Daniel and Kelly’s Extraordinary Universe - What is gravitoelectromagnetism?

Episode Date: April 30, 2024

Daniel and Katie bushwack their way between theories of gravity and electromagnetism, looking for the elusive connection.See omnystudio.com/listener for privacy information.

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It's the people. It's the failures. It's the heartache. Listen to the Brightside on the IHeart Radio app, Apple Podcasts, or wherever you get your podcasts. Hey, Daniel. Have you guys figured out how to make quantum mechanics and gravity work together yet? Ooh, hit me hard with a nasty question right off the bat, huh? Well, unfortunately, we haven't figured it out yet. Well, what have you guys been working on? And how long have you been working on it?

Like decades? More than a hundred years, actually. Oh, well, and I thought I was a little bit behind on my deadlines. So, you know, how long do you think it's going to take? Another weekend, another thousand years? Can I get it in by Monday? You know, the only progress we've really made is coming up with some long, confusing names for it. Like Mississippi or quantum gravity?

No, that would be much too clear. Okay, like Gravito Quantum Field hydrodynamically. I think you should be a physicist, Katie. You have the knack for it. I know how to throw a ball and look at it, go up and come down, so I'm already halfway there. Hi, I'm Daniel. I'm a particle physicist and a professor at UC Irvine, and I desperately want to know the underlying rules of the universe. I am Katie Golden. I am not a particle physicist. I host a podcast about animals, but that doesn't mean that I couldn't maybe try to smash quantum mechanics and gravity together if you give me a

government grant. I think everybody who's not a particle physicist should introduce themselves that way. Hi, I'm Sally. I'm not a particle physicist. I think that makes the most sense. In that case, I should start off by listing all the things that I'm not every time. I'm not an Olympic gymnast. I'm not a Wall Street trader. Dot, dot, dot. I am not a hot dog eating champion yet. We can all aspire to stuff. Well, welcome to the podcast, Daniel and Jorge Explain the Universe, a production of IHeartRadio, in which we aspire to be particle physicist. We all want to understand the way the universe works. We all want to figure it out,

to zoom down to the tiniest little bits of the universe, the basic building block, and the rules that intertangle them and zoom out from that picture to understand how it all comes together to make our amazing, our bonkers, our wonderful, our delicious universe. Yeah, like a nice stew of concepts all mingled up in the stars.

So, yeah, I mean, it is interesting because I think we've talked a little bit on the times that I've been on the show about quantum mechanics. We've talked about gravity. We've talked about sort of this distinction between the physics involved in the really tiny and the really huge and how it's a bit of a puzzle to fit those together.

Yeah, the basic strategy of physics has always been to zoom down to the littlest bits of the universe, to try to understand them, and then hope that we can carefully one step at a time zoom out and figure out how those things come together to make our world. You know, how electrons and protons and protons come together to make atoms and atoms come together to make molecules and molecules come together to make proteins and proteins come together to make steak and ice cream and all the delicious things that you eat. That's sort of like reductionist approach. We zoom down and then one at a time step back up to understand our world.

It's long been the approach we wanted to take to understand the universe and that's worked for lots of stuff like the way we understand ice cream and blueberries and steak and goats and all that stuff. But you're right, Katie, there's one big thing that it hasn't been able to explain. maybe the biggest most important thing that shapes our universe and that's gravity how everything seems to attract itself or how things flow through space time we still don't understand how that bubbles up from the tiniest little bits of the universe because gravity is sort of I guess like a big force that we observe so like you know you feel gravity on a planet

maybe you and I have our own gravitational pull but it's much weaker than a planet so we're not going to notice it. But is gravity something you can really measure much when you get really small? Like say you're looking at particles. Like does a particle have its own gravity or can you even measure gravity of say like a neutron or a proton or an electron? Yeah, that's exactly the puzzle. On a theoretical sense, we don't know how to stitch these two things together. We'll talk about that more during this podcast. But even more frustrating in experimental sense, we can't even see what the does. Basically, the job of physics is to explain what is the universe doing. What's happening out there and why does it make sense? And the first step there is to see what's happening in the

universe. And so the first thing you want to do if you want to explain the gravity of little particles, the quantum mechanical understanding of gravity is to see gravity operating on little particles. That's basically what you're asking. And the challenge there is that gravity is so dang weak compared to the other forces, electromagnetism, even the weak force and definitely the strong force, gravity is like a bigillion zillion quintillion times weaker, which is why, for example, like a simple fridge magnet can overpower the gravity of the earth and hold your recipe against your fridge or your pictures of your kids and their cousins. It's not hard to overcome the gravity of entire planet with a tiny little bit of electromagnetism. And so when you're looking at a tiny particle,

a proton or a neutron, its gravity is basically zero. It's so hard to measure. The small thing we've ever measured the gravity of is something like on the order of a gram, which means it has like 10 to the 20 particles in it. So no, we are nowhere close to being able to see gravity operate on particles so that we can then try to explain how it all works. That seems kind of hard because science is mostly about, say, either direct observation or setting up an experiment. So if you can't even see it happening or figure out how to observe it in particles,

how can you ever figure out how it works on such a small scale? Yeah, great question. Well, one is you don't give up. Oh, I was going to go for just give up. Never give up, never give it. People are doing these incredible experiments. It's really an amazing accomplishment to figure out how to test gravity on the smaller and smaller things. And there's this history dating all the way back to like Cavendish torsion experiments of lead balls away a few pounds, down to smaller objects and smaller objects.

