WEBVTT - Does gravity make rainbows? 0:00:08.520 --> 0:00:11.160 Hey, or hey. You know what's still amazes me that 0:00:11.200 --> 0:00:16.200 they give to introverts like us a podcast that blows 0:00:16.280 --> 0:00:22.239 my mind every week. But also, rainbows are awesome, But 0:00:22.400 --> 0:00:25.439 what about them amazes you? Everything is amazing about them. 0:00:25.480 --> 0:00:29.360 They are amazingly beautiful, But I'm amazed that they like exist, 0:00:29.560 --> 0:00:32.440 that they happen in the universe. You know that there's 0:00:32.479 --> 0:00:35.040 a science behind them, right, They're not just like magical. 0:00:35.640 --> 0:00:37.960 I get that there's science there, but I just think 0:00:37.960 --> 0:00:40.400 it's incredible that we live in the universe where this 0:00:40.479 --> 0:00:43.240 kind of thing actually happens. I mean, if you read 0:00:43.280 --> 0:00:45.400 about this in the science fiction book, you would think 0:00:45.440 --> 0:00:47.920 it's pretty farfetched. Well, it depends what what kind of 0:00:47.920 --> 0:00:51.800 science fiction you're reading. Does it also involve unicorns? Unicorns 0:00:51.840 --> 0:00:54.240 like a podcast with two introverts? Wait, who is the 0:00:54.320 --> 0:00:57.400 unicorn in this case? Because you can only have one, 0:00:57.440 --> 0:01:00.800 it's in the name unicorn. Collectively, we are one unicorn. 0:01:16.120 --> 0:01:19.800 Hi am Jorhemmack, cartoonists and the creator of PhD comics. Hi, 0:01:19.959 --> 0:01:22.560 I'm Daniel. I'm a particle physicist and a professor at 0:01:22.640 --> 0:01:25.360 U c Irvine, and I called dibbs on being the 0:01:25.400 --> 0:01:27.960 front two legs of the unicorn costume. Oh good, it's 0:01:27.959 --> 0:01:31.080 going to be the back end. Maybe you can have 0:01:31.120 --> 0:01:35.040 a guest host go. That's why we have guest hosts exactly. 0:01:35.120 --> 0:01:37.800 But anyways, welcome to our podcast, Daniel and Jorge Explain 0:01:37.880 --> 0:01:40.960 the Universe, a production of I Heart Radio, the podcasting 0:01:41.000 --> 0:01:43.360 which we talk about everything that's out there in the 0:01:43.440 --> 0:01:46.120 universe and try to explain all of it to you. 0:01:46.280 --> 0:01:51.360 We explore the complete spectrum of possible physical phenomena, including rainbows. 0:01:51.640 --> 0:01:54.800 If unicorns were real, we would talk about them as well. 0:01:55.000 --> 0:01:57.600 But we don't shy away from digging deep into the 0:01:57.640 --> 0:02:00.640 fabric of reality, understanding how it all works, and trying 0:02:00.640 --> 0:02:04.080 to explain to you what scientists are thinking about, what 0:02:04.120 --> 0:02:07.160 they are puzzling over, and what ideas they are bouncing 0:02:07.200 --> 0:02:10.480 around their unicorn brains. That's right, because it is a 0:02:10.560 --> 0:02:14.160 very colorful universe. Well have amazing sites like rainbows, and 0:02:14.200 --> 0:02:16.640 we like to follow that arc of science to see 0:02:16.680 --> 0:02:18.640 what is at the end of it if there is 0:02:18.680 --> 0:02:22.280 indeed a big part of gold or some other element, 0:02:22.400 --> 0:02:25.080 you know, because it just don't really discriminate between elements, 0:02:25.080 --> 0:02:27.160 do they We don't. But I would like to accept 0:02:27.160 --> 0:02:29.720 my grand funding in pots of gold if that was possible, 0:02:30.080 --> 0:02:32.920 you know, rather than just like dollars in a bank account. Yeah, 0:02:33.000 --> 0:02:36.680 but then then your grand funding is depending on gold 0:02:36.720 --> 0:02:41.639 currency markets. What is the exchange rate between gold and science? Anyway, 0:02:42.680 --> 0:02:45.520 I don't keep track, but he's made me think of 0:02:45.520 --> 0:02:48.519 another question, Daniel, in a multiverse, right, technically in a 0:02:48.600 --> 0:02:53.600 multiverse or maybe even in an infinite universe. Uh, unicorns 0:02:53.600 --> 0:02:57.240 probably exists, right, I mean it is possible, so therefore 0:02:57.320 --> 0:02:59.880 it must be true. It must be horses out there 0:03:00.000 --> 0:03:02.679 in the multiverse or an infinite universe with horns in 0:03:02.720 --> 0:03:05.800 their foreheads. Probably out there somewhere in the multiverse there 0:03:05.800 --> 0:03:09.640 are unicorn physicists being paid to do their science in 0:03:09.840 --> 0:03:13.720 pots of gold. Maybe even two unicorns on a podcast 0:03:13.800 --> 0:03:16.440 talking about what it would be like if humans were 0:03:16.440 --> 0:03:19.600 doing science instead of them humans were real, Like, maybe 0:03:19.680 --> 0:03:23.320 humans are the unicorns in the unicorn world. If you're 0:03:23.320 --> 0:03:26.200 already unicorns, why would you even think up humans? Right? 