WEBVTT - Can the Universe exist without space? 0:00:08.360 --> 0:00:11.200 Hey, Jorge, are you a hoarder or do you like 0:00:11.280 --> 0:00:15.680 to throw things away? We keep everything, we have, every drawing, 0:00:15.680 --> 0:00:20.320 my kids ever made. Man, not me. I value space 0:00:20.560 --> 0:00:24.400 more than stuff. I love to throw things away. Wow, 0:00:24.440 --> 0:00:26.320 what does your family give you for your birthday? Then? 0:00:26.600 --> 0:00:30.200 Empty space? Actually, my wife rent a dumpster and says 0:00:30.240 --> 0:00:33.320 I can throw out anything I want. It's like a 0:00:33.360 --> 0:00:36.600 negative present. Hey, space is precious. You know you can't 0:00:36.640 --> 0:00:38.680 have too much of it. You can't have too much 0:00:38.760 --> 0:00:42.519 nothing said nobody never, Nothing is better than nothing. This 0:00:42.640 --> 0:01:00.600 is the best nothing I ever got. Hi more handmade 0:01:00.600 --> 0:01:04.000 cartoonists and the creator of PhD comics. Hi. I'm Daniel, 0:01:04.080 --> 0:01:07.399 I'm a particle physicist and I really do love space. 0:01:07.720 --> 0:01:10.080 And Welcome to our podcast. Daniel and Jorge explain the 0:01:10.160 --> 0:01:13.160 university production of I Heart Radio, in which we explore 0:01:13.319 --> 0:01:17.240 all the stuff in space, empty space, not so empty space, 0:01:17.319 --> 0:01:20.840 space builled with really crazy bonk, or stuff that's hard 0:01:20.880 --> 0:01:24.960 to understand, and sometimes even the very nature of space. 0:01:25.120 --> 0:01:27.200 We talk about all of these things in this podcast, 0:01:27.280 --> 0:01:29.080 and we break them down, and our goal is to 0:01:29.200 --> 0:01:31.960 deliver them to you in a way that actually makes sense, 0:01:31.959 --> 0:01:34.840 so you go away thinking, huh, I get it, or 0:01:34.880 --> 0:01:37.760 at least I get it as much as scientists get it, 0:01:37.800 --> 0:01:40.720 which sometimes isn't that much. And sometimes it feels like 0:01:40.760 --> 0:01:43.760 we're talking about a whole lot of nothing, and sometimes 0:01:43.800 --> 0:01:46.400 we are literally talking about nothing, and sometimes we're trying 0:01:46.400 --> 0:01:51.360 to figure out what is nothing exactly right. Yeah, deep questions, now, Daniel, 0:01:51.400 --> 0:01:53.040 when you say you love space, do you mean like 0:01:53.120 --> 0:01:56.720 you love, you know, just space travel, like where the 0:01:56.760 --> 0:01:59.240 planets are, or did you just like, you know, having 0:01:59.520 --> 0:02:02.120 the idea of space in your life. I love all 0:02:02.160 --> 0:02:04.639 of it. I love outer space, I love deep space. 0:02:04.680 --> 0:02:07.160 I live near space. I also love having space in 0:02:07.160 --> 0:02:09.480 my living room, Like it's not unusual for me to 0:02:09.480 --> 0:02:11.240 toss out a piece of furniture and go, you know what, 0:02:11.560 --> 0:02:14.240 the room is just better with nothing there. You like 0:02:14.280 --> 0:02:16.840 everything about space. There's nothing negative about space for you. 0:02:17.800 --> 0:02:20.040 I'm pretty pro space. Yeah. Absolutely, you would live in 0:02:20.080 --> 0:02:23.480 an empty box if you could, exactly. I'm like a 0:02:23.520 --> 0:02:26.840 cat that way. Are you looking forward and to your 0:02:26.919 --> 0:02:29.519 children leaving the house then, because that's just more space, 0:02:30.400 --> 0:02:32.680 is more space. I'm not looking for to them leaving, 0:02:32.840 --> 0:02:34.560 but if they do, I'm looking forward to throwing all 0:02:34.560 --> 0:02:37.520 their stuff away. Oh man, that's going to come back 0:02:37.560 --> 0:02:40.720 to want you. They're like, why did you throw away 0:02:40.760 --> 0:02:45.119 my comic book collection that's worth three million dollars? Now, yeah, exactly, 0:02:45.160 --> 0:02:48.079 but this space is priceless, right, Well, we like to 0:02:48.120 --> 0:02:51.520 talk about space in this podcast and also about what 0:02:51.639 --> 0:02:53.880 it represents, what it means, because it's kind of a 0:02:54.000 --> 0:02:57.760 topic that businesses don't have a super clear idea about. 