And very recently down to stuff like smaller than a raisin, you know, a few grains of sand of material. And I really want to underscore that there's a special scientific skill there. It's not like mathematics or genius insight into philosophy. It's experimental bravura, you know, it's what Jorge might call engineering. It's like figuring out how to make your experimental system so quiet and so clean and so pristine that you can force the universe to reveal one of its secrets. It's a really special skill in science. And so those folks are working hard and drilling down. But yeah, they're like 20 orders of magnitude away from figuring it out.

So it's going to be a while. The other thing is you could, you know, try to visit a black hole. Inside a black hole, we think that gravity and quantum mechanics are both relevant because obviously there's strong gravity, but also things are squire. really, really small at the singularity inside the black hole. Of course, that's inside the black hole beyond the event horizon. So we still haven't figured out how to probe that. Yeah, we've talked about this. It is not in the budget to go to a black hole just yet.

No, so instead you might want to make your own black hole and then study the patterns of its hawking radiation to try to get some clues as to what might be inside of it. But nobody succeeded in making a black hole yet. And if they did, it might destroy the earth. And so there are some questions there. So while the experimental side is super-tuber frustrating, we can try to make some progress on the theoretical side,

thinking deeply about the universe, eating special mushrooms and having insights about, you know, connections and mathematical symmetries between these two ideas to look for links, to look for connections, to look for ways to fit them together in our minds that might give us some new clues as to how to bridge these two fundamental pillars of modern physics. Now, do you get university funding for mushroom tripping in the sake of theoretical physics? If you can convince the funding agency that it's essential for your research to make progress, then yeah, I bet you can. And so today on the podcast, we'll be

exploring one of those potential directions to bring gravity and quantum mechanics together to try to fit these two genius insights about the way the universe works into one mega insight. And And today on the podcast, we're asking the question. What is gravito-electro-magnetism? Boy, is that a mouthful? I feel like this must have been named by some German person. Every time they come up with a name for something, they just like stick a bunch of words together into one super long word.

Instead of coming up with a new word, it's used the words you already have, but stick them all together. Imagine if you came up with new ice cream flavors that way. And we're like, hmm, cookies and cream, all one word. Wait, it isn't already? No, I think that's exactly how they figured it out. I think it's interesting that I don't think I've ever seen a question before of the audience where people are just like, I can't even comprehend the name of this. That's right.

And so this was maybe a little bit unfair to drop this on the listeners. But what the heck, I think it's fun to ask you guys questions about things you never heard about. So thanks very much to everybody who volunteers for this audience. participation segment of the podcast and is caught aware by my very technical physics questions without an opportunity to prepare. We really appreciate you being game for this. If you would

like to play for future episodes of the podcast please write to me to questions at danielanhorpe.com. So before you hear these answers, think about it for a minute. What do you think gravito-electromagnetism could be? Here's what some listeners had to say.

Is it the electric charge put off by strong gravity maybe I don't know how you combine gravity and electromagnetism but it sounds like some kind of combo of the two so maybe it's the way in which electromagnetic fields are affected by gravity or vice versa I'm going to guess that gravito electromagnetism is the impact that gravity has on the electromagnetic force? I wonder what insane clown posse has to say about Gravito electromagnetism and if they know how it works.

Is that call back too old now? Am I old? I'm not going to comment on that. I will say that I am approaching 50 and so I've embraced being 50 by calling myself 50 before I even got there. And my kids think it's weird that I round myself up to 50. But I love it. I do that too. I round up so I'm not so shocked when it happens.

Exactly. That's what I was thinking. And then my daughter asked me, she said, well, does that mean when you turn 51, you're going to round yourself up to 100? Why not? Yeah, I thought, you know, for the sake of consistency, I guess I have to.

I mean, you know, then you could be the oldest person on earth even before you start getting a pension. That's true. I'm just hoping to get some of those compliments like, wow, Daniel, you look good for a hundred. All right, but back to the topic of quantum mechanics and gravity. We see people are struggling to understand what this word means, but there is a sense there that it's about some relationship between gravity and electromagnetism. Maybe gravity is caused by electromagnetism or maybe you get electric charges from gravity.

There's some fun ideas in there. It does sound like a little scammy. It sounds like something where someone's trying to sell something to me because it's just so many technical sounding words all smashed together. It's like, yeah, I kind of want to know what it is. The only thing I can think of like these listeners is just that it's like kind of trying to smush the concepts of gravity and electromagnetism together. But I kind of want to know more specifically what that is and how that works.