0:03:26.400 --> 0:03:28.720 Are do you think of something so boring and ugly 0:03:28.760 --> 0:03:31.360 compared to unicorns? Or maybe like regular horses are the 0:03:31.400 --> 0:03:34.320 unicorns for them? They're like can you imagine a horse 0:03:34.320 --> 0:03:36.480 without a horn? Or maybe it's the other direction, Maybe 0:03:36.480 --> 0:03:39.840 they're imagining two horned horses, right, Yeah, that would be 0:03:39.880 --> 0:03:42.560 like wild to them. That would be an imaginary and magic. 0:03:43.640 --> 0:03:45.880 And on this podcast, we do like to use our 0:03:45.920 --> 0:03:49.800 imagination to consider the ways that the universe might be. 0:03:50.200 --> 0:03:52.400 After all, we are trapped on this tiny little rock 0:03:52.400 --> 0:03:55.040 in a little corner of space, trying to understand the 0:03:55.320 --> 0:03:59.400 entire cosmos, which requires somehow developing a model for how 0:03:59.440 --> 0:04:01.960 it all works, and extrappling in that model out to 0:04:02.040 --> 0:04:04.960 the very far edges of the universe, far forward in 0:04:05.040 --> 0:04:07.920 time and far backwards in time. Because we want to 0:04:07.920 --> 0:04:10.920 do more than just tell stories about unicorns and rainbows. 0:04:11.000 --> 0:04:14.440 We want a mathematical story that explains what we see 0:04:14.480 --> 0:04:17.279 in the universe and tells us what has already happened 0:04:17.360 --> 0:04:20.800 and hopefully why. Yeah, because the nature of the universe 0:04:20.839 --> 0:04:23.240 doesn't just affect the cosmos out there in space and 0:04:23.400 --> 0:04:26.240 other galaxies. It affects us here and on Earth and 0:04:26.279 --> 0:04:29.359 in our everyday lives. Every time you look up after 0:04:29.400 --> 0:04:32.960 a nice rainfall and see a rainbow, that's physics kind 0:04:33.000 --> 0:04:35.320 of affecting how you see the world. And I don't 0:04:35.320 --> 0:04:37.919 want to talk more about rainbows and unicorns, but I 0:04:37.960 --> 0:04:41.400 do think rainbows are amazing. It's incredible that this physical 0:04:41.400 --> 0:04:43.800 effect happens, and it shimmers in the air, and it 0:04:43.880 --> 0:04:46.480 happens so often, and it's so beautiful. It's just like, 0:04:46.560 --> 0:04:48.640 how lucky are we to live in the universe where 0:04:48.680 --> 0:04:51.719 such beauty occurs? Makes me wonder about the whole nature 0:04:51.720 --> 0:04:54.560 of beauty. But that's a whole philosophical rainbow that we 0:04:54.640 --> 0:04:57.320 definitely don't want to walk down today. What we do 0:04:57.400 --> 0:05:00.040 want to wonder about is why the universe works this 0:05:00.200 --> 0:05:02.479 way and what it means about the history of the 0:05:02.560 --> 0:05:04.640 universe as well. He says, the way the universe works 0:05:04.640 --> 0:05:07.120 affects our daily lives because it tells us about the 0:05:07.200 --> 0:05:10.760 context of our lives. It tells us how the universe 0:05:10.800 --> 0:05:13.640 came to be and what it means that we are here. Yeah, 0:05:13.640 --> 0:05:17.160 and the history of humanity has been about making theories 0:05:17.200 --> 0:05:19.560 that hopefully explain what's going on and gives us an 0:05:19.600 --> 0:05:22.919 understanding about why things are the way they are and 0:05:22.960 --> 0:05:26.480 how we can maybe affect them or change them, or 0:05:26.800 --> 0:05:30.200 at least dream up of fantastical things. And while we've 0:05:30.200 --> 0:05:32.080 made a lot of progress and understand in the nature 0:05:32.120 --> 0:05:34.400 of the universe and its history, how it got to 0:05:34.440 --> 0:05:37.000 look the way that it is, and wondering about how 0:05:37.040 --> 0:05:39.440 it started, or at least the very first