Daniel and Kelly’s Extraordinary Universe - Listener Questions 50: Dark matter, photon wavelengths and rainbows!

Episode Date: March 21, 2024

Daniel and Jorge answer questions from listeners like you!See omnystudio.com/listener for privacy information.

This is an I-Heart podcast. It's important that we just reassure people that they're not alone, and there is help out there. The Good Stuff podcast, Season 2, takes a deep look into One Tribe Foundation, a nonprofit fighting suicide in the veteran community. September is National Suicide Prevention Month, so join host Jacob and Ashley Schick as they bring you to the front lines of One Tribe's mission. One Tribe saved my life twice. Welcome to Season 2 of The Good Stuff. Listen to the Good Stuff podcast on the IHeart Radio app, Apple Podcasts, or wherever you get your podcast. Hi, it's Honey German, and I'm back with season two of my podcast.

Grazias, come again. We got you when it comes to the latest in music and entertainment with interviews with some of your favorite Latin artists and celebrities. You didn't have to audition? No, I didn't audition. I haven't audition in like over 25 years. Oh, wow. That's a real G-talk right there. Oh, yeah.

We'll talk about all that's viral and trending with a little bit of time. Chisement and a whole lot of laughs. And of course, the great BVas you've come to expect. Listen to the new season of Dresses Come Again on the IHeartRadio app, Apple Podcasts, or wherever you get your podcast. Every case that is a cold case that has DNA. Right now in a backlog will be identified in our lifetime. On the new podcast, America's Crime Lab, every case has a story to tell. And the DNA holds the truth.

He never thought he was going to get caught. and I just looked at my computer screen, I was just like, ah, gotcha. This technology's already solving so many cases. Listen to America's Crime Lab on the IHeart Radio app, Apple Podcasts, or wherever you get your podcasts. I'm Dr. Scott Barry Kaufman, host of the Psychology Podcast. Here's a clip from an upcoming conversation about how to be a better you. When you think about emotion regulation, you're not going to choose an adaptive strategy, which is more effortful to use unless you think there's a good outcome.

Avoidance is easier. Ignoring is easier. Denials is easier. Complex problem solving takes effort. Listen to the psychology podcast on the iHeartRadio app, Apple Podcasts, or wherever you get your podcasts. Hey, Jorge, do you think that our podcast exists out there in the mold? divers. Like if I think there are other versions of us doing this podcast? Yeah. You know, do you think in other universes there are people puzzling over how the universe works and podcasts trying to

explain it to them? I guess if they live in a universe, then there are probably people wondering about the universe and there might be a cartoonist and a physicist also wondering about the universe and they might have also met and started a podcast. That's technically possible. I wonder if they also make the same chocolate and banana jokes. Maybe they make chocolate. covered banana jokes? Uh-uh. I think we're in danger of crossing over

into the multiverse. What if they're making white chocolate and strawberry jokes, which I'm allergic to? That'd be like the anti-version of this podcast.

Then we would annihilate if we ever met. Whoa. It's like the anti-Daniel and Jorge explained the universe. But would they still explain the universe

if it's an anti-podcast? Maybe they'd be explaining the anti-universe. They'd be not explaining the universe. So they're like how we do here most weeks? I just want to taste their exotic chocolate.

What if we're the anti-version of their podcast? It's all relative, man. Does that mean our listeners are anti-listeners? As long as they're not anti-listening. Hi, I'm Jorge May Cartoonist, and author of Oliver's Great Big Universe. Hi, I'm Daniel. I'm a particle physicist and a professor at UC Irvine.

And I definitely listen rather than anti-listen to all the questions from our listeners. But do you anti-answer them or do you actually answer them? I think of my answers are sort of like anti-questions because they annihilate the question when they receive them. Wait, what? Oh, I see. And then they become pure energy and they disappear into the air. So really, there's no substance or matter to them. Is that what you're saying?

The whole interaction just goes up in a flash of light. I'm hoping that my answer turns their question into pure mental energy, illuminating the inside of their mind. Wow. Sounds a little dangerous and hippie-dipy. A little bit crunchy, yeah. But anyways, welcome to our podcast, Daniel and Jorge, explain the universe, a production of iHeartRadio.

Where we try to light up the inside of your mind with our understanding of the universe. We tackle the biggest questions out there from the small, particles to the most vast astrophysical objects that humanity has ever observed. We don't stop at the deep questions. We go for the deepest questions. We don't stop at the big questions. We try to answer the biggest questions because we think all of those questions deserve our best

answers. That's right. This is the podcast where we're anti-ignorance and pro asking questions about the universe and learning how everything works and why we are here specifically in this part of the universe. That's right. And we are pros, some kinds of chocolate and some kinds of bananas. at certain times of the day. Actually, you can't be pro against other kinds of bananas

because most of the bananas out there are the same kind. Did you know that? That's true. Isn't it like a monoculture? Yeah, yeah. Like they found one banana that tastes it really good and then they're like, everybody makes the same banana. So they've just been cloning the same banana for all over the world, basically.

But I've had like little red bananas sometimes in Mexico. Aren't those different? Yeah, yeah. There are other kinds of bananas. But most of the ones that you see, like the yellow ones that you see in most supermarkets, everywhere, pretty much around the world, they're the same bananas. And welcome to our podcast, The Science of Bananas. Oh, hey, we did a podcast about chocolate.

I challenged you, Daniel, to do a podcast about the physics of bananas. We're doing it. Now, I know it's a slippery subject. I think it's quite appealing, actually. Yeah, it'll put a big yellow smile on your face. All right. If you are a professor of banana physics, please write to me. I want to talk to you about the physics of bananas.