Yeah, and so to lay the groundwork, I think we need to spell out a little bit of detail about like why this problem is hard. Why is it difficult to bring gravity and electromagnetism or gravity and quantum mechanical theories of forces together in general? And so we should probably start with those quantum mechanical theories. And you know, we talked about electromagnetism because it's one of the fundamental forces that we know about in the universe. And all of these fundamental forces are quantum mechanical, meaning that we have a theory of quantum mechanics that describes particles and how they move through space or how they exist and how they have probabilities to exist. And those quantum mechanical theories, those Schroninger

equations and the Lagrangians and the Hamiltonians, all those mathematical structures are quantum mechanical and they describe the forces. So we have electromagnetism, we have the weak force, and we have the strong force. All these things can be described using a quantum mechanical theory. It means we know how to calculate what happens when one particle pushes or pulls on another particle using one of these forces. Like when two electrons are coming near each other, they repel each other and they use these forces to do so. They use electromagnetism. And you can think about that quantum mechanically either as one electron has a big electromagnetic field and that's pushing on

the other electron or if you prefer the particle picture, you can imagine that the two electrons are exchanging photons. They're tossing photons back and forth and that's how they're pushing on each other. But either way, we have a nice quantum mechanical picture from the ground up, from the littlest bits of these three fundamental forces, electromagnetism, the weak force, and the strong force. So is gravity even weaker than the weak force? Gravity is like 10 to the 30 times weaker than the weak force. It's almost unimaginably weak.

It's so much weaker than the other forces that it's a big puzzle in physics. Like in physics, we look for patterns and clues. We expect things that are similar in nature to all operate in under similar principles and have similar numbers. So if you want to lump gravity in as one of the forces, then you've got to answer the question, why is it so much weaker than the other forces? Not by a factor of 10, not by a factor of 100, not by a million, but 10 with 30 zeros behind it. That's a big deal.

And so like the difference between electromagnetism, the weak force and strong force, like is not nearly as big as the difference between all those three and gravity. Yeah, exactly. The strong force is like 10 times more powerful than electromagnetism, which is like 100 times more powerful than the weak force, which is like a gazillion billion, a jillion times more powerful than gravity. Now, hang on. That doesn't even sound like a number.

Okay, but I get it. So gravity is so incredibly weak. It doesn't even seem like it's in the same category as these other things. It's like comparing like a blue whale to an ant. Yeah, that's exactly right. Now, fundamentally, that's not a problem. Like, it's possible that you could have four forces in the universe and one of them is just much weaker.

There are ways that you can do that. It's not an insurmountable issue. It's strange and it would make you ask like, hmm, why is that? And to look for explanations, but mathematically it doesn't prevent us from describing it. That's not the challenge with gravity. If you sit down and try to describe gravity using some kind of, kinds of math similar to the way we describe electromagnetism and the weak force and strong force to come up with like a quantum theory of gravity that describes it as a force, then you start

to build in gravitational fields and you can think about the quantized dribbles in those fields as particles. In this case, it would be the graviton. So when two planets come near each other and pull on each other, the quantum picture of gravity would have them exchanging gravitons. the way two electrons are like exchange photons. So you can start to go down that road mathematically and things seem okay. You just like dial the force way, way down to make it super duper weak. But then you run into a lot of mathematical problems actually making that theory work. How do you check your math in a situation like this?

Like what are the kinds of mathematical problems that you run into and how do you know that they're problems? Yeah, great question. The way that you know that your theory is working or not working is that. that you try to use it and you see if it gives reasonable results. Like if you ask, I want to push these two particles together. I want to calculate the probability of various outcomes. I want to know the particles are going to bounce off each other or if they're going to

scatter off at this angle or at that angle. So you try to calculate things. You try to make predictions. And in physics, for your predictions to be reasonable, there's some limits. There's some restrictions. Like your predictions can't have probabilities greater than one. If you ask, like, is my electron going to go left or right? And your theory says, you have 100.

75% chance of it going left, you're like, mm, well, that's, that seems wrong. That can't be right. Wait, so when my gym teacher told me to give it my 110%, like, that's not right. That's physically impossible. That's right. 110% of my all? Your gym teacher is violating the fundamental rules of physics. I'm going to call them up right now.

Or maybe your gym teacher is a quantum gravity theorist. Hmm. Because that's exactly what happens when we try to make a quantum gravity theory. Gravitons are really tricky because they don't just transmit gravity. They have energy themselves, which means they also couple to gravity. They feel gravity. They emit gravity. So like when you emit a photon, photons don't feel electromagnetism.

They don't bounce off of other photons. They don't emit other photons, right? Photons don't feel electric charges because they are neutral. They don't have a charge themselves. So they will fly right through an electric field. But a graviton has energy. and gravity is felt by everything with energy. So gravitons feel gravity, which means they emit more gravitons.

And those gravitons emit more gravitons. And pretty soon you have an infinite number of gravitons and you start to get nonsense answers out of your theory. When you say a graviton, right, I'm thinking of a particle, sort of like a photon. But photons we've actually measured, right? We've actually been able to sort of get physical evidence of their existence. Like, do we have, like, physical evidence of the existence of gravitons as, like, an existing thing other than just knowing that gravity exists?