few moments 0:05:39.480 --> 0:05:41.800 of it. There are still a lot of question marks 0:05:41.839 --> 0:05:44.640 there about what happened early on, a lot of things 0:05:44.680 --> 0:05:47.520 about our theories that don't quite make sense, leaving lots 0:05:47.520 --> 0:05:50.320 of room for creative people to imagine all sorts of 0:05:50.480 --> 0:05:53.800 theoretical rainbows and unicorns to fill in the gap. I 0:05:53.800 --> 0:05:55.800 thought you didn't want to talk about rainbows anymore, Daniel, 0:05:56.680 --> 0:05:59.640 keep bringing it up. Not literal rainbows. These are figurative 0:05:59.760 --> 0:06:02.640 rain us now. But the arc of history is an 0:06:02.640 --> 0:06:05.600 interesting wine, but it's not a necessarily straight line. Sometimes 0:06:05.600 --> 0:06:07.960 we come up with theories that explain what we can 0:06:07.960 --> 0:06:10.560 see and what we can experiment with out there, but 0:06:10.600 --> 0:06:12.800 then later they turn out to be wrong, and that's 0:06:12.839 --> 0:06:15.440 okay because that's part of science and it's an evolving process. 0:06:15.520 --> 0:06:18.960 It's a really interesting distinction, for example, between math and science, 0:06:19.279 --> 0:06:21.440 Like the science that we had two hundred years ago 0:06:21.720 --> 0:06:23.599 is now evolved to the science we have today, and 0:06:23.640 --> 0:06:26.200 we expect in the future we will have even crisper 0:06:26.240 --> 0:06:29.120 ideas of how the universe works. But mathematical proofs that 0:06:29.160 --> 0:06:31.760 were developed thousands of years ago. Those are still correct, 0:06:31.800 --> 0:06:33.960 and we expect those to still be correct in a 0:06:33.960 --> 0:06:37.440 few thousand years. So it's fascinating how science and math 0:06:37.520 --> 0:06:41.520 develop sort of differently, even though science is built on math. Yeah, 0:06:41.560 --> 0:06:44.240 and so we have theories that currently describe everything we 0:06:44.279 --> 0:06:47.400 can see around those quantum mechanics and gravity or I 0:06:47.440 --> 0:06:51.440 guess special relativity. But the question is are those actually right? 0:06:51.839 --> 0:06:55.400 Do those theories actually describe the universe in all instances 0:06:55.640 --> 0:06:57.520 or do they break down at some point? And what 0:06:57.560 --> 0:07:00.560 does that mean about our understanding of the universe. One 0:07:00.560 --> 0:07:03.320 of the most frustrating things about general relativity and quantum 0:07:03.320 --> 0:07:06.200 mechanics is that they don't agree about what happens, and 0:07:06.279 --> 0:07:09.840 maybe the most interesting moment of the universe, that is 0:07:09.920 --> 0:07:13.520 the very first few moments when things are very high 0:07:13.640 --> 0:07:16.880 energy and very dense, and we need both gravity and 0:07:16.960 --> 0:07:20.520 quantum mechanics to understand what happened. Was there singularity, was 0:07:20.560 --> 0:07:23.000 there something else? What was going on at the very 0:07:23.040 --> 0:07:25.880 beginning of the universe. We're pretty sure that our current 0:07:25.880 --> 0:07:28.320 theories can't be right, and so we're on the hunt 0:07:28.440 --> 0:07:31.400 for new ideas. So today on the podcast, we'll be 0:07:31.440 --> 0:07:41.600 tackling the question what is rainbow gravity, Daniel, is this like, 0:07:41.640 --> 0:07:45.120 how much does a rainbow way like it is a 0:07:45.200 --> 0:07:48.120 rainbow heavy? Can you measure the happiness in a rainbow? 0:07:50.560 --> 0:07:54.000 How many pots of gold are generated by general relativity? 0:07:54.240 --> 0:07:56.880 Maybe we have a new theory called golden relativity. Hey, 0:07:56.920 --> 0:08:00.440 that sounds good. No, this is literally a theory of 0:08:00.480 --> 0:08:05.440 the universe that predicts that gravity could make rainbows the 0:08:05.480 --> 0:08:08.400 same way that like prisms or drops of water make 0:08:08.560 --> 0:08:12.200 rainbows in your eyeball, Like gravity itself could bend white 0:08:12.280 --> 0:08:15.800 light and turn it into rainbows. M I guess the 0:08:15.840 --> 0:08:18.600 question is would those be regular rainbows or would you 0:08:18.640 --> 0:08:21.880 need to call them like gravitational rainbows. Yeah, those would 0:08:21.880 --> 0:08:24.360 be gravitational rainbows because you definitely wouldn't see them in 0:08:24.360 --> 0:08:27.160 the atmosphere on Earth. This would be like something you 0:08:27.200 --> 0:08:29.960 see in your spaceship as you're falling towards the edge 0:08:29.960 --> 0:08:32.040 of a black hole. But this wouldn't just be like 0:08:32.040 --> 0:08:34.440 a lens flare, like a J. J. Abrahm style lens 0:08:34.480 --> 0:08:38.160 flare on your camera or your glasses or your spaceship window. 