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Speaker 1: Hey, or hey. You know what's still amazes me that

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Speaker 1: they give to introverts like us a podcast that blows

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Speaker 1: my mind every week. But also, rainbows are awesome, But

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Speaker 1: what about them amazes you? Everything is amazing about them.

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Speaker 1: They are amazingly beautiful, But I'm amazed that they like exist,

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Speaker 1: that they happen in the universe. You know that there's

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Speaker 1: a science behind them, right, They're not just like magical.

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Speaker 1: I get that there's science there, but I just think

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Speaker 1: it's incredible that we live in the universe where this

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Speaker 1: kind of thing actually happens. I mean, if you read

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Speaker 1: about this in the science fiction book, you would think

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Speaker 1: it's pretty farfetched. Well, it depends what what kind of

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Speaker 1: science fiction you're reading. Does it also involve unicorns? Unicorns

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Speaker 1: like a podcast with two introverts? Wait, who is the

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Speaker 1: unicorn in this case? Because you can only have one,

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Speaker 1: it's in the name unicorn. Collectively, we are one unicorn.

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Speaker 1: Hi am Jorhemmack, cartoonists and the creator of PhD comics. Hi,

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Speaker 1: I'm Daniel. I'm a particle physicist and a professor at

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Speaker 1: U c Irvine, and I called dibbs on being the

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Speaker 1: front two legs of the unicorn costume. Oh good, it's

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Speaker 1: going to be the back end. Maybe you can have

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Speaker 1: a guest host go. That's why we have guest hosts exactly.

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Speaker 1: But anyways, welcome to our podcast, Daniel and Jorge Explain

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Speaker 1: the Universe, a production of I Heart Radio, the podcasting

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Speaker 1: which we talk about everything that's out there in the

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Speaker 1: universe and try to explain all of it to you.

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Speaker 1: We explore the complete spectrum of possible physical phenomena, including rainbows.

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Speaker 1: If unicorns were real, we would talk about them as well.

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Speaker 1: But we don't shy away from digging deep into the

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Speaker 1: fabric of reality, understanding how it all works, and trying

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Speaker 1: to explain to you what scientists are thinking about, what

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Speaker 1: they are puzzling over, and what ideas they are bouncing

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Speaker 1: around their unicorn brains. That's right, because it is a

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Speaker 1: very colorful universe. Well have amazing sites like rainbows, and

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Speaker 1: we like to follow that arc of science to see

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Speaker 1: what is at the end of it if there is

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Speaker 1: indeed a big part of gold or some other element,

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Speaker 1: you know, because it just don't really discriminate between elements,

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Speaker 1: do they We don't. But I would like to accept

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Speaker 1: my grand funding in pots of gold if that was possible,

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Speaker 1: you know, rather than just like dollars in a bank account. Yeah,

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Speaker 1: but then then your grand funding is depending on gold

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Speaker 1: currency markets. What is the exchange rate between gold and science? Anyway,

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Speaker 1: I don't keep track, but he's made me think of

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Speaker 1: another question, Daniel, in a multiverse, right, technically in a

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Speaker 1: multiverse or maybe even in an infinite universe. Uh, unicorns

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Speaker 1: probably exists, right, I mean it is possible, so therefore

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Speaker 1: it must be true. It must be horses out there

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Speaker 1: in the multiverse or an infinite universe with horns in

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Speaker 1: their foreheads. Probably out there somewhere in the multiverse there

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Speaker 1: are unicorn physicists being paid to do their science in

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Speaker 1: pots of gold. Maybe even two unicorns on a podcast

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Speaker 1: talking about what it would be like if humans were

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Speaker 1: doing science instead of them humans were real, Like, maybe

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Speaker 1: humans are the unicorns in the unicorn world. If you're

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Speaker 1: already unicorns, why would you even think up humans? Right?

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Speaker 1: Are do you think of something so boring and ugly

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Speaker 1: compared to unicorns? Or maybe like regular horses are the

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Speaker 1: unicorns for them? They're like can you imagine a horse

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Speaker 1: without a horn? Or maybe it's the other direction, Maybe

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Speaker 1: they're imagining two horned horses, right, Yeah, that would be

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Speaker 1: like wild to them. That would be an imaginary and magic.

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Speaker 1: And on this podcast, we do like to use our

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Speaker 1: imagination to consider the ways that the universe might be.

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Speaker 1: After all, we are trapped on this tiny little rock

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Speaker 1: in a little corner of space, trying to understand the

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Speaker 1: entire cosmos, which requires somehow developing a model for how

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Speaker 1: it all works, and extrappling in that model out to

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Speaker 1: the very far edges of the universe, far forward in

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Speaker 1: time and far backwards in time. Because we want to

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Speaker 1: do more than just tell stories about unicorns and rainbows.

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Speaker 1: We want a mathematical story that explains what we see

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Speaker 1: in the universe and tells us what has already happened

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Speaker 1: and hopefully why. Yeah, because the nature of the universe

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Speaker 1: doesn't just affect the cosmos out there in space and

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Speaker 1: other galaxies. It affects us here and on Earth and

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Speaker 1: in our everyday lives. Every time you look up after

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Speaker 1: a nice rainfall and see a rainbow, that's physics kind

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Speaker 1: of affecting how you see the world. And I don't

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Speaker 1: want to talk more about rainbows and unicorns, but I

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Speaker 1: do think rainbows are amazing. It's incredible that this physical

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Speaker 1: effect happens, and it shimmers in the air, and it

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Speaker 1: happens so often, and it's so beautiful. It's just like,

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Speaker 1: how lucky are we to live in the universe where

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Speaker 1: such beauty occurs? Makes me wonder about the whole nature

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Speaker 1: of beauty. But that's a whole philosophical rainbow that we

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Speaker 1: definitely don't want to walk down today. What we do

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Speaker 1: want to wonder about is why the universe works this

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Speaker 1: way and what it means about the history of the

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Speaker 1: universe as well. He says, the way the universe works

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Speaker 1: affects our daily lives because it tells us about the

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Speaker 1: context of our lives. It tells us how the universe

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Speaker 1: came to be and what it means that we are here. Yeah,

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Speaker 1: and the history of humanity has been about making theories

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Speaker 1: that hopefully explain what's going on and gives us an

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Speaker 1: understanding about why things are the way they are and

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Speaker 1: how we can maybe affect them or change them, or

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Speaker 1: at least dream up of fantastical things. And while we've

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Speaker 1: made a lot of progress and understand in the nature

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Speaker 1: of the universe and its history, how it got to

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Speaker 1: look the way that it is, and wondering about how

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Speaker 1: it started, or at least the very first few moments

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Speaker 1: of it. There are still a lot of question marks

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Speaker 1: there about what happened early on, a lot of things

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Speaker 1: about our theories that don't quite make sense, leaving lots

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Speaker 1: of room for creative people to imagine all sorts of

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Speaker 1: theoretical rainbows and unicorns to fill in the gap. I

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Speaker 1: thought you didn't want to talk about rainbows anymore, Daniel,

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Speaker 1: keep bringing it up. Not literal rainbows. These are figurative

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Speaker 1: rain us now. But the arc of history is an

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Speaker 1: interesting wine, but it's not a necessarily straight line. Sometimes

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Speaker 1: we come up with theories that explain what we can

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Speaker 1: see and what we can experiment with out there, but

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Speaker 1: then later they turn out to be wrong, and that's

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Speaker 1: okay because that's part of science and it's an evolving process.

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Speaker 1: It's a really interesting distinction, for example, between math and science,

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Speaker 1: Like the science that we had two hundred years ago

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Speaker 1: is now evolved to the science we have today, and

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Speaker 1: we expect in the future we will have even crisper

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Speaker 1: ideas of how the universe works. But mathematical proofs that

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Speaker 1: were developed thousands of years ago. Those are still correct,

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Speaker 1: and we expect those to still be correct in a

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Speaker 1: few thousand years. So it's fascinating how science and math

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Speaker 1: develop sort of differently, even though science is built on math. Yeah,

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Speaker 1: and so we have theories that currently describe everything we

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Speaker 1: can see around those quantum mechanics and gravity or I

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Speaker 1: guess special relativity. But the question is are those actually right?

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Speaker 1: Do those theories actually describe the universe in all instances

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Speaker 1: or do they break down at some point? And what

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Speaker 1: does that mean about our understanding of the universe. One

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Speaker 1: of the most frustrating things about general relativity and quantum

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Speaker 1: mechanics is that they don't agree about what happens, and

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Speaker 1: maybe the most interesting moment of the universe, that is

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Speaker 1: the very first few moments when things are very high

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Speaker 1: energy and very dense, and we need both gravity and

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Speaker 1: quantum mechanics to understand what happened. Was there singularity, was

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Speaker 1: there something else? What was going on at the very

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Speaker 1: beginning of the universe. We're pretty sure that our current

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Speaker 1: theories can't be right, and so we're on the hunt

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Speaker 1: for new ideas. So today on the podcast, we'll be

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Speaker 1: tackling the question what is rainbow gravity, Daniel, is this like,

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Speaker 1: how much does a rainbow way like it is a

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Speaker 1: rainbow heavy? Can you measure the happiness in a rainbow?

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Speaker 1: How many pots of gold are generated by general relativity?

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Speaker 1: Maybe we have a new theory called golden relativity. Hey,

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Speaker 1: that sounds good. No, this is literally a theory of

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Speaker 1: the universe that predicts that gravity could make rainbows the

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Speaker 1: same way that like prisms or drops of water make

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Speaker 1: rainbows in your eyeball, Like gravity itself could bend white

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Speaker 1: light and turn it into rainbows. M I guess the

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Speaker 1: question is would those be regular rainbows or would you

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Speaker 1: need to call them like gravitational rainbows. Yeah, those would

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Speaker 1: be gravitational rainbows because you definitely wouldn't see them in

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Speaker 1: the atmosphere on Earth. This would be like something you

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Speaker 1: see in your spaceship as you're falling towards the edge

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Speaker 1: of a black hole. But this wouldn't just be like

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Speaker 1: a lens flare, like a J. J. Abrahm style lens

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Speaker 1: flare on your camera or your glasses or your spaceship window.

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Speaker 1: This would be like real black hole rainbows, real black

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Speaker 1: hole rainbows. That's right, and you don't need to ride

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Speaker 1: a unicorn across the sky to see it. If this

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Speaker 1: theory is actually true, these rainbows exist in the universe,

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Speaker 1: and they might have existed very early on, and they

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Speaker 1: could completely change the way we think about the very

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Speaker 1: first moments of the cosmos. Well, you don't need to

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Speaker 1: be writing a unicorn, but obviously anything better while you're

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Speaker 1: writing a unicorn, surely, I mean, I wouldn't know, but

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Speaker 1: ice cream is better when you're writing a unicorn, for example? Absolutely,

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Speaker 1: Well depends. Can this unicorn fly just gallop along? Because

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Speaker 1: it might be hard to eat it a lick and

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Speaker 1: ice cream cone while you're gelping. You know, I am

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Speaker 1: not an expert on the categories of unicorns. Do unicorns

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Speaker 1: come with wings or is that a pegasus? Or pegasus

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Speaker 1: is just a horse with wings? What do you call

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Speaker 1: it if it's a unicorn with wings? I think unicorns

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Speaker 1: just fly on a on a rainbow, right? Is that

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Speaker 1: what happens? Like you're galloping and then like a rainbow

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Speaker 1: bridge pops up, and then then you're flying. It's like

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Speaker 1: the by Frost and Thor and Welcome to the Science

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Speaker 1: of Unicorns, a sub episode of rainbow gravity. Well, let's

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Speaker 1: get that. You're right, let's get back on topic here.

