Daniel and Kelly’s Extraordinary Universe - Does gravity make rainbows?

Episode Date: February 2, 2023

Daniel and Jorge talk about a speculative theory called "rainbow gravity" which might help us understand the origins of the Universe.See omnystudio.com/listener for privacy information.

This is an I-Heart podcast. Get fired up, y'all. Season two of Good Game with Sarah Spain is underway. We just welcomed one of my favorite people, an incomparable soccer icon, Megan Rapino, to the show, and we had a blast. Take a listen. Sue and I were, like, riding the lime bikes the other day,

and we're like, we're like, we're like, people ride bikes because it's fun. We got more incredible guests like Megan in store, plus news of the day and more. So make sure you listen to Good Game with Sarah Spain on the IHeartRadio app, Apple Podcasts, or wherever you get your podcasts. Brought to you by Novartis, founding partner of IHeart Women's Sports Network. I always had to be so good, no one could ignore me. Carve my path with data and drive. But some people only see who I am on paper.

The paper ceiling. The limitations from degree screens to stereotypes that are holding back over 70 million stars. Workers skilled through alternative routes. rather than a bachelor's degree. It's time for skills to speak for themselves. Find resources for breaking through barriers at tailorpapersealing.org, brought to you by Opportunity at Work and the Ad Council.

Tune in to All the Smoke Podcast, where Matt and Stacks sit down with former first lady, Michelle Obama. Folks find it hard to hate up close. And when you get to know people, you're sitting in their kitchen tables, and they're talking like we're talking. You know, you hear our story, how we grew up, how I grew up,

how Barack grew up, and you get a chance for people to unpack and get beyond race. All the Smoke featuring Michelle Obama. To hear this podcast and more, open your free IHeartRadio app, search all the smoke and listen now. Culture eats strategy for breakfast, right? On a recent episode of Culture Raises Us, I was joined by Belisha Butterfield, media founder, political strategist, and tech powerhouse for a powerful conversation on storytelling, impact, and the intersections of culture and leadership. I am a free black woman.

From the Obama White House to Google to the Grammys, Valicia's journey is a masterclass in shifting culture and using your voice to spark change. Listen to Culture raises us on the iHeartRadio app, Apple Podcasts, or wherever you get your podcasts. Hey, Jorge, you know what still amazes me? That they gave to introverts like us a podcast. That blows my mind every week, but also rainbows.

Yes, rainbows are awesome. But what about them amazes you? Everything is amazing about them. They are amazingly beautiful, but I'm amazed that they like exist, that they happen in the universe. You know that there's a science behind them, right? They're not just like magical. I get that there's science there, but I just think it's incredible that we live in the universe where this kind of thing actually happens.

I mean, if you read about this in a science fiction book, You think it's pretty far-fetched. Well, it depends on what kind of science fiction you're reading. Does it also involve unicorns? Unicorns like a podcast with two introverts. Wait, who's the unicorn in this case? Because you can only have one, it's in the name, unicorn. Collectively, we are one unicorn.

Hi, I'm Jorge. I'm a cartoonist and the creator of Ph.D. Comics. Hi, I'm Daniel. I'm a particle physicist and a professor at UC Irvine, and I call dibs on being the front two legs of the unicorn costume. Oh, good. Who's going to be the back end? Not me. Maybe you can have a guest host. There you go. That's why we have guest hosts, exactly. But anyways, welcome to our podcast, Daniel and Jorge, Explain the Universe, a production of I-Hard Radio.

The podcast in which we talk about everything that's out there in the universe and try to explain all of it to you. We explore the complete spectrum of possible physical phenomena, including rainbows. If unicorns were real, we would talk about them as well. But we don't shy away from digging deep into the fabric of reality, understanding how it all works and trying to explain to you what scientists are thinking about, what they are puzzling over, and what ideas they are bouncing around their unicorn brains. That's right, because it is a very colorful universe full of amazing sites like rainbows.

and we like to follow that arc of science to see what is at the end of it if there is indeed a big pot of gold or some other element because these don't really discriminate between elements, do they? We don't, but I would like to accept my grant funding in pots of gold

if that was possible, you know, rather than just like dollars in a bank account. Yeah, but then your grant funding is depending on gold currency markets. What is the exchange rate between gold and science anyway? I don't keep track. But you just made me think of another question, Daniel.

In a multiverse, right? Technically, in a multiverse or maybe even in an infinite universe, unicorns probably exist, right? I mean, it is possible, so therefore it must be true. It must be horses out there in the multiverse or an infinite universe with horns in their foreheads. Probably out there somewhere in the multiverse. There are unicorn physicists being paid to do their science in pots of gold,

maybe even two unicorns on a podcast. talking about what it would be like if humans were doing science instead of them. Humans were real. Like maybe humans are the unicorns in a unicorn world. If you're already unicorns, why would you even think up humans, right? How would you think up something so boring and ugly compared to unicorns? Or maybe like regular horses are the unicorns for them. You're like, can you imagine a horse without a horn?

Or maybe it's the other direction. Maybe they're imagining two horned horses, right? Yeah, that would be like wild to them. That would be imaginary and magic. And on this podcast, we do like to use our imagination to consider the ways that the universe might be. After all, we are trapped on this tiny little rock and a little corner of space trying to understand the entire cosmos, which requires somehow developing a model for how it all works and extrapolating that model out to the very far edges of the universe, far forward in time and far backwards in time.

Because we want to do more than just tell stories about unicorns and rainbows. We want a mathematical story that explains what we see in the universe and tells us what has already happened and hopefully why. Yeah, because the nature of the universe doesn't just affect the cosmos out there and space and other galaxies. It affects us here and on earth in our everyday lives. Every time you look up after a nice rainfall and see a rainbow, that's physics, kind of affecting how you see the world. And I don't want to talk more about rainbows and unicorns, but I do think rainbows are amazing. It's incredible that this physical effect happens and it shimmers in the air and it happens so often and it's so beautiful. It's just like, how lucky are we to live in a universe where such beauty occurs?

