Daniel and Kelly’s Extraordinary Universe - Why Is Gravity So Weird?

Episode Date: January 1, 2019

Why is gravity so much weaker than the other forces? Learn more about your ad-choices at https://www.iheartpodcastnetwork.comSee omnystudio.com/listener for privacy information.

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some of your favorite Latin artists and celebrities. You didn't have to audition? No, I didn't audition. I haven't auditioned in like over 25 years. Oh, wow. That's a real G-talk right there. Oh, yeah. We'll talk about all that's viral and trending, with a little bit of cheesement and a whole lot

of laughs. And of course, the great vivras you've come to expect. Listen to the new season of Dacius Come Again on the IHeartRadio app, Apple Podcast, or wherever you get your podcast. I just think it's fascinating that it's such a fundamental force

in the universe, right? Like, it's basically the thing that builds galaxies and keeps planets moving, right? It gives structure to the entire cosmos. That's right. On the largest scale, it's actually the most important force. It's the reason why things look the way they do. It's a reason why our planet is round.

It's the reason why we're on the planet. It's pretty important. And yet, we don't know a lot about it, right? Like there's some really deep and strange mysteries about it. On one hand, we have a theory which works really really well. On the other hand, we have questions about it, which seem really, really basic. And not only that, it's very different than all the other fortress of nature.

That's right. One of these things is not like the other ones. Hi, I'm Jorge. I'm a cartoonist. And I'm Daniel, I'm a particle physicist. And this is our podcast, Daniel and Jorge, explain the universe. In which a cartoonist and a physicist try to figure out how to make the universe understandable to anybody. Yeah. And today on the podcast, we are examining a very heavy topic. Gravity.

And specifically, why is gravity so weak? And strange. Gravity, as we said earlier, is something which controls the structure of the universe. I mean, the reason the solar system looks the way it does is because of gravity. The reason the Earth is round is because of gravity. The reason we have galaxies is because of gravity. The reason we weigh so much is because of gravity, right? It's totally not my fault.

No, that's because of late night cake eating. But it's such a fundamental force of nature, right? Like it's present in our everyday life. And we spent a lot of time thinking about gravity, right, how not to fall down, how not drop things, how to go up buildings, how to go down buildings, right? That's right. It seems like one of the most important forces. I mean, if you ask people, you know, to name a force or what kind of forces they experience in their life, gravity is the one that's present in their lives, right? You're climbing upstairs, you're fighting gravity. You trip, you fall down, you're feeling gravity. You look around you, the shape of things is controlled by gravity. And that's why it's particularly strange that gravity is the weakest force of all the forces we've discovered. It's by far the weakest.

Yeah, it's really strange to hear you say that. How can gravity be weak? Like, you know, like it's keeping the whole Earth together. It's making the entire planet go in a circle, basically. Without gravity, we would just shoot off into space. That's right. It's a really strange situation. And there's other things about gravity we don't understand as well.

It's really strange. It doesn't play well with the other forces. It's very, very weak. It's a total mystery to science, except that we have a theory which works beautifully, right? We can calculate exactly how Mercury orbits the sun. We can send things into outer space and know with two millimeter precision exactly where they're going to land. We have a working theory that we can use, right? But we don't understand it on a conceptual level. We have these basic, deep questions about what gravity is and how the universe works because of it. So it's a weird question, and maybe one that people hadn't thought about before. So Daniel went out as usual and asked people on the street, why do you think gravity is so weak? Here's what a random selection of folks who were willing to talk to me on a Tuesday morning had to say about gravity. I don't know. I actually don't know about that. All right.

I always thought it was a pretty strong force. I don't know. But yeah. Because it depends on the distance and it's a long-range one. So that's why we feel it very weak most of the time. Cool. No. Okay. I have no.

I'm sorry. It's not very fruitful. Hmm. I have no idea. But I'd be interested in finding out why. All right. That was pretty good. Most people weren't surprised when you said gravity's weak.

I don't know. I feel like of all the questions I've asked people, this is the one that flummoxed them the most. You know? People were like, what? I have no idea. Or they had crazy ideas why gravity. must be weak. I feel like usually we get one person who knows what the answer is or has a good clue about what's going on. But this time I feel like almost everybody was pretty clueless.