If you are the chief banana officer of Chiquita, also please reach out to me. Aren't all physicists technically banana physicists? We're all a little bit bananas. That's true. Yeah, yeah, yeah. I mean, you're discovering banana facts about the universe. The universe is bananas, that's for sure. But anyways, we do like to try to answer questions here on the podcast because everybody has questions. That's right. And we think that everybody's questions deserve answers. Not just professional physicists who've been spending their whole lives, working their ways to the forefront of human knowledge. Turns out everybody has questions that are tricky to answer. They bring us right into the abyss.

of human ignorance. Yeah, because as much as we've learned about the universe and discovered its laws and how it all works, there are still a whole lot that we don't know about how it's all put together and there are still lots of mysteries out there. And one of our goals on this podcast is to teach you to think about the universe like a physicist

to try to make in your mind a mental model for how it all works and then look for inconsistencies. Try to figure out if you really understand how it works. Does that mental model work in this scenario or that scenario? How does it explain this thing or that thing? Or do you have a new idea for how we can understand something? We want you to flex your brain in that direction. And when it doesn't quite work, reach out to us and ask us about it.

You might be surprised that lots of other people out there have the same questions you do. Daniel, does that mean you're trying to convert people to dark chocolate? This is starting to feel like a little cult here, like a physics cult. I think if becoming educated and thinking clearly about the universe leads people to eating dark chocolate, that tells you something about chocolate. You're saying that's like a win-win. I think the universe has a dark chocolate bias, yes. Well, we do like to answer questions, and so today on the podcast, we'll be tackling. Listener questions, number 50.

Whoa, should this be kind of a celebration? The 50th listener question episode. Yeah, congratulations us and congratulations our listeners for asking so many awesome questions. Now, did you have a rule that only people over 50 can, can ask questions in this episode? Oh, definitely not. I think one of our listeners is quite young, but I try not to ask them

because some people are sensitive. But yeah, 50 is kind of a big number. Are we supposed to have a midlife crisis here at some point? No, a midlife celebration. I'm turning 50 in a couple years, and I'm looking forward to it. I'm embracing it. Nice.

Do you have any big plans? Sit in the couch and eat dark chocolate is the big 50 party for you. Yeah, I was going to say that, but that sounds like every day around here, so I'm not sure how many distinct. that one day from the other days. Oh, well, you have to spin it the right way.

It means you celebrate life every day, Daniel. There you go. By sitting in your couch and eating dark time. And if you celebrate life and celebrate understanding the universe and you have questions about how it all works, you could have your question answered here on the podcast. Just write to us questions at Danielanhorpe.com. You will definitely get an answer to your question and you might even have it played on the podcast. Yeah, so we like to answer your listener questions here on the podcast.

And so today we have three great questions. people all over the world, and they are about dark matter, about rainbows, and the wavelength of light. Daniel, is there a theme to these questions? These are all questions that arrived on the same day. Are they like in the top 50 questions we've ever gotten? They're in the top 150 questions, yes, because we answer three per episode. I see. I see. There's a special selection process here. Just straight from the inbox into the microphone. That's right. That's the pipeline right now. Well, we do have some pretty cool questions here today, and so we'll start with this one from Johnny from Sweden. Hi, Daniel and Jorge. This is Johnny from Sweden.

I have a question about dark matter that I have thought about for a long time and haven't found an answer to. If you can shed some light on this question, I would be very grateful. Could dark matter actually be the gravity from matter that exists in a higher dimension? Thank you for the best podcast in the whole universe. All right. Great question from Johnny here. Kind of a trippy question. There's a lot going on here.

Higher dimensions, dark matter, gravity. I think Johnny is trying to find an out-of-the-box solution to the question of dark matter. It's a heavy question. It is a heavy question, one that physicists have been struggling with. I know that there's a lot of dissatisfaction out there with the concept of dark matter, being this weird, invisible matter that nobody ever noticed before, but actually dominates the universe, sounds like a conspiracy theory.

But we think it's real. Of course, we're open to other ideas and other theories and other explanations because in the history of physics, sometimes the craziest ideas turn out to be true. Yeah, even the banana ones, right? Dark matter could just be bananas. Yeah.

Okay, so the question here is kind of interesting. So dark matter is this thing out there in the universe that we don't know much about, but we feel its presence, but we can't see it. And it's pretty big. like a quarter of the mass and energy of the universe, right? That's right. It's like 80% of the stuff in the universe

and like a quarter of all the energy in the universe is this invisible source of gravity. And it's super mysterious because we know it's there from its gravity. Like we can feel its pull or at least we can see the effects of its gravitational pull, but we've never actually seen it or have any idea what it could be. Like it's super weird, right? Like it's there, but we can't see it or touch it.

Yeah, that's right. What we actually know, what we really observe, is gravity. So in the most pure sense, the mystery is what's the source of this unexplained gravity? There's no matter out there in the universe we can see that explains all the gravity that we measure, that's holding the universe together, that's keeping galaxies from spinning apart that shape the structure of the whole universe. So there's unexplained gravity out there. And dark matter is our best explanation for it to say there must be some new kind of matter that's invisible and probably intangible and that's creating all of this gravity. Which seems kind of

bonkers if you really think about it because most of the matter that we know about that we've known for hundreds or thousands of years you can see it and touch it but this kind of matter it's like you're almost inventing a new kind of matter to explain this gravitational phenomenon but we don't really know if that's true or not right it's true that it's kind of bonkers but maybe it's less bonkers than extrapolating from our kind of matter to the whole universe it's true that everything we've ever experienced is made of atoms but that doesn't mean that everything has to be made out of atoms The history of physics tells us we should be really careful about extrapolating from our little corner of the universe and our kind of experience to the whole universe. The revolutions of quantum mechanics and of relativity were moments when we realized we've been looking too narrowly at only our own experience.

So to say that the rest of the universe should also be made out of atoms because we are and the earth is seems like a pretty big leap. What we're doing here is saying, well, maybe there are other kinds of matter out there, ones that are not made out of atoms. and so don't interact in the same way that atoms do. Well, that's one possible explanation, and that seems to be where most of physics is leaning. But Johnny here has an alternate theory for what causes dark matter. Exactly. He's asking if this gravity could instead be coming from matter

that exists in a higher dimension rather than like a new invisible kind of matter in our 3D space. Yeah, fascinating idea. If he's right, he would get like all the Nobel Prizes, right? If he's right and we can test it and prove it, then, yeah, Johnny has changed the world and history. All right, well, let's dig into his idea. He's saying that maybe dark matter, what we experience or feel as dark matter is maybe actually matter that is not in the dimensions we're in, but they're in other dimensions.