We do not have any evidence of gravitons. We have a very successful theory of gravity. It's Einstein's theory of general relativity that describes how space and time bend around masses, and that affects how things move. And that's very, very precise. But that describes gravity is not a force. It's like a bending in space and time. We're going to switch over and try to think about gravity as a force instead of a bending in space and time, then you need these gravitons and nobody's ever seen them. The reason they're so hard to see is precisely because gravity is so weak.

Like electromagnetism is a pretty strong force. Electrons are radiating photons all the time. It's not a rare thing to happen in the universe. But gravitons are more rare because gravity is so weak and they're much harder to see because gravity is so weak. So the impact of like one graviton would be very, very hard to detect. So we don't know that gravitons are real, but they are a necessary part of a theory of quantum gravity that tries to make gravity look like a force

and fit it into this quantum mechanical framework. So far, nobody's even been able to make the math work to have like a consistent theory that we could even go out and test in experiments. So we can't make the math work. We can't even find any evidence that gravitons exist. Things are looking pretty good, pretty good so far. Maybe we should take a quick break.

I will look around, see if I've got any gravitons just kind of lying around. You never know. And then when we get back, maybe we can take another crack at this and see if there's anything that actually where the math, you carry the ones and it all works out. I had this like overwhelming sensation that I had. They call her right then, and I just hit call. I said, you know, hey, I'm Jacob Schick. I'm the CEO of One Tribe Foundation, and I just wanted to call on and let her know.

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Do you have any good news for me in our effort to smush together quantum mechanics and general relativity. I didn't figure it out in the last couple of minutes, but, you know, a lot of clever people have been thinking about this and trying to find some connections between gravity and electromagnetism or between electromagnetism and gravity, sort of going both directions, like trying to make gravity look more like electromagnetism and the theoretical side, or giving up on that and trying to make electromagnetism look more like gravity. So we don't have any experimental results to guide us, but we can still think deeply about the structure of these theories and try to make some theoretical progress in our minds,

magic mushrooms or no. Hmm. All right. So we're in the mindscape. What are we doing in order to solve the hurdle of the math not mathing in this idea? Because it sounds like we were sort of trying to think of planets as like scaled up particles and gravity as like a force between them as if they're giant particles and that didn't really work.

Like, is there another approach that you could use or is there a way to like fine tune that approach such that it actually does work? Yeah, so the short answer is there isn't a great approach, but that doesn't mean we can't make progress. And I think people should understand that in theoretical physics, it's not like you sit down one day and you just come up with the whole theory.

Movies lied to me. You're entering like a mathematical jungle. You're not sure if there is a path through and it takes exploration. Exploration is not just something we do in experimental physics or in experimental biology. We're like walking through a literal jungle looking for new kinds of frogs.

In theoretical physics, you can also explore. You can just like try stuff and say, well, I'm going to go in this direction and see if it works out. Kind of like when you're trying a proof in 10th grade geometry and you're like, well, I'm not sure this is going to get me where I need to go, but I'm going to play around with these angles.

And so in theoretical physics, people are trying something that has a long tradition, dating all the way, back to like Maxwell. James Clerk Maxwell in the 1800s was looking at theories of electricity and theories of magnetism and he tried something cool. He said, well, let me write down the equations for electricity and write down the equations for magnetism and try to smooch them together and make them look as much like each other as possible. And when he did that, he realized, oh my gosh, these basically have the same equations. And not only that, but you can click the equations

together because sometimes electric field cause magnetic field and vice versa to make one bigger picture. So we have this great insight, which is where we got the theory of electromagnetism. So now people are trying to do something similar. They're saying, let's look at the equations for electromagnetism and the equations for gravity and see if we can find relationships. Are they like a mirror image of each other? Can we somehow find patterns there and then use that to guide us through this intellectual jungle to a theory that combines gravity and electromagnetism into. one big theory. So for someone just theoretically who does not have a grasp of what theoretical math would look like and when you say equations like what that is, like are we talking about like

you have five equations that you have to memorize to understand gravity? Like are there hundreds of equations? And when you're trying to like smash together equations, you know, is it sort of like a brilliant mind where you just see floating numbers kind of going together and doing things like what in terms that someone like me who math is trying to calculate a tip uh how does that work yeah that's a great question and we can start off pretty simply you know people are probably familiar with Newton's law of gravity that just says that the force between two objects is proportional to the two masses divided by the distance between them squared and you multiply that whole thing by a constant big g newton's constant so newton's equation for the force between two

objects is like gmm over r squared all right so that's newton's theory of gravity then we can look over at electromagnetism we can say what's the equation for the force between two particles that have charge like remember our question was like what happens when two electrons come near each other can we calculate that well coolum's law tells us that the force between two particles goes like the charge of the two particles divided by the distance squared between them, all multiplied by a constant, in this case, K. So you look at these two equations, you notice instantly like, hmm, these have kind of similar structures. On the top of the equation is the charge of the two objects, where gravity, the charge would be the mass. And for electromagnetism, the charge is obviously the electric charge.