Makes me wonder about the whole nature of beauty, but that's a whole philosophical rainbow that we definitely don't want to walk down today. What we do want to wonder about is why the universe works this way and what it means about the history of the universe. As Jorge says, the way the universe works affects our daily lives because it tells us about the context of our lives. It tells us how the universe came to be and what it means that we are here. Yeah, and the history of humanity has been about making theories that hopefully explain what's going on and gives us an understanding about why things are the way they are and how we can maybe affect them or change them or at least dream up of fantastical things. And while we've made a lot of progress and understanding the nature of the universe and its history, how it got to look the way that it is and wondering about how it started or at least the very first. few moments of it, there are still a lot of question marks there about what happened early on. A lot of things about our theories that don't quite make sense, leaving lots of room for

creative people to imagine all sorts of theoretical rainbows and unicorns to fill in the gap. I thought you didn't want to talk about rainbows anymore, Daniel. You keep bringing it up. Not literal rainbows. These are figurative rainbows now. But the arc of history is an interesting one, but it's not necessarily straight line. Sometimes we come up with theories that explain what we can see and what we can experiment with out there. But then later, they turn out to be wrong, and that's okay because that's part of science and it's an evolving process.

It's a really interesting distinction, for example, between math and science. Like the science that we had 200 years ago is now evolved to the science we have today, and we expect in the future we will have even crisper ideas of how the universe works. But mathematical proofs that were developed thousands of years ago, those are still correct,

and we expect those to still be correct in a few thousand years. So it's fascinating how science and math develop sort of differently, even though science is built on math. Yeah, and so we have theories that currently describe everything we can see around those quantum mechanics and gravity, or I guess, special relativity. But the question is, are those actually right? Do those theories actually describe the universe in all instances? Or do they break down at some point?

And what does that mean about our understanding of the universe? One of the most frustrating things about general relativity and quantum mechanics is that they don't agree about what happens in maybe the most interesting, moment of the universe, that is the very first few moments, when things are very high energy and very dense, and we need both gravity and quantum mechanics to understand what happened. Was there singularity? Was there something else? What was going on at the very beginning of the universe? We're pretty sure that our current theories can't be right, and so we're on the hunt for new ideas. So today on the podcast, we'll be tackling the question,

rainbow gravity now Daniel is this like how much does a rainbow weigh like is it is a rainbow heavy can you measure the happiness in a rainbow how many pots of gold are generated by general relativity maybe we have a new theory called golden relativity hey that sounds good no this is literally a theory of the universe that predicts that gravity could make rainbows the same way that like prisms or drops of water make rainbows in your eyeball. Gravity itself could bend white light and turn it into rainbows. Now, I guess the question is, would those be regular rainbows or would you need to call them

like gravitational rainbows? Yeah, those would be gravitational rainbows because you definitely wouldn't see them in the atmosphere on Earth. This would be like something you see in your spaceship as you're falling towards the edge of a black hole. But this wouldn't just be like a lens flare, like a JJ Abrams style lens flare on your camera or your glasses or your spaceship window, this would be like real black hole rainbows. Real black hole rainbows, that's right.

And you don't need to ride a unicorn across the sky to see it. If this theory is actually true, these rainbows exist in the universe and they might have existed very early on and they could completely change the way we think about the very first moments of the cosmos. Well, you don't need to be riding a unicorn, but obviously anything is better

while you're riding a unicorn, surely. I mean, I wouldn't know, but... Ice cream is better when you're running a unicorn. you're riding a unicorn, for example? Absolutely. Well, it depends. Can this unicorn fly? Just gallop along because it might be hard to

lick an ice cream cone while you're galloping. Yeah, you know, I am not an expert on the categories of unicorns. Do unicorns come with wings, or is that a Pegasus? Or a Pegasus is just a horse with wings? What do you call it if it's a unicorn with wings? I think unicorns just fly on a rainbow, right? Isn't that what happens? Like you're galloping and then like a rainbow bridge pops up

and then you're flying. It's like the bifrost in Thor. And welcome to The Science of Unicorns, a sub-episode of rainbow gravity. Well, let's get back. You're right. Let's get back on topic here. We're talking about rainbow gravity or gravitational rainbow or what's the right way to call this? Is there such a thing as rainbow gravity?

There is really a theory out there in the community called rainbow gravity. And that's what we're talking about today. We're going to try to avoid talking about unicorns, but I suspect the gravitational attraction of their gorgeousness is going to pull us back in anyway. You're saying the sequel is called Unicorn Gravity? Flying Unicorn Gravity. That's the title of my next paper on this topic. Well, you're going to take one theory combined it with an imaginary theory to get an X for imaginary theory. In some version of the multiverse, that earns me a huge pot of grand funding, which I get in delivery of gold coins. Well, I'm going to one up you and put

wings on that unicorn. So my theory is going to be the rainbow unicorn Pegasus Gravity Theory. All right. Well, then I'm going to put horns on the wings on that unicorn. Okay. This is kidding. A little HP Lovecraft in here. But it is an interesting theory. This idea of rainbow gravity or gravitational rainbows and can gravity make rainbows. As usual, we were wondering how many people out there had thought about this or maybe dreamt it in one of their dreams.

So thank you to all the people and unicorns who volunteer to answer these questions. We greatly appreciate it and enjoy hearing your thoughts. If you would like to participate for future episodes, please don't be shy. Write to me to questions at Danielanhorpe.com. Think about it for a second. What do you think is rainbow gravity? Here's what people have to say. Okay, so rainbows are created by the refraction of light,

and the wavelength of that light depends on what we see in terms of its color. So rainbow gravity, if I think of gravitational waves, maybe as those waves are passing through or having light pass through them, maybe it's the effect that the light and the different wavelengths of the light has on those gravitational waves maybe I don't know maybe like moist that split the light based on frequency gravity split the thing based of their density and you call the outcome rainbow gravity I don't know well I've definitely never heard of rainbow gravity so my best guess is that it is something that has to do with the way gravity affects light maybe it's a property of gravitational lensing.

Oh, geez. I do not know. I would imagine that it has to do with a spectrum of light and how gravity could affect light, but I'm not sure. Maybe how gravity could split light. All right. We've got a nice spectrum of answers here. Very colorful.

Yeah. That was low-hanging fruit. But yeah, a lot of some people had never heard of it. And some people had some pretty good ideas. Like it's maybe gravity-causing lensing, which might create. a rainbow effect. Yeah, exactly. This seems to be a well-named theory

because it inspired some good ideas in the listeners. Well, I would obviously disagree, but that's never-stop physicists from naming things in counterintuitive ways. Let's see how this goes, Daniel. I mean, rainbow gravity, but is the gravity actually a rainbow? I don't know.

Yeah, it's a really fun theory. It tries to solve a problem at the heart of physics, the connection between general relativity and quantum mechanics, or more specifically, the lack of the connection. And along the way, predicts beautiful events like rainbows popping out of black holes. Wait, out of black holes? That would be impossible. Or maybe I guess it's the rainbow, so maybe it's magical. Perhaps I should have said at the edge of black holes.