Yeah, I wasn't exactly sure what he meant by matter that exists in a higher dimension because the word dimension is a little bit fuzzy. Like in physics, there's a crisp definition of it. But in popular science and in science fiction and a normal everyday conversation, I think Dimension means something else. Like, often I think people say dimension when they mean like a parallel universe. You know, like people talk about interdimensional aliens visiting the earth, right? I think what they mean there are aliens from like a parallel universe, from like another

copy of the universe, like a different set of space. Right. And we've talked about this in our books and in previous episodes. And I know that you're sort of against this sci-fi idea of the dimension as being like in a separate universe that you go into. But it sort of kind of is, right? It is sort of the idea of a separate part of space than the one we're sitting on. I'm not against it. I mean, the idea of a parallel universe is certainly possible.

This concept of the multiverse that we could have multiple universes, maybe with different starting conditions or different even laws of physics. Who knows, right? I think that's totally plausible scientifically. I'm just pointing out that that's not what we mean by a dimension. when we talk about it mathematically or physically. But you know, that's just semantics. So let's assume first that this is what he means by dimension. Like is dark matter actually gravity from a parallel universe?

Like maybe in another universe there's a huge blob of normal matter and we're feeling its gravity somehow leak out into our universe. And that's what we're calling dark matter. That's how you're interpreting his question, his scenario. Yeah, that's one possibility. We can also talk about the other definition. Well, let's do it one at a time. So in this scenario where a dimension means a

parallel universe and you're wondering if dark matter is actually like some blob of stuff in another universe that's creating gravity in our universe, I don't think that can work because, you know, gravity is the bending of space and time. And so if matter is bending our space and time, then it's in our space time. Like that's sort of what it means to be in our space time. If we have a shared space time, like that matter can bend our space time, then it's part of our universe. So you can't both be in another universe and affect things in this universe. Well, I think you're sort of arguing semantics now. It's like you're saying like if there is sort of this whole part of this whole universe,

basically that you can exist in, but that we don't have a lot of access to. But if it's somehow connected to our universe, you're saying that means both universes are really just one universe. Exactly. I'm saying it's one universe. And then it's really the same idea, right? Then it's just some kind of matter that we can't interact with for some reason, but is able to bend our space time, therefore cause gravity, that's just the same idea as dark matter.

Well, you sort of sound like my daughter, because she's always saying, like, if the multiverse exists, wouldn't it all just be the universe? So, I mean, like, physicists do have a name for, like, a universe and something bigger than a universe, which is a multiverse. Yeah, I think this is a tiny bit different from your daughter's point, and though she has a good one. You know, the idea of a multiverse is that these universes don't interact. They really are separate universes.

But if they do interact, why would you call them separate universes? How are these higher dimensions if we're able to interact with this kind of matter? And if we can interact with it, why can't we see it? Well, the answer has to be with some other new kind of matter, which basically we're back at dark matter. Right, right. Well, I feel like it's kind of like, you know, if I dig a tunnel from my house to your house, I mean it'd be a pretty long tunnel, but if we do that, would that mean that we all live in one house? Or could you still say that we live in separate houses, which is the tunnel connecting them?

You know, I think if I can go from my house to your house without going outside, then, yeah, it's probably just one house. What if I put a big door in the tunnel and I lock it? Interesting. I'm sure there's some California legal statute that defines what is a residence and what is not, and I'm not qualified to opine on that question. All right, all right, all right. So you're shooting down this idea that his question actually means that dark matter is matter in a separate universe because then it would just be the same. Yeah, exactly. Then it would just be dark matter.

I think maybe John is trying to get at the idea that we can. sort of feel it, but sort of not feel dark matter. So, like, maybe this is matter that exists in another universe or another huge chunk of the universe, but that is not fully connected to our universe. Like, it's maybe totally connected to a tunnel, which in this case would be gravity. Yeah, potentially. But then you have to ask, like, why we can't interact with that other kind of matter. And then you have to make it another kind of matter.

If it's sharing our space, bending our space time, it doesn't interact with us. Then you have to ask, you know, why not? what makes our matter, our matter, and that matter, that matter. And so you have to make it another kind of matter. And then it becomes dark matter all over again. All right. Now say that quickly, seven times in a row. But there is another way to interpret his question, which I think is much more interesting,

which is the physics definition of dimension. Because he doesn't say another dimension. He says a higher dimension, which I think might be a useful clue. Because in physics, we think of dimensions not as, you know, it came from another dimension, but as directions of motion. Like we describe our space as three-dimensional space or four-dimensional space time because we say there are three directions of motion. Like if you draw axes out in space, you get X, Y, and Z. There's three directions you can move.

You don't need four directions to describe our space. And so I think maybe he's asking like, what if our space actually is higher dimensional? What if there are four, five, six, ten dimensions of space? And we're only seeing a slice of it. And dark matter somehow exists in those higher dimensions and is influence. influencing us. Interesting. Okay, so, and I think maybe this is what he means because he uses the word higher dimension, right?

Yeah. Like if he meant like an alternate dimension, he wouldn't say the word higher. Yeah, I think so. Although maybe he's smoking something and he's higher, you never know. Yeah. Or maybe he's more, you know, elevated or enlightened. Exactly. And this can be hard to visualize what is higher dimensional space because 3D space sort of fills up

your mind because we're so. So you're used to thinking in 3D space because we live in 3D space. So it's easier to take a step from 2D space to like take a step back and imagine what if our universe was 2D, what would it be like to have a three dimensional universe rather than trying to go from 3 to 4. So imagine, for example, we're living on the surface of the ocean. You know, our universe is just the 2D surface of the ocean, but what if the universe actually has another dimension that can influence us, like the depth of the ocean?

And so then Johnny's idea is that maybe there's matter in our universe that maybe only exists in these other dimensions that are not our regular 3D dimensions. Now, is that possible? Like, can matter exist in some dimensions and not others? If there is maybe a fourth or fifth dimension to our universe, am I moving around in it? Or do I have to be moving around in it? Or do you know what I mean? I do know what you mean. And I think there's an important, but maybe subtle distinction here.