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Speaker 1: We're talking about rainbow gravity or gravitational rainbow or what's

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Speaker 1: the right way to call this. Is there such a

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Speaker 1: thing as rainbow gravity. There is really a theory out

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Speaker 1: there in the community called rainbow gravity, and that's what

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Speaker 1: we're talking about today. We're gonna try to avoid talking

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Speaker 1: about unicorns, but I suspect the gravitational attraction of their

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Speaker 1: gorgeousness is going to pull us back in anyway. You're

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Speaker 1: saying this is sequels called unicorn gravity, lying unicorn gravity,

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Speaker 1: that's the title of my next paper on this topic. Well,

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Speaker 1: you're gonna take one theory combined with an imaginary theory

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Speaker 1: to get an X ray imaginary in some version of

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Speaker 1: the mole diverse that earns me a huge pot of

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Speaker 1: grand funding, which I get in delivery of gold coins. Well,

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Speaker 1: I'm gonna have one up. Even put wings on that unicorn.

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Speaker 1: So my theory is gonna be the rainbow unicorn pegass

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Speaker 1: gravity theory. All right, Well, then I'm gonna put horns

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Speaker 1: on the wings on that unicorn. Okay, this is kidding

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Speaker 1: a little HP Lovecraft in here, but it is an

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Speaker 1: interesting theory. This idea of rainbow gravity or gravitational rainbows?

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Speaker 1: And can gravity rainbows? So, as usual, we were wondering

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Speaker 1: how many people out there had thought about this or

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Speaker 1: maybe dreamt it in one of their dreams. So thank

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Speaker 1: you to all the people in Unicorns who volunteered to

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Speaker 1: answer these questions. We greatly appreciate it and enjoy hearing

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Speaker 1: your thoughts. If you would like to participate for a

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Speaker 1: future your episodes, please don't be shy. Right to me

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Speaker 1: two questions at Daniel and Jorge dot com. Think about

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Speaker 1: it for a second. What do you think is rainbow gravity?

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Speaker 1: He was what people had to say. Okay, So rainbows

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Speaker 1: are created by the reflection refraction of light, and the

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Speaker 1: wavelength of that light depends on what we see in

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Speaker 1: terms of its color. So rainbow gravity. If I think

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Speaker 1: of gravitational waves, maybe as those waves are passing through

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Speaker 1: or having light passed through. Um, maybe it's the effect

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Speaker 1: that the light and the different wavelengths of the light

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Speaker 1: has on those gravitational waves. Maybe I don't know. Maybe

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Speaker 1: like moist that split the light based on frequency, gravity

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Speaker 1: split the think based off their density, and you call

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Speaker 1: the outcome rainbow gravity. And well, I've definitely never heard

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Speaker 1: of rainbow gravity. So my best guess is that it

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Speaker 1: is something that has to do with the way gravity

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Speaker 1: effects light. Um, maybe it's a property of gravitational lensing.

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Speaker 1: Oh jeez, I do not know. I would imagine that

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Speaker 1: it has to do with the spectrum of light and

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Speaker 1: how gravity could affect light, but I'm not sure. Maybe

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Speaker 1: how gravity could split light. All right, we got a

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Speaker 1: nice spectrum of answers here, very colorful, powerful. Yeah that

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Speaker 1: was low hanging fruit. But yeah, a lot of some

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Speaker 1: people have never heard of it, and some people had

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Speaker 1: some pretty good ideas, like it's maybe gravity causing lensing,

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Speaker 1: which might create a rainbow effect. Yeah, exactly. This seems

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Speaker 1: to be a well named theory because it inspired some

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Speaker 1: good ideas and listeners. Well, I would obviously disagree, but

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Speaker 1: that's never stop physicists from naming things in counterintuitive ways.

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Speaker 1: Let's see how this goes, Daniel, I mean rainbow gravity,

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Speaker 1: but it is gravity actually a rainbow? I don't know.

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Speaker 1: It's a really fun theory that tries to solve a

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Speaker 1: problem at the heart of physics, the connection between general

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Speaker 1: relativity and quantum mechanics, or more specifically, the lack of

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Speaker 1: the connection along the way predicts beautiful events like rain

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Speaker 1: those popping out of black holes, wait out of black holes,

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Speaker 1: that would be impossible, or maybe that gets it's the rainbow,

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Speaker 1: so maybe it's magical. Perhaps I should have said at

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Speaker 1: the edge of black holes, Well, let's dig into it.

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Speaker 1: Um you said, it's a new theory or a potential

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Speaker 1: theory that's out there in the physics community that maybe

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Speaker 1: try to explain the intersection between quantum mechanics and gravity,

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Speaker 1: because those two things are not quite compatible with each other, right, Yeah,

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Speaker 1: all of modern physics is built on these two ideas,

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Speaker 1: quantum mechanics and general relativity. But at their hearts, these

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Speaker 1: two theories are incompatible. They have completely different views of

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Speaker 1: the world. Even though they're in philosophical contradiction with each other,

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Speaker 1: they've survived together as twin pillars of our theory of

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Speaker 1: physics because they're never actually relevant at the same time.

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Speaker 1: So you can use gravity talk about really big, massive things,

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Speaker 1: and you can use quantum mechanics talk about really small things,

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Speaker 1: and you never really need to use both at the

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Speaker 1: same time. So they've sort of survived without having to

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Speaker 1: talk to each other. They're like a married couple that

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Speaker 1: turned into roommates. Well that's kind of said, Well, you know,

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Speaker 1: if they do try to talk to each other, it's

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Speaker 1: gonna be a big argument, so they just try to

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Speaker 1: avoid it. Why did another physics theoretical committee was um

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Speaker 1: dysfunctional and ahead of for our potential split in the future.

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Speaker 1: It's not all rainbows and unicorns. Man, all right, well,

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Speaker 1: maybe I can help us understand this a little bit.

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Speaker 1: Where is that incompatibility? Is it just that you do

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Speaker 1: is this haven't been able to make it work in

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Speaker 1: the mathematical way, or is it is there something fundamental

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Speaker 1: about how they view the universe that is just totally incompatible.

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Speaker 1: So there's something fundamental about the way they view the

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Speaker 1: universe that is just incompatible. We'll talk about exactly what

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Speaker 1: that is in a minute. And all attempts so far

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Speaker 1: to unify them have failed. Mathematically just do not work.

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Speaker 1: So that's essentially what the struggle is. And so let's

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Speaker 1: start with quantum mechanics. Quantum mechanics specifically quantum field theory,

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Speaker 1: which is this description we talked about in the podcast.

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Speaker 1: A lot of space being filled with quantum fields, and

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Speaker 1: particles are like ripples in those fields that propagate through

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Speaker 1: space and to with each other. That's very, very successful, right.

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Speaker 1: It's an amazing theory. It describes all of the particle

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Speaker 1: experiments that we've done. It's made very specific predictions of

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Speaker 1: numbers like ten decimal places that have all been verified experimentally.

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Speaker 1: It seems like a very accurate description of what happens

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Speaker 1: to particles. But it assumes that space is not curved,

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Speaker 1: that space is flat, that the shortest distance between two

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Speaker 1: points is always what appears to us to be a

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Speaker 1: straight line, and operating in flat space essentially means that

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Speaker 1: we're ignoring gravity. Quantum field theory is very successful because

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Speaker 1: basically gravity is irrelevant. If you have two particles and

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Speaker 1: they're pushing against each other with powerful forces, you don't

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Speaker 1: really care about the gravitational effects on two electrons because

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Speaker 1: gravity is so weak compared to the other forces. So

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Speaker 1: quantum field theory assumes that gravity is irrelevant and does

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Speaker 1: a great job of describing what happens to quantum particles. Right.

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Speaker 1: Quantum mechanics assumes a flat, spased universe, but general relativity

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Speaker 1: kind of assumes the opposite. Yeah, general relativity tells us

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Speaker 1: that the reason we have gravity is not because there's

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Speaker 1: some force out there tugging on masses, but that space

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Speaker 1: bends that when you put mass into a space, it

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Speaker 1: curves space. And this is not curvature like relative to

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Speaker 1: some external ruler. This is intrinsic curvature, which means that

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Speaker 1: it changes the relative distances between points, and effectively, it

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Speaker 1: makes the shortest distance between two points seem to us

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Speaker 1: like a curve because we can't see this curvature directly,

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Speaker 1: and so it appears to us like there's a force

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Speaker 1: because things are moving along these curves. In reality, it's

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Speaker 1: just the curvature of space. But general relativity assumes that

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Speaker 1: everything has a specific location and velocity, and that can

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Speaker 1: be perfectly well known. We call it a classical theory

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Speaker 1: because it ignores the quantum mechanical nature of the world,

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Speaker 1: the fact that particles, for example, can't be pinned down

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Speaker 1: to have a specific location and velocity at all times.

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Speaker 1: They don't have a trajectory like that. But general relativity

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Speaker 1: assumes that everything does. Fortunately, because gravity is so weak,

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Speaker 1: we've only tested general relativity in scenarios where you have

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Speaker 1: a huge mass like a planet or a star or

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Speaker 1: a black hole, where you can basically ignore quantum mechanics,

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Speaker 1: so they sort of have each their own domains. They

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Speaker 1: view the world very very differently. They make totally different,

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Speaker 1: incompatible assumptions about the world, and they make predictions about

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Speaker 1: different parts of the world, and they're both correct in

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Speaker 1: their own regimes, right, Although I guess, you know, coming

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Speaker 1: at this from the outside, not having been too in mercendies,

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Speaker 1: they don't sound that incompatible to me. I guess it's

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Speaker 1: maybe that's one of that something other people struggle with.

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Speaker 1: I mean, it's sort of like one of them says

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Speaker 1: that Daniel is tall, and the other one says Daniel

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Speaker 1: wards glasses like those are not necessarily incompatible. Things like

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Speaker 1: couldn't quantum fields exists in space that is also bending,

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Speaker 1: And couldn't bending space exists in also in the universe

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Speaker 1: where particles have a minimum size and are uncertain. Yeah,

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Speaker 1: we think that probably it's possible to describe both because

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Speaker 1: the universe exists and it seems to be self consistent.

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Speaker 1: So we think it probably is possible to reconcile gravity

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Speaker 1: and quantum mechanics because both things are happening in our world.

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Speaker 1: We haven't been able to do that, Like light is

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Speaker 1: being bent around the Sun and it's being bent around

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Speaker 1: black holes. And we know light is quantized as well.