0:08:38.240 --> 0:08:41.800 This would be like real black hole rainbows, real black 0:08:41.800 --> 0:08:44.520 hole rainbows. That's right, and you don't need to ride 0:08:44.520 --> 0:08:46.600 a unicorn across the sky to see it. If this 0:08:46.679 --> 0:08:49.680 theory is actually true, these rainbows exist in the universe, 0:08:49.720 --> 0:08:52.200 and they might have existed very early on, and they 0:08:52.240 --> 0:08:54.840 could completely change the way we think about the very 0:08:54.880 --> 0:08:57.719 first moments of the cosmos. Well, you don't need to 0:08:57.720 --> 0:09:00.959 be writing a unicorn, but obviously anything better while you're 0:09:00.960 --> 0:09:04.079 writing a unicorn, surely, I mean, I wouldn't know, but 0:09:04.320 --> 0:09:08.320 ice cream is better when you're writing a unicorn, for example? Absolutely, 0:09:09.480 --> 0:09:12.720 Well depends. Can this unicorn fly just gallop along? Because 0:09:12.800 --> 0:09:14.719 it might be hard to eat it a lick and 0:09:14.800 --> 0:09:17.600 ice cream cone while you're gelping. You know, I am 0:09:17.600 --> 0:09:20.360 not an expert on the categories of unicorns. Do unicorns 0:09:20.400 --> 0:09:22.720 come with wings or is that a pegasus? Or pegasus 0:09:22.840 --> 0:09:25.000 is just a horse with wings? What do you call 0:09:25.080 --> 0:09:28.480 it if it's a unicorn with wings? I think unicorns 0:09:28.520 --> 0:09:30.920 just fly on a on a rainbow, right? Is that 0:09:30.960 --> 0:09:33.160 what happens? Like you're galloping and then like a rainbow 0:09:33.200 --> 0:09:35.680 bridge pops up, and then then you're flying. It's like 0:09:35.720 --> 0:09:39.439 the by Frost and Thor and Welcome to the Science 0:09:39.520 --> 0:09:45.240 of Unicorns, a sub episode of rainbow gravity. Well, let's 0:09:45.240 --> 0:09:47.040 get that. You're right, let's get back on topic here. 0:09:47.080 --> 0:09:50.920 We're talking about rainbow gravity or gravitational rainbow or what's 0:09:50.960 --> 0:09:52.400 the right way to call this. Is there such a 0:09:52.400 --> 0:09:55.000 thing as rainbow gravity. There is really a theory out 0:09:55.040 --> 0:09:58.080 there in the community called rainbow gravity, and that's what 0:09:58.120 --> 0:10:00.640 we're talking about today. We're gonna try to avoid talking 0:10:00.640 --> 0:10:03.840 about unicorns, but I suspect the gravitational attraction of their 0:10:03.920 --> 0:10:06.520 gorgeousness is going to pull us back in anyway. You're 0:10:06.520 --> 0:10:10.040 saying this is sequels called unicorn gravity, lying unicorn gravity, 0:10:10.080 --> 0:10:12.280 that's the title of my next paper on this topic. Well, 0:10:12.320 --> 0:10:15.480 you're gonna take one theory combined with an imaginary theory 0:10:15.559 --> 0:10:18.120 to get an X ray imaginary in some version of 0:10:18.160 --> 0:10:20.080 the mole diverse that earns me a huge pot of 0:10:20.120 --> 0:10:23.040 grand funding, which I get in delivery of gold coins. Well, 0:10:23.040 --> 0:10:25.400 I'm gonna have one up. Even put wings on that unicorn. 0:10:25.440 --> 0:10:28.400 So my theory is gonna be the rainbow unicorn pegass 0:10:28.440 --> 0:10:30.880 gravity theory. All right, Well, then I'm gonna put horns 0:10:30.880 --> 0:10:34.840 on the wings on that unicorn. Okay, this is kidding 0:10:35.559 --> 0:10:38.400 a little HP Lovecraft in here, but it is an 0:10:38.400 --> 0:10:42.280 interesting theory. This idea of rainbow gravity or gravitational rainbows? 