And both of them get weaker as the distance grows by the same power. You get twice as far apart, gravity and electromagnetism both get four times weaker. You go 10 times further away, the force of gravity and electromagnetism both go down by a power of 100. So they have very similar structures there. Already, that's encouraging. But if it was just as simple as finding sort of some of these equations that seem to look kind of similar and match them together, like it seems like we would have already

figured this out. So what is the scale of the complexity? Like, why haven't we been able to find just like a bunch of these equations that kind of look similar and seem to have the same general structure and have them work together? Yeah, well, one issue, of course, is that we know that Newton's theory of gravity is not the right theory of gravity. Whoops. Newton was a very clever man and he has a very nice theory, which mostly works, but not quite. Irresponsible with apples, too.

Einstein's theory of gravity is not just a reimagining. It's not just saying, look, the story is wrong. It's not a force between objects. It's a bending of space and time. It also gives different predictions. Like, for example, Newton says that the force just depends on the mass. It doesn't depend on whether the object is spinning or not. So according to Newton, if you're in orbit around the earth, whether the earth is spinning

or if it's stopped spinning or spinning the other way makes no difference for gravity. Einstein says, nope, that's not true. If the earth is spinning, that has more energy. since gravity is linked to energy of all kinds, not just mass, that changes the gravitational force on the object in a complicated way. So Einstein's equations are much more complicated than Newton's. He doesn't just have like one simple force equation. He's got a really complicated tensor equation where a tensor is just like a matrix.

It's like an array in computer programming, you know, a way to keep track of a bunch of numbers all at once. So he has more complicated equations. And so you can't just say, look, Newton's law and Kulam's law, similar, you've got to dig deep into Einstein's rules for gravity. So how do we know Einstein is right and Newton is wrong? It can't just be that Einstein's got cooler hair or more complex equations. Well, Einstein and Newton make different predictions. And famously, Einstein's predictions were right. Einstein predicted stuff about how light bends around the

sun during an eclipse. And he predicted stuff about how Mercury orbits the sun and the angle of the eclipse of Mercury, how that twists as Mercury is orbiting the sun, all these little differences between Newton and Einstein add up in a few special cases. So we know that Einstein's theory was right. So then people took this on. They're like, okay, well, can I take Einstein's equations and try to make them look like electromagnetism? Like we were able to take Newton's law and make it look like Kulam's law. Can we take Einstein's gravity and make it look like electromagnetism? And people have actually succeeded in doing this. There are these gravito-electromagnetic equations when if you write them down, you get equations that look very similar to Maxwell's equations for electromagnetism.

Maxwell has four equations, and I won't get into the math with you. Thank you. There's like a divergence and a curl for electricity and magnetism. And in the gravito-electromagnetic equations, there are also four equations, and they have a very similar structure to Maxwell's equations. You should look them up and write them side by side. They look very, very similar. It's eerie. It's spooky. It's like the universe is saying, oh, look, you found the pattern. It's the same over here in the gravity world and in the electromagnetic world. This does feel like a conspiracy theorist sort of aligning charts and with a cork board and yarn and trying to make these connections. But yeah, I mean, I'm looking at this and, you know, I don't know a lick of complex math, but it, yes, they look very similar. But if we've found

this, right? It doesn't mean that we've figured out how they interlock. Like, we found some similarities, some equations that seem to match, but the bigger picture has not yet become clear. Yeah, that's right. And I hear you setting me up to deliver the bad news of why they're going to work. But first, there's a little bit more good news. Oh, okay. Which I think is a fun insight into how this works. You know, the thing about Einstein's equations for gravity, as we were saying before, is that it gives you more than just like a straight force between two objects, spinning, objects can create like torque and drag in space time itself, which gives all sorts of weird forces. Like if you are orbiting the earth and the earth is spinning, then there's some frame

dragging effects there. Check out our whole episode about that if you want more details. But effectively it gives like a twist on things that are orbiting the earth. So according to Einstein's gravity, it's not just a force between two objects. There are more subtle effects there. And the really cool thing is that in the gravito-electromagnetic equations, the ones where you take Einstein's gravity and try to convert them to look like electromagnetism, you can see this emerge. And in those equations, you have what they call a gravito-electric field, which is sort of like the straight-up Newtonian version, plus this graviton magnetic field. So basically, to explain all of Einstein's gravity, you break it up into two pieces, this analogy to the electric field and this analogy

to the magnetic field and it goes even deeper than that because it's not just notation it's not just like hey let's write this down in a cute way that looks sort of similar there really is a conceptual connection there because in electromagnetism the way you get magnetic fields is you take electric fields and you wiggle them like currents of electrons give you magnetic field so it's like velocity dependent right well the cool thing about the graviton magnetic field this other component of these equations you have to add on to be able to describe Einstein's gravity with equations that look like electromagnetism is that they create velocity dependent acceleration in just the same way for example those spinning masses when the earth is spinning that's an acceleration because

any sort of rotation is an acceleration and that gives an acceleration on satellites it gives a twist it gives a pull so when you force gravity into this structure that looks like electromagnetism you learn some things about gravity. It like sorts it in your mind in a way that actually gives you a little bit of insight. And that's a good sign. Like when you're bushwhacking your way through the theoretical jungle,

trying to make connections between things, you don't want to have to force things into categories. When they sort of naturally fall into those categories and reveal something deep about the nature of that force or the nature of the phenomenon, it's a sign that you might be on the right track. So that's the good news

that there really is something satisfying about making gravity. look like the equations of electromagnetism. It's not just like hacking it up into bits and shoving it in boxes. It's not just using the same colored gel pins to write the equation. Exactly. That sounds very promising, right? That sounds like a very promising path.

