxm.com/podcastsplus. Hosted by Simplecast, an AdsWizz company. See pcm.adswizz.com for information about our collection and use of personal data for advertising.

Coming up on StarTalks, 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 begin right now.

I'm talking 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 scientist. Albedo. Hey, how you know what? I'm Albedo.

Perhaps you're familiar with my equino. But albedo, 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, for example, if you have an albedo of, by the, an albedo can range from zero to one. Okay?

So think of it as a percentage. So zero percent to 100 percent. So an albedo of 0.5, that means half the light that hits it gets reflected. Gotcha. So what happens to the other half? It's absorbed? Absorbed? Absorbed, absorbed, okay.

An albed 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? Yes, it's called a black hole. But, no, but also, stars have basically zero albedo, but no one thinks about it that way because they're generating light over there. Right.

They're radiating lights. 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 onto itself. So let's see how Obedo affects us. So if you didn't have anthropologists saying, let us divide the world into races, okay? Right. If they really want it to be sort of scientific about it, they could just... have an albedo. You just get to have an albedo. Right. Because that's a full spectrum. Right. I mean, that's so much, that's so much more specific. There's more information. 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 right, 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. Okay. They're very highly reflective white people.

They're very highly absorptive black people. Right. And so dark-skinned people. Like, so like, like, Jiamen, Han-Su. 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're very fair skin, you're reflecting most of the sunlight that hits you.

Right. Even so, fair skin 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. Okay. 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 its, what the sun radiates it. Albedo is a reflectivity. 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, I'm going to say five.

Point five. Yeah, point five. Okay. So, no, no. The albedo of the moon is around point one. Wow. The moon is almost as dark as the sidewall tires on a car. Wow.

That's just how bright the sun is. Yes, yes. That's how bright the sun is. Yes. That it takes 0.1 albedo and makes it look like ambient light. And you can read by the light of the moon at night from Earth. That's right. How romantic.

I love it. So point one. And so the moon is basically dark. Dark. Now, so, when you measure the daytime temperature on the moon, that's kind of why it gets up to the hundreds of degrees. Right. Okay. Where's it getting this temperature?

Because it's absorbing all that sunlight. Wow. If you're absorbing the energy, reflecting very little, the consequence is your temperature rises. That's cool. Okay. So now. I mean, that's hot. Okay.

That's good. That was good. That was good. All right. So now, let's look at the fashion industry. Summertime. Right. Okay. Are they rolling out their black shirts and black dresses and black blouses and black... No. Super light colors and white. The 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. Right. And if you wore dark clothes, not only are you hot because they're outdoors, because they're not. the air is hot, you'll get hot because you're actively absorbing sunlight. Right.

And so it's not just a fashion thing. It's a physics thing that if you want to stay cooler in the summer, then you wear lighter colored clothes. Unless it's the Arctic summer. And it might warm up. And the Antarctic, it might warm up to 28 degrees, you know, in the heat of the summer. Oh, that's a hot day in the summer, huh? And a hot day and so there you might want to wear extra black to absorb as much sunlight as you can. Or you're just from New York.

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 am strategic when I put on clothes depending on the weather. 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. Wow. Okay, so now, go ahead. What do you think of the albedo the earth is? Okay, so I'm looking at the earth. It's mostly water. I'm going to say that it's 0.3. That's exactly 0.3.

What? Well, it fluctuates. It depends. Chuck doing a happy dance. 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 0.3.

Cool. Okay. So that means 70% of the sun's energy that's hitting the earth is absorbed. 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 going to be reflected. We're stupid as hell. What is wrong with us? What is wrong with us? I didn't mean for you to blow a gasket on that little bit of data there. It's like, why is we doing that? 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 surface. Wow. And gets absorbed. Look at that. And what happens later is how much greenhouse gases are there and this sort of thing. All right. So, but wait, there's more.

I love it. 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 four times away. 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. That's. If you do the math.