0:02:57.880 --> 0:03:00.320 That's right. It's one of these really fun quite in 0:03:00.360 --> 0:03:03.240 physics because only recently did we figure out that it's 0:03:03.280 --> 0:03:05.720 a question that sort of has an answer. It's a 0:03:05.800 --> 0:03:08.720 question that's worth asking. It's one of these questions that's 0:03:08.760 --> 0:03:11.000 so basic that we just sort of assumed we knew 0:03:11.040 --> 0:03:13.520 the answer. You know, space is space. It's the nothing, 0:03:13.560 --> 0:03:16.840 it's the emptiness. And only recently have we realized, Wow, 0:03:16.880 --> 0:03:19.639 space could be much more than that, and it really 0:03:19.680 --> 0:03:23.160 deserves our attention. Right. Even more important is this sort 0:03:23.160 --> 0:03:27.080 of idea that maybe we don't need space, Like maybe 0:03:27.160 --> 0:03:30.080 it's just sort of like an add on to the universe. Yeah, 0:03:30.200 --> 0:03:32.640 is it at the foundation of reality or is it 0:03:32.720 --> 0:03:35.800 just something that fills up something else? You know, imagine 0:03:35.840 --> 0:03:37.560 what it would have been like to be a person 0:03:37.640 --> 0:03:40.600 ten thousand years ago. You never would have experienced reality 0:03:40.640 --> 0:03:43.880 without air, for example, So the concept of like a vacuum, 0:03:43.880 --> 0:03:46.040 a place where there was no air would have been 0:03:46.080 --> 0:03:48.640 totally alien to you. So now, of course we know 0:03:48.720 --> 0:03:50.920 that that's possible. It seems obvious that air is not 0:03:51.040 --> 0:03:53.560 a fundamental property of the universe. But we're at the 0:03:53.600 --> 0:03:56.640 next level and wondering, like, well, is space fundamental? Could 0:03:56.640 --> 0:03:59.240 you take it apart? Do you really need it? Yeah? 0:03:59.480 --> 0:04:02.280 In fact, so the universe, it doesn't have any air 0:04:02.360 --> 0:04:06.120 in it, right, most of the universe is pretty empty. Yeah, 0:04:06.240 --> 0:04:08.320 from that point of view, exactly, we were dealing with 0:04:08.360 --> 0:04:11.720 a very unrepresentative example. And we do this all the 0:04:11.800 --> 0:04:15.000 time in science. We assume that the things we experience 0:04:15.080 --> 0:04:18.400 our universal and we can generalize from these examples to 0:04:18.480 --> 0:04:21.039 the whole universe. We're doing this all the time, left 0:04:21.080 --> 0:04:23.760 and right without even realizing it. So now we're asking 0:04:23.760 --> 0:04:27.200 a similar question about space. You know, our our assumptions 0:04:27.200 --> 0:04:30.160 about space valid. Can we break it apart? Do we 0:04:30.240 --> 0:04:32.120 even need it? Is it possible for it to have 0:04:32.200 --> 0:04:35.640 bubbled up from something else? Yeah, it's a space topic. 0:04:35.839 --> 0:04:37.800 But space is pretty empty. I think we have a 0:04:37.800 --> 0:04:40.599 whole podcast episode about that, right, Like, what's the average 0:04:40.640 --> 0:04:43.040 density of the universe or like how much stuff is 0:04:43.080 --> 0:04:46.560 there really on a like cubic foot Yeah, we do 0:04:46.640 --> 0:04:48.960 have a whole podcast about how empty spaces and we 0:04:49.000 --> 0:04:50.640 take you on a journey from the top of the 0:04:50.680 --> 0:04:54.520 atmosphere into the Solar System and then out into interstellar 0:04:54.560 --> 0:04:58.520 space and then finally into intergalactic space. And mostly space 0:04:58.680 --> 0:05:02.640 is intergalactic space, right, Like there are these huge streams 0:05:02.680 --> 0:05:06.520 of galactic clusters of galaxies swinging around each other, but 0:05:06.640 --> 0:05:09.480 between them there are these vast bubbles and voids that 0:05:09.720 --> 0:05:12.720 don't have galaxies in them. So most of the universe 0:05:12.760 --> 0:05:17.120 sort of by volume, is this intergalactic space, which is 0:05:17.120 --> 0:05:19.120 not totally empty. There's still stuff in there. That's a 0:05:19.160 --> 0:05:22.120 little bit of dark matter, there's definitely dark energy. But 0:05:22.400 --> 0:05:24.839 it's most of the universe and it's pretty empty, but 0:05:25.040 --> 0:05:28.280 not down to zero. Yeah, and there's a lot of 0:05:28.320 --> 0:05:31.400 it space, I mean, in the universe, there's a whole 0:05:31.400 --> 0:05:32.800 bunch of it. Like if you are going at the 0:05:32.800 --> 0:05:35.240 speed of light, it would still take you as far 0:05:35.279 --> 0:05:37.799 as we know right now, you know, tens of billions 0:05:37.880 --> 0:05:40.040 of years just to go from one side to the other. 