Well, let's dig into it. You said it's a new theory or a potential theory that's out there in the physics community that maybe tracks to explain the intersection between quantum mechanics and gravity because those two things are not quite compatible with each other, right? Yeah, all of modern physics is built on these two ideas. Quantum mechanics, and general relativity. But at their hearts, these two theories are incompatible. They have completely different views of the world. Even though they're in philosophical contradiction with each other, they've survived together as twin pillars of our theory of physics because they're never actually relevant at the same time. So you can use gravity, talk about really big, massive things,

and you can use quantum mechanics, talk about really small things, and you never really need to use both at the same time. So they've sort of survived without having to talk to each other. They're like a married couple that have turned into roommates. Oh, that's kind of sad. Well, you know, if they do try to talk to each other, it's going to be a big argument. So they just try to avoid it. Why, I didn't know the physics theoretical committee was so dysfunctional and headed for a potential split in the future. It's not all rainbows and unicorns, man.

All right. Well, maybe help us understand this a little bit. Where is that incompatibility? Is it just that you, is this having been able to make it work in the mathematical way? Or is there something fundamental about it? how they view the universe that is just totally incompatible. So there's something fundamental about the way they view the universe that is just incompatible. We'll talk about exactly what that is in a minute.

And all attempts so far to unify them have failed mathematically. Just do not work. So that's essentially what the struggle is. And so let's start with quantum mechanics. Quantum mechanics, specifically quantum field theory, which is this description we talk about in the podcast, a lot of space being filled with quantum fields and particles are like ripples in those fields. that propagate through space and interact with each other.

That's very, very successful, right? It's an amazing theory. It describes all of the particle experiments that we've done. It's made very specific predictions of numbers like 10 decimal places that have all been verified experimentally. It seems like a very accurate description of what happens to particles.

But it assumes that space is not curved, that space is flat, that the shortest distance between two points is always what appears to us to be a straight line. And operating in flat space, essentially means that we're ignoring gravity. Quantum field theory is very successful because basically gravity is irrelevant. If you have two particles and they're pushing

against each other with powerful forces, you don't really care about the gravitational effects on two electrons because gravity is so weak compared to the other forces. So quantum field theory assumes that gravity is irrelevant and does a great job of describing what happens to quantum particles. Right. Quantum mechanics assumes

a flat space universe, but general relativity kind of assumes the opposite. Yeah. General relativity tells us that the reason we have gravity is not because there's some force out there tugging on masses, but that space bends, that when you put mass into a space, it curves space. And this is not curvature like relative to some external ruler. This is intrinsic curvature, which means that it changes the relative distances between points and effectively it makes the shortest distance between two points seem to us like a curve because we can't see this curvature directly. And so it appears to us like there's a force because things are moving along these curves. In reality, it's just the curvature of space. But general relativity assumes that everything has a specific location and velocity, and that can be perfectly well known. We call it a classical theory because it ignores the quantum mechanical nature of the world.

The fact that particles, for example, can't be pinned down to have a specific location and velocity at all times. They don't have a trajectory like that. but general relativity assumes that everything does. Fortunately, because gravity is so weak, we've only tested general relativity in scenarios where you have a huge mass like a planet or a star or a black hole where you can basically ignore quantum mechanics. So they sort of have each of their own domains.

They view the world very, very differently. They make totally different incompatible assumptions about the world and they make predictions about different parts of the world and they're both correct in their own regimes. Right. Although I guess, you know, coming at this from the, outside not having been too in mercanties, they don't sound that

incompatible to me, I guess. Maybe that's one of that's something other people struggle with. I mean, it's sort of like one of them says that Daniel is tall and the other one says Daniel wears glasses. Those are not necessarily incompatible things. Like couldn't quantum

fields exist in space that is also bending? And couldn't bending space exist also in a universe where particles have a minimum size and are uncertain? Yeah, we think that probably is possible to describe both because the universe exists and it seems to be self-consistent. So we think it probably is possible to reconcile gravity and quantum mechanics because both things are happening in our world. We haven't been able to do that.

Like light is being bent around the sun and it's being bent around black holes and we know light is quantized as well, right? Well, let me give you an example of something that we can't do because we can't unify gravity in quantum mechanics is that we don't know how to calculate the gravity of. particles. Quantum particles, for example, don't have a specific location. They have probabilities to be in different locations. Like an electron could be on the other side of the room or it could be right next to you. What is the gravity of that electron whose position is uncertain? General relativity doesn't allow for any uncertainty in the position. It says your gravity depends on where you are. If where you are is uncertain, then where is your gravity? Is your gravity also uncertain? Or is it shared between the two different locations? Does gravity collapse that wave function

forcing the electron to be in one spot from where its gravity emanates or is gravity quantum mechanical and it allows the superposition of different gravitational attractions? That's something we don't know the answer to. That's something we can't calculate right now because we don't have a theory that does gravity for quantum objects. Right. But I guess a particle has some uncertain to it in terms of where it is and where it's going. But if you step back far enough, it does have sort of a location, right?

I mean, you step back far enough from a particle, you can calculate what its gravity is. Yeah, if you step back far enough or you lump enough particles together, then they start to act like classical objects, like a baseball. Baseball effectively has no uncertainty on where it is and its velocity because it acts like a classical object, which is 10 to the 26 quantum objects all moving together. And so general relativity assumes that that is still true, the baseball description of the world when you get down to one electron. But we know that one electron doesn't move like a baseball.

doesn't have a whole path. And so we don't know how to talk about, like, how two electrons interact with each other gravitationally. And we can't test it either. We can't just, like, go and look and watch two electrons pushing against each other gravitationally because the gravitational force is so weak that we could never measure that. And so it's a big question.

Right. But you, for example, you are able to, for example, calculate the force between two electrons to, like, the electromagnetic force between two electrons, right? Like, you can do that? I guess the question is, why can you do it with gravity? like why can you just kind of like average it out or use probability to figure out what the you know most probable gravity is so we can calculate the gravitational force between two electrons if their positions are known but because they're quantum objects we don't know their positions so what you're proposing basically is a theory of quantum gravity that says gravity is a quantum force and interacts not with the location of the objects but with their probabilities that it actually interacts with the wave functions of these guys so they're trying to turn gravity into a quantum field theory, which is fine, and that's cool. And a lot of people are working on that.