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Speaker 1: Right well, let me give you an example of something

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Speaker 1: that we can't do because we can't unify gravity and

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Speaker 1: quantum mechanics, is that we don't know how to calculate

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Speaker 1: the gravity of particles. Quantum particles, for example, don't have

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Speaker 1: a specific location that have probabilities to be in different locations,

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Speaker 1: Like electron could be on the other side of the

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Speaker 1: room or could be right next to you. What is

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Speaker 1: the gravity of that electron whose position is uncertain? General

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Speaker 1: relativity doesn't allow for any uncertainty in the position. It

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Speaker 1: says your gravity depends on where you are. If where

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Speaker 1: you are is uncertain, then where is your gravity? Is

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Speaker 1: your gravity also uncertain or is it shared between the

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Speaker 1: two different locations? Does gravity collapse that wave function forcing

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Speaker 1: the electron to be in one spot from where it's

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Speaker 1: gravity emanates, or is have any quantum mechanical and it

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Speaker 1: allows the superposition of different gravitational attractions. That's something we

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Speaker 1: don't know the answer to. That's something we can't calculate

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Speaker 1: right now because we don't have a theory that does

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Speaker 1: gravity for quantum objects. Right, But I guess you know,

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Speaker 1: particle has some uncertain to it to it in terms

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Speaker 1: of where it is and where it's going. But if

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Speaker 1: you step back far enough, it does have sort of

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Speaker 1: a location, right. I mean, you step back far enough

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Speaker 1: from a particle, you can calculate what its gravity is. Yeah,

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Speaker 1: if you step back far enough or you love enough

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Speaker 1: particles together, then they start to act like classical objects

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Speaker 1: like a baseball. Baseball effectively has no uncertainty on where

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Speaker 1: it is and it's velocity because it acts like a

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Speaker 1: classical object, which is ten to twenty six quantum objects

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Speaker 1: all moving together. And so general relativity assumes that that

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Speaker 1: is still true the baseball description of the world when

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Speaker 1: you get down to one electron. But we know that

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Speaker 1: one electron doesn't move like a baseball. It doesn't have

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Speaker 1: a whole path, and so we don't know how to

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Speaker 1: talk about like how two electrons interact with each other gravitationally,

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Speaker 1: And we can't usted either. We can't just go and

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Speaker 1: look and watch two electrons pushing against each other gravitationally

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Speaker 1: because the gravitational force is so weak that we could

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Speaker 1: never measure that. And so it's a big question. Right.

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Speaker 1: But you, for example, you are able to, for example,

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Speaker 1: calculate the force between two electrons to like the electromagnetic

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Speaker 1: force between two electrons, right, Like, you can do that,

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Speaker 1: I guess the question is why can't you do it

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Speaker 1: with gravity, Like why can't you juice kind of like

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Speaker 1: average it out or use probability to figure out what

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Speaker 1: the most probable gravity is. So we can calculate the

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Speaker 1: gravitational force between two electrons if their positions are known,

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Speaker 1: but because they're quantum objects, we don't know their positions.

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Speaker 1: So what you're proposing, basically, is a theory of quantum

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Speaker 1: gravity that says gravity is a quantum force and interacts

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Speaker 1: not with the location of the objects but with their probabilities,

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Speaker 1: that it actually interacts with the wave functions of these guys.

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Speaker 1: So they're trying to turn gravity into a quantum field theory,

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Speaker 1: which is fine and that's cool, and a lot of

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Speaker 1: people are working on that. But when you do that,

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Speaker 1: you run into a lot of mathematical problems. Basically, you

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Speaker 1: get lots of infinities when you try to do these calculations,

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Speaker 1: and we get infinities when we do all quantum field theories.

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Speaker 1: Like we talked on the podcast about something called renormalization

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Speaker 1: where we tuck infinities under the rug. For example, the

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Speaker 1: true charge of the electron, if you look at it

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Speaker 1: really really close, seems to be negative infinity, which makes

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Speaker 1: no sense. But you can sort of like wrap it

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Speaker 1: in a cloud of particles and renormalize it and subtract

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Speaker 1: away that infinity and say that's all fine. You can't

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Speaker 1: do that for gravity, because you get an infinite number

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Speaker 1: of those infinities. Gravity couples to itself and it couples

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Speaker 1: to everything, and so it just sort of goes crazy,

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Speaker 1: and we just don't know how to do those calculations.

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Speaker 1: We don't have the mathematical framework that can successfully do that.

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Speaker 1: Something has to change when particles have a really really

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Speaker 1: high energy in order for those infinities to go away,

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Speaker 1: all right, So that it's hard from you, uh, and

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Speaker 1: nobody has been able to do it. But there is

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Speaker 1: maybe a new theory or a theory out there that

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Speaker 1: does seem to have maybe a magical solution to this problem,

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Speaker 1: gravitational rainbows or rainbow gravity, and so let's dig into

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Speaker 1: the details of that. But first let's take a quick break. Alright,

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Speaker 1: we're talking about rainbow gravity, which sounds great. Who doesn't

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Speaker 1: want gravity to have its own, you know, spectrum of awesomeness. Yeah, exactly.

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Speaker 1: It's a very colorful theory. And you know, during the break,

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Speaker 1: I went off and did a little bit of research,

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Speaker 1: and I discovered the answer to one of the open

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Speaker 1: questions we left dangling before. Is the answer unicorns? You know,

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Speaker 1: the answer actually is alcorn, and alcorn is a unicorn

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Speaker 1: with wings or a pegasus with a horn. There's a

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Speaker 1: name for this thing. So somebody already did that theory.

428
00:22:45,920 --> 00:22:48,119
Speaker 1: I think it's my little pony universe that might have

429
00:22:48,160 --> 00:22:49,920
Speaker 1: coined this phrase. What if I crossed it with a

430
00:22:50,000 --> 00:22:53,679
Speaker 1: lion that and then like a griffin unicorn pegasus. I

431
00:22:53,680 --> 00:22:55,960
Speaker 1: think we better trademark that and start selling plush dollars

432
00:22:56,000 --> 00:23:00,840
Speaker 1: of those lion ala corn maybe griffin corn. But we

433
00:23:00,880 --> 00:23:04,160
Speaker 1: are talking about rainbow gravity, which sounds great, and it's

434
00:23:04,200 --> 00:23:08,199
Speaker 1: maybe a theory that tries to unify quantum mechanics and

435
00:23:08,359 --> 00:23:10,720
Speaker 1: general relativity, which are the two big theories that try

436
00:23:10,760 --> 00:23:13,359
Speaker 1: to explain us, which don't quite match up when you

437
00:23:13,400 --> 00:23:16,240
Speaker 1: get to certain situations. Daniel, we talked about how quantum

438
00:23:16,240 --> 00:23:19,000
Speaker 1: mechanics is not good at describing gravity, and we talked

439
00:23:19,000 --> 00:23:21,480
Speaker 1: about how general relativity is not good at describing things

440
00:23:21,520 --> 00:23:24,720
Speaker 1: at the microscopic level exactly, and most of the time

441
00:23:24,840 --> 00:23:28,399
Speaker 1: they don't conflict because quantum mechanics is king of the

442
00:23:28,440 --> 00:23:32,119
Speaker 1: microscopic particles and gravity is king of the big massive stuff.

443
00:23:32,440 --> 00:23:35,720
Speaker 1: But there are scenarios we think when gravity and quantum

444
00:23:35,720 --> 00:23:40,320
Speaker 1: mechanics are both important. One of those is inside black holes,

445
00:23:40,560 --> 00:23:44,440
Speaker 1: where things are obviously very powerful gravitationally, but they're also

446
00:23:44,520 --> 00:23:48,399
Speaker 1: compressed to super tiny little divots. Right, if there is

447
00:23:48,440 --> 00:23:50,920
Speaker 1: a singularity at the hart of a black hole, then

448
00:23:50,960 --> 00:23:54,080
Speaker 1: that's small enough to be a quantum mechanical object. So

449
00:23:54,160 --> 00:23:56,960
Speaker 1: general relativity and quantum mechanics both have something to say

450
00:23:57,000 --> 00:23:59,920
Speaker 1: about what happens there. We can't see inside black hole,

451
00:24:00,080 --> 00:24:02,240
Speaker 1: and so we're left only just wondering about what's going

452
00:24:02,280 --> 00:24:05,480
Speaker 1: on inside. But there are scenarios outside of black holes

453
00:24:05,640 --> 00:24:08,720
Speaker 1: where we think both general relativity and quantum mechanics have

454
00:24:08,920 --> 00:24:11,560
Speaker 1: something to say, and that's the case of very very

455
00:24:11,640 --> 00:24:14,439
Speaker 1: high energy particles. Yeah, but I guess I wonder if

456
00:24:14,480 --> 00:24:16,440
Speaker 1: you need to go that extreme just to kind of

457
00:24:16,560 --> 00:24:19,760
Speaker 1: see where the two theories take effect, right, because I

458
00:24:19,800 --> 00:24:23,679
Speaker 1: think Einstein kind of famously proved general relativity, or at

459
00:24:23,760 --> 00:24:26,360
Speaker 1: least the bending of space by looking at how light

460
00:24:26,480 --> 00:24:30,440
Speaker 1: bends around solar eclipse, for example. We know that light

461
00:24:30,600 --> 00:24:34,000
Speaker 1: is quantized, it follows quantum mechanical rules. So isn't that

462
00:24:34,000 --> 00:24:38,560
Speaker 1: an example for example of a quantized thing following gravity

463
00:24:38,800 --> 00:24:41,960
Speaker 1: technically as opposed but technically everything is a quantized thing.

464
00:24:42,119 --> 00:24:44,680
Speaker 1: You are a quantized thing. I am a quantized thing.

465
00:24:44,760 --> 00:24:47,199
Speaker 1: We are affected by the Earth's gravity. You know, in

466
00:24:47,240 --> 00:24:50,720
Speaker 1: that case, they're not relying on the quantum nature of light.

467
00:24:51,000 --> 00:24:53,800
Speaker 1: Light could have just been classical electromagnetic waves and the

468
00:24:53,840 --> 00:24:57,160
Speaker 1: same thing would have happened, because in that scenario, light

469
00:24:57,280 --> 00:25:00,760
Speaker 1: is moving through curved space, and so light everything else

470
00:25:01,000 --> 00:25:03,960
Speaker 1: would move in a curve. So you're not relying on

471
00:25:04,000 --> 00:25:06,800
Speaker 1: the quantum nature of the object there. So like a

472
00:25:06,880 --> 00:25:10,440
Speaker 1: quantized particle like light or an electron, it can move

473
00:25:10,520 --> 00:25:13,200
Speaker 1: through bent space, but due to gravity, you know, I

474
00:25:13,240 --> 00:25:15,960
Speaker 1: mean you can you have the mass to describe a

475
00:25:16,040 --> 00:25:20,000
Speaker 1: single particle, single quantum particle moving through bent space. That

476
00:25:20,119 --> 00:25:23,000
Speaker 1: possible or is that is not possible? That's certainly possible,

477
00:25:23,240 --> 00:25:25,240
Speaker 1: But there you're not relying on the gravity of the

478
00:25:25,320 --> 00:25:28,520
Speaker 1: quantum particle. You have something else something really big and

479
00:25:28,600 --> 00:25:30,680
Speaker 1: massive like the Earth or the Sun or the Moon

480
00:25:30,800 --> 00:25:33,639
Speaker 1: or a black hole that's doing the bending. And so

481
00:25:33,680 --> 00:25:36,720
Speaker 1: we do know how to talk about quantum particles moving

482
00:25:36,840 --> 00:25:40,360
Speaker 1: through bent space that we can calculate or we don't

483
00:25:40,359 --> 00:25:43,840
Speaker 1: know how to calculate is the gravity of those particles

484
00:25:43,880 --> 00:25:46,639
Speaker 1: and how that contributes to bent space? Right? But doesn't

485
00:25:46,640 --> 00:25:50,600
Speaker 1: the bending a space depend on the gravity on the particle? Right,

486
00:25:50,680 --> 00:25:53,679
Speaker 1: Like technically you're talking about space time, right, Like if

487
00:25:53,680 --> 00:25:55,159
Speaker 1: I throw a baseball at the Sun, it's not going

488
00:25:55,200 --> 00:25:57,800
Speaker 1: to curve the same way that a photon is going