0:05:40.480 --> 0:05:42.760 That's a lot of time. Absolutely, And remember the speed 0:05:42.760 --> 0:05:45.080 of light is like mind boggling lee fast, right, It's 0:05:45.120 --> 0:05:49.440 incredibly fast. And yet these distances, even inside our Solar 0:05:49.480 --> 0:05:53.080 System are incredible, Like it takes minutes for light to 0:05:53.120 --> 0:05:55.880 get from here just to Mars, which is our neighbor, 0:05:56.360 --> 0:05:58.839 and hours to get out to the outer Solar system. 0:05:59.000 --> 0:06:01.960 You know, when we communicate with probes and rovers and 0:06:02.000 --> 0:06:04.600 stuff on other planets, the reason you can't drive them 0:06:04.680 --> 0:06:07.400 is because they are so far away. You can't do 0:06:07.480 --> 0:06:09.880 real time driving because the lag is too long. And 0:06:09.880 --> 0:06:13.200 that's just inside our Solar system. So the distances to 0:06:13.320 --> 0:06:16.880 other galaxies millions of light years and deeper into space 0:06:16.960 --> 0:06:19.040 billions of light years, they're hard for us to get 0:06:19.080 --> 0:06:22.200 our mind around. So, yeah, space is pretty spacious. I 0:06:22.200 --> 0:06:23.960 guess I hadn't thought about it before. Like if even 0:06:24.000 --> 0:06:26.720 if you're Superman or Superwoman and you're traveling, you can 0:06:26.800 --> 0:06:28.200 you're able to fly at the speed of light, it 0:06:28.200 --> 0:06:31.039 would still take you like a billion years just to 0:06:31.320 --> 0:06:33.880 you know, go to the other galaxies out there in 0:06:33.880 --> 0:06:36.560 the universe. Yeah, well that's an interesting question. Does Superman 0:06:36.640 --> 0:06:38.440 have to travel at the speed of light? Can he 0:06:38.520 --> 0:06:41.880 be superluminal? I mean, how far away is his home 0:06:41.920 --> 0:06:44.640 planet anyway, I don't know you're the physicist. I just 0:06:44.640 --> 0:06:47.760 read the comic books. I don't dissect them scientifically. I'll 0:06:47.800 --> 0:06:49.880 go find out exactly where his home planet is and 0:06:49.920 --> 0:06:52.360 figure out if he broke the law on the way here, 0:06:52.360 --> 0:06:54.560 and if so, I'll issue him a physics ticket. Well, 0:06:54.560 --> 0:06:56.600 he can just bring it up with his heat visioned Daniel. 0:06:57.040 --> 0:06:58.600 And also, how are you going to arrest him? Good 0:06:58.680 --> 0:07:04.719 luck with that, citizens arrest Mr Superman. But yeah, there's 0:07:04.760 --> 0:07:06.719 a lot of space out there. It's definitely not a 0:07:06.760 --> 0:07:09.360 small part of the universe. But I guess the question 0:07:09.520 --> 0:07:13.280 is it a necessary part of the universe. So today 0:07:13.280 --> 0:07:20.960 on the podcast, we'll be asking the question can the 0:07:21.080 --> 0:07:27.520 universe exist without space? Space? Space? Space space? That question 0:07:27.600 --> 0:07:29.840 is so profound it needs an echo. It echoes through 0:07:29.840 --> 0:07:33.480 the vacuum of infinity, through the vacuum of our understanding 0:07:33.600 --> 0:07:36.800 of the universe. Absolutely, through the empty space in my head. 0:07:37.560 --> 0:07:39.800 But it's a fun question, and it sort of mirrors 0:07:39.840 --> 0:07:42.120 the way I treat furniture. You know, I look around 0:07:42.160 --> 0:07:44.440 my house and I asked myself, do we need that chair? 0:07:44.520 --> 0:07:46.760 Nobody ever sits there and we get rid of it. 0:07:46.800 --> 0:07:49.880 We're like, ah, it's better off. And now we're cycling 0:07:49.880 --> 0:07:52.400 through modern physics and we're like, m, do we really 0:07:52.440 --> 0:07:55.560 need the whole concept of space? Like is it really 0:07:55.920 --> 0:07:58.400 have to be included in the sort of fundamental list 0:07:58.440 --> 0:08:00.960 of things you need to build a universe or is 0:08:00.960 --> 0:08:03.840 it like you know, ice cubes or atoms or hurricanes, 0:08:04.200 --> 0:08:07.560 something that you know comes from your more basic ingredients. 