But when you do that, you run into a lot of mathematical problems. Basically, you get lots of infinities when you try to do these calculations. And we get infinities when we do all quantum field theories. Like we talked on the podcast about something called renormalization, where we tuck infinities under the rug. For example, the true charge of the electron, if you look at it really, really close, seems to be negative infinity, which makes no sense.

But you can sort of like wrap it in a cloud of particles and renormalize it and subtract away that infinity and say, that's all fine. You can't do that for gravity because you get an infinite number of those infinities. Gravity couples to itself and it couples to everything. And so it just sort of goes crazy. And we just don't know how to do those calculations. We don't have the mathematical framework that can successfully do that. Something has to change when particles have a really, really high energy in order for those

infinities to go away. All right. So it's hard. I'm getting from you. And nobody has been able to. to do it, but there is maybe a new theory or a theory out there that does seem to have maybe a magical solution to this problem. Gravitational rainbows or rainbow gravity. And so let's dig into the details of that. But first, let's take a quick break.

I'm Dr. Scott Barry Kaufman, host of the psychology podcast. Here's a clip from an upcoming conversation about exploring human potential. I was going to schools to try to teach kids these skills and I get eye rolling from teachers or I get students who would be like it's easier to punch someone in the face. When you think about emotion regulation, like you're not going to choose an adapted strategy which is more effortful to use unless you think there's a good outcome as a result of it if it's going to be beneficial to you because it's easy to say like go you go blank yourself right? It's easy. It's easy to just drink the extra beer. It's easy to ignore to suppress seeing a colleague who's bothering you and just like walk the other way. Avoidance is

easier. Ignoring is easier. Denials is easier. Drinking is easier. Yelling, screaming is easy. Complex problem solving, meditating, you know, takes effort. Listen to the psychology podcast on the iHeartRadio app, Apple Podcasts, or wherever you get your podcasts. How serious is youth vaping? Irreversible lung damage serious. One in 10 kids vape serious, which warrants a serious conversation from a serious parental figure, like yourself. Not the seriously know-it-all sports dad or the seriously smart podcaster? It requires a serious conversation that is best had by you. No, seriously. The best person to talk to your child about vaping is you. To start the conversation, visit talk about vaping.org. Brought to you by the American Lung Association and the Ad Council.

Have you ever wished for a change but weren't sure how to make it? Maybe you felt stuck in a job, a place, or even a relationship. I'm Emily Tish Sussman, and on she pivots, I dive into the inspiring pivots of women who have taken big leaps in their lives and careers. I'm Gretchen Whitmer, Jody Sweeten. Monica Patton. Elaine Welter-off.

I'm Jessica Voss. And that's when I was like, I got to go. I don't know how, but that kicked off the pivot of how to make the transition. Learn how to get comfortable pivoting because your life is going to be full of them. Every episode gets real about the why behind these changes and gives you the inspiration

and maybe the push to make your next pivot. Listen to these women and more on She Pivotts, now on the IHeartRadio app, Apple Podcasts, or wherever you get your podcasts. Culture eats strategy for breakfast. I would love for you to share your breakdown on pivoting. We feel sometimes like we're leaving a part of us behind when we enter a new space, but we're just building. On a recent episode of Culture Raises Us, I was joined by Volisha Butterfield, media founder, political strategist, and tech powerhouse for a powerful conversation on storytelling,

impact, and the intersections of culture and leadership. I am a free black woman who worked really hard to be able to say that. I'd love for you to break down. Why was so important for you to do C? You can't win as something you didn't create. From the Obama White House to Google to the Grammys, Belichia's journey is a masterclass in shifting culture and using your voice to spark change. A very fake, capital-driven environment and society will have a lot of people tell half-truths. I'm telling you, I'm on the energy committee.

Like, if the energy is not right, we're not doing it, whatever that it is. Listen to Culture raises us on the iHeart radio app, Apple Podcasts, or wherever you get your podcasts. All right, we're talking about rainbow gravity. Which sounds great. Who doesn't want gravity to have its own, you know, spectrum of awesomeness? Yeah, exactly. It's a very colorful theory. And, you know, during the break, I went off and did a little bit of research.

And I discovered the answer to one of the open questions we left dangling before. Is the answer unicorns? No, the answer actually is Alicorn. An alicorn is a unicorn with wings or a Pegasus with a horn. There's a name for this thing. Oh, so somebody already did that theory. I think it's the My Little Pony universe that might have coined this phrase. What if I cross it with a lion then, like a griffin unicorn Pegasus?

I think we better trademark that and start selling plush dolls of those. Lion-a-corn, maybe. Grifficorn. We are talking about rainbow gravity, which sounds great. And it's maybe a theory that tries to unify quantum mechanics and general relativity, which are the two big theories that try to explain the universe, which don't quite match up when you get to certain situations. Daniel, we talked about how quantum mechanics is not good at describing gravity.

and we talked about how general relativity is not good at describing things at the microscopic level. Exactly. And most of the time, they don't conflict because quantum mechanics is king of the microscopic particles and gravity is king of the big, massive stuff. But there are scenarios we think when gravity and quantum mechanics are both important. One of those is inside black holes where things are obviously very powerful gravitationally, but they're also compressed to super tiny little divots, right? if there is a singularity at the heart of a black hole, then that's small enough to be a quantum

mechanical object. So general relativity and quantum mechanics both have something to say about what happens there. We can't see inside black holes. And so we're left only just wondering about what's going on inside. But there are scenarios outside of black holes where we think both general relativity and quantum mechanics have something to say. And that's the case of very, very high energy particles. Yeah, but I guess I wonder if you need to go that extreme just to kind of see where the two theories take effect, right? Because I think Einstein kind of famously prove general relativity or at least the bending of space

by looking at how light bends around solar eclipse, for example. We know that light is quantized. It follows quantum mechanical rules. So isn't that an example, for example, of a quantized thing following gravity? Technically, I suppose, but technically everything is a quantized thing. You are a quantized thing.

I am a quantized thing. We are affected by the Earth's gravity. You know, in that case, they're not relying on the quantum nature of light. Light could have just been classical electromagnetic waves and the same thing would have happened because in that scenario, light is moving through curved space. And so light like everything else would move in a curve. So you're not relying on the quantum nature of the object there. So like a quantized particle like light or an electron, it can move through bent space due to gravity.