489
00:25:57,840 --> 00:26:00,280
Speaker 1: to curve. Right, So, like eat, the bend thing of

490
00:26:00,320 --> 00:26:03,800
Speaker 1: space depends on the thing that's moving. So if you

491
00:26:03,800 --> 00:26:08,520
Speaker 1: can calculate the bending of space for a particle, what's

492
00:26:08,560 --> 00:26:11,600
Speaker 1: worth the contradiction there? Well, because there you're ignoring the

493
00:26:11,640 --> 00:26:14,760
Speaker 1: gravity of the object, like you're through a baseball or

494
00:26:14,800 --> 00:26:17,480
Speaker 1: a photon near the Moon. You're not taking to account

495
00:26:17,520 --> 00:26:20,440
Speaker 1: the bending of space due to the baseball or due

496
00:26:20,440 --> 00:26:23,359
Speaker 1: to the photon. You're just calculate the trajectory of a

497
00:26:23,400 --> 00:26:26,320
Speaker 1: test particle through the bent space due to the Moon

498
00:26:26,480 --> 00:26:28,920
Speaker 1: or due to the black hole. You're not taking to

499
00:26:29,000 --> 00:26:31,800
Speaker 1: account the gravity of the object itself. Don't you need

500
00:26:31,840 --> 00:26:34,040
Speaker 1: that to calculate how it's going to curve around how

501
00:26:34,080 --> 00:26:36,480
Speaker 1: it's gonna bend around the Moon. Now, you just need

502
00:26:36,520 --> 00:26:38,439
Speaker 1: to know it's inertial mass. You don't need to know

503
00:26:38,600 --> 00:26:41,280
Speaker 1: the effect of it on space time itself. You just

504
00:26:41,320 --> 00:26:43,480
Speaker 1: need to understand what it's inertia is and so that

505
00:26:43,480 --> 00:26:46,800
Speaker 1: you're can understand how it moves through bent space. M

506
00:26:46,520 --> 00:26:48,520
Speaker 1: M I see. So the real problem is not in

507
00:26:48,640 --> 00:26:51,719
Speaker 1: like how to calculate how quantum particles move through bent space,

508
00:26:52,119 --> 00:26:57,120
Speaker 1: but more about how quantum particles give off gravity or

509
00:26:57,359 --> 00:27:00,280
Speaker 1: you know, how they attract other particles through gravity. Yes,

510
00:27:00,359 --> 00:27:03,080
Speaker 1: do they bend space exactly? And and do they bend

511
00:27:03,119 --> 00:27:05,960
Speaker 1: space where they are or where they might be. That's

512
00:27:06,000 --> 00:27:08,119
Speaker 1: really the question, all right, So then talk to us

513
00:27:08,320 --> 00:27:11,440
Speaker 1: about this new theory rainbow gravity. So the problem comes

514
00:27:11,520 --> 00:27:14,080
Speaker 1: up at very very high energies. If you have particles

515
00:27:14,080 --> 00:27:18,159
Speaker 1: with super duper crazy high energies, energies like the plant

516
00:27:18,280 --> 00:27:21,240
Speaker 1: energy or energies that particles had at the very beginning

517
00:27:21,320 --> 00:27:23,280
Speaker 1: of the universe, they have so much energy that their

518
00:27:23,280 --> 00:27:26,360
Speaker 1: gravity starts to not be ignorable. Usually when you talk

519
00:27:26,359 --> 00:27:28,920
Speaker 1: about like two protons bouncing against each other. You can

520
00:27:28,960 --> 00:27:31,960
Speaker 1: ignore the gravitational effects, but if those two protons have

521
00:27:32,200 --> 00:27:36,600
Speaker 1: enough energy, then their gravity becomes really really powerful. Because remember,

522
00:27:36,880 --> 00:27:39,800
Speaker 1: gravity is the bending of space time in response not

523
00:27:39,880 --> 00:27:42,600
Speaker 1: just to mass, but in response to energy. And so

524
00:27:42,680 --> 00:27:45,240
Speaker 1: take for example, two particles and collide them at super

525
00:27:45,280 --> 00:27:48,159
Speaker 1: duper high energy, much higher energy than we've done before,

526
00:27:48,440 --> 00:27:50,959
Speaker 1: you might get, for example, a black hole, or at

527
00:27:51,000 --> 00:27:53,800
Speaker 1: least you have to take into account the gravitational interaction.

528
00:27:53,920 --> 00:27:56,600
Speaker 1: So we think that maybe the solution to this problem

529
00:27:56,640 --> 00:28:00,000
Speaker 1: lies in understanding what happens to particles at very very

530
00:28:00,080 --> 00:28:04,280
Speaker 1: high energy, and rainbow gravity says, maybe a very high energy,

531
00:28:04,359 --> 00:28:07,640
Speaker 1: the rules change a little bit, and gravity for those

532
00:28:07,680 --> 00:28:11,240
Speaker 1: really high energies is a little bit different. What so,

533
00:28:11,280 --> 00:28:15,760
Speaker 1: as a particle gets moving faster and faster, it accumulates energy, right,

534
00:28:15,800 --> 00:28:18,840
Speaker 1: that's what you're saying. And for when you have that

535
00:28:18,920 --> 00:28:21,480
Speaker 1: much energy in the small package, then you kind of

536
00:28:21,480 --> 00:28:25,280
Speaker 1: have to think about how that affects gravity because gravity,

537
00:28:25,359 --> 00:28:28,280
Speaker 1: I mean, we always talk about gravity being a function

538
00:28:28,320 --> 00:28:30,159
Speaker 1: of mass, like the more mass you have, the more

539
00:28:30,200 --> 00:28:32,239
Speaker 1: gravity you have, but it's really just about how much

540
00:28:32,359 --> 00:28:34,520
Speaker 1: energy you have, right, Like the bending of space is

541
00:28:34,600 --> 00:28:36,720
Speaker 1: due to the energy that you have, yes, due to

542
00:28:36,840 --> 00:28:40,320
Speaker 1: energy density, not literally mass. Mass is a component of

543
00:28:40,360 --> 00:28:43,960
Speaker 1: the energy density, but it's not the only contribution. Right. So,

544
00:28:44,000 --> 00:28:46,400
Speaker 1: now you have like a quantum particle. It's moving really fast,

545
00:28:46,440 --> 00:28:48,280
Speaker 1: but it has a lot of energy in a small place.

546
00:28:48,320 --> 00:28:52,320
Speaker 1: But it's quantum, so there are some uncertainties to it.

547
00:28:52,560 --> 00:28:54,680
Speaker 1: And so now the question is like, can you explain

548
00:28:54,720 --> 00:28:58,360
Speaker 1: gravity in that situation. Yeah, So rainbow gravity theory says,

549
00:28:58,760 --> 00:29:02,200
Speaker 1: let's change the rules gravity as you move up in energy.

550
00:29:02,360 --> 00:29:05,120
Speaker 1: That currently we think that all particles feel gravity the

551
00:29:05,160 --> 00:29:06,880
Speaker 1: same way. If, for example, you have a big massive

552
00:29:06,880 --> 00:29:09,960
Speaker 1: objects and it's bending space, and you shoot a red

553
00:29:09,960 --> 00:29:13,000
Speaker 1: photon through it or a green photon through it, those

554
00:29:13,040 --> 00:29:15,880
Speaker 1: things will bend around that object the same way. They'll

555
00:29:16,000 --> 00:29:18,840
Speaker 1: end up at the same place. Right that all different

556
00:29:18,920 --> 00:29:21,600
Speaker 1: energies of photons all get bent the same way because

557
00:29:21,640 --> 00:29:23,680
Speaker 1: they all see the same curvature of space. They're like

558
00:29:23,800 --> 00:29:26,320
Speaker 1: running along the same track. But wait, don't each of

559
00:29:26,360 --> 00:29:28,800
Speaker 1: those photons have a different amount of energy. Yeah, but

560
00:29:28,840 --> 00:29:32,520
Speaker 1: remember we're not considering the gravitational effect of the particle,

561
00:29:32,680 --> 00:29:35,320
Speaker 1: just of the other object that's curving space, that's guiding

562
00:29:35,360 --> 00:29:39,200
Speaker 1: these particles. We're ignoring the gravitational effect of those particles,

563
00:29:39,280 --> 00:29:42,320
Speaker 1: and the rainbow gravity says, what if that's not true?

564
00:29:42,720 --> 00:29:46,320
Speaker 1: What if as you move through space, how much curvature

565
00:29:46,360 --> 00:29:49,800
Speaker 1: you see depends on your energy. So for example, maybe

566
00:29:49,800 --> 00:29:52,680
Speaker 1: a red photon and a green photon see a different

567
00:29:52,720 --> 00:29:56,760
Speaker 1: amount of curvature. That somehow, the curvature you see depends

568
00:29:56,920 --> 00:30:00,680
Speaker 1: on your energy, and so as the photons wavelength or

569
00:30:00,680 --> 00:30:03,200
Speaker 1: its color, or its energy, these are all equivalent changes

570
00:30:03,440 --> 00:30:06,280
Speaker 1: you see different curvature. If that happens, then if you take,

571
00:30:06,320 --> 00:30:08,520
Speaker 1: for example, a beam of white light and you bend

572
00:30:08,560 --> 00:30:11,440
Speaker 1: it around a black hole, each different wavelength would get

573
00:30:11,480 --> 00:30:15,520
Speaker 1: bent a different amount, resulting in a rainbow. So the

574
00:30:15,600 --> 00:30:19,000
Speaker 1: idea of rainbow gravity is to say, maybe gravity depends

575
00:30:19,040 --> 00:30:21,400
Speaker 1: on the energy of the particle in this way, so

576
00:30:21,440 --> 00:30:23,680
Speaker 1: they see a different amount of curvature, which would change

577
00:30:23,720 --> 00:30:27,160
Speaker 1: how things happen at very very high energies. You're saying,

578
00:30:27,160 --> 00:30:31,840
Speaker 1: like many, gravity is not constant throughout all situations, like somehow,

579
00:30:31,880 --> 00:30:35,480
Speaker 1: gravity is you know, depending on how fast you're going. Technically,

580
00:30:35,560 --> 00:30:38,440
Speaker 1: this is called an energy dependent metric. Metric is like

581
00:30:38,560 --> 00:30:41,960
Speaker 1: the curvature of space in general relativity theory, and so

582
00:30:42,120 --> 00:30:44,440
Speaker 1: typically that metric is constant, doesn't depend on what your

583
00:30:44,520 --> 00:30:46,880
Speaker 1: energy is. But now they say, well, let's take that

584
00:30:46,920 --> 00:30:49,520
Speaker 1: metric and make it energy dependent. Let's say that if

585
00:30:49,520 --> 00:30:52,000
Speaker 1: you're moving through the universe, you might see different curvature

586
00:30:52,120 --> 00:30:56,000
Speaker 1: depending on the energy you have. But then isn't like

587
00:30:56,200 --> 00:30:59,280
Speaker 1: mass the same as energy? Right? So are you saying

588
00:30:59,280 --> 00:31:01,320
Speaker 1: that if I have or or less mass, I'm going

589
00:31:01,360 --> 00:31:04,760
Speaker 1: to see space bend differently. I think that's probably true.