0:08:07.680 --> 0:08:09.320 I would hate to be a furniture in your house. 0:08:09.360 --> 0:08:12.400 I feel like I would live in constant fear. Yes, absolutely, 0:08:12.520 --> 0:08:15.840 you must constantly justify your existence in my house, or 0:08:16.000 --> 0:08:19.640 you're on the trashy. It's like huff Post reporters. You know, 0:08:19.920 --> 0:08:23.160 hopefully that's just for your furniture, not your family as well. 0:08:23.320 --> 0:08:26.960 Or pets. Absolutely, living creatures definitely belong to the family. 0:08:27.040 --> 0:08:29.360 Chairs not so much so if you could have a 0:08:29.360 --> 0:08:31.920 bigger house, would you have a bigger house? No? No, 0:08:32.000 --> 0:08:33.960 I don't need a bigger house. In fact, I had 0:08:34.040 --> 0:08:36.120 some friends who once moved to a bigger house and 0:08:36.120 --> 0:08:38.360 I almost ruin their marriage because they ended up shouting 0:08:38.400 --> 0:08:41.439 each other from different rooms across the house. And they 0:08:41.480 --> 0:08:43.040 did better when they had to, you know, share a 0:08:43.040 --> 0:08:45.640 small apartment. Yeah, we talked about this and I offered 0:08:45.640 --> 0:08:49.760 the better solution of just getting an intercom system. You 0:08:49.800 --> 0:08:52.079 are going to engineer everybody's marriage. Huh. I'm gonna go 0:08:52.120 --> 0:08:54.840 to your your couple's counseling. There's a solution for everything 0:08:54.840 --> 0:08:58.280 in engineering, marital engineering. Wow, that's a better name for therapist. 0:08:58.760 --> 0:09:00.840 But anyways, Yeah, it's a big question whether or not 0:09:00.960 --> 0:09:04.240 we need space in the universe. It seems pretty fundamental, 0:09:04.480 --> 0:09:07.280 you know, like, how can you have a universe without space? Like, 0:09:07.400 --> 0:09:10.440 isn't space the universe? Yeah, but just because it's hard 0:09:10.440 --> 0:09:13.640 to imagine doesn't mean it's not reality. Right. A lot 0:09:13.720 --> 0:09:16.320 of what reality is was difficult for us to wrap 0:09:16.360 --> 0:09:19.040 our minds around. So when you do this kind of exploration, 0:09:19.040 --> 0:09:21.480 you got to sort of be willing to give up 0:09:21.559 --> 0:09:25.400 something you thought was fundamental, something you assumed was inherent, 0:09:25.480 --> 0:09:28.760 and ask your question whether it can come from something else. 0:09:28.880 --> 0:09:31.080 All right, Well, as usual, we were wondering how many 0:09:31.080 --> 0:09:34.440 people out there have thought about this spacious question, whether 0:09:34.559 --> 0:09:37.760 or not we need space. So Daniel went out there 0:09:37.840 --> 0:09:40.480 into the well to the internet to ask people is 0:09:40.520 --> 0:09:43.679 it possible to have a universe without space. Here's what 0:09:43.720 --> 0:09:47.240 they had to say. Oh, that's a good question. I 0:09:47.280 --> 0:09:52.120 don't think, so okay, why, Well, I don't know. I 0:09:52.280 --> 0:09:54.520 don't know. I don't know. I don't know why. I 0:09:54.640 --> 0:09:59.400 just know I think space is only one of the dimensions, right, 0:10:00.160 --> 0:10:01.920 you can probably have a universe. It's just time and 0:10:01.960 --> 0:10:06.760 maybe not space. I'm gonna say yes. Well, my understanding 0:10:06.840 --> 0:10:11.360 is that, yeah, I guess you can. Um. I mean, 0:10:11.520 --> 0:10:14.600 was this space when the Big Bang occurred in the 0:10:14.640 --> 0:10:17.560 moments after that, or was it all dense metal with 0:10:17.679 --> 0:10:22.080 zero space? But my understanding is that if you have 0:10:22.120 --> 0:10:24.680 a different universe that could operate off a completely different 0:10:24.679 --> 0:10:27.800 set of physical laws. So I guess never say never 0:10:27.880 --> 0:10:32.480 in that regard. You can have a universe without space. 