0:10:42.760 --> 0:10:46.040 And can gravity rainbows? So, as usual, we were wondering 0:10:46.040 --> 0:10:48.559 how many people out there had thought about this or 0:10:48.600 --> 0:10:50.760 maybe dreamt it in one of their dreams. So thank 0:10:50.840 --> 0:10:53.680 you to all the people in Unicorns who volunteered to 0:10:53.760 --> 0:10:57.480 answer these questions. We greatly appreciate it and enjoy hearing 0:10:57.559 --> 0:10:59.719 your thoughts. If you would like to participate for a 0:10:59.760 --> 0:11:01.880 future your episodes, please don't be shy. Right to me 0:11:01.960 --> 0:11:05.040 two questions at Daniel and Jorge dot com. Think about 0:11:05.040 --> 0:11:08.679 it for a second. What do you think is rainbow gravity? 0:11:08.800 --> 0:11:11.079 He was what people had to say. Okay, So rainbows 0:11:11.120 --> 0:11:16.200 are created by the reflection refraction of light, and the 0:11:16.240 --> 0:11:19.720 wavelength of that light depends on what we see in 0:11:19.800 --> 0:11:24.320 terms of its color. So rainbow gravity. If I think 0:11:24.320 --> 0:11:29.319 of gravitational waves, maybe as those waves are passing through 0:11:29.880 --> 0:11:33.960 or having light passed through. Um, maybe it's the effect 0:11:34.040 --> 0:11:36.040 that the light and the different wavelengths of the light 0:11:36.120 --> 0:11:39.720 has on those gravitational waves. Maybe I don't know. Maybe 0:11:40.160 --> 0:11:44.440 like moist that split the light based on frequency, gravity 0:11:44.559 --> 0:11:48.640 split the think based off their density, and you call 0:11:48.800 --> 0:11:53.160 the outcome rainbow gravity. And well, I've definitely never heard 0:11:53.200 --> 0:11:56.280 of rainbow gravity. So my best guess is that it 0:11:56.360 --> 0:11:58.520 is something that has to do with the way gravity 0:11:58.520 --> 0:12:03.120 effects light. Um, maybe it's a property of gravitational lensing. 0:12:03.360 --> 0:12:07.800 Oh jeez, I do not know. I would imagine that 0:12:08.559 --> 0:12:10.480 it has to do with the spectrum of light and 0:12:10.520 --> 0:12:13.839 how gravity could affect light, but I'm not sure. Maybe 0:12:13.880 --> 0:12:16.760 how gravity could split light. All right, we got a 0:12:16.800 --> 0:12:20.920 nice spectrum of answers here, very colorful, powerful. Yeah that 0:12:21.000 --> 0:12:22.880 was low hanging fruit. But yeah, a lot of some 0:12:22.880 --> 0:12:24.440 people have never heard of it, and some people had 0:12:24.440 --> 0:12:27.880 some pretty good ideas, like it's maybe gravity causing lensing, 0:12:28.240 --> 0:12:31.600 which might create a rainbow effect. Yeah, exactly. This seems 0:12:31.600 --> 0:12:33.960 to be a well named theory because it inspired some 0:12:34.040 --> 0:12:37.960 good ideas and listeners. Well, I would obviously disagree, but 0:12:38.400 --> 0:12:42.559 that's never stop physicists from naming things in counterintuitive ways. 0:12:42.720 --> 0:12:45.240 Let's see how this goes, Daniel, I mean rainbow gravity, 0:12:45.280 --> 0:12:47.720 but it is gravity actually a rainbow? I don't know. 0:12:48.000 --> 0:12:49.959 It's a really fun theory that tries to solve a 0:12:50.000 --> 0:12:53.800 problem at the heart of physics, the connection between general 0:12:53.800 --> 0:12:57.000 relativity and quantum mechanics, or more specifically, the lack of 0:12:57.040 --> 0:12:59.880 the connection along the way predicts beautiful events like rain 0:13:00.000 --> 0:13:03.400 those popping out of black holes, wait out of black holes, 0:13:03.400 --> 0:13:06.080 that would be impossible, or maybe that gets it's the rainbow, 0:13:06.160 --> 0:13:08.520 so maybe it's magical. Perhaps I should have said at 0:13:08.520 --> 0:13:11.000 the edge of black holes, Well, let's dig into it. 0:13:11.120 --> 0:13:13.800 Um you said, it's a new theory or a potential 0:13:13.840 --> 0:13:16.120 theory that's out there in the physics community that maybe 0:13:16.160 --> 0:13:19.880 try to explain the intersection between quantum mechanics and gravity, 0:13:20.240 --> 0:13:24.000 because those two things are not quite compatible with each other, right, Yeah, 0:13:24.040 --> 0:13:27.280 all of modern physics is built on these two ideas, 0:13:27.360 --> 0:13:31.000 quantum mechanics and general relativity. But at their hearts, these 0:13:31.000 --> 0:13:35.000 two theories are incompatible. They have completely different views of 0:13:35.040 --> 0:13:38.440 the world. Even though they're in philosophical