You know what I mean? You can, you have the math to describe a single particle. single quantum particle moving through bent space. Is that possible or is that just not possible? That's certainly possible, but there you're not relying on the gravity of the quantum particle. You have something else, something really big and massive, like the Earth or the sun or the moon or a black hole that's doing the bending.

And so we do know how to talk about quantum particles moving through bent space. That we can calculate. What we don't know how to calculate is the gravity of those particles and how that contributes to bent space. Right. But doesn't the bending of space depend on the gravity on the particle, right? Like technically you're talking about space time, right? Like if I throw a baseball at the sun, it's not going to curve the same way that a photon is going to curve, right?

So like the bending of space depends on the thing that's moving. So if you can calculate the bending of space for a particle, what's worse the contradiction there? Well, because there you're ignoring the gravity of the object. Like if you throw a baseball or a photon near the moon, you're not taking into account the bending of space due to the baseball or due to the photon. You're just calculating the trajectory of a test particle through the bent space due to the moon

or due to the black hole. You're not taking to account the gravity of the object itself. Don't you need that to calculate how it's going to curve around, how it's going to bend around the moon? No, you just need to know it's inertial mass. You don't need to know the effect of it on space time itself. You just need to understand what its inertia is.

is and so that you can understand how it moves through bent space. I see. So the real problem is not in like how to calculate how quantum particles move through bent space, but more about how quantum particles give off gravity or, you know, how they attract other particles through gravity. Yes. Do they bend space? Exactly.

And do they bend space where they are or where they might be? That's really the question. All right. So then talk to us about this new theory, rainbow gravity. So the problem comes up at very, very high energy. If you have particles with super-duper crazy high energies, energies like the Planck energy, or energies that particles had at the very beginning of the universe,

they have so much energy that their gravity starts to not be ignorable. Usually when you talk about like two protons bouncing against each other, you can ignore the gravitational effects. But if those two protons have enough energy, then their gravity becomes really, really powerful. Because remember, gravity is the bending of space time in response, not just to mass, but in response to energy. And so take, for example, two particles and collide them at super duper high energy, much higher energy than we've done before.

You might get, for example, a black hole, or at least you have to take into account the gravitational interaction. So we think that maybe the solution to this problem lies in understanding what happens to particles at very, very high energy. And rainbow gravity says maybe at very high energy, the rules change a little bit. And gravity for those really high energies is a little bit different. What? What? So as a particle gets moving faster and faster, it accumulates energy, right? That's what you're saying. And for when you have that much energy in the small package, then you kind of have to think about how that affects gravity because gravity, I mean, we always talk about gravity being a function of mass. Like the more mass you have, the more gravity you have. But it's really just about how much energy you have, right?

Like the bending of space is due to the energy that you have. Yeah, it's due to energy density, not literally mass. Mass is a component. of the energy density, but it's not the only contribution. Right. So now you have like a quantum particle. It's moving really fast, so it has a lot of energy in a small place, but it's quantum, so there are some uncertainties to it. And so now the question is like, can you explain gravity in that situation? Yeah. So rainbow gravity theory says, let's change the rules of gravity as you move up in energy. Now currently, we think that all particles feel gravity the same way. If, for example,

you have a big mass of objects and it's bending space and you shoot a red photo, photon through it or a green photon through it, those things will bend around that object the same way. They'll end up at the same place, right? That all different energies of photons all get bent the same way because they all see the same curvature of space. They're like running along the same track. But wait, don't each of those photons have a different amount of energy? Yeah, but remember, we're not considering the gravitational effect of the particle, just of the other object that's curving space, that's guiding these particles. We're ignoring the gravitational effect of those particles. And so rainbow gravity says, what if that's not true?

What if, as you move through space, how much curvature you see depends on your energy? So, for example, maybe a red photon and a green photon see a different amount of curvature, that somehow the curvature you see depends on your energy. And so as the photon's wavelength or its color or its energy, these are all equivalent changes, you see different curvature. If that happens, then if you take, for example, a beam of white light and you bend it around a black hole, each different wavelength would get bent a different amount, resulting in a rainbow. So the idea of rainbow gravity is to say maybe gravity depends on the energy of the particle in this way. So they see a different amount of curvature, which would change how things happen at very, very high energies. You're saying like maybe

gravity is not constant throughout all situations. Like somehow gravity is, you know, dependent on how faster going. Technically this is called an energy dependent metric. Metric is like the curvature of space in general relativity theory. And so typically that metric is constant. It doesn't depend on what your energy is. But now they say, well, let's take that metric and make it energy dependent. Let's say that if you're moving to the universe, you might see different curvature depending on the energy you have. But then isn't like mass the same as energy, right? So are you saying that if I have more or less mass, I'm going to see space bent differently? I think that's probably true. Very, very massive particles would see space bent differently than lower mass

particles. Okay. So the idea is that gravity is different depending on how fast you're moving or how much energy or mass you have, which is very different than what we have we think about it now, right? Right now, general relativity says that gravity is the same everywhere. Exactly. It says that gravity is the same everywhere. And you might be wondering like, well, how does this solve the problem of general relativity and quantum mechanics? It's not exactly a solution. It's just sort of like maybe in this direction a solution lies. It's sort of like exploratory. Remember, you know, we talked about science as a developing process.

We don't always have like the final answer all at once. Sometimes what we do is we say, what's in this direction and what happens if we try this kind of thing? Does this lead to a solution? So it's not clear yet whether this might lead to a solution, but there's a little bit of a sketch of an argument for why it might. People have this idea for how to solve the problem of like, what's the gravity of an uncertain quantum particle of saying maybe the curvature itself has uncertainty. Like I think you were

saying earlier, if an electron has uncertainty and it's bending space time, then maybe space time itself has an uncertainty. A quantum uncertainty. Like maybe we live in this universe with this bent space time or maybe we live in that universe with that bent space time. So people have done a bunch of calculations and shown that if the curvature itself has some uncertainty, it would lead to an energy dependence of that curvature. Basically that particles moving through the universe with different would see different aspects of this uncertainty. So this is like saying, if space itself has some uncertainty, then you might get this kind of effect for very high energy particles.