And the fact that there's this wiggle connection where wiggling or velocity movement for gravity like creates this field is very interesting. I just, I feel a butt is coming. There is a big butt. Oh, man, I knew it. Exactly right. I like big butts and I cannot lie. Now that's a reference.

I hope everybody enjoys it. Hopefully still, yeah. The other brothers can't deny. Well, the thing that the other brothers can deny is that this works in difficult situations. Like, we said that you could take Einstein's rules and you can express them in mathematical equations that look like electromagnetism. But there was a butt there I left off. And the butt is. this only works if gravity is kind of weak.

Like when the curvature of space time is not very strong, when you're far from any intense mass, when you're far away from a black hole, for example, or even from the sun, then this works pretty well. But when the curvature of space time gets more intense, this breaks down. Like the equations are just too complicated, too intense. We have no way to fit them into these boxes

to make them look like electromagnetism. In order to do that, to take the complicated tensor equations of general relativity and to make them look like electromagnetism, you have to make a bunch of assumptions. And one of those assumptions is gravity is pretty weak. So basically what's happened here is you've avoided the hard problem. You know, the hard problem of making quantum gravity work was figuring out what happens when gravitons, amid other gravitons, emit other gravitons.

Basically, when gravity gets very, very strong, when it can no longer be neglected. And that's exactly the situation that graviton electromagnetism doesn't. know how to answer. So it's some progress in the sense of like, hmm, you found some cool connections between these theories, but only in the easy parts, not in the hard parts at all. When you get to the hard part of gravity being very strong and every graviton is emitting 10 other gravitons, then this breaks down and it doesn't help us at all. So it's like an interesting island of understanding, but it doesn't make any progress on the really hard part of the problem of describing gravity as a quantum theory when gravity is very, very strong.

Could it be revealing something about gravity still? Like maybe that there is a significant difference between a strong or large amount of gravity, like the gravity of the sun versus the earth. If there is some kind of fundamental difference between like weak levels of gravity and strong levels of gravity, that seems like that could itself be an interesting kind of finding, even if it still doesn't solve the bigger question of how to merge the concepts. Yeah, exactly. And that was the point I was trying to make earlier, that even intermediate progress is progress. You don't have to know if this is going to fundamentally

solve the question of quantum mechanical gravity for it to be cool that you figured something out, that you've made some headway, you found some island of understanding, whether it actually connects to the mainland and reveals all the deep secrets. We don't know yet. But that doesn't mean it's not worth doing and not worth exploring, right? We've made it to this stage where we've been able to accomplish this connection between electromagnetism and gravity, it might be that hunting around and digging around and poking in various directions lets us build from this, right, that we can go from here to figure out how to describe strong gravity. Nobody knows how to do that yet, but this is like another avenue of attack. This gives us another way to think about it at least.

It might be a total dead end or might be the wave of the future. We haven't figured that out yet. It's on the forefront of knowledge. I mean, let's go with not being a dead end. We'll take a quick break and try to keep up the optimism that this is actually going towards finding a fundamental answer that'll change everyone's lives. And we're probably not going to figure it out in the ad break, but, you know, we'll think about it.

Hello, it's Honey German. And my podcast, Grasas 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. I feel like this is my destiny. 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 vivras 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 what I'm me? Yeah. But the whole pretending and. And, 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.

I had this, like, overwhelming sensation that I had to call her right then. And I just hit call. I said, you know, hey, I'm Jacob Schick. I'm the CEO of One Tribe Foundation. And I just wanted to call on and let her know there's a lot of people battling some of the very same things you're battling. And there is help out there. The Good Stuff Podcast, Season 2, takes a deep. look into One Tribe Foundation, a non-profit 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. I was married to a combat army veteran and he actually took his own life to suicide. One Tribe saved my life twice. There's a lot of love that flows through this place and it's sincere. Now it's a personal mission. Don't have to go to any more funerals, you know. I got blown up on a React mission. I ended up having amputation below the knee of my right leg and a traumatic brain injury because I landed on my head. Welcome to Season 2 of the Good Stuff. Listen to the Good Stuff podcast on the IHeart Radio app, Apple Podcasts, or wherever you