0:10:34.120 --> 0:10:41.720 Our situation with matter having out competed antimatter, I think 0:10:41.920 --> 0:10:48.960 is actually pretty unique. Um there, and I would I 0:10:49.000 --> 0:10:52.840 think they're a little universe blips all over where universe 0:10:52.920 --> 0:10:58.320 pops into existence and annihilates and no spaces created. I 0:10:58.320 --> 0:11:02.880 guess you can have universe with out just this dimension space, 0:11:04.160 --> 0:11:08.640 and you can have all the other dimensions possible, but 0:11:09.600 --> 0:11:12.720 it will be crowded. I guess it would mean what 0:11:12.800 --> 0:11:16.920 you mean by universe, because before the Big Bang all 0:11:17.000 --> 0:11:20.200 the universe was there. It was just compressed and to 0:11:20.320 --> 0:11:23.520 my knowledge, there was no space. So if you can't 0:11:23.559 --> 0:11:26.959 that just the universe then yeah, all right, some mixed 0:11:27.000 --> 0:11:29.559 reactions here. Some people could live without it, some people 0:11:29.640 --> 0:11:32.079 could really want it. Yeah. It basically wraps up the 0:11:32.120 --> 0:11:35.280 whole question of what spaces and where it comes from 0:11:35.280 --> 0:11:38.160 and all these answers I see echoes of general relativity 0:11:38.160 --> 0:11:41.880 and quantum mechanical perspectives on this question. So good job listeners, 0:11:42.160 --> 0:11:44.199 And to those of you who would like to participate 0:11:44.240 --> 0:11:48.200 in future rounds of answer random questions for the podcast, 0:11:48.280 --> 0:11:51.079 please write to us two questions at Daniel and Jorge 0:11:51.120 --> 0:11:53.000 dot com. There's a lot of reference here and the 0:11:53.000 --> 0:11:55.640 answers to the Big Bang to write that's something I 0:11:55.640 --> 0:11:58.560 hadn't thought about before. Was their space before the Big Bang? 0:11:58.640 --> 0:12:01.600 At the Big Bang? Or was space created at some 0:12:01.720 --> 0:12:05.760 point in the history of the universe? Yeah, space and time? Right, 0:12:06.000 --> 0:12:08.840 all right, Well, let's dig into it, Daniel. Let's start 0:12:08.840 --> 0:12:11.280 with maybe the basic stuff, like what is space? How 0:12:11.320 --> 0:12:15.000 do physicists think about what space is? Yeah, this is 0:12:15.000 --> 0:12:18.440 a great question, and we have sort of two answers 0:12:18.520 --> 0:12:22.040 for what space is based on whether you're thinking about 0:12:22.040 --> 0:12:24.400 it from the point of view of like quantum mechanics 0:12:24.760 --> 0:12:26.400 or whether you're thinking about it from the point of 0:12:26.440 --> 0:12:29.480 view of general relativity. And remember that these are the 0:12:29.520 --> 0:12:33.320 two pillars of thinking in modern physics, too great ways 0:12:33.360 --> 0:12:37.160 to describe parts of the experiments we've done. Quantum Mechanics 0:12:37.240 --> 0:12:40.280 describes basically everything that has to do with little particles 0:12:40.280 --> 0:12:43.280 at small scales and all the forces that were familiar 0:12:43.320 --> 0:12:46.640 with except for gravity, and general relativity talks about how 0:12:46.720 --> 0:12:49.320 space is curved and it's bent, and that's really what 0:12:49.520 --> 0:12:52.200 gravity is. And so the answer to the question what 0:12:52.440 --> 0:12:55.440 is space sort of depends on whose perspective you want 0:12:55.480 --> 0:12:57.360 to take first? What do you mean, how can something 0:12:57.440 --> 0:13:00.400 depend on your perspective? Aren't you looking for like one answer? 0:13:00.559 --> 0:13:03.400 We are absolutely looking for one answer, but we don't 0:13:03.480 --> 0:13:06.640 have one answer. We have two theories, quantum mechanics and 0:13:06.679 --> 0:13:10.480 general relativity. They treat space very differently and we haven't 0:13:10.480 --> 0:13:12.880 been able to unify them. So the short answer is 0:13:13.000 --> 0:13:15.000 we don't know what space is because we don't have 0:13:15.040 --> 0:13:18.400 a single coherent theory for the whole universe, and the 0:13:18.440 --> 0:13:21.760 two theories we do have disagree about what space is, 0:13:21.800 --> 0:13:23.959 all right, So what are the two theories about space? 