contradiction with each other, 0:13:38.840 --> 0:13:42.640 they've survived together as twin pillars of our theory of 0:13:42.640 --> 0:13:46.200 physics because they're never actually relevant at the same time. 0:13:46.760 --> 0:13:49.800 So you can use gravity talk about really big, massive things, 0:13:49.840 --> 0:13:52.680 and you can use quantum mechanics talk about really small things, 0:13:52.960 --> 0:13:54.920 and you never really need to use both at the 0:13:54.960 --> 0:13:57.439 same time. So they've sort of survived without having to 0:13:57.480 --> 0:13:59.800 talk to each other. They're like a married couple that 0:14:00.040 --> 0:14:02.520 turned into roommates. Well that's kind of said, Well, you know, 0:14:02.559 --> 0:14:03.840 if they do try to talk to each other, it's 0:14:03.840 --> 0:14:05.880 gonna be a big argument, so they just try to 0:14:05.920 --> 0:14:09.320 avoid it. Why did another physics theoretical committee was um 0:14:10.120 --> 0:14:14.120 dysfunctional and ahead of for our potential split in the future. 0:14:14.240 --> 0:14:16.400 It's not all rainbows and unicorns. Man, all right, well, 0:14:16.440 --> 0:14:18.760 maybe I can help us understand this a little bit. 0:14:19.040 --> 0:14:21.720 Where is that incompatibility? Is it just that you do 0:14:21.840 --> 0:14:24.440 is this haven't been able to make it work in 0:14:24.480 --> 0:14:28.000 the mathematical way, or is it is there something fundamental 0:14:28.040 --> 0:14:31.360 about how they view the universe that is just totally incompatible. 0:14:31.480 --> 0:14:33.720 So there's something fundamental about the way they view the 0:14:33.840 --> 0:14:36.760 universe that is just incompatible. We'll talk about exactly what 0:14:36.760 --> 0:14:39.200 that is in a minute. And all attempts so far 0:14:39.320 --> 0:14:43.440 to unify them have failed. Mathematically just do not work. 0:14:43.840 --> 0:14:46.080 So that's essentially what the struggle is. And so let's 0:14:46.080 --> 0:14:50.400 start with quantum mechanics. Quantum mechanics specifically quantum field theory, 0:14:50.440 --> 0:14:52.680 which is this description we talked about in the podcast. 0:14:52.680 --> 0:14:56.000 A lot of space being filled with quantum fields, and 0:14:56.120 --> 0:14:59.120 particles are like ripples in those fields that propagate through 0:14:59.160 --> 0:15:02.640 space and to with each other. That's very, very successful, right. 0:15:02.720 --> 0:15:05.840 It's an amazing theory. It describes all of the particle 0:15:05.920 --> 0:15:08.880 experiments that we've done. It's made very specific predictions of 0:15:08.960 --> 0:15:12.800 numbers like ten decimal places that have all been verified experimentally. 0:15:13.360 --> 0:15:16.000 It seems like a very accurate description of what happens 0:15:16.160 --> 0:15:20.120 to particles. But it assumes that space is not curved, 0:15:20.280 --> 0:15:23.280 that space is flat, that the shortest distance between two 0:15:23.280 --> 0:15:25.680 points is always what appears to us to be a 0:15:25.800 --> 0:15:29.080 straight line, and operating in flat space essentially means that 0:15:29.120 --> 0:15:32.760 we're ignoring gravity. Quantum field theory is very successful because 0:15:32.800 --> 0:15:35.920 basically gravity is irrelevant. If you have two particles and 0:15:35.920 --> 0:15:38.520 they're pushing against each other with powerful forces, you don't 0:15:38.520 --> 0:15:42.000 really care about the gravitational effects on two electrons because 0:15:42.000 --> 0:15:45.320 gravity is so weak compared to the other forces. So 0:15:45.440 --> 0:15:48.600 quantum field theory assumes that gravity is irrelevant and does 0:15:48.640 --> 0:15:51.840 a great job of describing what happens to quantum particles. Right. 