Matter has to exist in all of the dimensions of space time. You have to have a location in all of those directions. But it could be that there's matter that has a different location in this new dimension. Like say, for example, our universe is the 2D surface of the ocean. So we have a location in the depth dimension, but you could imagine having matter that exists deeper in the ocean. So it doesn't intersect our 2D surface at all. It's in the universe.

It exists in all three dimensions of that 3D universe. but no part of it overlaps in our 2D slice of the universe. But it could still influence us. It could still influence it because it's connected to us three dimensions. Exactly. It's part of our space time, right? And so then Johnny's question is like, well, what if there's matter that's part of a four dimensional space, but its location in that 4D space means we can't see it.

It's like in a different location along that new fourth dimension than we are. Like we're on the 3D surface of that 4D ocean and it's like deeper down along that fourth dimension. If gravity is the curvature of space time and there's matter in that part of the universe, the deeper ocean of the universe, wouldn't it also affect our space time and therefore look like dark matter? Right. It might affect us gravitationally because let's say like we're on the surface of the ocean, as you're saying, and this other matter is right below us. We might feel its gravity, it might pull us in a certain direction. But when we try to look around and feel for it and touch it and see it, we can't because it's actually underneath this. Exactly. And this is a really compelling idea.

There's sort of two problems with it. One is you need an explanation for why we can't touch it. Like, why are we restricted to the surface of this four-dimensional ocean? Why can this kind of matter exist and move in four dimensions and we're stuck at this one location in that fourth dimension? Like, why are we on the surface of this ocean and this other matter can sink or swim or whatever? You mean like, why are we stuck in two dimensions? Why can we go down into the ocean? Exactly. Yeah. And why does that matter never surface? Right. How can we never see it? But the real problem is mathematical, which is that we know how many dimensions there are to space time.

We can measure how many dimensions there are to space time. Because the dimensionality of space time, like how many ways you can move, changes how gravity works. But isn't higher dimensions or other dimensions part of things like? string theory? Like, isn't this an active possibility that physicists are considering? Yeah, you're exactly right. People do look for extra dimensions, but one of the big challenges to those ideas, like string theory that requires the universe has 10 or 26 dimensions or other crazy theories that look for additional dimensions of space time, is that we're not seeing them. We can go out in the universe and we can pretty easily look for extra dimensions and we don't see them. You know, for example, the number of dimensions of space time changes how gravity varies with

distance. We know in the Newtonian description that gravity gets weaker as you get further away, but it doesn't just fall off linearly. It's not like twice as far away gravity is twice as weak, twice as far away gravity is four times this week. It goes like one over the distance squared. And that number, the square, tells you the dimensionality of space time. If we lived in four dimensional universe, that would be one over the distance cubed. If we lived in a 19 dimensional universe, it would be one over the distance to the 18th power. But isn't that only if you're that gravity works a certain way? Like what if the gravity doesn't work the way you think it does? Yeah, if you want to also overthrow general relativity, then you got a lot more work ahead of you.

Yeah, I'm not afraid of work. I got all day here. You and Johnny should get to that higher dimension and get to work on it. But, you know, if we're not changing gravity, if we're not changing how gravity works, we're just asking, does the universe have additional dimensions? And could there be matter hiding those dimensions that creates gravity that we see that could be explaining what we're seeing instead of dark matter? Then if we're sticking with our theory of gravity, that's pretty hard to make it happen. Isn't your assumption here that this theory of gravity that you're saying that you're sticking by, isn't that a theory of gravity that we've gotten by doing experiments in the dimensions that we have access to? Yeah, absolutely. Could maybe gravity be actually

more powerful than you think? And so therefore, when you try to measure it, there are other dimensions, but it drops off as one over R square, as they're saying. There are some really cool theories that there are these other dimensions, but those dimensions are not like our dimensions. They don't go out to negative and positive infinity like ours, but they're like curled up little rings so that you can only have like two centimeters or one centimeter. And that would solve this problem with gravity getting stronger or weaker. It actually would solve the problem in a really fascinating way because if you get really close to something, then gravity would get very, very powerful. And that would actually help us understand why gravity is so weirdly weak. But go check out

our podcast on extra dimensions. But you got to assume something, right? And so if you're assuming our theory of gravity, that I don't think this quite works because if those extra dimensions exist, they would have to be super duper tiny and there wouldn't be mass in them. But if we're also getting rid of our theory of gravity, then yeah, anything's possible. Well, it sounds like you kind of have to have that open mind, right, when you explore physics? Yeah, absolutely, you do. And we do think that there are problems with our theory of gravity. We think that general relativity is probably not the final answer to how space time works

because it ignores the quantum nature of it. So we're definitely open to modification of those ideas, yeah. All right. Well, then what's the final answer for Johnny here? I would say that it's possible that there are additional dimensions with matter in them that doesn't appear in our 3D slice of space, but it would be pretty hard to explain all of the dark matter using that because those dimensions would be tiny and would be curled up.

I think it's much more likely that dark matter really is a new kind of matter that exists in our universe. Unless, of course, our whole theory of gravity is wrong, right? Yeah, absolutely. All right, well, great question, Johnny. Thanks for sending that in. Now, let's get to our other questions. We have a question here about rainbows and one about the wavelength of light.

So let's dig into those. But first, let's take a quick break. Imagine that you're on an airplane and all of a sudden you hear this. Attention passengers. The pilot is having a... An emergency, and we need someone, anyone, to land this plane. Think you could do it? It turns out that nearly 50% of men think that they could land the plane with the help of air traffic control.

And they're saying like, okay, pull this, until this. Do this. Turn this. It's just... I can do it my eyes close. I'm Mani. I'm Noah. This is Devon.

And on our new show, no such thing. We get to the bottom of questions like these. Join us as we talk to the leading expert on overconfidence. Those who lack expertise lack the expertise they need to recognize that they lack expertise. And then, as we try the whole thing out

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I hope you'll join me and my extraordinary guests for this new season of Family Secrets. Listen to Family Secrets Season 12 on the IHeart Radio app, Apple Podcasts, or wherever you get your podcasts. All right, we're answering listener questions here today. And our next question comes from Sonia. Hi, Daniel and Jorge. My name is Sonia, and I was wondering if there was a minimum and or maximum wavelength for light.