0:13:24.240 --> 0:13:27.160 And is there enough space between them to tell the difference. Well, 0:13:27.200 --> 0:13:30.920 you know, let's start with quantum mechanics. Quantum mechanics is 0:13:30.960 --> 0:13:34.240 the theory that tells us how electromagnetism works, how the 0:13:34.280 --> 0:13:37.440 weak force works, you know, how photons move, and it 0:13:37.520 --> 0:13:41.840 tells us that space is fundamental. It assumes that space 0:13:41.880 --> 0:13:44.320 exists and it adds stuff to it. So if you're 0:13:44.320 --> 0:13:47.280 gonna build a universe using at least our current theory 0:13:47.320 --> 0:13:49.960 of quantum mechanics, then you start from space. You say, 0:13:50.080 --> 0:13:52.600 let's assume there's a space, and then at every point 0:13:52.640 --> 0:13:54.560 in that space, I'm gonna say whether or not there's 0:13:54.559 --> 0:13:56.840 a quantum field and how much energy it has. But 0:13:56.960 --> 0:13:59.160 it's sort of like at the bedrock of the whole theory, 0:13:59.240 --> 0:14:03.040 just like assuming that space and time are things that 0:14:03.120 --> 0:14:05.480 you can put fields in them, right, because that's kind 0:14:05.520 --> 0:14:08.680 of baked into the definition of a field, right, Like 0:14:08.760 --> 0:14:11.280 you can't have a field without space, like a field 0:14:11.440 --> 0:14:15.240 is by definition like how things vary in a space. 0:14:15.360 --> 0:14:17.920 That's right exactly. And we'll talk later about whether you 0:14:17.920 --> 0:14:21.600 can generalize that to like abstract spaces rather than physical 0:14:21.680 --> 0:14:24.160 spaces and what that means. But you're right for the 0:14:24.160 --> 0:14:26.600 physical fields that we're talking about, you know, like the 0:14:26.600 --> 0:14:30.560 photon field. It's just a value all through space. But 0:14:30.640 --> 0:14:32.800 as you say, space is fundamental to that. You need 0:14:32.880 --> 0:14:35.320 to know like there's a certain value of field here 0:14:35.440 --> 0:14:39.160 and over there at a different location in space, it 0:14:39.240 --> 0:14:41.560 has a different value. And for example, the shrouding your 0:14:41.600 --> 0:14:46.080 equation tells us how a wave function exists across space, 0:14:46.120 --> 0:14:49.120 and how that wave function evolves through time it spreads 0:14:49.120 --> 0:14:52.880 out through space, for example. So it's pretty deeply baked in. 0:14:53.120 --> 0:14:55.680 So quantum field theory sort of the modern version of it, 0:14:55.720 --> 0:14:57.960 as we think about it, doesn't really have an answer 0:14:58.000 --> 0:15:00.800 to the question of what is space. It just sort 0:15:00.800 --> 0:15:03.840 of like assumes it exists and starts from there. It's 0:15:03.880 --> 0:15:06.640 like the basical list of ingredients. Would you say then 0:15:06.640 --> 0:15:10.600 that maybe quantum fields defined space or do you think 0:15:10.840 --> 0:15:14.000 space could exist without quantum fields. Well, that's a great question. 0:15:14.200 --> 0:15:17.880 In our current theory, you can't have space without quantum fields, 0:15:17.880 --> 0:15:21.240 Like quantum fields filled the entire universe. There's no sense 0:15:21.280 --> 0:15:23.280 in which you could have space without them. That's just 0:15:23.280 --> 0:15:26.520 sort of according to the theory. But do they define space? 0:15:27.040 --> 0:15:30.200 I think they're deeply coupled to it. Yeah, absolutely, so 0:15:30.200 --> 0:15:32.680 I think it's definitely part of the inherent nature of 0:15:32.720 --> 0:15:36.080 space in quantum field theory that you have these fields 0:15:36.120 --> 0:15:38.480 that live on top of it. But remember that quantum 0:15:38.520 --> 0:15:41.400 field theory can also have stuff in it that doesn't 0:15:41.400 --> 0:15:43.920 sort of come into the very beginning, right, Like we 0:15:43.960 --> 0:15:47.400 can talk about the very basic ingredients of the universe, 0:15:47.680 --> 0:15:50.840 space and quantum fields, but we don't add to that 0:15:50.920 --> 0:15:53.840 things like you know the atom, right, The atom is 0:15:53.880 --> 0:15:56.760 not a required element of the definition of the universe. 