590
00:31:05,160 --> 00:31:09,160
Speaker 1: Very very massive particles would see space meant differently than

591
00:31:09,320 --> 00:31:12,600
Speaker 1: lower mass particles. Okay, so the ideas that gravity is

592
00:31:12,600 --> 00:31:14,920
Speaker 1: different depending on how fast you're moving or how much

593
00:31:15,000 --> 00:31:17,840
Speaker 1: energy or mass you have, which is very different than

594
00:31:17,880 --> 00:31:20,040
Speaker 1: what we we how we think about it now? Right

595
00:31:20,520 --> 00:31:24,960
Speaker 1: right now, general relativity says that gravity is the same everywhere. Exactly.

596
00:31:25,000 --> 00:31:27,560
Speaker 1: It says that gravity is the same everywhere. And you

597
00:31:27,640 --> 00:31:29,400
Speaker 1: might be wondering, like, well, how does this solve the

598
00:31:29,400 --> 00:31:32,520
Speaker 1: problem of general relativity and quantum mechanics. It's not exactly

599
00:31:32,560 --> 00:31:35,280
Speaker 1: a solution. It's just sort of like maybe in this

600
00:31:35,400 --> 00:31:39,760
Speaker 1: direction a solution lies. It's sort of like exploratory. Remember,

601
00:31:39,800 --> 00:31:42,760
Speaker 1: you know we talked about sciences and developing process We

602
00:31:42,800 --> 00:31:45,480
Speaker 1: don't always have like the final answer all at once.

603
00:31:45,800 --> 00:31:48,160
Speaker 1: Sometimes what we do is we say, what's in this direction,

604
00:31:48,280 --> 00:31:50,360
Speaker 1: and what happens if we try this kind of thing?

605
00:31:50,680 --> 00:31:52,680
Speaker 1: Does this lead to a solution? And so it's not

606
00:31:52,720 --> 00:31:55,560
Speaker 1: clear yet whether this might lead to a solution, but

607
00:31:55,600 --> 00:31:57,400
Speaker 1: there's a little bit of a sketch of an argument

608
00:31:57,440 --> 00:31:59,840
Speaker 1: for why it might. People have this idea for how

609
00:31:59,880 --> 00:32:02,400
Speaker 1: to solve the problem of like what's the gravity of

610
00:32:02,440 --> 00:32:05,840
Speaker 1: an uncertain quantum particle, of saying maybe the curvature itself

611
00:32:05,920 --> 00:32:08,880
Speaker 1: has uncertainty, like I think you were saying earlier, if

612
00:32:08,920 --> 00:32:12,080
Speaker 1: an electron has uncertainty and it's bending space time, then

613
00:32:12,120 --> 00:32:15,640
Speaker 1: maybe spacetime itself has an uncertainty, a quantum uncertainty, like

614
00:32:15,680 --> 00:32:17,920
Speaker 1: maybe we live in this universe with this bent spacetime,

615
00:32:18,000 --> 00:32:20,720
Speaker 1: or maybe we live in that universe with that bent spacetime.

616
00:32:20,840 --> 00:32:22,840
Speaker 1: So people have done a bunch of calculations and shown

617
00:32:23,160 --> 00:32:26,640
Speaker 1: that if the curvature itself has some uncertainty, it would

618
00:32:26,720 --> 00:32:30,480
Speaker 1: lead to an energy dependence of that curvature, Basically that

619
00:32:30,560 --> 00:32:33,760
Speaker 1: particles moving through the universe with different energies would see

620
00:32:33,840 --> 00:32:37,320
Speaker 1: different aspects of this uncertainty. So this is like saying,

621
00:32:37,560 --> 00:32:40,520
Speaker 1: if space itself has some uncertainty, then you might get

622
00:32:40,520 --> 00:32:43,680
Speaker 1: this kind of effect for very high energy particles I see,

623
00:32:43,680 --> 00:32:47,600
Speaker 1: because you sort of maybe need gravity to be not

624
00:32:47,800 --> 00:32:51,600
Speaker 1: constant throughout the universe, because you know, if these particles

625
00:32:51,640 --> 00:32:54,160
Speaker 1: are quantum, that means they're here and they're there. And

626
00:32:54,200 --> 00:32:56,640
Speaker 1: if they're here and there, then that can't mean that

627
00:32:56,720 --> 00:33:00,400
Speaker 1: they have gravity here and they have gravity there. Or

628
00:33:00,560 --> 00:33:03,440
Speaker 1: but maybe if gravity is different in the two situations,

629
00:33:03,440 --> 00:33:06,080
Speaker 1: then it's like maybe has half gravity here half every there,

630
00:33:06,120 --> 00:33:09,720
Speaker 1: which kind of makes a full one gravity. Yeah, exactly,

631
00:33:09,920 --> 00:33:11,760
Speaker 1: And we don't know, right We do not know if

632
00:33:11,800 --> 00:33:14,800
Speaker 1: gravity operates that way, if it really can be probabilistic

633
00:33:14,880 --> 00:33:17,600
Speaker 1: or not. This is an attempt to incorporate that quantum

634
00:33:17,640 --> 00:33:20,239
Speaker 1: uncertainty into the theory of gravity. And if you do

635
00:33:20,280 --> 00:33:22,880
Speaker 1: the calculations and say what happens to particles moving to

636
00:33:23,120 --> 00:33:26,320
Speaker 1: space that's uncertain, how do they bend? It turns out

637
00:33:26,360 --> 00:33:29,320
Speaker 1: that particles at different energies interact with that space different

638
00:33:29,320 --> 00:33:32,160
Speaker 1: that that's see a different slice of that uncertainty. So

639
00:33:32,240 --> 00:33:35,600
Speaker 1: particles with really high energy would bend differently than particles

640
00:33:35,640 --> 00:33:38,600
Speaker 1: with low energy as they move through that uncertain space,

641
00:33:39,000 --> 00:33:41,479
Speaker 1: and that gives you rainbows and again, how does that

642
00:33:41,520 --> 00:33:44,600
Speaker 1: help bring together quantum mechanics and gravity. If this is

643
00:33:44,600 --> 00:33:46,600
Speaker 1: true and you see it and you confirm it's actually

644
00:33:46,680 --> 00:33:48,760
Speaker 1: part of our universe, for example, it gives you a

645
00:33:48,800 --> 00:33:52,560
Speaker 1: very strong hint. It tells you that spacetime itself is uncertain.

646
00:33:52,800 --> 00:33:55,760
Speaker 1: One possibility is that gravity is quantum mechanical, right, that

647
00:33:55,880 --> 00:33:58,400
Speaker 1: spacetime has uncertainty to it, that we live in a

648
00:33:58,480 --> 00:34:01,719
Speaker 1: universe where spacetime can have two different possibilities and they

649
00:34:01,760 --> 00:34:04,560
Speaker 1: get collapsed when you test them. Right. The other is

650
00:34:04,560 --> 00:34:07,120
Speaker 1: that gravity is not quantum mechanical, and that gravity itself

651
00:34:07,120 --> 00:34:11,319
Speaker 1: collapses those wave functions that when two electrons interact gravitationally,

652
00:34:11,680 --> 00:34:15,240
Speaker 1: their wave functions don't interact. They collapse each other's wave functions.

653
00:34:15,440 --> 00:34:18,319
Speaker 1: And then electron has a location here in another location there,

654
00:34:18,320 --> 00:34:21,000
Speaker 1: and you have very specific sort of classical gravity. So

655
00:34:21,120 --> 00:34:23,840
Speaker 1: if we see rainbow gravity, that tells us that gravity

656
00:34:23,880 --> 00:34:28,680
Speaker 1: can accommodate uncertain space times, and that single particles can

657
00:34:28,760 --> 00:34:32,600
Speaker 1: have gravity themselves, right, just like a planet does exactly,

658
00:34:32,640 --> 00:34:35,319
Speaker 1: And I have been electron over here and over there,

659
00:34:35,480 --> 00:34:38,160
Speaker 1: then space time is also fifty percent bend over here

660
00:34:38,200 --> 00:34:40,880
Speaker 1: and fifty bent over there, all right, Yeah, then that's

661
00:34:40,920 --> 00:34:43,680
Speaker 1: how you avoid the infinities that you're talking about earlier. Yeah,

662
00:34:43,680 --> 00:34:46,720
Speaker 1: because it changes how particles move at very very high energies,

663
00:34:46,800 --> 00:34:49,960
Speaker 1: which is exactly where these infinities crop up. Thinking about

664
00:34:50,000 --> 00:34:52,440
Speaker 1: like what happens to particles with really high energies which

665
00:34:52,520 --> 00:34:55,239
Speaker 1: bend space time, which create more gravitons, and you get

666
00:34:55,239 --> 00:34:58,319
Speaker 1: this infinite pile of gravitons and a runaway energy. So

667
00:34:58,360 --> 00:35:00,680
Speaker 1: if you change the behavior of the articles are very

668
00:35:00,760 --> 00:35:03,719
Speaker 1: very high energy, you can basically delete those infinities because

669
00:35:03,760 --> 00:35:07,040
Speaker 1: you change the rules when you get near infinity, so

670
00:35:07,120 --> 00:35:10,120
Speaker 1: the infinities basically go away. Cool. All right, Well that's

671
00:35:10,160 --> 00:35:12,760
Speaker 1: the theory of rainbow gravity, and so let's talk about

672
00:35:12,840 --> 00:35:15,160
Speaker 1: what would happen if it is true. What kinds of

673
00:35:15,160 --> 00:35:17,200
Speaker 1: things would we see out there where we see rainbows

674
00:35:17,560 --> 00:35:21,600
Speaker 1: around black holes? Would we see unicorns? And would that

675
00:35:21,640 --> 00:35:24,200
Speaker 1: mean that unicorns are also quantized? I hope? So I

676
00:35:24,200 --> 00:35:26,839
Speaker 1: don't ever want to see one and a half unicorns. Well,

677
00:35:26,840 --> 00:35:28,800
Speaker 1: if nobody wants to be your back end, then you

678
00:35:28,880 --> 00:35:31,840
Speaker 1: might have to be a halfy unicorn. That's a good

679
00:35:32,840 --> 00:35:35,200
Speaker 1: All right, we'll get into that, but first let's take

680
00:35:35,239 --> 00:35:50,799
Speaker 1: another quick break. All right, we're talking about rainbow gravity, uh,

681
00:35:50,840 --> 00:35:52,960
Speaker 1: and we're talking about what it is. And it's the

682
00:35:53,040 --> 00:35:55,480
Speaker 1: new theory that kind of tries to bring together quantum

683
00:35:55,480 --> 00:35:59,480
Speaker 1: mechanics and general relativity by saying that maybe gravity is

684
00:35:59,520 --> 00:36:03,280
Speaker 1: not the same aim everywhere, maybe it's different for different

685
00:36:03,480 --> 00:36:06,840
Speaker 1: energy particles, which would sort of help explain how gravity

686
00:36:06,840 --> 00:36:09,960
Speaker 1: works at the quantum level. Now this theory was true, Daniel,

687
00:36:10,320 --> 00:36:12,720
Speaker 1: does that mean we would see rainbows around black holes?

688
00:36:12,800 --> 00:36:15,800
Speaker 1: It does exactly mean that we would see rainbows around

689
00:36:15,880 --> 00:36:18,400
Speaker 1: black holes. Because this is a theory that tries to

690
00:36:18,480 --> 00:36:21,680
Speaker 1: unify quantum mechanics and gravity, which mostly ignore each other

691
00:36:21,680 --> 00:36:24,200
Speaker 1: and live in different regimes. It's a hard kind of

692
00:36:24,200 --> 00:36:27,360
Speaker 1: thing to test. You need special circumstances. So this doesn't

693
00:36:27,400 --> 00:36:29,879
Speaker 1: mean that we should expect to see gravitational rainbows all

694
00:36:29,880 --> 00:36:32,200
Speaker 1: over the place, you know, through the moon or the sun.