I see, because you sort of maybe need gravity to be not constant throughout the universe, because if these particles are quantum, that means they're here and they're there. And if they're here and there, then that can't mean that they have gravity here and they have gravity there. But maybe if gravity is different in the two situations, then it's like maybe it has half gravity here or half gravity there, which kind of makes a full one gravity. Yeah, exactly. And we don't know, right? We do not know if gravity operates that way. If it really can be probabilistic or not. This is an attempt to incorporate that quantum uncertainty into the theory of gravity. And if you do the calculations and say what happens to particles moving through space that's uncertain, how do they bend? It turns out that particles at different energies interact with that space differently, like see a different. slice of that uncertainty. So particles with really high energy would bend differently than particles

with low energy as they move through that uncertain space. And that gives you rainbows. And again, how does that help bring together quantum mechanics and gravity? If this is true and you see it and you confirm it's actually part of our universe, for example, that gives you a very strong hint. It tells you that space time itself is uncertain. One possibility is that gravity is quantum mechanical, right? That space time has uncertainty to it, that we live in the universe where space time can have two different possibilities and they get collapsed when you test them, right? The other is that gravity is not quantum mechanical, that gravity itself collapses those wave functions. That when two electrons interact gravitationally, their wave functions don't interact. They collapse each other's

wave functions and then the electron has a location here and another location there and you have very specific sort of classical gravity. So if we see rainbow gravity, that tells us that gravity can accommodate uncertain space times. And that single particles can have gravity, the themselves, right? Just like a planet does. Exactly. And like if an electron is 50% over here and 50% over there, then space time is also 50% bent over here and 50% bent over there. All right. Yeah. And that's how you avoid the infinities that you were talking about earlier. Yeah, because it changes how particles move at very, very high energies, which is exactly where these infinities crop up. Thinking about like what happens to particles with really high energies, which bend space time, which create more

gravitons. And you get this infinite pile of gravitons and a runaway energy. So if you change the behavior, the particles of very, very high energy, you can basically delete those infinities because you change the rules when you get near infinity. So the infinities basically go away. Cool. All right. Well, that's the theory of rainbow gravity. And so let's talk about what would happen if it is true. What kinds of things would we see out there? Would we see rainbows around black holes? Would we see unicorns? And would that mean that unicorns are also quantized? I hope so. I don't ever want to see one and a half unicorns. Well, if nobody wants to be your back end, then you might have to be a happy unicorn.

That's a good point. All right, well, let's get into that. But first, let's take another quick break. I'm Dr. Scott Barry Kaufman, host of the psychology podcast. Here's a clip from an upcoming conversation about exploring human potential. I was going to schools to try to teach kids these skills, and I get eye rolling from teachers or I get students who would be like, it's easier to punch someone in the face. when you think about emotion regulation, like, you're not going to choose an adaptive strategy

which is more effortful to use unless you think there's a good outcome as a result of it if it's going to be beneficial to you. Because it's easy to say like, like go you, go blank yourself, right? It's easy. It's easy to just drink the extra beer. It's easy to ignore, to suppress, seeing a colleague who's bothering you and just like walk the other way. Avoidance is easier. Ignoring is easier. Denials is easier. Drinking is easier. Yelling, screaming is easy. complex problem solving, meditating, you know, takes effort. Listen to the psychology podcast on the IHartRadio app, Apple Podcasts, or wherever you get your podcasts. How serious is youth vaping?

Irreversible lung damage serious. One in ten kids vape serious, which warrants a serious conversation from a serious parental figure like yourself. Not the seriously know-at-all sports dad or the seriously smart podcaster. It requires a serious conversation that is best had by you. No, seriously, the best person to talk to your child about vaping is you. To start the conversation, visit Talk Aboutvaping.org. Brought to you by the American Lung Association and the Ad Council. Have you ever wished for a change but weren't sure how to make it?

Maybe you felt stuck in a job, a place, or even a relationship. I'm Emily Tish Sussman, and on she pivots, I dive into the inspiring pivots of women who have taken big leaps in their lives and careers. I'm Gretchen Whitmer, Jody Sweeten. Monica Penn. Elaine Welteroff. I'm Jessica Voss. And that's when I was like, I got to go. I don't know how, but that kicked off the pivot of how to make the transition.

Learn how to get comfortable pivoting because your life is going to be full of them. Every episode gets real about the why behind these changes and gives you the inspiration and maybe the push to make your next pivot. Listen to these women and more on She Pivots, now on the IHeart Radio app, Apple Podcasts, or wherever you get your podcast. I don't write songs. God write songs. I take dictation. I didn't even know you've been a pastor for over 10 years. I think culture is any space that you live in that develops you. On a recent episode of Culture Raises Us podcast, I sat down with Warren Campbell, Grammy winning producer, pastor, and music executive to talk about the beats, the business, and the legacy behind some of the biggest names in gospel, R&B, and hip-hop. This is like watching Michael Jackson talk about

thoroughly before it happened. Was there a particular moment where you realize just how instrumental music culture was to shaping all of our global ecosystem? I was eight years old and the Motown 25 special came on and all the great Motown artists, Marvin, Stevie Wonder, Temptations, Diana Raw. From Mary Mary to Jennifer Hudson, we get into the soul of the music and the purpose that drives it. Listen to Culture raises us on the iHeart radio app, Apple Podcasts, or wherever you get your podcasts. All right, we're talking about rainbow gravity. And we're talking about what it is, and it's the new theory that kind of tries to bring

together quantum mechanics and general relativity by saying that maybe gravity is not the same everywhere. Maybe it's different for different energy particles, which would sort of help explain how gravity works at the quantum level. Now, if this theory was true, Daniel, does that mean? we would see rainbows around black holes? It does exactly mean that we would see rainbows around black holes.

Because this is a theory that tries to unify quantum mechanics and gravity, which mostly ignore each other and live in different regimes, it's a hard kind of thing to test. You need special circumstances. So this doesn't mean that we should expect to see gravitational rainbows all over the place, you know, do the moon or the sun.

It's only in extreme conditions because this is a very, very small effect until you get to very, very high energies or very, very strong curvature of space. like around a black hole. So you're in a spaceship and you're falling towards a black hole, then white light near the event horizon would be split into all the colors and you would see rainbows before you get squished.

Meaning like I shoot a beam of light of white light at a black hole at the very edge. And as this beam of light gets very close to the black hole, the photons that are more red would get pulled one way and the photons that are more blue would get pulled another way and the purple ones would be pulled a little bit differently. And so that would actually kind of prism or split the beam of white light. Yeah, prism exactly is the right analogy. That's what a prism does, is that it bends light based on its wavelength.