0:15:56.960 --> 0:16:00.040 It comes from that other stuff. So the ad and 0:16:00.200 --> 0:16:02.920 we think it exists, but it's not like fundamental. And 0:16:03.000 --> 0:16:04.920 remember the goal of physics, as you say, is to 0:16:05.000 --> 0:16:09.040 come to one theory, one explanation, one most basic list 0:16:09.120 --> 0:16:11.760 of ingredients and the rules for combining them that then 0:16:11.840 --> 0:16:16.040 explains everything else. So we're constantly trying to throw stuff 0:16:16.120 --> 0:16:18.680 out on purpose so we can get like the minimal 0:16:18.760 --> 0:16:22.160 list of fundamental things that can then explain everything else. 0:16:22.600 --> 0:16:25.320 As emergent. We want to explain ice cream and atoms 0:16:25.320 --> 0:16:28.800 and hurricanes in terms of the simpler, more basic elements. 0:16:28.880 --> 0:16:30.840 Do you guys want the dumpster then too, so you 0:16:30.880 --> 0:16:34.640 can throw out theories. I definitely want to throw space 0:16:34.680 --> 0:16:37.800 out on the physics dumpster. I would love to explain 0:16:37.880 --> 0:16:40.920 space in terms of something more basic and fundamental and say, man, 0:16:40.960 --> 0:16:43.760 remember when we had space criming in here and we 0:16:43.800 --> 0:16:46.920 had no space because we had so much space. But 0:16:46.960 --> 0:16:49.080 then if there's no space, then there's no space in 0:16:49.080 --> 0:16:53.640 the dumpster either, Daniel, where would you throw it out? Oh? Man, 0:16:53.760 --> 0:16:55.880 I'll get a bigger dumpster, all right, So then that's 0:16:56.080 --> 0:16:59.960 quantum mechanics. But then general relativity has a different view 0:17:00.160 --> 0:17:03.640 of space. Yeah, General relativity tells us that space is 0:17:03.640 --> 0:17:06.560 not something which is just like inherent and that you 0:17:06.600 --> 0:17:11.000 can assume. General relativity tells us that space is really different. 0:17:11.200 --> 0:17:14.960 It's dynamical. It's not like the backdrop for everything. Instead, 0:17:14.960 --> 0:17:17.479 it's in this dance with matter. Right. When you have 0:17:17.600 --> 0:17:21.320 matter and energy around, space bends and it curves, and 0:17:21.359 --> 0:17:24.040 it can do weird things like it can ripple, right, 0:17:24.119 --> 0:17:26.240 and it can expand. And this is the things that 0:17:26.280 --> 0:17:29.280 we see, like we see ripples in space. We know 0:17:29.400 --> 0:17:32.879 that this general relativity picture is at least approximately correct. 0:17:32.880 --> 0:17:35.400 It might not be the fundamental theory of the universe, 0:17:35.560 --> 0:17:39.000 but it's really accurate. It predicts these gravitational waves and 0:17:39.040 --> 0:17:42.600 we see them. It can accommodate at least the accelerated 0:17:42.640 --> 0:17:46.200 expansion of the universe in terms of a cosmological constant. 0:17:46.320 --> 0:17:49.359 We don't understand why that's there, what's happening, etcetera, but 0:17:49.400 --> 0:17:52.119 it can be accommodated in general relativity. So it's very 0:17:52.119 --> 0:17:56.159 successful description of how matter and space interact. And it 0:17:56.280 --> 0:17:58.399 suggests that space is not fundamental, that it sort of 0:17:58.400 --> 0:18:00.800 states at the same level as matter our energy, because 0:18:00.840 --> 0:18:03.600 the too sort of have this feedback loop between each other. 0:18:04.000 --> 0:18:06.600 Basically says that space is a thing, right like, it's 0:18:06.600 --> 0:18:10.919 not static, it doesn't exist, it doesn't ignore matter, you know, 0:18:11.040 --> 0:18:13.600 like it responds to matter, and you know, it's not 0:18:13.680 --> 0:18:16.760 independent of matter exactly. And you can do these weird 0:18:16.800 --> 0:18:19.160 things that we never imagined that it could do, which 0:18:19.200 --> 0:18:21.679 means it might be able to do other weird things 0:18:21.760 --> 0:18:25.240 we also hadn't yet had the imagination to do. Anytime, 0:18:25.240 --> 0:18:28.080 we're limited by our imagination. I'm always skeptical that we've 0:18:28.160 --> 0:18:31.399 thought of everything. I know, the theorists are very smart, 0:18:31.440 --> 0:18:33.800 