I mean, one person said, I always thought gravity was pretty strong, right? Which kind of sums up the situation, right? Gravity is omnipresent in our lives. It dominates our experience. And yet, it's so weak compared to the other really powerful forces we've discovered. Well, some people, a couple of answers were that it had to do with distance. Like, gravity gets really weak with distance. That's right. And the problem there is that all the forces get weak with distance. Like electromagnetism also falls as the distance grows, right? So all of these forces follow this one over R squared rule, or R is your distance from the thing that's giving you the force. Right. Maybe, maybe, right? Maybe. Yeah, mostly we think. And so that can't be the answer, right?

Because all the other forces have that same feature. So when you say it's the weak as it's not that it changes over distances differently than the other forces. That's right. So maybe we should talk about what the forces are and compare them to each other. So we focus and get an understanding of how crazy weak gravity is. All right. So, Daniel, what are the forces of nature besides a bad movie with Ben Affleck and Sandra Bullock? Well, I think comedy.

Comedy is definitely a force of nature. You know, it solves big problems around the world. No, the fundamental forces are electromagnetism, right? That's the one that controls electricity and magnetism, obviously, and is responsible for the cool things like light and lightning and all that cool stuff. And then there's the weak nuclear force, which is a force which is responsible for radioactive decay of a nuclei, right? And the cool thing about electricity and magnetism and the weak nuclear force is that we actually have shown that they're two sides of the same coin. As a particle physicist, we refer to them as one force. We call it the electro-week.

So it was sort of magnetism lost out there in the name merger, right? It should be electromagnetic weak, but nobody voted to keep magnetism in the, so the name of the partners on the law firm. Nobody lobbied for weak electro or. Magneto weak force, yeah. Yeah. Yeah, again, we are suffering the fate of some anonymous committee of scientists that get to name these things, right? Who are these people?

It's probably some grad student, right, or some, you know, like this is really weird. we'll call it this. Yeah. So we have electricity and magnetism, which is a single force. We have the weak nuclear force, which is really should be combined with electricity and magnetism.

And then there's the strong nuclear force. And this is the one that holds the nucleus together. You know, the nucleus is just a bunch of positively charged protons and neutral neutrons, right? So there's only positively charged particles in the nucleus. So you might think, what even holds the nucleus together, right? You have all this positively charged stuff

should be repelling themselves. Well, it's the strong nuclear force. and it does so by exchanging these crazy little particles we call gluons and that holds the nucleus together and it's pretty strong. It's even stronger than electromagnetism. Well, let's take it step back. So in the universe, there's

stuff. There's like... Yes. I can confirm that there is stuff in the universe, yes. Yes, good. Without reservation, there is stuff. I'm glad we solve that question. But I mean, it's like there's stuff that has substance to it, that has mass to it, or, you know, that sort of exists. And then there's also, besides

that how these things interact with each other, like how they affect each other. That's right. There's the matter and then there's the forces, right? The forces affect how they interact with each other. And that's pretty much the universe. That's like, it's matter and forces. Yeah, one way to look at the universe is that it's particles, right? Or you would say matter and their forces. In modern particle physics, we think about one level deeper, which is we think of quantum fields, and quantum fields are responsible both for matter and for forces. So we can talk about that maybe in another podcast, what is a quantum field and how can I get one for lease or rent? What can they do for me?

But yeah, I think it's fair still to think about the universe in terms of particles and forces. On that note, let's take a quick break. A foot washed up a shoe with some bones in it. They had no idea who it was. Most everything was burned up pretty good from the fire that not a whole lot was. salvageable. These are the coldest of cold cases, but everything is about to change. Every case that is a cold case that has DNA right now in a backlog will be identified in our lifetime. A small lab in Texas is cracking the code on DNA. Using new scientific tools,

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

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We've got some of the biggest actors, musicians, content creators, and culture shifters sharing their real stories of failure and success. You were destined to be a start. We talk all about what's viral and trending with a little bit of chisement, a lot of laughs and those amazing 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, I'm me.

But the whole pretending and code, you know, it takes a toll on you. Listen to the new season of Grasasas Come Again as part of my Cultura podcast network on the IHartRadio app, Apple Podcast, or wherever you get your podcast. I'm Dr. Joy Harden Bradford, and in session 421 of therapy for black girls, I sit down with Dr. Ophia and Billy Shaka to explore how our hair connects to our identity, mental health, and the ways we heal. Because I think hair is a complex language system, right, in terms of it can tell how old you are, your marital status, where you're from, you're a spiritual belief. But I think with social media, there's like a hyperfixation and observation of our hair. right, that this is sometimes the first thing someone sees when we make a post or a reel is how our hair is styled.