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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. Your entire identity has been fabricated. Your beloved brother goes missing without a trace. You discover the depths of your mother's illness, the way it has echoed and reverberated throughout your life, impacting your very legacy. Hi, I'm Danny Shapiro. And these are just a few of the profound and powerful stories I'll be mining on our 12th season of Family Secrets. With over 37 million downloads,

we continue to be moved and inspired by our guests and their courageously told stories. I can't wait to share 10 powerful new episodes with you, stories of tangled up identities, concealed truths, and the way in which family secrets almost always need to be told. 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. general relativity or gravity, but there has been some interesting progress that has been made

that is perhaps instructive and perhaps interesting. So we had that issue that these equations, when gravity is weak, they seem to kind of align like you have the equations associated with general relativity and then Maxwell's equations that looked similar. then when gravity got strong like the sun or a black hole that kind of broke down and no longer worked in that way

so is there another sort of angle of attack that is being explored yeah people are trying so many different things at once and you know this is the way we make progress you push your way through the jungle maybe you make it all the way through maybe you run into somebody else coming from the other direction right

and you can join you two efforts and so that's what's happening is a bunch of people are working on trying to make gravity look like electromagnetism. So that's the gravito-electromagnetic approach that we just talked about. But some people are working on the other direction. They're saying, let's not make gravity look like electromagnetism.

Let's make electromagnetism look like gravity. Einstein's big idea was, let's not think of gravity is a force. Let's think of it as the curvature of space time. And so people are wondering, like, can we extend that idea? Can we also do that for electromagnetism? Remember that the way Einstein did this is he said, look, it feels like there's a force between you and the earth. Newton's description of gravity as a force is compelling because when you throw a ball in the

air, it falls to the earth and it looks like it's getting pulled on, right? We have this experience of gravity as a force. But he said that it's not actually a force. That's something of an illusion. What's happening when you toss a ball is that you're releasing it into free fall. Space itself is curved in the vicinity of mass. So there's a natural path for objects to follow in curved space time. So the ball naturally falls towards the center of the earth.

So Newton's picture is there's a force pulling on the ball and then it hits the earth and it stops it because the earth is balancing that force of gravity. Einstein's picture is different. Einstein says when the ball is in the air, it's in free fall. There is no force on the ball at all. It's just following the motion of space and time. And then the earth stops it because the earth itself is perfect. providing a force. It's accelerating against that natural motion of space time. Yeah. And I think you've told me this is actually measurable, right? That there is acceleration acting when you are, say, standing on the floor. Exactly. If you jump off a building instead of the ball and you take a scale with you and as you're falling through the air, hurtling towards the earth, you stand on the scale.

What are you going to measure? Nothing. You're going to measure nothing, right? You have no weight. And that's because you're in free fall. There's no acceleration there. You're not measuring anything. If you're standing on the surface of the earth and you stand on the scale, then you measure your weight. That's where there's a force, right? So there really is no force on you when you are in free fall. There's a force on you when you're standing on the surface of the earth. That's the earth pushing up against that natural motion. So the explanation is that there is no force there. There's just a curvature of space and time. We couldn't see that curvature and that's why it looks to us like there is a force. Having this as the theory about

gravity like how do you then fit the quantum forces into this framework right because like that seems fundamentally different those are forces they're pulling or pushing against each other how does that fit into this kind of idea of gravity being like the shape of existence which sounds it's hard for me to kind of think about that right like the shape of the universe the shape of the fabric of the universe and then we're just kind of following along it and then you have these particles Have we observed anything in particles that could sort of fit within that framework? So we haven't observed anything yet, but there are some theoretical ideas. The idea is to say, well, maybe electromagnetism also isn't the force, maybe it just looks like a force,

and it's actually the result of a second kind of curvature. So we have like first kind of curvature is Einstein's curvature of space-time that gives us the apparent force of gravity. What if space can also be curved in another way and that curvature gives us the appearance of the force of electromagnetism. And in order to have curvature in another way, you need more dimensions of space in time. The idea is like Einstein space is three plus one dimensions. You start with one dimension which is a line. You draw a second dimension which is perpendicular to that. Now you have like a plane.

You can add a third dimension which is perpendicular to both of the first two and that gives you like three. D space, right, where each of those three lines are perpendicular to each other. And that's it. There's no more room to add another line perpendicular to all three, right? Because space is three dimensional. Yeah, it doesn't want. It's sort of crazy and mind bending. And I remember as like an eight-year-old trying to imagine that fourth dimension, but not being able to do it. But we do think of time as sort of a fourth dimension, how those three change. So Einstein space is four dimensional. But we can extend it by adding another dimension of space and having that curvature be in that additional dimension, that fifth dimension. You might ask, well, I can't see that

dimension. I can't imagine where that dimension would be. How does that even work? Yeah. And this fifth dimension is sort of similar to the way we think about time. Or like time we think about as the fourth dimension, imagine three dimensional space and then imagine that changing through time. I save your full three dimensional space, but now you have like another axis, a lot of along which that three dimensional space is changing. So to imagine another dimension of space itself, imagine three dimensional space, and then imagine a bunch of copies of it.

And this new dimension is not like the original three, instead of going on forever, it's like a little loop. It's more like in polar coordinates, how you have an angle and the angle can't go from zero to infinity, just goes from zero to 360 degrees, and then it goes back to zero again, right? Imagine a new dimension of space, that's sort of similar.

has a maximum length. It's a circle instead of an infinite line. Take 3D space and sort of move it around this circle. That's how we imagine the universe with four spatial dimensions. First three that are normal and then this weird rolled up dimension. Is it like when your windows computer crashes and you're dragging like your cursor or a window around and then there's a bunch of little copies of that that all get stacked up and messed up? Is that what we're talking about here?