695
00:36:32,640 --> 00:36:35,239
Speaker 1: It's only in extreme conditions because this is a very

696
00:36:35,320 --> 00:36:38,000
Speaker 1: very small effect until you get two very very high

697
00:36:38,200 --> 00:36:41,960
Speaker 1: energies or very very strong curvature of space, like around

698
00:36:41,960 --> 00:36:44,680
Speaker 1: a black hole. So you're in a spaceship and you're

699
00:36:44,719 --> 00:36:47,080
Speaker 1: falling towards a black hole, and then white light near

700
00:36:47,120 --> 00:36:49,960
Speaker 1: the event horizon would be split into all of the colors,

701
00:36:50,000 --> 00:36:53,320
Speaker 1: and you would see rainbows before you get squished. Meaning

702
00:36:53,360 --> 00:36:56,040
Speaker 1: like I shoot a beam of light of white light

703
00:36:56,400 --> 00:36:59,040
Speaker 1: at a black hole at the very edge, and as

704
00:36:59,160 --> 00:37:01,680
Speaker 1: this beam of light gets very close to the black hole,

705
00:37:01,800 --> 00:37:04,520
Speaker 1: the photos that are more red would get pulled one way,

706
00:37:04,760 --> 00:37:06,960
Speaker 1: and the photons that are more blue would get pulled

707
00:37:06,960 --> 00:37:08,920
Speaker 1: another way, and the purple ones a bit pulled a

708
00:37:08,960 --> 00:37:11,920
Speaker 1: little bit differently, And so that would actually kind of

709
00:37:11,960 --> 00:37:15,760
Speaker 1: prism or split the beam of white light. Yeah, prism

710
00:37:15,800 --> 00:37:18,319
Speaker 1: exactly is the right analogy. That's what a prism does,

711
00:37:18,840 --> 00:37:22,160
Speaker 1: is it it bends light based on its wavelength. Different

712
00:37:22,200 --> 00:37:24,680
Speaker 1: wavelengths of light get bent differently as you go from

713
00:37:24,719 --> 00:37:27,600
Speaker 1: air to glass and back to air, and so they

714
00:37:27,680 --> 00:37:31,680
Speaker 1: spread out white light into a rainbow. And because now

715
00:37:31,719 --> 00:37:35,280
Speaker 1: we're introducing an energy dependent effect or a wavelength dependent

716
00:37:35,280 --> 00:37:38,759
Speaker 1: effect on gravity, than black holes are basically prisms, and

717
00:37:38,800 --> 00:37:40,960
Speaker 1: they would change a beam of white light into a

718
00:37:41,200 --> 00:37:46,440
Speaker 1: spread based on the colors. Yeah, their prisms and their prisons.

719
00:37:46,520 --> 00:37:48,839
Speaker 1: Because I guess you know, white light, it's not like

720
00:37:48,880 --> 00:37:52,400
Speaker 1: the each photon is white. Is that you have a

721
00:37:52,520 --> 00:37:54,680
Speaker 1: combination of photons, some of them are white, some of

722
00:37:54,719 --> 00:37:56,920
Speaker 1: them are higher and lower energy. Right, that's what what

723
00:37:57,040 --> 00:37:59,839
Speaker 1: white light is. It's not like the photons are white. Yeah,

724
00:37:59,840 --> 00:38:02,879
Speaker 1: there is no individual photon that has the color white. Right.

725
00:38:02,920 --> 00:38:05,759
Speaker 1: White is not a single color. It's a combination of

726
00:38:05,840 --> 00:38:08,800
Speaker 1: many photons of different colors. Right. And so around a

727
00:38:08,840 --> 00:38:10,920
Speaker 1: black hole in the gravity, we would be so strong

728
00:38:10,960 --> 00:38:13,960
Speaker 1: that it would actually start to affect each of those

729
00:38:13,960 --> 00:38:16,400
Speaker 1: photons differently, which is sort of like a prism or

730
00:38:16,480 --> 00:38:19,040
Speaker 1: or a lens. I guess, which makes me wonder, like,

731
00:38:19,280 --> 00:38:22,640
Speaker 1: why have we seen this effect? Have we seen? I mean,

732
00:38:22,760 --> 00:38:24,480
Speaker 1: now we now have pictures of black holes that we

733
00:38:24,520 --> 00:38:27,000
Speaker 1: see any rainbows around it. We do not see any

734
00:38:27,080 --> 00:38:29,680
Speaker 1: rainbows around black holes yet. This would be a very

735
00:38:29,800 --> 00:38:32,480
Speaker 1: very slight effect. And you need to look very carefully

736
00:38:32,560 --> 00:38:34,480
Speaker 1: right at the edge of a black hole. You need

737
00:38:34,520 --> 00:38:37,600
Speaker 1: a well calibrated source also to know whether you're seeing

738
00:38:37,640 --> 00:38:39,800
Speaker 1: any distortion. To know whether it's a story, you have

739
00:38:39,840 --> 00:38:41,760
Speaker 1: to know what it looked like before it went around

740
00:38:41,760 --> 00:38:45,000
Speaker 1: the black hole. And so we don't have any nice, clear,

741
00:38:45,040 --> 00:38:48,040
Speaker 1: crisp examples of that. Even around black holes. This would

742
00:38:48,040 --> 00:38:49,920
Speaker 1: be a very small effect. But what do you mean

743
00:38:49,920 --> 00:38:52,680
Speaker 1: it would be a small effect? Like this effect is

744
00:38:52,719 --> 00:38:56,520
Speaker 1: not very strong. It's very small that the way gravity

745
00:38:57,000 --> 00:38:59,640
Speaker 1: varies depending on the energy. Yeah, and this theory gravity

746
00:38:59,680 --> 00:39:03,120
Speaker 1: does pen on the energy, but it's basically unobservable until

747
00:39:03,160 --> 00:39:05,839
Speaker 1: you get too super duper high energies. In the same

748
00:39:05,880 --> 00:39:08,520
Speaker 1: way that like effects of special relativity, you can't really

749
00:39:08,560 --> 00:39:10,719
Speaker 1: observe them when you're throwing a baseball around. You don't

750
00:39:10,760 --> 00:39:14,280
Speaker 1: notice clocks going slow. Your baseball doesn't seem to shrink

751
00:39:14,480 --> 00:39:16,920
Speaker 1: when you throw it even though it's going faster. You

752
00:39:16,920 --> 00:39:19,760
Speaker 1: don't notice the effects of special relativity here on Earth

753
00:39:19,960 --> 00:39:22,960
Speaker 1: because they're negligible. In the same way, this energy dependent

754
00:39:23,000 --> 00:39:26,759
Speaker 1: effect of gravity is negligible except in extreme circumstances. And

755
00:39:26,800 --> 00:39:28,799
Speaker 1: so you need like a very crisp, clear setup of

756
00:39:28,800 --> 00:39:30,560
Speaker 1: a beam of white light right next to a black

757
00:39:30,600 --> 00:39:33,040
Speaker 1: hole and basically nothing else around so that you can

758
00:39:33,080 --> 00:39:35,719
Speaker 1: observe it. But there are some other ways we might

759
00:39:35,719 --> 00:39:39,080
Speaker 1: be able to test this theory. Yeah. They involved gamma rays. Yeah.

760
00:39:39,160 --> 00:39:41,600
Speaker 1: So gamma rays are basically just a fancy name for

761
00:39:41,760 --> 00:39:44,799
Speaker 1: super high energy photons. And there are these strange phenomena

762
00:39:44,800 --> 00:39:46,680
Speaker 1: that we've talked about the podcast a few times called

763
00:39:46,680 --> 00:39:49,680
Speaker 1: gamma ray bursts, where something out there in the universe

764
00:39:49,840 --> 00:39:53,239
Speaker 1: sends a huge spray of very high energy gamma raise

765
00:39:53,520 --> 00:39:56,360
Speaker 1: all about the same time. These things can laster like

766
00:39:56,440 --> 00:39:59,480
Speaker 1: seconds or minutes. We don't really understand the source of them.

767
00:39:59,560 --> 00:40:02,239
Speaker 1: Check out our whole podcast episode on that topic for

768
00:40:02,280 --> 00:40:04,200
Speaker 1: a deeper dive into it. But the cool thing is

769
00:40:04,239 --> 00:40:06,520
Speaker 1: that it's a nice test of this theory because it

770
00:40:06,560 --> 00:40:09,399
Speaker 1: sends us a big packet of photons, some of which

771
00:40:09,440 --> 00:40:13,600
Speaker 1: have huge energy, like crazy high energy photons, and they

772
00:40:13,600 --> 00:40:15,719
Speaker 1: all come to us about the same time, so we

773
00:40:15,719 --> 00:40:18,279
Speaker 1: can sort of use them as a probe of how

774
00:40:18,320 --> 00:40:20,839
Speaker 1: they've responded to the gravity of the universe that they

775
00:40:20,880 --> 00:40:24,440
Speaker 1: have flown through. Right, they might like arrive at different

776
00:40:24,440 --> 00:40:27,640
Speaker 1: places in our sensor or you know, like a rainbow

777
00:40:27,840 --> 00:40:30,080
Speaker 1: kind of get split, or are you saying they might

778
00:40:30,200 --> 00:40:33,120
Speaker 1: arrive at different times? So if for example, they whizz

779
00:40:33,120 --> 00:40:35,520
Speaker 1: around a black hole, they would get bent differently. But

780
00:40:35,640 --> 00:40:38,359
Speaker 1: the universe has some curvature, and as you move through it,

781
00:40:38,719 --> 00:40:41,040
Speaker 1: you're slowed down by that curvature, so they would be

782
00:40:41,080 --> 00:40:44,600
Speaker 1: differently time dilated as they move through the universe if

783
00:40:44,600 --> 00:40:47,600
Speaker 1: they see different curvature, so they would effectively arrive at

784
00:40:47,640 --> 00:40:49,799
Speaker 1: different times. If you send like a green or red

785
00:40:49,840 --> 00:40:53,399
Speaker 1: and blue photon across the universe to us. Then if

786
00:40:53,400 --> 00:40:56,360
Speaker 1: this is true, those photons would arrive at different times

787
00:40:56,440 --> 00:40:59,719
Speaker 1: here on Earth because they would see different amounts of curvature.

788
00:41:00,200 --> 00:41:03,919
Speaker 1: Curvature affects the passage of time and effectively how long

789
00:41:03,920 --> 00:41:06,880
Speaker 1: it takes light to traverse from the source. So like

790
00:41:06,960 --> 00:41:11,520
Speaker 1: some of the photons would get blue shifted more than others,

791
00:41:11,680 --> 00:41:13,640
Speaker 1: or wretch shifted more than others. That's kind of what

792
00:41:13,640 --> 00:41:16,080
Speaker 1: you're saying, because they have to arrive at the same time,

793
00:41:16,200 --> 00:41:18,480
Speaker 1: don't they Because they're moving at the speed of light,

794
00:41:18,680 --> 00:41:20,680
Speaker 1: these would actually arrive at different times. I mean from

795
00:41:20,719 --> 00:41:24,000
Speaker 1: their point of view, they would see different distances between

796
00:41:24,160 --> 00:41:27,160
Speaker 1: the source and the destination because they're seeing different amounts

797
00:41:27,160 --> 00:41:29,960
Speaker 1: of curvature of the universe. Well, that's pretty interesting, But

798
00:41:30,000 --> 00:41:32,040
Speaker 1: I guess couldn't we do that experiment here on Earth?