We talk about the important role hairstylists play in our community, the pressure to always look put together, and how breaking up with perfection can actually free us. Plus, if you're someone who gets anxious about flying, don't miss Session 418 with Dr. Angela Neil Barnett, where we dive into managing flight anxiety. Listen to Therapy for Black Girls on the IHeart Radio app, Apple Podcast. or wherever you get your podcast. There are only four kinds of forces. Yeah, there are four kinds of forces. So electromagnetism, weak nuclear force, strong nuclear force, and then, of course, gravity, right?

That's the fourth force that we've discovered. Okay. The fascinating thing is that different particles feel different forces, right? Like some particles feel this set of forces, some particles feel those set of forces, for example, right? Particles with electric charge feel electromagnetism, right? The electron, for example, is negatively charged. The proton is positively charged.

You bring them close together, they're going to pull on each other. They're going to suck each other together, right? Because they have opposite charges. We all know that. But you bring a neutral particle nearby. It just totally ignores it, right? It doesn't feel it at all. Right.

It's like somebody's walking through a crowd of people shouting, but they have headphones on, so they can't hear anything. They're totally oblivious to it. It's kind of like how we talked about in a previous podcast. They're almost like languages or like social media platforms. Like some people are on Twitter, some people are on Facebook, but some people are not on this.

And so if somebody, if you're not on Twitter and somebody sends you a tweet, you're not going to get it. And so it's just different ways that particles interact. That's right. Gravity is the Google Plus of social media, right? Because nobody uses it. The Frenchster. The Frenchster.

It's ancient but powerless. Yeah, and so different particles feel different forces. And for example, an electron, while it feels electromagnetism because it has a negative charge, it doesn't feel a strong force at all. It'll pass right by a bunch of particles that are really tugging on each other with a strong force and not be affected at all. Whereas quarks, corks feel all the forces. They feel a strong force, which is how they get pulled together in the nucleus.

Remember, protons and neutrons are made of quarks. Quarks feel electromagnetism because they have electric charge. they feel the weak force they also feel gravity of course because they have mass so quarks get their fingers in everything they feel they feel they get the feels for everything they feel everything that's right they got the strong feels of course they're really deeply emotional part of it's and on the other side of the spectrum you got things like neutrinos neutrinos don't have electric charge so they ignore all electricity magnetism right they don't interact with light they're invisible they pass right through anything that they ignore

electromagnetic bonds, so they pass through most materials. They don't feel the strong force. The only way they interact is with the weak force, and the weak force is pretty weak, which is why neutrinos can mostly just pass through matter unaffected. So we have four fundamental forces, right? And gravity is one of these forces.

And so when you say that gravity is weak, you actually mean it's weak compared to these other three forces. That's right. And so the ranking is the strong force is the strongest, right? So that one is actually well-named. Congratulations. For now, right?

You know, anonymous group of scientists. Yeah, we should be called the, as of 2018, currently known to be the strongest force force, right? After that comes electromagnetism. And, you know, we know that force is pretty powerful. You stick your finger in a socket, you're going to feel the wrath of electromagnetism, right? It's not an unfamiliar feeling, right?

Try to stick your finger in anything you feel it, right? Because it's, electromagneticism is the force that keeps you from basically passing through the table or passing through your car, right? That's right, because electromagnetism is the basis of chemical bonds, right? And chemical bonds are really the thing that form the structure of your body, right? You think of your body is like a bunch of particles, but it's held together by all these forces. It's like a chain link fence binding together these little particles and prevents you from passing through something else.

Yeah, so we got the strong force and then electromagnetism and then actually the weak nuclear force, right? This is the force that, like, powers neutrinos and radioactive decay. It's much weaker than electromagnetism and much weaker than the strong force. Even weaker than the weak is gravity. That's right. If you make a list, like strong force, electromagneticism, the weak force, then you should leave, like, 100 blank pages, and then you get to gravity. Because when we compare these forces, we put things like an equal distance apart, and we compare the strength of the forces. gravity is 10 to the 36 times weaker than the weak force.

