WEBVTT - What is space? 0:00:06.360 --> 0:00:09.680 Some of the deepest mysteries of the universe are so big, 0:00:10.039 --> 0:00:14.480 so imposing, so important that even asking questions about what 0:00:14.560 --> 0:00:17.520 they are and how they work it can leave us confused. 0:00:17.760 --> 0:00:20.320 That's because we have to spend some time thinking about 0:00:20.400 --> 0:00:24.600 what exactly we're asking and what kind of answer we want. 0:00:25.079 --> 0:00:27.760 But we shouldn't shy away from these kinds of questions 0:00:27.800 --> 0:00:32.000 because they are the most important questions. Understanding the nature 0:00:32.120 --> 0:00:35.360 of our reality means understanding the context of our lives, 0:00:35.800 --> 0:00:38.920 where we live, how we live, maybe even why we live. 0:00:39.400 --> 0:00:42.159 And what the universe has taught us is that it 0:00:42.200 --> 0:00:47.240 always requires persistent, careful effort to unpack the deepest mysteries. 0:00:47.479 --> 0:00:49.680 We have been chiseling away at the rock face of 0:00:49.680 --> 0:00:54.520 physics for thousands of years, mostly cluelessly, but occasionally a 0:00:54.720 --> 0:00:57.520 great hunk of understanding will open up and will see 0:00:57.560 --> 0:01:00.640 everything in a new light. So it's worth asking the 0:01:00.680 --> 0:01:04.840 biggest questions, the ones where the question itself can be confusing, 0:01:05.200 --> 0:01:08.319 because looking for answers might eventually help us figure it 0:01:08.360 --> 0:01:11.759 all out, or help us realize we're asking the wrong question. 0:01:12.040 --> 0:01:14.440 So today on the podcast, we're going to dig deep 0:01:14.600 --> 0:01:17.679 into what we know about maybe the most basic question 0:01:17.959 --> 0:01:23.240 about the universe. We'll be asking what is space. 0:01:37.520 --> 0:01:40.960 Welcome to Daniel and Kelly's Extraordinary Universe. Today we are 0:01:41.000 --> 0:01:44.920 talking about what is space? And I am Kelly Wienersmith, 0:01:45.000 --> 0:01:47.240 and I take up space. How about you? 0:01:49.640 --> 0:01:52.600 I'm Daniel Whitson. I'm a professor of physics, which means 0:01:52.600 --> 0:01:55.640 I probably should understand something about space. 0:01:56.080 --> 0:01:57.840 I'm going to start with a confession. So, like when 0:01:57.880 --> 0:02:00.480 I was in high school and college, I did really 0:02:00.560 --> 0:02:02.600 well in physics. I was in the honors classes, I 0:02:02.640 --> 0:02:04.960 got a's. I really liked the stuff about circuitry. But 0:02:05.040 --> 0:02:07.840 whenever we would talk about what is space or what 0:02:07.960 --> 0:02:11.760 is time? I would feel very frustrated because like you 0:02:11.880 --> 0:02:14.079 were taking this thing that I felt like I could 0:02:14.120 --> 0:02:16.000 work with in my day to day life, and it 0:02:16.040 --> 0:02:20.800 felt like it was being made unnecessarily complicated. And I 0:02:20.800 --> 0:02:23.160 think I also felt a little insecure because it's like 0:02:23.200 --> 0:02:26.079 I can't even understand what is space, and I think 0:02:26.080 --> 0:02:27.840 it just made me frustrated and I would kind of 0:02:27.840 --> 0:02:30.480 shut down. And as an adult, I feel different about it. 0:02:30.639 --> 0:02:33.160 I think it's interesting. I think thinking about it creates 0:02:33.200 --> 0:02:35.800 like testable predictions that teach us about the universe and 0:02:35.800 --> 0:02:38.120 then we can do practical things with that knowledge. But like, 0:02:38.440 --> 0:02:41.400 what was your journey along questions like this? And am 0:02:41.400 --> 0:02:44.720 I the only physics student in classes who isn't like, oh, 0:02:44.760 --> 0:02:46.760 this is fun and is like, no, I knew this, 0:02:46.880 --> 0:02:48.000 Why are you doing this to me? 0:02:49.200 --> 0:02:51.840 I think that's a whole spectrum of people in physics, 0:02:52.080 --> 0:02:53.960 and I think it's a big tent, and I'm glad 0:02:54.080 --> 0:02:56.280 there are people who