799
00:41:32,120 --> 00:41:34,560
Speaker 1: Like you know, we can create gamma rays, and we

800
00:41:34,600 --> 00:41:37,799
Speaker 1: can also create you know, like ultra violet or here

801
00:41:37,800 --> 00:41:40,040
Speaker 1: in other can create high energy light and super low

802
00:41:40,120 --> 00:41:42,720
Speaker 1: energy light. Couldn't we do some experiment where we shoot

803
00:41:42,760 --> 00:41:45,120
Speaker 1: both and see what happens. Yes, but we can't create

804
00:41:45,280 --> 00:41:49,120
Speaker 1: very strong gravitational curvature right, So we can create pretty

805
00:41:49,200 --> 00:41:51,880
Speaker 1: high energy photons, but not that high energy, not as

806
00:41:51,960 --> 00:41:54,840
Speaker 1: high energies exist out there in the universe. Also, we

807
00:41:54,880 --> 00:41:57,440
Speaker 1: don't have very strong curvature. The value of this test

808
00:41:57,480 --> 00:41:59,680
Speaker 1: is that the photons are super duper high energy because

809
00:41:59,719 --> 00:42:02,680
Speaker 1: they come from some astrophysical source and they fly through

810
00:42:02,719 --> 00:42:06,200
Speaker 1: a huge amount of curvature. So even the small effects

811
00:42:06,200 --> 00:42:09,080
Speaker 1: of curvature add up over very very long distances. What

812
00:42:09,120 --> 00:42:12,160
Speaker 1: do you mean, like curvature not due to any particular

813
00:42:12,200 --> 00:42:14,440
Speaker 1: thing like a black hole, which is like the general

814
00:42:14,520 --> 00:42:17,479
Speaker 1: curvature of space from having stuff in it, from having

815
00:42:17,520 --> 00:42:19,880
Speaker 1: stuff in it. Yeah, exactly, as you fly through the galaxy,

816
00:42:19,880 --> 00:42:22,600
Speaker 1: for example, there's a small gravitational well that the whole

817
00:42:22,640 --> 00:42:25,960
Speaker 1: galaxy sits in. That's the curvature of our local space.

818
00:42:26,160 --> 00:42:28,560
Speaker 1: But wouldn't we see that regular light because I know

819
00:42:28,600 --> 00:42:32,239
Speaker 1: there's something called gravitational lensing out there, where like a

820
00:42:32,239 --> 00:42:34,759
Speaker 1: planet can sort of lens and bend light to give

821
00:42:34,840 --> 00:42:38,240
Speaker 1: us a better view of another galaxy or another star,

822
00:42:38,680 --> 00:42:41,440
Speaker 1: or you know, a dark matter can also kind of

823
00:42:41,560 --> 00:42:45,680
Speaker 1: lens light. Wouldn't we see rainbows caused by dark matter? Too?

824
00:42:45,920 --> 00:42:48,279
Speaker 1: So I think that's exactly what this is suggesting to

825
00:42:48,440 --> 00:42:51,960
Speaker 1: probe right. Send a bunch of really high energy photons

826
00:42:52,280 --> 00:42:55,680
Speaker 1: through space, and all the matter that's in space creates

827
00:42:55,680 --> 00:42:58,880
Speaker 1: some curvature, and those photons would respond to that curvature

828
00:42:58,920 --> 00:43:02,080
Speaker 1: differently based on their energies. And so you would see

829
00:43:02,080 --> 00:43:04,520
Speaker 1: that then on Earth, and so yes, the galaxy and

830
00:43:04,520 --> 00:43:07,400
Speaker 1: all the dark matter and are all contributing to that.

831
00:43:07,480 --> 00:43:10,560
Speaker 1: The vanilla version of general relativity predicts that that wouldn't happen, right,

832
00:43:10,560 --> 00:43:12,880
Speaker 1: that they all get bent the same way. And you're

833
00:43:12,960 --> 00:43:15,080
Speaker 1: right that that's something that is predicted. As photons fall

834
00:43:15,160 --> 00:43:17,759
Speaker 1: into a gravitational well or dig themselves out of a

835
00:43:17,800 --> 00:43:21,080
Speaker 1: gravitational well, they do get shifted in frequency, for example.

836
00:43:21,360 --> 00:43:24,480
Speaker 1: But we think that happens equally for photons of all energy.

837
00:43:24,800 --> 00:43:28,080
Speaker 1: Rainbow gravity says that happens differently. So for very very

838
00:43:28,120 --> 00:43:30,799
Speaker 1: long distances, these would accumulate, do it, all the dark

839
00:43:30,840 --> 00:43:33,080
Speaker 1: matter and the other stuff in the galaxy and create

840
00:43:33,120 --> 00:43:35,640
Speaker 1: a small difference in the arrival time of those photons,

841
00:43:35,920 --> 00:43:38,480
Speaker 1: but not in their location, like they would all arrive

842
00:43:38,520 --> 00:43:41,440
Speaker 1: at the same spot. They would use maybe be colored

843
00:43:41,480 --> 00:43:44,239
Speaker 1: a little bit different, or would they actually split like

844
00:43:44,320 --> 00:43:46,440
Speaker 1: a rainbow. They would actually split like a rainbow, so

845
00:43:46,480 --> 00:43:49,080
Speaker 1: we wouldn't see the whole thing, right, So the whole

846
00:43:49,120 --> 00:43:50,880
Speaker 1: thing we get spread out across the universe, but we

847
00:43:50,920 --> 00:43:53,000
Speaker 1: would get a slice of it, and in theory we

848
00:43:53,080 --> 00:43:55,040
Speaker 1: might get ones of different color that we could also

849
00:43:55,200 --> 00:43:57,680
Speaker 1: test their time of arrival. So we've actually done this,

850
00:43:57,760 --> 00:44:00,120
Speaker 1: and we've looked at gamma ray bursts and we've i

851
00:44:00,280 --> 00:44:02,400
Speaker 1: to see if we see effects for it. There's no

852
00:44:02,480 --> 00:44:05,280
Speaker 1: evidence for it so far. Even these gamma ray bursts.

853
00:44:05,320 --> 00:44:07,680
Speaker 1: The evidence would be pretty subtle, and we don't have

854
00:44:07,760 --> 00:44:10,160
Speaker 1: that many examples of it. So the jury is still

855
00:44:10,160 --> 00:44:12,239
Speaker 1: sort of out on this theory. We don't have any

856
00:44:12,320 --> 00:44:14,799
Speaker 1: evidence for it, but we also can't yet rule it out.

857
00:44:15,360 --> 00:44:17,160
Speaker 1: It sounds like it's not an effect that you would

858
00:44:17,200 --> 00:44:20,160
Speaker 1: see in our everyday lives, like when we see galaxies

859
00:44:20,200 --> 00:44:22,920
Speaker 1: being lensed by dark matter out there, even that is

860
00:44:22,920 --> 00:44:26,200
Speaker 1: not strong enough to split light due to rainbow gravity. Yeah,

861
00:44:26,239 --> 00:44:29,520
Speaker 1: it requires a huge amount of energy or integration over

862
00:44:29,640 --> 00:44:32,560
Speaker 1: very very long distances. I guess what maybe we are

863
00:44:32,560 --> 00:44:34,640
Speaker 1: just saying is that if rainbow gravity is true, it

864
00:44:34,760 --> 00:44:37,600
Speaker 1: is happening even around us, all around us, you know,

865
00:44:37,960 --> 00:44:39,600
Speaker 1: like if I look at my hand, or if we

866
00:44:39,640 --> 00:44:42,600
Speaker 1: look at galaxies through a dark matter gravitational lens. It

867
00:44:42,640 --> 00:44:44,560
Speaker 1: is happening, but maybe just at a level that we

868
00:44:44,640 --> 00:44:47,520
Speaker 1: can't discern. In the same way that like time dilation

869
00:44:47,600 --> 00:44:50,520
Speaker 1: is happening all the time, length contraction is happening all

870
00:44:50,560 --> 00:44:53,560
Speaker 1: the time, you just can't tell because it's so negligible.

871
00:44:53,600 --> 00:44:56,040
Speaker 1: All right, well, let's talk about now what would happen

872
00:44:56,200 --> 00:44:58,440
Speaker 1: if this was true. We don't have evidence for it

873
00:44:58,520 --> 00:45:00,759
Speaker 1: either way, whether it's true or not, but what would

874
00:45:00,760 --> 00:45:02,680
Speaker 1: it mean if it If it is true that rainbow

875
00:45:02,680 --> 00:45:05,680
Speaker 1: gravity exists, or like gravity is not the same everywhere

876
00:45:06,520 --> 00:45:10,440
Speaker 1: for everyone except unicorns, it has really interesting consequences if

877
00:45:10,440 --> 00:45:13,799
Speaker 1: you run the clock of the universe backwards. Currently we

878
00:45:13,880 --> 00:45:16,880
Speaker 1: see the universes expanding, and we run the clock backwards

879
00:45:17,200 --> 00:45:19,879
Speaker 1: and we do the calculations in general relativity, and they

880
00:45:19,880 --> 00:45:23,359
Speaker 1: predict something really weird. They predict a singularity that as

881
00:45:23,360 --> 00:45:25,719
Speaker 1: the universe got denser and denser, there's a sort of

882
00:45:25,800 --> 00:45:29,200
Speaker 1: runaway gravitational effect in reverse where you end up with

883
00:45:29,200 --> 00:45:31,960
Speaker 1: a singularity, but with the universe is basically compressed into

884
00:45:32,040 --> 00:45:35,719
Speaker 1: incredible density. So that's the prediction of general relativity, and

885
00:45:35,760 --> 00:45:38,000
Speaker 1: you know, we think that's kind of bonkers. We think

886
00:45:38,040 --> 00:45:41,280
Speaker 1: that those kind of infinities probably don't exist in our universe.

887
00:45:41,680 --> 00:45:44,040
Speaker 1: And this, to most physicists is a sign that general

888
00:45:44,040 --> 00:45:47,160
Speaker 1: relativity needs some work right where this is a problem,

889
00:45:47,320 --> 00:45:49,880
Speaker 1: and so this is where we look for alternatives, and

890
00:45:49,880 --> 00:45:52,839
Speaker 1: so rainbow gravity. If you modify gravity in this way,

891
00:45:52,840 --> 00:45:55,680
Speaker 1: it says well, in very high energies, things actually do change.

892
00:45:55,800 --> 00:45:58,080
Speaker 1: And so you put this into the calculations instead of

893
00:45:58,120 --> 00:46:01,880
Speaker 1: general relativity, and now particles that different energy are affected

894
00:46:01,880 --> 00:46:04,759
Speaker 1: slightly differently by that curvature, and you don't end up

895
00:46:04,800 --> 00:46:06,960
Speaker 1: with a singularity. You end up with something which like

896
00:46:07,040 --> 00:46:09,680
Speaker 1: smoothly gets denser and denser. But we just sort of

897
00:46:09,719 --> 00:46:13,239
Speaker 1: a minimum plateau. It's like, intuitively, you can't just like

898
00:46:13,320 --> 00:46:16,200
Speaker 1: squeeze all the particles down to the same place because

899
00:46:16,200 --> 00:46:20,120
Speaker 1: the particles are all now bent differently by space. M M.