Thank you. All right, great question, Sonia. I wonder what made her think about the nature of light. I get this question all the time, which is one of the reasons why I wanted to answer it on the podcast. It's something that a lot of people seem to wonder about. Because you learn that light is described by this wavelength and the wavelength is connected to the color. And then I think it just makes people wonder about the extremes. Like we talk about the extreme nature of the universe all the time.

What is the beginning? What is the end? What is the biggest? What is the smallest? People's curiosity make them want to push to the extreme edges of knowledge. All right. Well, her question is whether light has a minimum or maximum wavelength. So, Daniel, how do you describe what the wavelength of light is?

So we understand light to be electromagnetic oscillations. That just means waves in electrical and magnetic fields. Like electrical fields are things we're very familiar with. You have charged particles. They make electric fields. Magnetic fields are something we're familiar with. You have magnets. Moving electric charges can make magnetic fields. And so light is this particular configuration of electromagnetic fields where the electric field creates a magnetic field, which creates an electric field, sloshes back and forth.

But it's fundamentally a wave. It's a wave in these fields that fill space. And those waves are described like all waves by a wave length, which is like how long it takes in distance as the light travels before it repeats the same configuration. So the electric field is going up and down, the magnetic field is going up and down. How far does the light travel before the electric field is back

into its original configuration? That's the wavelength of the light. Sort of like a wave in the ocean, right? Yeah, exactly. something I understand about these waves is people see visualizations of light traveling and they see it as like a sinusoidal wave moving through space and they get the impression that the light is like wiggling sideways that has like a width to it but light moves along a line and what's changing is the magnitude of the electric and magnetic field which are like little arrows that are pegged to that line sometimes those arrows are drawn like with their base pointing in some direction and their tip away from the line that's just telling you that magnitude of the electric field. The electric field doesn't like reach out sideways. It's a vector field and so it can point in different directions. Okay. So it's an oscillation of these fields. And so things can have a wavelength, which as far as we know can vary, right? Like that's

how we get different colors when we look at things. Exactly. Like comes in all kinds of different wavelengths and different wavelengths are interpreted by our eye as different colors. So there's a very narrow set of those wavelengths that we can actually see. You call that the visible spectrum. It goes, you know, from the reddest colors we can see up to the most violet colors we can see. But light extends its spectrum well above that and well below that. The ultraviolet, the infrared, x-rays, gamma rays, radio waves, all these are just light with different wavelengths. Yeah, I think that's basically Sonya's question is like light can go up in frequency from what we can see and it can go down in frequency. And their question is, how far can that go?

Yeah, exactly. And there's a few different concepts there. Right now we're just talking. talking about wavelength, right? Long wavelengths are like radio waves, short wavelengths or like ultraviolet gamma rays. You can also talk about frequency. Frequency is the inverse of wavelength because light always has the same velocity. So short wavelengths means high frequency. Radio waves that have long wavelengths have very low frequency. It's all the same thing. You can just express it in different ways, but the frequency is useful because it's connected to the energy. Like the energy of light is connected to its frequency. Higher frequency light, ultraviolet x-rays have more energy than lower

frequency light, like radio waves. But it's all the same thing, right? Like for light, it's all tied to the speed of light. And so you can also say that the energy of a light wave is tied to its wavelength as well. Yeah, absolutely. It has an inverse relationship to its wavelength and it's linearly proportional to its frequency. Right. It's the same thing. So you can also say that the energy of something is tied to its wavelength. The higher the wavelength, the lower the energy of light? Yeah, that's exactly right. Okay, so her question is, how far up and down the frequency spectrum or the wavelength spectrum can you go with light? Yeah, and so in theory there's no limit.

Like, as you say, it's just controlled by the energy. Is there any limit to how much energy a photon can have? Is there any minimum to how much energy a photon can have? The only limit there is zero. Theoretically, it can't have zero energy, but it could have any tiny amount of energy. Any number you want, 0.000,000,000, 100 zeros, and then a one. joules or whatever, you could have a photon with that energy. Could you though? Are you sure about that? Like what if the electromagnetic fields are quantized?

So if we're still just talking theoretically, then electromagnetic fields are quantized, but they're quantized in number of photons, not in energy of those photons. And so if we're just talking about like photons out in free space, they're not confined or anything, then they can have any wavelength and therefore any energy. This is just in theory. There are some maybe practical limits to like how long a wavelength the photon might have or how short a wavelength the photon might have. But according to like theoretical quantum field theory of electromagnetism, there are no limits there except for zero.

You can't have a photon with zero energy. According to the theory, right? Yeah, according to the theory. Is it possible that maybe it'll turn out later that these magnetic fields are quantized or have a minimum wavelength to them? Yeah, it's possible. Like we might extend our theory

to understand the universe, differently. For example, this theory assumes that space is continuous, that it's smooth, that there's no shortest possible distance in space, and therefore no minimum wavelength, that you can keep getting smaller and smaller and smaller distances and those things are meaningful. But that might be wrong. It might be that space is not smooth and continuous, but it's pixelated, that there's a minimum meaningful distance to space, in which case there would be a minimal possible wavelength to light. Or at least a meaningful minimum wavelength, right?

Like maybe you could still have minimum wavelengths, smaller wavelengths, which you just wouldn't be able to see them? Or are you saying they might not exist at all? In this scenario, they wouldn't exist at all because remember that light is an oscillation of the electromagnetic field, which is part of space. And so if you have like a fundamental unit of space, like a space pixel, then you can't have anything very inside that pixel. The electromagnetic field can only have like one value in that pixel. pixel, which means you couldn't have an oscillation with a wavelength smaller than a pixel. Sort of like on your screen, each pixel can only have one color, right? It's like it's green or it's blue or it's pumpkin or whatever the color is, but it can't be

two colors at the same time. That's what a pixel is. And so if space is quantized, then every unit of space can only have one value of the electromagnetic field, and therefore you couldn't have oscillations smaller than the size of that pixel. I see. All right, well, that's only if space is pixelated. Can you imagine other scenarios, like maybe inside of a black hole at the singularity could maybe the wavelength of light go to zero there? Yeah, that's a really cool question.