Different wavelengths of light get bent differently as you go from air to glass and back to air. And so they spread out white light into a rainbow. And because now we're introducing an energy dependent effect or a wavelength dependent effect on gravity, then black holes are basically prisms. and they would change a beam of white light into a spread based on the colors. Yeah, they're prisms and they're prisons. Because I guess, you know, white light,

it's not like each photon is white. Is that you have a combination of photons. Some of them are white, some of them are higher and lower energy, right? That's what white light is. It's not like the photons are white. Yeah, there is no individual photon that has the color white, right? White is not a single color. It's a combination of many photons of different colors.

Right. And so around a black hole, the gravity would be so strong that it would actually start to affect each of those photons differently, which is sort of like a prism or a lens, I guess, which makes me wonder, like, why have we seen this effect? Are we seen, I mean, we now have pictures of black holes. Do we see any rainbows around it? We do not see any rainbows around black holes yet. This would be a very, very slight effect, and you'd need to look very carefully right at the edge of a black hole. You need a well-calibrated source also to know whether you're seeing. any distortion. To know whether it's distorted, you have to know what it looked like before it went around the black hole. And so we don't have any nice, clear, crisp examples of that. Even around black holes, this would be a very small effect. What do you mean it would be a small effect? Like, this effect is not very strong. It's very small. The way gravity varies depending on the energy. Yeah, and this theory, gravity does depend on the energy, but it's basically unobservable until you get to super duper high energies. In the same way that like effects of special

relativity, you can't really observe them when you're throwing a baseball around. You don't notice clocks going slow. Your baseball doesn't seem to shrink when you throw it even though it's going faster. You don't notice the effects of special relativity here on Earth because they're negligible. In the same way, this energy dependent effect of gravity is negligible except in extreme circumstances. And so you need like a very crisp, clear setup of a beam of white light right next to a black hole and basically nothing else around so that you can observe it. But there are some other ways we might be able to test this theory. Yeah, they involve gamma rays. Yeah, so gamma rays are basically just a fancy name for super high energy photons. And there are these strange phenomena that we've talked

about in the podcast a few times called gamma ray bursts, where something out there in the universe sends a huge spray of very high energy gamma rays all about the same time. These things can last for like seconds or minutes. We don't really understand the source of them. Check out our whole podcast episode on that topic for a deeper dive into it. But the cool thing is that it's a nice test of this theory because it sends us a big packet of photons, some of which have huge energy, like crazy high energy photons. And they all come to us about the same time. So we can sort of use them as a probe of how they've responded to the gravity of the universe that they have flown through. Right. They might like arrive at different places in our sensor or, you know, like a rainbow

kind of get split. Or are you saying they might arrive at different times? So if, for example, they whizz around a black hole, they would get bent differently. But the universe has some curvature, and as you move through it, you're slowed down by that curvature, so that they would be differently time dilated as they move through the universe if they see different curvature. So they would effectively arrive at different times. If you sent like a green or red and a blue photon across the universe to us, then if this is true, those photons would arrive at different times here on Earth, because they would

see different amounts of curvature. And, you know, curvature affects the passage of time. effectively how long it takes light to traverse from the source. So like some of the photons would get blue shifted more than others or redshifted more than others. That's kind of what you're saying because they have to arrive at the same time, don't they? They're moving at the speed of light. These would actually arrive at different times. I mean, from their point of view, they would see different distances between the source and the destination because they're seeing different amounts

of curvature of the universe. Well, that's pretty interesting. But I guess couldn't we do that experiment here on Earth, like, you know, we can create camera rays and we can also create, you know, like ultraviolet or here on Earth that can create high energy light and super low energy light. Couldn't we do some experiment where we shoot both and see what happens? Yes, but we can't create very strong gravitational curvature, right? So we can create pretty high energy photons, but not that high energy, not as high energies exist out there in the universe. Also, we don't have very strong curvature. The value of this test is that the photons are super duper high energy because they come from some astrophysical source.

And they fly through a huge amount of curvature. So even the small effects of curvature add up over very, very long distances. What do you mean? Like curvature not due to any particular thing, like a black hole, but just like the general curvature of space from having stuff in it. From having stuff in it. Yeah, exactly. As you fly through the galaxy, for example,

there's a small gravitational well that the whole galaxy sits in. That's the curvature of our local space. But wouldn't we see that with regular light? because I know there's something called gravitational lensing out there where a planet can sort of lens and bend light to give us a better view of another galaxy or another star or, you know, dark matter can also kind of lens light. Wouldn't we see rainbows caused by dark matter too?

So I think that's exactly what this is suggesting to probe, right? Send a bunch of really high energy photons through space and all the matter that's in space creates some curvature and those photons would respond to that curvature differently based on their energies. And so you would see that then on Earth. And so, yes, the galaxy and all the dark matter and are all contributing to that. The vanilla version of general relativity predicts that that wouldn't happen, right? That they all get bent the same way.

And you're right that that's something that is predicted. As photons fall into a gravitational well or dig themselves out of a gravitational well, they do get shifted in frequency, for example. But we think that happens equally for photons of all energy. rainbow gravity says it happens differently. So over very, very long distances, these would accumulate due to all the dark matter and the other stuff in the galaxy

and create a small difference in the arrival time of those photons. But not in their location? Like, they would all arrive at the same spot. They would just maybe be colored a little bit different. Or would they actually split like a rainbow? They would actually split like a rainbow. So we wouldn't see the whole thing, right?

So the whole thing, we get spread out across the universe, but we would get a slice of it. And in theory, we might get ones of different colors. that we could also test their time of arrival. So we've actually done this and we've looked at gamma ray bursts and we've tried to see if we see effects for it. There is no evidence for it so far. Even these gamma ray bursts, the evidence would be pretty subtle and we don't have that many

examples of it. So the jury is still sort of out on this theory. We don't have any evidence for it, but we also can't yet rule it out. It sounds like it's not an effect that you would see in our everyday lives. Like when we see galaxies being landspied, dark matter out there, even that is not strong enough to split light due to rainbow gravity. Yeah, it requires a huge amount of energy or integration over very, very long distances. I guess what you're saying is that if rainbow gravity is true, it is happening even around us,

all around us, you know, like if I look at my hand or if we look at galaxies through a dark matter gravitational lens, it is happening, but maybe just at a level that we can't discern. In the same way that like time dilation is happening all the time, length contraction is happening all the time, you just can't tell because it's so negligible. All right, well, let's talk about now what would happen if this was true. We don't have evidence for it either way, whether it's true or not. But what would it mean if it is true that rainbow gravity exists or that gravity is not the same everywhere for everyone, except unicorns? It has really interesting consequences if you run the clock of the universe backwards.