Exactly. Or like when you win solitaire and the cards all stack on top of each other. It's difficult to imagine because we're used to 3D space and we think in three dimensions. And so squeezing that four dimension into your brain is really a challenge. But mathematically, it allows something very cool. It allows you to have another kind of curvature. A curvature in this new dimension might be able to explain what we see as the force of electromagnetism. So in this case, not just the curvature, but the curvature. The whole dimension would be basically invisible to us.

This is an ancient idea in physics. It goes all the way back to 1919. The guy Theodore Kaluza came up with this just after Einstein came up with his idea of relativity. And then a few years later, a guy named Oscar Klein turned it into a quantum theory in 1926 and tried to calculate the size of this new fifth dimension and figured out it had to be like 20 times the plank length, which means it's like super duper tiny. It's like 10 to the minus 35 meters long. So this seemed really exciting.

I have so many questions just about that. Like, what do you mean calculating the size of a dimension, right? Like... Remember that this new dimension is not infinite. Right. We think that you can go as far as you want in X or in Y or in Z. But this new dimension is a loop, which means it has a length. Now, there's a maximum distance in this dimension.

It's unlike the other ones in a really weird way. And that means that you can calculate it like, well, how big could it be? What is the radius of curvature? What is the length around this dimension? So it's very different in a really counterintuitive way. And then Einstein got to work on it. And he was like, all right, this is exciting. Oh, good.

I trust him more than I trust me to think about it. He thought, maybe this is exciting. Maybe I can make this work. Maybe I can explain all of electromagnetism using curvature in this new fifth dimension. And yeah, he died before he figured out. And people had been working on it. it for a long time and nobody's been able to crack it. There are some versions of this theory which sort of work, but they all predict that we

would have seen a bunch of new particles. They predict that electrons would like vibrate in this other dimension and it would vibrate in different ways. So you would see like different versions of the electron. The way like a string can vibrate, but it can vibrate like one mode or two modes or three modes or four modes. Electrons could vibrate in this other dimension in various ways and you would see like heavier and heavier.

versions of the electron where the heavy ones are like vibrating in this new dimension with more energy, which gives them effectively more mass. But we haven't seen any heavy electrons or any heavy muons or any heavy versions of these other particles at all. People thought for a while, oh, maybe the muon is a heavy version of the electron and that's actually like, you know, something vibrating in this new dimension. But that doesn't quite work out because the electron and the muon feel the weak force a little bit differently. So the bottom line is it's an exciting direction theoretically to try to make electromagnetism work in this kaluza-Klein theory, but it's made predictions that haven't been born out in the data.

And so it's not so promising. Well, we need to make a time machine, go back in time, and then ask Einstein, first of all, how to make a time machine so that in the future we can go back in time and talk to them, and then present them with all of this information, or maybe there will be, you know, a new kind of Einstein or collectively instead of one super genius, just a bunch of very smart people working together figuring this out. Exactly. But it's promising. It's exciting that people are trying to push their way through the theoretical jungle. You know, until we figure out how to make a black hole here on Earth, or we've come up with some clever quantum gravity experiment that lets us

see particles feeling gravity and understand whether they're like bending space time, probabilistically, or whether gravity collapses their wave functions or what's going on, we can only make progress theoretically. That means trying to find mathematical relationships between these theories, either making electromagnetism look more like gravity or make gravity look more like electromagnetism. So far, both paths have been sort of stuck in the jungle, but maybe one day people will find a connection between them

and will all be illuminated. That is beautiful. But you do also keep breezing past this plan to make a black hole on earth. It sounds dangerous to me. It is very dangerous, but also potentially we could learn a lot about the universe. So, you know, maybe worth the risk. Yeah. Ultimate knowledge right before oblivion. Sign me up. Sounds good. Well, stay tuned for more hints about potential ultimate knowledge about the universe just before you get sucked into oblivion. Thanks so very much, Katie, for joining me on this journey of theoretical understanding. And thanks to everybody for tuning in.

Awesome. Tune in 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. 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, 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. If a baby is giggling in the back seat, they're probably happy. If a baby is crying in the back seat, they're probably hungry.

But if a baby is sleeping in the back seat, will you remember they're even there? When you're distracted, stressed, or not usually the one who drives them, the chances of forgetting them in the back seat are much higher. It can happen to anyone. Parked cars get hot fast and can be deadly. So get in the habit of checking the back seat when you leave. The message from NHTSA and the Ad Council. I'm Simone Boys, host of the Brightside podcast, and on this week's episode, I'm talking to Olympian, World Cup champion, and podcast host, Ashlyn Harris. My worth is not wrapped up in how many things I've won. because what I came to realize is I valued winning so much that once it was over, I got the blues, and I was like, this is it. For me, it's the pursuit of greatness.

It's the journey. It's the people. It's the failures. It's the heartache. Listen to The Bright Side on the IHeart Radio app, Apple Podcasts, or wherever you get your podcasts. This is an IHeart podcast. Thank you.