900
00:46:20,520 --> 00:46:23,120
Speaker 1: What would that mean for black holes? Two? Does that

901
00:46:23,200 --> 00:46:25,919
Speaker 1: mean there's no singularity at the center of black holes? Yes?

902
00:46:26,000 --> 00:46:29,680
Speaker 1: This basically a racist singularities in the universe, both singularities

903
00:46:29,719 --> 00:46:31,680
Speaker 1: in time like what might have happened before the Big

904
00:46:31,680 --> 00:46:35,560
Speaker 1: Bang and singularities in space like what's inside a black hole?

905
00:46:35,920 --> 00:46:38,600
Speaker 1: Doesn't mean black holes shouldn't exist. It tails us maybe

906
00:46:38,640 --> 00:46:41,200
Speaker 1: that the structure of matter inside the black hole isn't

907
00:46:41,280 --> 00:46:45,320
Speaker 1: a singularity, it's something else, weirder. It's controlled by rainbow gravity.

908
00:46:45,560 --> 00:46:48,320
Speaker 1: It's going to be something with a non zero size

909
00:46:48,360 --> 00:46:51,360
Speaker 1: to it. It'll have a fuzzy core to it, not

910
00:46:51,520 --> 00:46:55,239
Speaker 1: like a single point. Yeah, a fuzzy, colorful core probably. Yeah.

911
00:46:55,520 --> 00:46:58,680
Speaker 1: There are many colors of black, absolutely glossy black, matt

912
00:46:58,800 --> 00:47:03,160
Speaker 1: black right at black. Yeah. So maybe this sounds amazing,

913
00:47:03,280 --> 00:47:05,120
Speaker 1: and it sounds like it would solve a big problem

914
00:47:05,120 --> 00:47:08,040
Speaker 1: and maybe the biggest problem in physics right now theoretically

915
00:47:08,080 --> 00:47:11,040
Speaker 1: at least, But we haven't seen evidence for it experimentally,

916
00:47:11,200 --> 00:47:14,279
Speaker 1: and are there any reservations about just the theory of it.

917
00:47:14,520 --> 00:47:17,879
Speaker 1: Most mainstream physicists think that this is crazy, right. They

918
00:47:18,000 --> 00:47:21,000
Speaker 1: think that this is a monker's idea and just wouldn't

919
00:47:21,000 --> 00:47:25,480
Speaker 1: fly basically because it violates as a central principle something

920
00:47:25,560 --> 00:47:28,360
Speaker 1: that we all think probably is true, which is that

921
00:47:28,440 --> 00:47:32,440
Speaker 1: observers can all agree about the physical laws. Like in

922
00:47:32,480 --> 00:47:36,320
Speaker 1: our universe, we think that observers all see different things happening.

923
00:47:36,400 --> 00:47:39,120
Speaker 1: But one of the foundational principles of special relativity is

924
00:47:39,160 --> 00:47:41,600
Speaker 1: that the universe always follows the same laws. You might

925
00:47:41,640 --> 00:47:44,400
Speaker 1: tell a different story about what happened, but everybody's story

926
00:47:44,480 --> 00:47:48,400
Speaker 1: follows the same laws. This breaks that because now everything

927
00:47:48,480 --> 00:47:51,920
Speaker 1: is like energy dependent, and so the amount of curvature

928
00:47:51,960 --> 00:47:55,200
Speaker 1: you see depends on the energy you have. It breaks

929
00:47:55,239 --> 00:47:59,040
Speaker 1: this thing we call Lorentz invariants, right, because I guess

930
00:47:59,120 --> 00:48:02,720
Speaker 1: if gravity the anson how much energy you have, energy

931
00:48:02,840 --> 00:48:06,759
Speaker 1: can be a relative concept, right, energy depends on how

932
00:48:06,840 --> 00:48:10,120
Speaker 1: fast you're moving your kinetic energy. Then that can look

933
00:48:10,120 --> 00:48:13,399
Speaker 1: differently to different people, right, Like, if you're moving super

934
00:48:13,480 --> 00:48:17,040
Speaker 1: duper duper duper fast to somebody outside of yourself, you

935
00:48:17,080 --> 00:48:19,360
Speaker 1: would have a lot of energy, but to you yourself,

936
00:48:19,440 --> 00:48:20,840
Speaker 1: you wouldn't have a lot of energy. Is that what

937
00:48:20,880 --> 00:48:22,920
Speaker 1: you mean? Yeah, there's that aspect to it, but it

938
00:48:22,920 --> 00:48:25,399
Speaker 1: goes a little bit deeper than that. You know. Right now,

939
00:48:25,480 --> 00:48:28,799
Speaker 1: we think that space is relative in an important way,

940
00:48:28,800 --> 00:48:31,800
Speaker 1: but that there are some invariants that some things hold fast,

941
00:48:31,880 --> 00:48:34,319
Speaker 1: Like the speed of light is the same for all observers.

942
00:48:34,920 --> 00:48:37,680
Speaker 1: But if this theory is true, then the speed of

943
00:48:37,760 --> 00:48:41,080
Speaker 1: light sort of depends on the energy of the photons. Right,

944
00:48:41,120 --> 00:48:45,080
Speaker 1: These photons traveling through space effectively have different speeds and

945
00:48:45,160 --> 00:48:49,279
Speaker 1: that's pretty weird. There's a lot of really strong constraints

946
00:48:49,320 --> 00:48:53,000
Speaker 1: on measurements of variable speed of light, energy dependent speed

947
00:48:53,000 --> 00:48:55,040
Speaker 1: of light, and so it would require, you know, a

948
00:48:55,080 --> 00:48:57,360
Speaker 1: real revolution in the way we think about the nature

949
00:48:57,360 --> 00:49:00,239
Speaker 1: of the universe. But maybe that's what's required, right. Our

950
00:49:00,280 --> 00:49:04,640
Speaker 1: current principles general relativity and quantum mechanics have completely incompatible

951
00:49:04,640 --> 00:49:07,640
Speaker 1: assumptions at their foundation, and so to unify them, we

952
00:49:07,719 --> 00:49:09,560
Speaker 1: are going to have to get rid of something that

953
00:49:09,640 --> 00:49:13,000
Speaker 1: we hold, choose something that we cherish. Maybe it's Lorentz

954
00:49:13,040 --> 00:49:16,560
Speaker 1: and variants, maybe it's not. But before this theory is accepted,

955
00:49:16,600 --> 00:49:18,920
Speaker 1: it would require us to really rebuild a lot of

956
00:49:18,920 --> 00:49:21,800
Speaker 1: physics from the ground up. Yeah, I get a Physicists

957
00:49:22,000 --> 00:49:26,200
Speaker 1: don't like things to change. We love things to change. Actually,

958
00:49:26,400 --> 00:49:29,200
Speaker 1: our dream is to find some new theory which blows

959
00:49:29,239 --> 00:49:31,399
Speaker 1: everything up. But yeah, it doesn't mean a lot of work.

960
00:49:31,440 --> 00:49:33,680
Speaker 1: But that also means, you know, hey, more grand funding,

961
00:49:33,719 --> 00:49:35,359
Speaker 1: more piles of gold. But I guess what you mean

962
00:49:35,440 --> 00:49:37,640
Speaker 1: is like, you don't like the laws of physics to

963
00:49:37,760 --> 00:49:40,279
Speaker 1: be different, and depending on where you are in the universe, yes,

964
00:49:40,360 --> 00:49:42,439
Speaker 1: that's true. It would be very nice if the laws

965
00:49:42,440 --> 00:49:44,880
Speaker 1: of physics were the same for everybody, and you're a

966
00:49:44,880 --> 00:49:48,279
Speaker 1: guest that because it would mean slop your math, or

967
00:49:48,280 --> 00:49:50,880
Speaker 1: because you haven't seen any experimental proof of that. We

968
00:49:50,920 --> 00:49:53,200
Speaker 1: haven't seen any experimental proof of it. And also it's

969
00:49:53,360 --> 00:49:56,399
Speaker 1: kind of a nice principle if philosophically, it just sort

970
00:49:56,400 --> 00:49:58,839
Speaker 1: of like makes sense to imagine that the universe runs

971
00:49:58,840 --> 00:50:00,680
Speaker 1: on a certain set of laws. Those laws are the

972
00:50:00,680 --> 00:50:03,640
Speaker 1: same for everybody. It doesn't have to be true, you know,

973
00:50:03,680 --> 00:50:05,160
Speaker 1: the same sense, Like, we don't even know why the

974
00:50:05,239 --> 00:50:08,880
Speaker 1: universe has laws and why those laws don't change with time.

975
00:50:09,560 --> 00:50:12,440
Speaker 1: There's a lot of just basic assumptions at the foundation

976
00:50:12,800 --> 00:50:16,319
Speaker 1: of fundamental physics that we make and seem to work,

977
00:50:16,360 --> 00:50:18,680
Speaker 1: but we don't really understand why, and we might have

978
00:50:18,760 --> 00:50:21,719
Speaker 1: to revisit. Cool. Well, I guess once again, it's a

979
00:50:21,920 --> 00:50:24,560
Speaker 1: stay tuned. It might be true. It might be that

980
00:50:24,760 --> 00:50:27,840
Speaker 1: special thing that solves a lot of problems and feels

981
00:50:27,840 --> 00:50:30,640
Speaker 1: magical to everyone. What does that term people use for

982
00:50:30,680 --> 00:50:35,960
Speaker 1: something like that, a unicorn? A unicorn, right, right, So

983
00:50:36,040 --> 00:50:39,440
Speaker 1: the rainbow gravity theory might be at unicorn in itself,

984
00:50:40,040 --> 00:50:42,520
Speaker 1: according to a physicist right here on the podcast, Yeah,

985
00:50:42,640 --> 00:50:45,400
Speaker 1: it might fly in on rainbows and solve all the

986
00:50:45,440 --> 00:50:47,959
Speaker 1: problems that we have, and that will let us see

987
00:50:48,000 --> 00:50:50,359
Speaker 1: the full spectrum of the universe, see all of its

988
00:50:50,360 --> 00:50:54,120
Speaker 1: beautiful colors, and also let us see how it changes

989
00:50:54,440 --> 00:50:57,040
Speaker 1: in space and in time. So remember that science is

990
00:50:57,080 --> 00:51:00,960
Speaker 1: a continual process that involves and changes. Are understanding of

991
00:51:01,000 --> 00:51:03,600
Speaker 1: the universe out there, how it works, and where it

992
00:51:03,680 --> 00:51:05,560
Speaker 1: came from. And as we learned more and more about

993
00:51:05,560 --> 00:51:07,560
Speaker 1: the nature of the universe, we understand more and more

994
00:51:07,640 --> 00:51:10,319
Speaker 1: about how it began and what it means to be here.

995
00:51:10,600 --> 00:51:12,960
Speaker 1: We hope you enjoyed that. Thanks for joining us, See

996
00:51:12,960 --> 00:51:23,280
Speaker 1: you next time. Thanks for listening, and remember that Daniel

997
00:51:23,320 --> 00:51:25,840
Speaker 1: and Jorge explained The Universe is a production of I

998
00:51:26,080 --> 00:51:29,480
Speaker 1: Heart Radio. Or more podcast from my heart Radio visit

999
00:51:29,520 --> 00:51:33,040
Speaker 1: the I heart Radio app, Apple Podcasts, or wherever you

1000
00:51:33,120 --> 00:51:34,640
Speaker 1: listen to your favorite shows.