But that's 10 with 36 zeros in front of it. But isn't that sort of a matter of units or scale? Do you know what I mean? Like, it's much weaker, but only if you compare apples to apples, right? Or oranges to oranges. That's right. But put two protons next to each other, right? Two protons have a certain amount of mass and a certain amount of electric charge.

And the force of their charges is going to be much, much, stronger than the force from their masses. Oh, I see. So, yeah, if everything was much, much more massive, then there would be stronger gravity. But you can compare these things apples to apples by comparing them at the same distance and the same basic unit of interaction.

Right, but what if you take an apple, put it next to another apple? Well, I think you can do that experiment. Nothing's going to happen because gravity is so weak, right? You don't see two apples like pulling themselves together on the counter, right? There's no built-in apple collider. You know, the apples are not drawn to each other.

Gravity is a super weak force. And you can see this yourself, right? You can do an experiment where you counter the entire gravitational force of an enormous celestial body like the Earth, right? Take a small kitchen magnet and use it to hold up a nail. And think about what's happening there. You have the nails being pulled down by every single rock in the earth. It's pulling with all of its gravity. But a tiny little kitchen magnet totally overcomes that.

It can lift the nail even though it's pulling, it's being pulled down by the whole. entire planet earth. Right, exactly. Now imagine a magnet the size of the earth, right? I mean, that would be extraordinarily powerful. And so you have basically like a gravitational blob the size of the earth still pretty ineffective compared to electromagnetism. So it's weak if you sort of compare it by object. Like you said, if you take a proton, put it next to a proton, the force you're going to feel from electromagnetism is so much bigger than the... force of gravity they're going to feel towards each other. The same with like two electrons or two quarks and things. So in the scale of like the particles that we know, it's a really weak force.

That's right. Exactly. And yet, and yet it seems to dominate, right? That's a bit of a puzzle. Like on one hand, it's super duper weak and we're telling you that it hardly counts for anything. On the other hand, it's responsible for the structure of the solar system and for the galaxy. And it's the reason the universe looks the way it is, right? And so that can be confusing to people. Like, how do you reconcile those two things in your head? Yeah. Like, why doesn't the Earth feel an electromagnetic force with the sun, which would be so much bigger than the force of gravity?

Yeah, well, it would be pretty shocking. And that's actually the reason is gravity is different from the other forces and that it can't be canceled out, right? If there was some huge electrostatic difference between the sun and the Earth, like a bunch of positive charges there and a bunch of negative charges here, it would create such an enormous force that it would be very quickly, balanced. That's what lightning is, right? When there's a charge differential between clouds and the ground, it doesn't take that much before those charges want to rearrange themselves to a lower

energy configuration. They rush down to the ground or they rush up to the clouds or they jump from cloud to cloud to balance themselves out because you have two kinds of charges. You have positive and you have negative. So you can find an arrangement where basically everybody's happy. It's an equilibrium, right? But that's not true for gravity. Okay, I get it. So for example, if the Earth was every particle on Earth had a positive electromagnetic charge and every particle in the sun had a negative electromagnetic charge, there would be a humongous pull from electromagnetism pulling the Earth into the sun.

Yeah, we'd be toast pretty quick. Yeah, right? That would not be a very long-lived experiment. Yeah, it would be huge. Even the opposite, if we were all positive and the sun was all positive, we would get shot out of the solar system very quickly. That's right. And that's why early days of the solar system,

system being formed, you have these gases and the gas and dust coalescing and very rapidly things neutralize, right? Because anything that feels an electrostatic force to something else is going to find the opposite charge and they're going to coalesce and they're going to make something neutral, right? That's why most of the things around you are neutral, right? Most of the elements are neutral because any deviation from neutral results in a powerful force to neutralize it. So thankfully, the earth is made out of both like equal amounts of positive negative particles, right? Thankfully, we're sort of balanced

electromagnetically. And so even if the sun was all positive, we would look like neutral, like a neutral ball to the sun. Yeah, that's right. We're on large scales, the Earth is neutral, right? I mean, there might be some residual positive or negative charge depending on the solar wind, etc.

But basically the Earth is neutral. And so the largest force of the Earth feels is the gravity from the sun, even though gravity is super duper weak, right? It doesn't take a lot to counteract gravity, but it's the only player left because everybody else is sort of pair it up and danced off for the night, and gravity's just there left holding the bag. And gravity can't be balanced, right? You feel gravity if you have any mass, right?