Okay. It must be so great to stand on the moon and earth. 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. Oh. Because it has an albedo of point three instead of point one.

So that means full earth seen from the moon is three times 16. so it's nearly 50 times brighter. Brighter. On the moon than full moon is on Earth. Oh, God, the moon has it so much better than we do. It's like you can sit there. I mean, to watch an earth rise on the moon is just like so much better than what we get. Yeah, yeah.

So you talk about lunar, lunar beings. Yeah, lunar beings. Have it real good. Moon men. The 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, the crescent moon, 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. Okay. So what that means is, if you're going to be, 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.

That's why you can see the outline of the rest of the moon, from the crescent. Have you seen this? Yes. I was just about to say. That happens. You can't see. The sun isn't illuminating that.

There's no reason at all in this universe for that to be visible to you, except that is double reflecting earthlight. Oh, that's amazing. That is really cool. I mean, that is just, that's amazing. And it's called Earth Shine. Earth, oh.

And I think it really should have been called moonshine. That's 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. That's, you know, that's great. And it's all about the albedo.

It's all about, mm-hmm. You know what? I'm going to make some moonshine and call it albedo. Albedo moonshine, baby. When you want to shine twice as bright. Count me in on that. I want to be an early investor on your moonshine albedo. And one last thing, before we land this plane here,

for the longest while, people assumed that the moon was the source of its own light. Right. Okay, then you have to come up with explanation for why it would go through phases, which was hard, but that was just assumed. And 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's shine was unexplained until Leonardo da Vinci. My man. 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 his Codex Likeschester, Codex Likeser, which is the these opuses of his writings.

And in it, he draws a ray of sunlight coming to the Earth, going back to the moon, and then coming back to Earth. Wow. And so he first figured it out, 15th century. Guys, a genius. We got it. That's auditors to it. That's amazing. There it is.

So that's Albito. 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. Including Earth shine, which is my new thing. I love it. All right, Chuck. That was great, man.

That was Albedo. Yes. I got an applause for that one. Thank you. I'm telling you that was really cool, man. I'm going to name my next son. Al. Okay.

All right. And if you have a daughter, you're going to name her Clairvoyant. Right. And people, then that's when child services comes to your house. Right. Exactly. They say.

Yeah, we're going to pick up albedo and clairvoyant because you certainly are in no mental state to take care of these kids. 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. So, Chuck, how often do you think about pollution? Quite a bit, honestly. I mean, I actually... You're a green guy. You're a green guy. I think about it quite a bit and the deleterious effect that is having on our existence. 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. Nice. 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. I don't know. All that is up there? 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. Fake news. It was totally fake news. And to this day, from

mountaintops, when I've gone to high-level mountaintops, with high-level telescopes, I look up at the night sky and it reminds me of the Hayden planetarium. Wow. That's an urban urban frame of reference. 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 the 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. 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 dimest stars. So you start hacking away at the dimest 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 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, International Dark Sky Association. Okay. They sound like a group of supervillains. The IDA. That's all I'm saying.

That's all I can tell you about them. Yes, exactly. We've called this meaning 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, this one will let you know that's not a lot of money. States. Okay. Five million dollars? What's the inflation rate? How much should we ask for? Should we ask for something more? Did he add? With 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? So they, that organization has gotten more and more powerful and more. It powered 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. Right. Do you know why you can see the street light? Because it's bright. I don't know. 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. I got you. So I got you. Like a lantern, the light's going everywhere. Everywhere. It's not directed. You don't need the light everywhere, do you? Why? Why? If I see your light, it means you are paying to illuminate my airplane flying overhead. If you can see any light at all directly from its source, somebody's paying to illuminate the sky. Right. So the IDA simply makes the economic argument. Do you want to save money?

Okay, so you put a little hat on each lamp. Oh, that's adorable. 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. Right. Right.