But singularities are a feature of general relativity, and general relativity assumes that space is smooth and continuous. The whole idea of having a singularity is having a bunch of mass in an infinitely small space. So you can't both have a bunch of stuff in an infinitely small space and a minimum wavelength of light. because having stuff in an infinitely small space assumes that there's no limit to how small stuff can get. So near singularities or near the event horizon of black holes, light can go to very extremely long or short wavelengths. I see.

But what about the singularity then? Would light have a zero wavelength if a singularity exists? What is the wavelength of light inside a singularity? Yeah, that's a cool question. That's why they paid me the big bucks. That's a really cool question. I don't think it could have zero wavelength because that would imply infinite energy.

And a singularity is infinite density, but it's not infinite energy. It's finite energy. And so in principle, you can make a black hole and singularities just piling up a bunch of high energy photons in a small space. You don't need infinite energy to do that.

All right. Well, that's the minimum of light for a wavelength. What about the maximum? Can light have a maximum wavelength? In order to generate a photon, in order to generate light, you usually need an antenna. You need something to oscillate to make these electromagnetic fields. Like you want to make radio waves, you need to have an antenna that's pretty big, where the electrons can zoom up and down that antenna to make wiggles in the electromagnetic field.

So in principle, if you want to make a photon that's like a galaxy wide, you need an antenna that's like a galaxy wide. So, for example, if the universe is not infinitely big, if it's a finite size, that limits the practical size of a photon's wavelength because you couldn't make an antenna bigger than the universe and therefore you couldn't make a photon with a wavelength bigger than the universe. I feel like now you're sort of mixing practicality with theory. Oh, yeah.

So if we stick with theory, is there a theoretical maximum wavelength of light? I don't think there is theoretically, even if the universe is finite because you could just have like a part of the photons wave. So theoretically, I don't think there's any limit to the wavelength of a photon. You're talking really, really low energy photons with really long wavelengths, so long that even if the universe is finite size, you might only be able to fit a part of that wave in. It still technically would have that very low wavelength. So I think there's only a practical limit, not a theoretical limit.

So like theoretically, you could have a photon that's bigger than the universe. Well, you would have a photon whose wavelength is bigger than the universe. universe, you wouldn't have the full period of that photon's oscillation inside the universe. Well, I mean, like, let's say the universe is much bigger than what we can see than the observable universe. Technically, the whole observable universe could right now be sitting inside of a photon. Yeah. It sounds like a cool title of a book, The Photon Bigger Than the Universe. The light that contains our universe.

Oh, my gosh. Bestseller. Boom. Let's get Anthony Doer to write that one. all the light we cannot fit in the universe yeah there you go all the light wait didn't somebody already write that I think you want to poulter for it but I'm sure we can just copy it yeah we're changing a few words

you know that counts is fair game fair use well so you talked about the theory of it now you were sort of getting into the practicality of it and you said there's maybe a practical limitation to making a photon bigger than the observable universe what about is there a practical limitation to making a minimum or smallest photon Because isn't all light sort of generated by the motions or interactions of particles, which are quantized?

Which are quantized, but you only need one electron. Like a single electron wiggling can make a photon. The only practical limit to making a photon with a really short wavelength is that it's really high energy. So you need a lot of energy. So if you took, like, for example, all the light the sun emitted in a year and poured that into a single, like really powerful photon, that would be very, very short wavelength. Well, there might be a limitation to like how much energy there is in the universe, in which case that would give you maybe limitation to how small a photon you can make.

Yeah. If you annihilated all of the particles in the universe and converted all of their energy into a single photon, then number one, you would no longer exist to observe this amazing photon. But even then, it would be finite because the amount of energy in the universe, the observable universe, at least, is finite. So yeah, you're right. That's a practical limit to how short wavelength photon you can make. Yeah, that would be the sequel novel.

All the light we cannot make in the universe. The other limitation there is the black hole, right? You make a very short wavelength photon. You're going to make a black hole. Oh, interesting. And so if you use all the energy in the universe to make a photon, it would just instantly turn into a giant black hole. Or would it?

I don't know. No, it definitely would. I mean, you're talking about putting all the energy in the universe in one spot, that's definitely a black hole for sure. Oh, so maybe that is maybe a limitation on the minimum size of a photon. Like at some point, a photon would be so small, it would turn into a black hole. Yeah, a photon with energy greater than the plank energy would turn into a black hole. That's basically how you calculate the plank energy.

So there is a limitation to a minimum wavelength of light then. Yeah, that's the practical limitation. Because after that, you get a black hole. Unless that's what you wanted, right? That's sort of what you were going for. Like, I want a black hole singularity photon. So there is a direct. and practical minimum wavelength of light.

Yeah, the asterisk there is we don't really know what happens in that scenario. Like if you make a photon with energy greater than the plank energy, so it collapses into a black hole, is it still a photon? Does it turn into like singularity stuff? We don't know what goes on inside a black hole. So I don't know if that really is technically a limit. It might just be like, okay, you made a photon, but now it's also a black hole at the same time. Is it still a photon?

I don't know. All right. Well, I guess that's all the answer that we can fit in this universe podcast. That was both the longest and shortest answer we could find. Yeah, we reached the maximum in both directions here. We need another dimension just to fully explore this question. That was a great question. Thank you, Sonia.

And so let's get into our last question of the day, which is about rainbows. Let's jump into that rainbow. But first, let's take another quick break. Imagine that you're on an airplane. and all of a sudden you hear this. Attention passengers, the pilot is having an emergency and we need someone, anyone, to land this plane. Think you could do it?

It turns out that nearly 50% of men think that they could land the plane with the help of air traffic control. And they're saying like, okay, pull this, do this, pull that, turn this. It's just... I can do it my eyes close. I'm Manny. I'm Noah.