0:15:51.880 --> 0:15:56.360 Quantum mechanics assumes a flat, spased universe, but general relativity 0:15:56.480 --> 0:15:59.760 kind of assumes the opposite. Yeah, general relativity tells us 0:16:00.160 --> 0:16:02.960 that the reason we have gravity is not because there's 0:16:03.000 --> 0:16:06.560 some force out there tugging on masses, but that space 0:16:06.760 --> 0:16:09.600 bends that when you put mass into a space, it 0:16:09.640 --> 0:16:13.200 curves space. And this is not curvature like relative to 0:16:13.440 --> 0:16:17.360 some external ruler. This is intrinsic curvature, which means that 0:16:17.400 --> 0:16:20.880 it changes the relative distances between points, and effectively, it 0:16:20.920 --> 0:16:24.400 makes the shortest distance between two points seem to us 0:16:24.560 --> 0:16:27.400 like a curve because we can't see this curvature directly, 0:16:27.760 --> 0:16:30.040 and so it appears to us like there's a force 0:16:30.360 --> 0:16:33.520 because things are moving along these curves. In reality, it's 0:16:33.560 --> 0:16:36.880 just the curvature of space. But general relativity assumes that 0:16:36.960 --> 0:16:40.560 everything has a specific location and velocity, and that can 0:16:40.640 --> 0:16:43.960 be perfectly well known. We call it a classical theory 0:16:44.000 --> 0:16:47.200 because it ignores the quantum mechanical nature of the world, 0:16:47.520 --> 0:16:50.640 the fact that particles, for example, can't be pinned down 0:16:50.680 --> 0:16:53.840 to have a specific location and velocity at all times. 0:16:54.200 --> 0:16:56.880 They don't have a trajectory like that. But general relativity 0:16:57.040 --> 0:17:01.160 assumes that everything does. Fortunately, because gravity is so weak, 0:17:01.360 --> 0:17:04.480 we've only tested general relativity in scenarios where you have 0:17:04.520 --> 0:17:07.280 a huge mass like a planet or a star or 0:17:07.320 --> 0:17:10.800 a black hole, where you can basically ignore quantum mechanics, 0:17:10.840 --> 0:17:13.359 so they sort of have each their own domains. They 0:17:13.440 --> 0:17:16.399 view the world very very differently. They make totally different, 0:17:16.440 --> 0:17:19.520 incompatible assumptions about the world, and they make predictions about 0:17:19.560 --> 0:17:21.960 different parts of the world, and they're both correct in 0:17:22.000 --> 0:17:25.080 their own regimes, right, Although I guess, you know, coming 0:17:25.119 --> 0:17:28.639 at this from the outside, not having been too in mercendies, 0:17:29.200 --> 0:17:32.160 they don't sound that incompatible to me. I guess it's 0:17:32.320 --> 0:17:35.320 maybe that's one of that something other people struggle with. 0:17:35.920 --> 0:17:37.640 I mean, it's sort of like one of them says 0:17:37.680 --> 0:17:40.160 that Daniel is tall, and the other one says Daniel 0:17:40.200 --> 0:17:44.560 wards glasses like those are not necessarily incompatible. Things like 0:17:44.600 --> 0:17:48.520 couldn't quantum fields exists in space that is also bending, 0:17:48.920 --> 0:17:52.520 And couldn't bending space exists in also in the universe 0:17:52.600 --> 0:17:55.920 where particles have a minimum size and are uncertain. Yeah, 0:17:55.960 --> 0:17:58.560 we think that probably it's possible to describe both because 0:17:58.560 --> 0:18:00.840 the universe exists and it seems to be self consistent. 0:18:01.119 --> 0:18:04.080 So we think it probably is possible to reconcile gravity 0:18:04.080 --> 0:18:07.600 and quantum mechanics because both things are happening in our world. 0:18:08.160 --> 0:18:10.159 We haven't been able to do that, Like light is 0:18:10.200 --> 0:18:12.960 being bent around the Sun and it's being bent around 0:18:13.200 --> 0:18:16.360 black holes. And we know light is quantized as well. 0:18:16.440 --> 0:18:18.760 Right well, let me give you an example of something 0:18:18.760 --> 0:18:21.720 that we can't do because we can't unify gravity and 0:18:21.760 --> 0:18:24.680 quantum mechanics, is that we don't know how to calculate 0:18:24.720 --> 0:18:28.280 the gravity of particles. Quantum particles, for example, don't have 0:18:28.320 --> 0:18:31.960 a specific location that have probabilities to be in different locations, 0:18:32.040 --> 0:18:33.800 Like electron could be on the other side of the 0:18:33.840 --> 0:18:35.960 room or could be right next to you. What is 0:18:35.960 --> 0:18:40.080 the gravity of that electron whose position is uncertain? General 0:18:40.080 --> 0:18:42.800 relativity doesn't allow for any uncertainty in the position. It 0:18:42.880 --> 0:18:45.800 says your gravity depends on where you are. If where 0:18:45.840 --> 0:18:48.639 you are is uncertain, then