Use less light, and now I'm not illuminating the airplanes flying overhead. It's that simple. And that's why we don't do it. Because it's that simple. And anything that's simple, we just can't do. Which can't wrap our head on. So the town of Tucson, Arizona, which is proximal to Kit 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 a municipal, leaders to say, look, if your place keeps getting brighter, we can't do our science. We got to 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, 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. So that's the light pollution. 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 from incinerated garbage that had gone into the sky and descended back to Earth. That is just crazy. It was snowing garbage? Snowing ash, correct. every day.

That's amazing. Yeah, yeah, yeah. So now, so that's that, but we have more pollution than that. Right. Wait, let me just say this about the light pollution that I just thought about right now because of what you just said. 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. And the conservationists and the air and the air,

the scientists that, you know, care for animals and sea life and birds, they basically realize that you're killing all the birds because they never know that it's nighttime. Yeah. And people... Okay, so at least I didn't lose my life over this channel. Yeah. Wow. So the bird is just completely disrupting all of their...

Just all, everything. They have no more circadian rhythm and they were flying until they... and they were dying of exhaustion and all kinds of crazy stuff. It was a weird little study that they did. But 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? Seagulls and pigeons, right?

Seagulls and pigeons? Plenty more than where they came from. You want us to care about that? First of all, we could see if they were chickens. They're delicious. But it was terrible. was terrible. 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, 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 that prevents our radio telescopes from seeing dim objects. Right. 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. Well, there you go, people. Cool it on the hot pockets.

Microwave. Take it easy on the hot pockets, people. And you know what else? The remote fobs for cars also creates a background noise of radio waves to a radio telescope that is extremely sensitive. Right. So 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.

So other parts of your photo might be okay, but suppose that streak goes to the one object you're trying to look at. Right. 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 preloading our data reduction utilities just to try to subtract them out. I'm told I just attended a workshop on satellite pollution where there was an agreement with Elon Musk for some of his satellites to use a sunshade. Okay.

So even though they're up there, they will, the sun, the sun, the sun, the sun, the sun, not reflect off of it down to us. And it did improve the seeing conditions. Gotcha. It did improve it. But I think whatever might be a long-term solution to this has not yet arrived. So that's what we're in the middle of now. That is kind of crazy.

And the current most powerful telescope on Earth is called the Vera Rubin Telescope, and it is designed to take movies of the night sky every single night. That is pretty dope. Okay, because think about it. Up till now, we've been taking a snapshot, okay? So if the thing did something different an hour later after you're on the way back to the computer. Tough tucks. You missed it.

Tough tough. You missed it. Missed out. Okay. So it's taking a movie so that it's called, there's an entire branch of my field that concerns itself with things that change over time. Right. 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, this will be a delight for them.

But now they'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. 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? That's some old Elon Musk junk. Don't worry about it.

And then it ends up being a killer asteroid. Yeah, and what is that? Oh, that's a killer asteroid that we almost mistook for an Elon Musk satellite. Right, right, yeah. Right. So, yeah, that's what we're confronting with right now. The buckets of pollution that influence the modern astrophysicist knows no bounds. Wow.

And none of it has anything to do with plastic or carbon dioxide. What do you think of that? Well, what we should have is an astrophysicist standing next to a rocket with a single tear rolling down their face. Oh, stop! Stop! Ah! That'll be a public service announcement. All right.

Well, I'll volunteer. I'll be the tiering astrophysicist for that. That would be great. Space pollution. Only you can stop. You can stop space booze. This is Ken the nerdneck Zabera from Michigan, and I support StarTalk on Patreon. This is StarTalk Radio with Neil deGrasse Tyson.

Tell you story from a child. Okay. So, yeah. So I, as a kid or even as adult, who doesn't love potato chips, right? Okay. So I have 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. Yes. Okay. I think I was 11, maybe 10, before I figured out that all of those were the same food. Right. Well, I mean, it's nothing to think about when you're 11 or 12.