This is Devon. And on our new show, no such thing. We get to the bottom of the bottom of this. bottom of questions like these. Join us as we talk to the leading expert on overconfidence. Those who lack expertise lack the expertise they need to recognize that they lack expertise. And then as we try the whole thing out for real. Wait, what? Oh, that's the runway. I'm looking at this thing. Listen to no such thing on the IHeart radio app, Apple Podcasts, or wherever you get your podcasts.

Hello, it's Honey German And my podcast Grasias Come Again is back This season we're going even deeper Into the world of music and entertainment With raw and honest conversations With some of your favorite Latin artists and celebrities You didn't have to audition?

No, I didn't audition I haven't audition in like over 25 years Oh wow That's a real G talk right there Oh yeah We've got some of the biggest actors Musicians, content creators and culture shifters

sharing their real stories of failure and success You were destined to be a start. We talk all about what's viral and trending with a little bit of chisement, a lot of laughs, and those amazing Vibras you've come to expect. And of course, we'll explore deeper topics dealing with identity, struggles,

and all the issues affecting our Latin community. You feel like you get a little whitewash because you have to do the code switching? I won't say whitewash because at the end of the day, you know, I'm me. Yeah? But the whole pretending and code, you know, it takes a toll on you. Listen to the new season of Grasasas Come Again as part of My Cultura Podcast Network on the IHartRadio app, Apple Podcasts, or wherever you get your podcast.

Hey, sis, what if I could promise you you never had to listen to a condescending finance, bro? Tell you how to manage your money again. Welcome to Brown Ambition. This is the hard part when you pay down those credit cards. If you haven't gotten to the bottom of why you were racking up credit or turning to credit cards, you may just recreate the same problem a year from now. When you do feel like you are bleeding. from these high interest rates, I would start shopping for a debt consolidation loan, starting

with your local credit union, shopping around online, looking for some online lenders because they tend to have fewer fees and be more affordable. Listen, I am not here to judge. It is so expensive in these streets. I 100% can see how in just a few months you can have this much credit card debt when it weighs on you. It's really easy to just like stick your head in the sand. It's nice and dark in the sand. Even if it's scary, it's not going to go away just because you're avoiding it, and in fact, it may get even worse. For more judgment-free money advice, listen to Brown Ambition on the IHeart Radio app, Apple podcast, or wherever you get your podcast.

A foot washed up a shoe with some bones in it. They had no idea who it was. Most everything was burned up pretty good from the fire that not a whole lot was salvageable. These are the coldest of cold cases, but everything is about to change. Every case that is a cold case that has DNA. Right now in a backlog will be. identified in our lifetime. A small lab in Texas is cracking the code on DNA.

Using new scientific tools, they're finding clues in evidence so tiny you might just miss it. He never thought he was going to get caught. And I just looked at my computer screen. I was just like, ah, gotcha. On America's Crime Lab, we'll learn about victims and survivors. And you'll meet the team behind the scenes at Othrum, the Houston Lab that takes on the most hopeless cases to finally solve the unsolvable. Listen to America's Crime Lab on the IHeart Radio app, Apple Podcasts, or wherever you get your

podcasts. We're answering listeners here today. And our last question comes from Clark, who is seven years old. And I love getting questions from kids. I love when kids listen to our podcast. I love when kids listen with our parents and talk about it. Thanks to all of you parents who are raising the next generation of scientists.

Why do we always see rainbows bend the same way? Why can't they bend sideways or upside down? All right, great question from Clark. I guess basically the question is, why does a rainbow look like a rainbow? Like, why does it look like an arc, not an S shape or any other shape? And specifically, why is it always an arch

bending down from what we can see. Could you have a smiley face rainbow or a sea shade rainbow without turning your head? Yeah, it is very cool. Rainbows actually do bend sideways and upside down. Rainbows are actually circles. You're only seeing part of it because the earth is blocking the rest of the view. They're not actually circles, right? Because they're not actually things.

Yeah, so rainbows are not physical objects. They're an image that you are seeing. Your brain reconstructs what he thinks is going on out there, on the directions of light that hit your eye. And so you can see things that are like not there, the same way you can like see yourself in the mirror, but you're not actually behind the mirror. It's just an image of yourself in the mirror.

Right. A rainbow is like a mirage or like a hologram basically, right? Yeah. It's an image your brain has reconstructed. It says all this light is coming in in this direction. So it looks like there is something they are giving off this light. But it doesn't have to be like just like with a mirror. You don't have to have somebody standing through a window to create that

you can just use a mirror and it looks exactly as if there's an inverted copy of you standing on the other side of the wall. Right. Although I guess philosophically, you could say that a rainbow is a physical object, right? Because it's the water droplets that make up the rainbow that is the rainbow. Yeah, in the same way that the mirror is a physical object and it's creating this image in your mind. And you're right about the physical mechanism also. The reason you see a rainbow is that the sunlight is hitting the water droplets and those water droplets are spreading out the

light. When light passes from air to water, different colors of light bend a different amount as that happens. And so when they go into the water droplet and then back out of the water droplet, different colors, green, red, blue, yellow, all take a slightly different path. And that's why you see a rainbow. It spreads the light out into those different colors. Right. I wonder if it would help to sort of paint the situation that leads to a rainbow, right? Because we don't see rainbows every day. You also don't see them anywhere in the sky. They have to mean a certain position in the sky relative to the sun for you to see a rainbow. And there also has to be a lot of rain or water in the air, right?

Yeah, exactly. So in order to make a rainbow, you need to distribute a bunch of water droplets in the air and have the sun behind you. Then the sun will pass like over your head. It will enter those water droplets, bounce off the back of the water droplet, come back out, and then hit your eye. And so if you imagine just like a single water droplet, it's going to be spreading the light out in different colors, green, red, orange, purple, whatever.

And you will see one color of light from each droplet. But if the droplet is a little bit higher, you're going to be seeing red light from it. If the droplet is a little bit lower, you're going to be seeing purple light from it. Because those different colors come out of the droplets at slightly different angles. Right. You can have to imagine like a wall of water drops floating in the air in front of you. And the light, the sun is right behind you. It's shining in light, sort of like a projector or a flat.