where is your gravity? Is 0:18:48.640 --> 0:18:51.760 your gravity also uncertain or is it shared between the 0:18:51.760 --> 0:18:55.639 two different locations? Does gravity collapse that wave function forcing 0:18:55.640 --> 0:18:58.240 the electron to be in one spot from where it's 0:18:58.240 --> 0:19:01.919 gravity emanates, or is have any quantum mechanical and it 0:19:01.960 --> 0:19:06.840 allows the superposition of different gravitational attractions. That's something we 0:19:06.880 --> 0:19:09.280 don't know the answer to. That's something we can't calculate 0:19:09.640 --> 0:19:11.520 right now because we don't have a theory that does 0:19:11.560 --> 0:19:15.040 gravity for quantum objects. Right, But I guess you know, 0:19:15.160 --> 0:19:18.160 particle has some uncertain to it to it in terms 0:19:18.160 --> 0:19:19.680 of where it is and where it's going. But if 0:19:19.720 --> 0:19:22.000 you step back far enough, it does have sort of 0:19:22.000 --> 0:19:24.159 a location, right. I mean, you step back far enough 0:19:24.200 --> 0:19:27.640 from a particle, you can calculate what its gravity is. Yeah, 0:19:27.640 --> 0:19:29.760 if you step back far enough or you love enough 0:19:29.840 --> 0:19:32.960 particles together, then they start to act like classical objects 0:19:33.000 --> 0:19:36.800 like a baseball. Baseball effectively has no uncertainty on where 0:19:36.840 --> 0:19:39.080 it is and it's velocity because it acts like a 0:19:39.080 --> 0:19:42.440 classical object, which is ten to twenty six quantum objects 0:19:42.480 --> 0:19:46.000 all moving together. And so general relativity assumes that that 0:19:46.080 --> 0:19:48.440 is still true the baseball description of the world when 0:19:48.440 --> 0:19:50.520 you get down to one electron. But we know that 0:19:50.560 --> 0:19:53.199 one electron doesn't move like a baseball. It doesn't have 0:19:53.280 --> 0:19:55.639 a whole path, and so we don't know how to 0:19:55.680 --> 0:19:59.360 talk about like how two electrons interact with each other gravitationally, 0:19:59.440 --> 0:20:01.359 And we can't usted either. We can't just go and 0:20:01.400 --> 0:20:04.600 look and watch two electrons pushing against each other gravitationally 0:20:04.840 --> 0:20:07.320 because the gravitational force is so weak that we could 0:20:07.320 --> 0:20:09.920 never measure that. And so it's a big question. Right. 0:20:09.920 --> 0:20:12.679 But you, for example, you are able to, for example, 0:20:12.720 --> 0:20:16.600 calculate the force between two electrons to like the electromagnetic 0:20:16.600 --> 0:20:19.479 force between two electrons, right, Like, you can do that, 0:20:19.640 --> 0:20:21.159 I guess the question is why can't you do it 0:20:21.240 --> 0:20:23.760 with gravity, Like why can't you juice kind of like 0:20:23.840 --> 0:20:27.359 average it out or use probability to figure out what 0:20:27.400 --> 0:20:30.879 the most probable gravity is. So we can calculate the 0:20:30.920 --> 0:20:34.440 gravitational force between two electrons if their positions are known, 0:20:35.040 --> 0:20:37.960 but because they're quantum objects, we don't know their positions. 0:20:38.160 --> 0:20:40.480 So what you're proposing, basically, is a theory of quantum 0:20:40.480 --> 0:20:43.840 gravity that says gravity is a quantum force and interacts 0:20:44.119 --> 0:20:47.400 not with the location of the objects but with their probabilities, 0:20:47.760 --> 0:20:50.840 that it actually interacts with the wave functions of these guys. 0:20:50.960 --> 0:20:53.800 So they're trying to turn gravity into a quantum field theory, 0:20:53.880 --> 0:20:55.600 which is fine and that's cool, and a lot of 0:20:55.600 --> 0:20:57.320 people are working on that. But when you do that, 0:20:57.320 --> 0:21:00.080 you run into a lot of mathematical problems. Basically, you 0:21:00.080 --> 0:21:03.080 get lots of infinities when you try to do these calculations, 0:21:03.160 --> 0:21:05.760 and we get infinities when we do all quantum field theories. 0:21:05.840 --> 0:21:08.480 Like we talked on the podcast about something called renormalization 0:21:08.480 --> 0:21:11.800 where we tuck infinities under the rug. For example, the 0:21:11.840 --> 0:21:14.159