It's just food. It's just food and it's delicious. And only one of them, two of them have the word potato in it. Mashed potatoes and potato chips, but they are completely different from each other. Oh, without a day. And French fries, no one says potato. And hash browns, they don't say potato. Right.

So. And my kids grew up on Freedom fries, so they don't even know what French fries. Freedom fries, okay. 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 like were the potato sticks. Do you remember those?

Oh, God, yes. Man, do you remember the potato sticks that, 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 match sticks potato sticks. The match stick, those were the best because there was like a lot of salt. Okay. Okay.

So the point is... Okay, I am starving. I'll be right back. So they were all different, yet they were the same. Right. Right. And so too was my revelation of middle school, early middle school. It was 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. Right. It is just different ways of preparing your light. Okay? To use my potato analogy. And so you're basically 11 years old and you're making this discovery for yourself. After I realized about the potatoes, yes. Okay. Because that was 37. 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 our favorite light colors, red, orange, yellow, green, blue, violet. White D.Bail. Okay. Continue there and 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 violent. And we abbreviated UV, but I like flesh and ultraviolet. Give me all the syllables that it's got. Okay? And this is the... Sounds far more harmful. In fact, it is.

Because 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 light and so the energy goes up okay okay so the higher the frequency is how many crest 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 and this will give you skin burn 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. The point of the sunblock is to block just the UV.

Just the UV. Okay. Right. So. So you still get dark and crispy no matter what you want to do. Yeah. You'll get toasted. You're toasted, right.

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 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? They go to a bomb shelter. They leave the room. They say, are you okay? Are you comfortable? Yeah, okay.

Boom. Door closes. Exactly. And they look through a lead, 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 can 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. Right. 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. Get omega rays or something like that. Ooh. I wonder what superhero would be made from omega rays. Well, gamma rays are 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 particles, alpha.

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, 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. 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. Right.

Okay, there's a little bit of violet spilling out. The actual ultraviolet, you don't see it 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. Right. You're not predator.

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. you detect infrared as warmth. Right. 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. 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. And so it's the shortest of the radio waves.

And they call them micro waves. Sweet. Short radio waves, micro waves. So that got labeled right there between infrared and radio waves. And beyond microwaves, we have radio waves. And now we're getting physically, realisably 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 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 as those just frequencies, but the frequency... Yeah, the frequency...

The frequency is the wave. You can call... They call them wavelengths. Right. But it's our habit to call them frequencies. Right. Right. So each frequency, when you're tuning...

Right. 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 explaining how he discovered. I'll do it real quick now. You ready? I love this. I love this. Yeah, I do remember. Okay. Herschel's a big fan of Newton.

Newton has a spectrum. He shows sunlight is composed of colors. And you put a sort of slit in the curtains, so the 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. Yeah.

All right. So he's got a thermometer, and he puts it in the blue. And then he put, and by the way, it's an experiment. So you need a control thermometer. So you put the control thermometer 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 rode out down all these temperatures. And what he noticed is that the temperature sitting outside of the visible spectrum read the highest temperature of them all. Right. And now, why didn't he just say, oh, it must be hot in this room. I didn't realize how hot it wasn't here. Maybe there's something wrong with me. I can't feel heat anymore. So there it was.

And because he didn't put the thermometer somewhere else. He put it next to the other. Right. He put it right next to it. Right next to it because at the same environment is there. And he said, oh my gosh, there must be a form of light, quote, unfit for vision. That's a, I love the terminology. Unfit for vision.

Light that is unfit for vision. 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 cell phone, and I look at my lamp on my table, it is one happy family of Electromagnetic spectrum coming to us.

That's, that's so cool. That, yeah. It's dope. and it's called electromagnetic because 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, to vibrate, to send it through, like sound does. Right. 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 a self-propagating electrical and magnetic wave. That's what we call it the electromagnetic spectrum. There you have it, Chuck.

That's great. And it all started with my potatoes. Just saying. And what wave length are they on? A delicious wave. Delicious. We keep them warm with infrared. It all comes full circle.

That's so true.