It's shining the light behind you. It's going over your head and it's hitting this giant wall of water drops. Some of the light will just go through, right? Yeah. And you'll never see that light again. But over the arch of the rainbow, light actually gets reflected back to you in different colors. That's right. And every droplet there is sending every color of light out.

So it's like a big screen. Every droplet is sending out a whole spectrum, purple, blue, green, orange, red, all in different directions. where you're standing, you're seeing a ring of droplets that are all sending you red light. And then you see another ring of droplets that are all sending you green light, and then another ones that are all sending you purple light. And you see them in a ring

because they all have the same angle relative to you. Yeah, I think this is maybe where it gets kind of hairy to describe in an audio podcast. But basically the answer to Clark's question is geometry, right? Basically, the reason it looks like an arch is that the physics, the phenomenon that creates this illusion of a rainbow,

So basically it depends on the geometry of you and your eyeball and the sun. And that's why it looks like a semicircle. Yeah, exactly. And if the ground wasn't in the way and there was water down there as well, like if you were floating up in the atmosphere and you were looking at a sheet of water, you would see the rainbow as a complete circle. Right. And so the reason it's not like an arch bending upwards or to decide has to do with the fact that the sun is a circle or because your eyeball is a circle or is. it, oh, because the water drops are circular, right? They're little spheres.

That's the real reason, right? Well, the water drop is our little spheres, but they don't have to be spheres for this to work. The reason that the rainbow is an arch is because actually it's a circle and you're only seeing part of it. Circle because any drop along that circle has the same angle relative to your eye of the same color light coming out of it. No, but I think if the water drops were a different shape, the rainbow would be a different shape, wouldn't it? like let's say all the raindrops were shaped like a cylinder pointing vertically then you wouldn't see maybe an arch or maybe they were all football shape pointing in the same direction then the arch would be kind of distorted oh yeah I see what you're saying that's definitely true the reason it's a circle is that there's a symmetry right

that the water droplets can hit you from any angle because there's spheres yeah I get your point so if they all were distorted then that would definitely would distort the rainbow it wouldn't be a circle anymore There's other interesting things going on there with the geometry, like sometimes you can see a second rainbow, and that happens because the light bounces twice within the raindrop, like it goes into the raindrop, it bounces off the back of the raindrop, and then bounces off again from the back of the raindrop, and then comes out of the raindrop. So it comes out at a different angle than the like primary beam, which is why you see it in a different location. And because it bounces twice, it actually flips the colors. So the normal rainbow has like red on the top and purple on the bottom, the double bow, the second one, has purple on the top and red on the bottom. So maybe the real answer for Clark here is that the reason it bends the same way is because you're always looking at it the same way and because the ground is always beneath you. It's generated by the angle between the sun and your eyeball and the raindrops, and so you're going to see it wherever that relationship exists, which is why it always looks the same.

Right. But I think as you were saying, like, so let's say we were out there in space. and there was a huge cloud of water drops in front of me and the sun was behind me, I would see a rainbow as a circle. Yes. And if there was, you know, a planet blocking some of that water on top, then I would see the rainbow as an up-pointing arch. Yeah, exactly. Yeah, or somehow the water drops ended on the right side of this cloud

or there was a planet on my right, then the rainbow would look like a sea. Exactly. And if you were an alien or a different species, they could see different wavelengths of light. then you would see the rainbow extend because rainbows have not just visible light but also UV and infrared light in them. They're invisible rings to the rainbow. So it would look like a thicker rainbow.

There'd be more stripes to it depending how your alien or mantis shrimp brain interpreted it. Interesting. Okay, so here's the answer for Clark. The reason rainbows are circular is because the water drops are little spheres. They're also little circles, little balls of water. And the reason you only see the top arch

of that circle is because usually the ground is blocking the bottom half. But if the ground was blocking the side half or the top half, then we would see rainbows as a different shape. Or if you just tilt your head. Yeah, exactly. If you stood next to a cliff, you could see a rainbow sideways. All right. Well, great question, Clark.

Thanks for sending that in. And thanks to everyone who sent a question in today. And thanks to everybody who asks questions and thinks about the universe and joins this community of curious people wanting to understand. Yeah. And thank you for listening to this program and telling all your friends about it and posting it on social media

and reviewing us on the podcast apps. And playing it for your children. And liking banana jokes. All right, well, we hope you enjoyed that. Thanks for joining us. See you next time. For more science and curiosity, come find us on social media

where we answer questions and post videos. We're on Twitter, Discord, Insta, and now TikTok. Thanks for listening and remember that Daniel and Jorge Explain the Universe is a production of IHeartRadio. For more podcasts from IHeartRadio, visit the IHeartRadio app, Apple Podcasts, or wherever you listen to your favorite shows. Every case that is a cold case that has DNA. Right now in a backlog will be identified in our lifetime. On the new podcast, America's Crime Lab, every case has a story to tell. and the DNA holds the truth.

He never thought he was going to get caught, and I just looked at my computer screen. I was just like, ah, gotcha. This technology's already solving so many cases. Listen to America's Crime Lab on the IHeart Radio app, Apple Podcasts, or wherever you get your podcasts. I'm Dr. Scott Barry Kaufman, host of the Psychology Podcast. Here's a clip from an upcoming conversation about how to be a better you.

When you think about emotion regulation, You're not going to choose an adaptive strategy which is more effortful to use unless you think there's a good outcome. Avoidance is easier. Ignoring is easier. Denials easier. Complex problem solving takes effort. Listen to the psychology podcast on the Iheart radio app, Apple Podcasts, or wherever you get your podcasts. Let's start with a quick puzzle.

The answer is Ken Jennings' appearance on The Puzzler with A.J. Jacobs. The question is, what? is the most entertaining listening experience in podcast land. Jeopardy Truthers believe in... I guess they would be conspiracy theorists. That's right. They gave you the answers and you still blew it. The puzzler.

Listen on the IHeart radio app, Apple Podcasts, or wherever you get your podcasts. This is an IHeart podcast.