But it's only positive masses. There's no such thing as a negative mass to give anti-gravity. Wow. Well, let's keep going, but first, let's take a quick break. A foot washed up, a shoe, with some bones in it. They had no idea who it was. Most everything was burned up pretty good from the fire that not a whole lot was salvageable. These are the coldest of cold cases, but everything is about to change. Every case that is a cold case that has DNA right now in a backlog will be identified in our lifetime.

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

And my podcast, Grazacus come again, is back. This season, we're going even deeper into the world of music and entertainment with raw and honest conversations with some of your favorite Latin artists and celebrities. You didn't have to audition? No, I didn't audition.

I haven't audition in, like, over 25 years. Oh, wow. That's a real G-talk right there. Oh, yeah. We've got some of the biggest actors, musicians, content creators, and culture shifters sharing their real stories of failure and success. You were destined to be a start.

We talk all about what's viral and trending with a little bit of chisement, a lot of laughs, and those amazing Vibras you've come to expect. And of course, we'll explore deeper topics dealing with identity, struggles, and all the issues affecting our Latin community. You feel like you get a little whitewash because you have to do the code switching?

I won't say whitewash because at the end of the day, you know, I'm me. But the whole pretending and code, you know, it takes a toll on you. Listen to the new. Season of Grasas Has Come Again as part of My Cultura Podcast Network on the IHartRadio app, Apple Podcasts, or wherever you get your podcast. I'm Dr. Joy Hardin Bradford. And in session 421 of Therapy for Black Girls, I sit down with Dr. Afea and Billy Shaka to explore how our hair connects to our identity, mental health, and the ways we heal.

Because I think hair is a complex language system, right? In terms of it can tell how old you are, your marital status, where you're from, you're a spiritual, believe. But I think with social media, there's like a hyper fixation and observation of our hair, right, that this is sometimes the first thing someone sees when we make a post or a reel is how our hair is styled. You talk about the important role hairstylist play in our community, the pressure to always look put together, and how breaking up with perfection can actually free us. Plus, if you're someone who gets anxious about flying, don't miss session 418 with Dr. Angela Neal-Barnett, where we dive into managing flight anxiety.

Listen to therapy for black girls on the iHeart Radio app, Apple Podcasts, or wherever you get your podcasts. Okay, so that's how gravity is so much weaker than the other forces. So how's it different than the other three forces of nature? There's like no end to ways that gravity is weird. You know, there's no end to like the puzzles of gravity. It's fascinating. Bottomless pit.

That's right. It's a black hole of questions. And one of my favorites is just that we have no way to sort of fit gravity in with the way the way the universe works according to everything else. You know, we talked earlier about how we have particles and we have forces or quantum fields equivalently. And that's a really successful way to describe the universe. You know, we have the large Hager.

Collider to explore these things really high energies and we've understood all sorts of things using this theory. But that theory uses quantum mechanics. So the way we describe interactions, you know, the way we talk about two electrons repelling each other or the way lightning is formed or anything involves passing quantum particles back and forth. And that's just not true for gravity. What does that mean passing particles back and forth? Like when, like if I have two magnets and they're attracted to each other, they're not, it's not like an invisible telekinesis pulling on each other. They're actually swapping particles, and I can't see that.

Is that kind of what you mean? That's exactly what I mean, that the way two things interact via some force is by exchanging particles. And so, for example, electromagnetism, right, is the force behind a magnet. And the way electromagnetism works, we think at a sort of microscopic particle level is that there's a particle that transmits that force

that sends sort of the information back and forth between two things that are feeling it. And in the case of electromagnetism, that particle is the photon, right? The particle is also a packet of light. So each of the quantum forces that we talked about before, electromagnetism, the weak force, and the strong force, each of them have a particle we associate with it. And that's not just like some name tag we put on and say, hey, you get this one, you get this one. We think that that's the particle that's responsible for making the force work.

So when two electrons come near each other, how do they repel each other? How does that actually happen? Well, we think that they send photons out, right? The electric field of a moving electron, an accelerating electron, generates photons, and those photons interact with the other electrons. And so basically the passing messages back and forth using these quantum particles. So gravity is weird because we don't know that there is a quantum particle being exchanged when two things get attracted gravitationally.

That's right. So we have this great framework. We say, oh, maybe all forces are quantum mechanical fields interacting with each other, right? Let's apply that to the electromagnetic field. Yeah, it works. Let's apply that to the weak force. Yeah, it works. Let's apply that to the strong force.