Currently, we see the universe is expanding and we run the clock backwards and we do the calculations in general relativity. And they predict something really weird. They predict a singularity. that as the universe got denser and denser, there's a sort of runaway gravitational effect in reverse, where you end up with a singularity, where the universe is basically compressed into incredible density. So that's the prediction of general relativity. And, you know, we think that's kind of bonkers. We think that those kind of infinities probably don't exist in our universe. And this to most physicists is a sign that general relativity needs some work, right, where this

is a problem. And so this is where we look for alternatives. And so rainbow gravity, if you modify gravity in this way it says well in very high energies things actually do change and so you put this into the calculations instead of general relativity and now particles that different energy are affected slightly differently by that curvature and you don't end up with a singularity you end up with something which like smoothly gets denser and denser but reaches sort of a minimum plateau it's like intuitively you can't just like squeeze all the particles down to the same place because the particles are all now bent differently by the space. Hmm. What would that mean for black holes, too? Does that mean there's no singularity at the center of black holes?

Yes, this basically erases singularities in the universe, both singularities in time, like what might have happened before the Big Bang and singularities in space, like what's inside a black hole. It doesn't mean black holes us maybe that the structure of matter inside the black hole isn't a singularity. It's something else weirder. It's controlled by rainbow gravity. It's going to be something with a non-zero size to it. it'll have a fuzzy core to it, not like a single point. Yeah, a fuzzy, colorful core probably. Yeah, there are many colors of black, absolutely. Glossy black, matte black, right, jet black. Yeah. So maybe now this sounds amazing and sounds like it would solve a big problem,

maybe the biggest problem in physics right now, theoretically at least, but we haven't seen evidence for it experimentally. And are there any reservations about just the theory of it? Most mainstream physicists think that this is crazy, right? They think that this is a monk. idea and just wouldn't fly. Basically because it violates a central principle something that we all think probably is true, which is that observers can all agree about the physical laws. Like in our universe, we think that observers all see different things happening. But one of the foundational

principles of special relativity is that the universe always follows the same laws. You might tell a different story about what happened, but everybody's story follows the same laws. This breaks that because now everything is like energy dependent. And so the amount of curvature you see depends on the energy you have. It breaks this thing we call Lorentz invariance. Right. Because I guess if gravity depends on how much energy you have, energy can be a relative concept, right?

If energy depends on how fast you're moving, your kinetic energy, then that can look differently to different people, right? Like if you're moving super duper, duper, duper fast to somebody outside of yourself, you would have a lot of energy, but to you, yourself, you wouldn't have a lot of energy. Is that what you mean? Yeah, there's that aspect to it, but it goes a little bit deeper than that. Right now, we think that space is relative in an important way, but that there are some invariants. Some things hold fast, like the speed of light is the same for all observers. But if this theory is true, then the speed of light sort of depends on the energy of the photons, right? These photons traveling through space effectively have different speeds. And that's pretty weird. There's a lot of really strong constraints on measurements of variable speed of light, energy-dependent speed of light. And so it would require a real revolution in the way we think about the nature of the universe.

But maybe that's what's required, right? Our current principles, general relativity and quantum mechanics have completely incompatible assumptions at their foundation. And so to unify them, we are going to have to get rid of something that we hold true, something that we cherish. Maybe it's Lorentzen variance. Maybe it's not. But before this theory is accepted, it would require us to really rebuild a lot of physics from the ground up.

Yeah, I get it. Physicist don't like things to change. We love things to change, actually. Our dream is to find some new theory, which blows everything up. But yeah, it does mean a lot of work. But that also means, you know, hey, more grand funding, more piles of gold. But I guess what you mean is, like you don't like the laws of physics to be different depending on where you are in the universe. Yes, that's true.

It would be very nice if the laws of physics were the same for everybody. and you're against that because it would mean sloppier math or because you haven't seen any experimental proof of that we haven't seen any experimental proof of it and also it's kind of a nice principle it philosophically it just sort of like makes sense to imagine that the universe runs on a certain set of laws and those laws are the same for everybody it doesn't have to be true in the same sense like we don't even know why the universe has laws and why those laws don't change with time there's a lot of just basic assumptions at the foundation of fundamental physics that we make and seem to work,

but we don't really understand why, and we might have to revisit. Cool. Well, I guess once again, it's stay tuned. It might be true. It might be that special thing that solves a lot of problems and feels magical to everyone.

What does that term people use for something like that? A unicorn? A unicorn. Right, right. So the rainbow gravity theory might be a unicorn in itself, according to a physicist right here on the podcast.

Yeah, it might fly in on rainbow and solve all the problems that we have. And that will let us see the full spectrum of the universe, see all of its beautiful colors, and also let us see how it changes in space and in time. So remember that science is a continual process that evolves and changes our understanding of the universe out there, how it works, and where it came from.

And as we learn more and more about the nature of the universe, we understand more and more about how it began and what it means to be here. We hope you enjoyed that. Thanks for joining us. See you next time. 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.

Get fired up, y'all. Season two of Good Game with Sarah Spain is underway. We just welcomed one of my favorite people, an incomparable soccer icon, Megan Rapino, to the show, and we had a blast. Take a listen. Sue and I were, like, riding the lime bikes the other day, and we're like, we!

People ride bikes because it's fun. We got more incredible guests like Megan in store, plus news of the day and more. So make sure you listen to Good Game with Sarah Spain on the IHeart Radio app, Apple Podcasts, or wherever you get your podcasts. Brought to you by Novartis, founding partner of IHeart Women's Sports Network. Tune in to All the Smoke Podcast, where Matt and Stacks sit down with former first lady, Michelle Obama. Folks find it hard to hate up close.

And when you get to know people and you're sitting in their kitchen tables and they're talking like we're talking. You know, you hear our story, how we grew up, how I grew up. And you get a chance for people to unpack and get people. beyond race. All the Smoke featuring Michelle Obama. To hear this podcast and more, open your free IHeart Radio app. Search all the smoke and listen now. And here's Heather with the weather.

Well, it's beautiful out there, sunny and 75, almost a little chilly in the shade. Now, let's get a read on the inside of your car. It is hot. You've only been parked a short time, and it's already 99 degrees in there. Let's not leave children in the back seat while running errands. It only takes a few minutes for their body temperatures to rise, and that could be fatal. Cars get hot, fast, and can be deadly. Never leave a child in a car.

A message from NHTSA and the ad council. This is an IHeart podcast.