and even our science fiction authors are always pushing the 0:18:33.840 --> 0:18:36.520 boundaries of creativity when it comes to like, you know, 0:18:36.600 --> 0:18:40.159 intellectual concepts. But there's always the possibility that there's always 0:18:40.160 --> 0:18:42.240 something else out there we just haven't thought of that 0:18:42.280 --> 0:18:44.960 could be happening in our universe. So space could have 0:18:45.080 --> 0:18:49.040 really weird properties that we never imagined. Imagine, for example, 0:18:49.119 --> 0:18:52.480 being a scientist that's a fish swimming through water all 0:18:52.520 --> 0:18:54.920 the time and not realizing, you know, that space could end, 0:18:55.280 --> 0:18:58.040 or that your water wasn't actually fundamental, and they could 0:18:58.040 --> 0:19:00.760 do other weird things like boil and turn into a gas. 0:19:01.200 --> 0:19:03.920 You know, space like that could have other phases, other 0:19:03.960 --> 0:19:06.840 weird properties we just haven't observed yet, and so we 0:19:06.880 --> 0:19:09.440 assume are impossible because I guess, once you can get 0:19:09.600 --> 0:19:12.560 space to bend or ripple or expand then who knows 0:19:12.560 --> 0:19:14.399 what you can make it do? Who knows what you 0:19:14.440 --> 0:19:17.399 can make it do exactly? And the solutions to general 0:19:17.400 --> 0:19:19.959 relativity are so complicated and difficult, and that it's not 0:19:20.040 --> 0:19:23.600 possible to conceive of all the possible configurations that are 0:19:23.600 --> 0:19:26.080 consistent with it. Those are the two views of space. 0:19:26.160 --> 0:19:28.879 One says that it's something that you know, can't touch 0:19:29.080 --> 0:19:31.080 or that you live on top of, and the other 0:19:31.119 --> 0:19:33.120 one says that it's something that it's more of a thing, 0:19:33.200 --> 0:19:36.280 like it's dynamic and you can manipulate it and it 0:19:36.359 --> 0:19:39.240 can change, So that those are the two basic views 0:19:39.240 --> 0:19:41.679 about space, right, But it doesn't sort of explain what 0:19:41.840 --> 0:19:45.000 space is. It's just sort of like how you regard space. Yeah, 0:19:45.000 --> 0:19:47.479 but that's sort of what space is. You know, space 0:19:47.560 --> 0:19:50.199 is how we treat it. Some people might say space 0:19:50.280 --> 0:19:54.000 is just like a mathematical construct in our minds. You know, 0:19:54.080 --> 0:19:57.600 that's not actually something that's physical. For example, in quantum mechanics, 0:19:57.720 --> 0:20:01.240 we never deal with space itself directly, right, All we 0:20:01.320 --> 0:20:04.280 ever do is deal with the fields in space. We 0:20:04.400 --> 0:20:07.600 never like interact with space itself, and so it's sort 0:20:07.600 --> 0:20:10.359 of like just an abstraction. It's just like a way 0:20:10.359 --> 0:20:13.800 of thinking about organizing these fields. Whereas in general relativity, 0:20:13.920 --> 0:20:16.439 like spaces the thing. It's the thing that's keeping us 0:20:16.480 --> 0:20:19.520 on the Earth. It explains gravity, which is pretty important. 0:20:19.640 --> 0:20:22.119 So you know, how we represent them in our theories 0:20:22.200 --> 0:20:24.040 goes a long way to telling you what we think 0:20:24.080 --> 0:20:26.159 they are. All right, Well, I think that sets the 0:20:26.200 --> 0:20:30.080 space for a deeper discussion about space and whether or 0:20:30.119 --> 0:20:32.280 not Daniel can through it in the dumpster or not. 0:20:32.480 --> 0:20:36.639 Please please please, please, please please please. I would be 0:20:36.680 --> 0:20:40.240 so offended if I was space right now, I would 0:20:40.359 --> 0:20:43.760 limit your space Daniel. But let's get into that question 0:20:43.800 --> 0:20:46.440 and also whether or not we will ever be able 0:20:46.520 --> 0:20:49.560 to know what the answer is. But first, let's take 0:20:49.600 --> 0:21:05.119 a quick break. All right, we're talking about space and 0:21:05.160 --> 0:21:07.560 whether or not we can just toss it out, Daniel, 0:21:07.800 --> 0:21:10.840 I feel like that's so unappreciative. How can you just 0:21:11.000 --> 0:21:14.439