Ooh, cool, it works. Maybe this is something deep about the way the universe works. Let's apply it to gravity. Uh-oh, it doesn't work. Right, right? So what does that mean? What does it mean when it say it doesn't work? Well, for a theory to work, it has to provide predictions for experiments.

You have to be able to say, okay, theory, what would happen in this configuration? If I shot a proton and another particle, predict what would happen. And then you can go off and do the experiments and compare it, right? Well, when you do that for gravity, you try to form a quantum theory of gravity, it doesn't work. You get nonsense answers. You get answers like infinity, right, or things disappear, or it doesn't mathematically function. There's no way to build a theory of gravity that we've discovered so far that works. That actually explains the way these things happen.

There are a few candidates out there. They're pretty far from being a functional theory of quantum gravity, things like loop quantum gravity or string theory. But the basic problem is that quantum mechanics and general relativity, which is our best theory of gravity, do not play well together. We have no functioning quantum theory of gravity. Oh. So does that mean that we don't have the right theory or is that gravity is just not quantum in nature? That's exactly the question we don't know the answer to, right? In a hundred years from now, somebody will know the answer to, I hope. and they'll look back and they'll wonder, you know, oh, why do those guys see the clues?

But we don't know. It could be that there is a quantum theory of gravity. We're just not smart enough to think it up yet, right? Like the right person hasn't been born yet to put the math together. Or maybe it requires a different kind of math that we're using, right? There's some assumption we're making that's a mistake. Or maybe we're just giving it a wrong name. Like maybe it should be Gravitunis or.

Gravitinos. Gravitinos. Gravitas. The way that's taken. Exactly. That's definitely the problem. That's step number one. We made a mistake in step number one

when we could define the particle. The other option, of course, is that maybe gravity is not a quantum force, the way the other forces are, right? The other forces, we call them quantum forces because they're well-described by quantum mechanics. But gravity is kind of different. I mean, the current theory we have a gravity,

general relativity, it doesn't like to describe gravity as a force. It describes gravity instead as a bending of space. It says that when you have mass, somewhere in space, space no longer becomes straight, becomes bent. So the things move in curves and circles. And it's not like an actual,

just a mathematical nuance or a mathematical perspective. What really confirms it is the idea that gravity can affect things that don't have mass, right? That's how we know it's more than just a force between things that have mass. It actually affects space

for things that don't have mass, right? That's exactly right. So if you shoot a photon through space, that has mass nearby, the photon will not move in what we consider to be a straight line, right? It'll find a path through this bent space that involves basically curving. And this is what Einstein predicted with his theory, and they saw it. You know, and you can see in space, it's called gravitational lensing. You can see photons get bent by heavy objects.

And it's because, as you say, the heavy objects are bending space itself. Right. It's not like gravity is pulling the photon because the photon doesn't have any mass, right? That's right. The photon doesn't have any mass. So that's how it's different. Gravity seems to affect things that don't have sort of its fundamental property. Like electromagnetic forces can affect something that does not have an electric charge. Gravity can affect everything else, right?

Yeah, that's a pretty deep insight there already. Not bad for a cartoonist. Not bad at all. Yeah. That's a fascinating way to think about it. I think that's totally correct. Yeah, and so if gravity is instead of being a force, if it's a way we change the shape of space itself, then maybe that's why we don't have a quantum theory of it, right?

And that's amazing, and it's fantastic, and it's exciting. And another reason why we have a hard time bringing these two things together is that quantum mechanics, the theory we've developed, only works so far in flat space. That is, if there's really heavy stuff nearby, we don't know how to do those quantum calculations. We can basically only do quantum mechanics in places where there isn't really strong gravity. So wait, so quantum physics doesn't work in reality, basically.

Is that what you're saying? Like it doesn't work in the space that we actually live in? Well, it works basically everywhere except for close to black holes. Right? You need basically a black hole that have enough gravity to break down quantum mechanics. Because it's when space gets really distorted that you start to see the effects of gravity on space and then it becomes comparable to the strength of other stuff. And that's when quantum mechanics breaks down.

Yeah, quantum field theory works basically what we call flat space, whereas gravity bends space. Wow. So earlier when we categorize gravity as part of these four fundamental forces, maybe that's just the wrong approach. Do you know what I mean? Like maybe we shouldn't be categorizing these four things as one category of, quote, forces, unquote.

That's right. It could be that there is no quantum theory of gravity as a fundamental force because it isn't one. And it's just a feature of space, right? Absolutely, that's one possible explanation. But then we still need a way to make quantum mechanics work in bent space, right? And we still need

to understand how to make our theory of general relativity play well with quantum mechanics. Because we think quantum mechanics describes the universe, right? And general relativity is not a quantized theory. It's, it's continuous. It treats space and everything as if it's infinitely divisible. It's not a quantum theory at all. In fact, it came about before quantum mechanics was even invented. And so while the

basic tenets of it and how it distorts space are probably correct, I mean, been verified to zillion degrees of accuracy, it doesn't feel like it can be a fundamental description of nature because it's not quantum mechanical. So like we want to call it a force because it seems to move things like all the other forces, but it's maybe it's not a force. Maybe it's just kind of like some other weird property of space. Yeah, exactly. You know, maybe we've been trying to put a round peg into a square hole all these years. A gravity peg in a quantum hole.

That's right. That's right. And there are other ways that people are trying to solve this problem. Like one way is thinking that maybe gravity is a fundamental force, but it just works a little bit differently from the other forces. For example, people think about how the universe might have additional spatial dimensions. You know, like instead of just being able to move. in three directions, maybe there's like four or five, six dimensions that you can move in.

And folks who are interested in that should listen to our podcast on extra dimensions. No, yeah, we did a whole episode on extra dimensions, but we didn't sort of get into this particular topic. So tell us how extra dimensions might explain why gravity is so weak. Yeah, the idea is that maybe gravity isn't so weak. Maybe gravity's just as strong as all the other forces. But if there's a whole other set of dimensions out there, there is ways directions that thing can move, it might be that gravity is the only thing that feels those dimensions, right? It might be that those dimensions are invisible to electromagnetism and to the weak force and to the strong force, but visible to gravity. And what that means is that gravity

might be basically leaking out into those other dimensions. You know, we talked about how the farther away you get from something, the weak of the force is. So like Mercury feels the force of the sun's gravity much more strongly than Pluto does, right? Irrelevant of whether or not you call it a planet, it doesn't feel gravity very strongly. And that's because it's further from the sun, right? I mean, that goes like one over R squared, or R is the distance. It's one over R squared because we have three dimensions. If we had six dimensions, it would be one over R5, right, which falls much more rapidly.

So if there are additional dimensions out there, okay, and only gravity feels them, that might be the reason why gravitational force falls so quickly. Maybe gravity is actually just as strong as everything else. get really, really close, but then these extra dimensions exist and most of gravity leaks out into those other dimensions. Sort of like between you and me, there's not just the three dimensions between you and me. May there are other secret hidden spaces kind of between you and me or these other dimensions. Exactly. Other ways for gravity to spread out.

So gravity would be like just as strong as all the other forces, but it's just flexing its muscles in these other spaces that we can't see. feel. Exactly. It's like, you know, if somebody's at the center of a crowd and they let go a really stinky fart, right? The people next to them, they smell it strongly. And the people further away, they smell it much more weakly and people outside don't smell it at all. Okay. Yeah. We jump into farts really suddenly, but let's go with it. Hey, I'm trying to make this accessible, you know. This is something everybody can appreciate it. You're trying to make win. I get it, cut it. And, but if there was somewhere else for that fart to go, you know,

if it could move not just sideways, but also it could float up. Right. Say you had a really tall room and the fart floated up, then people wouldn't feel it as much because most of the far would dissipate into the upper corners of the room. And so gravity might be the same way. It might be that, you know, for the first millimeter or so, the first centimeter or so, gravity gets very weak, very quickly. It falls off really rapidly. And that then, you know, at normal distances, like a meter or 10 meters or whatever, you don't feel those other dimensions anymore because other dimensions only activate it really, really short distances. This is the thing. theory people came up with, and we don't know if it's real. You know, we've tested it. So far, it seems that gravity works the same way for galactic scales and for Earth scales and for microscopic scales. It seems to always fall off at the same rate as a function of distance. So nobody's ever seen any evidence of these extra dimensions. But it's a fascinating theory, and it's one that would give kind of a natural explanation for why gravity would fall off so quickly and why gravity is so weak. It wouldn't

explain all these other things, but... In fact, people sort of try to use gravity to use gravity to see if there are other dimensions, right? Yeah, that's right. It would be a really cool clue, right? And that's a fascinating way that science is done. You know, you try to look at everything around you and see if you can fit it all into one framework. Like, can I use this one set of ideas to describe everything?

Right. Can I merge everything into one set of concepts? Yep. That's right. Yeah, my fart theory of the universe. The best possible way, I think, to unravel this is to actually go visit a black hole because quantum mechanics and general

relativity tell you very different things about what's happening inside a black hole right as we said before general relativity tells you it's an infinitesimal dot of almost infinite density quantum mechanics says you know the universe is quantized first of all so you can't have infinitesimal dots

and also there's sort of a minimum size to stuff right and you can't have all that stuff compressed in such a tiny little area and so if you could see inside a black hole you would learn a lot about gravity. So what would be the plan? You would go into a black hole,

you would observe and discover how the universe works, and then you'd be stuck there. That's right. They would have to send you a Nobel Prize into the black hole after you. They'd just assume you'd figure it out and shoot the Nobel Prize

into space, into the black hole. Congratulations. Anybody who's listening, please do not go into a black hole. Please, please do not go into a black hole. But, you know, we don't need to visit black holes. We could try to create them here on Earth. That sounds like a great idea.

Yeah, doesn't that sound like a great idea? I mean, wow, I'm excited. Make a black hole on Earth? So sell me. Yeah, let's create a black hole and study it, right? If gravity gets really, really powerful when you get to really short distances because of this extra dimension theory, then it might be that if you shoot two protons together really, really hard and they get really, really close to each other, that you can create a super-duper mini, extra cute little fuzzy black hole, right? I'm trying to make it sound like a cozy thing, not a dangerous thing. Yeah, you're trying to sell it.

Sell it merchandising rights. And so before we turned on the Large Hadron Collider about 10 years ago, people thought maybe by smashing these protons together, we could actually create black holes and we could study them. We could reveal the deep secrets of gravity, right? So then the idea would be to try to make them at the Large Hadron Collider and just kind of see what happens. Like, does it tell us something about gravity or quantum physics at the same time?

Yeah, exactly, by seeing how often they're made and how strong they are and what they turn into, what they decay. We could understand something about the way black holes work. And that would have been really powerful. But unfortunately, or fortunately, depending on how you feel about black holes, we haven't made any black holes at the Large Hadron Collider that we've discovered. But isn't it true that maybe you've made them, but they evaporate? Yes, these black holes would be very short-lived.

But, you know, everything we make at the Large Hadron Collider is really short-lived. These things last for like 10 to the negative 30 seconds or 10 to the negative 23 seconds. We're pretty good at seeing short-lived stuff. it usually blows up into other things. And a black hole would have a really unusual signature in our detectors. It would be pretty clear to see if we had made them. Okay. But short of going into a black hole or detecting farts in extra dimensions,

we may not know in the near future what makes gravity so different. That's right. It's going to take some work. I mean, the other direction is theoretical, is to build up a theory of quantum gravity sort of from the bottom up. Like start from the beauty of math and physics and then try to, to build it up to our level. Exactly.

And that's a wonderful way to do, is to say, like, maybe the universe works in this way, this most basic fundamental nature and build it up from there and see if you can describe the universe that we see around us. Wow.

All right. Well, that's pretty shocking to think gravity plays such a big role in our lives, and yet it's like the weakling in the universe, right? It's like, imagine if gravity was stronger. life would be a lot more chaotic right and crazy yeah exactly we would be closer to the sun and everything would feel more intense it's fascinating to me that gravity has been a mystery to physics for hundreds of years I mean it was the focus of Isaac Newton's studies you know like hundreds of

years ago people working on gravity and still today even though we've made so much progress in terms of gravity we still have so much so many basic questions about it that we don't we don't know the answers to not even the really beginning of how to answer them to me that's fascinating I think gravity is such a rich source of mystery for physics and for everybody. Wow. All right, cool. I think it's maybe time to push down this question. Thanks for joining us.

If you still have a question after listening to all these explanations, please drop us a line. We'd love to hear from you. You can find us at Facebook, Twitter, and Instagram at Daniel and Jorge. That's one word. or email us at Feedback at Danielandhorpe.com. I'm Dr. Scott Barry Kaufman, host of the Psychology podcast. Here's a clip from an upcoming conversation about how to be a better you.

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