are like, hey, look, this gives 0:02:56.320 --> 0:02:59.280 us tools so that we can calculate how our cannonballs 0:02:59.320 --> 0:03:02.320 fly over castle walls. That's really all we care about, 0:03:02.360 --> 0:03:04.680 So let's just do that and move on. And then 0:03:04.720 --> 0:03:07.280 there's the folks on the sort of philosophical side of 0:03:07.320 --> 0:03:10.680 things that really want to understand why balls fly over 0:03:10.720 --> 0:03:14.160 castle walls because they have deeper questions about like why 0:03:14.200 --> 0:03:16.360 is there anything and how does it all work? And 0:03:16.360 --> 0:03:18.760 the amazing thing about physics is that it not only 0:03:19.000 --> 0:03:22.240 lets you do practical stuff bill transistors and iPhones, but 0:03:22.280 --> 0:03:24.000 then you get to turn around and ask like, well, 0:03:24.040 --> 0:03:26.240 why does this work at all? And what does that 0:03:26.320 --> 0:03:29.639 tell us about the actual universe we live in? So yeah, 0:03:29.760 --> 0:03:33.520 touches on like technological, fascinating, useful stuff all the way 0:03:33.560 --> 0:03:36.760 to philosophical stuff, and yeah, I always found myself sort 0:03:36.760 --> 0:03:39.320 of on the philosophical side of things, and I was 0:03:39.320 --> 0:03:41.080 the kind of kid who was like, whoa, what is 0:03:41.160 --> 0:03:44.560 space anyway? Man? And this is before I smoked any 0:03:44.600 --> 0:03:46.920 banana peels. I was wondering about what would it be 0:03:47.040 --> 0:03:49.040 like to live in space that was four dimensions or 0:03:49.080 --> 0:03:51.160 two dimensions? And why is it that we can only 0:03:51.200 --> 0:03:53.839 think in three dimensions? So for me, these questions were 0:03:53.840 --> 0:03:56.440 cat in it, even though I didn't understand anything about them. 0:03:56.680 --> 0:03:59.280 And it's only now as a professional physicist that I 0:03:59.360 --> 0:04:01.960 understand why we don't understand anything about them. 0:04:03.800 --> 0:04:06.040 I hope that we can get to that in the 0:04:06.080 --> 0:04:09.400 show today so that the people like me who are 0:04:09.440 --> 0:04:12.200 just like, well now you've just made me confused, have 0:04:12.280 --> 0:04:15.600 a better sense of why we're asking these questions and 0:04:15.640 --> 0:04:19.760 why they're fundamentally important and not just physicists making things complicated. 0:04:19.839 --> 0:04:21.200 Like every once in a while, I'll be like, well, 0:04:21.240 --> 0:04:25.760 we haven't married relativity and quantum mechanics, and so what 0:04:25.839 --> 0:04:29.479 if when people say like space bends and time is blow, Like, 0:04:29.520 --> 0:04:31.520 what if none of that is true because we haven't 0:04:31.560 --> 0:04:33.359 married these things, And so then why do I have 0:04:33.480 --> 0:04:35.960 to do this, and then I get super frustrated, and 0:04:36.320 --> 0:04:37.960 I don't know, maybe I shouldn't be so negative. At 0:04:37.960 --> 0:04:40.080 the beginning of our show. I'm not actually negative, like 0:04:40.120 --> 0:04:42.720 I'm excited about it, but I'm remembering Kelly from the 0:04:42.760 --> 0:04:45.960 past feeling very frustrated about this stuff. 0:04:46.080 --> 0:04:48.000 Well, I think we're going to be aiming today's episode 0:04:48.040 --> 0:04:50.680 at Kelly of the past, somebody who is curious about 0:04:50.720 --> 0:04:53.200 how the world works but doesn't want like a wall 0:04:53.200 --> 0:04:56.040 of confusing language where words suddenly mean things that they 0:04:56.080 --> 0:04:59.160 didn't mean before. And let's remember that that's the whole 0:04:59.200 --> 0:05:01.520 project of physical We take the world that we kind 0:05:01.560 --> 0:05:04.200 of understand we've been living in any way, and we 0:05:04.279 --> 0:05:06.839 try to systematize it. We try to say, well, you know, 0:05:07.000 --> 0:05:09.440 at what angle will your cannon ball fly over the 0:05:09.440 --> 0:05:11.640 council walls? And do you have to factor in the 0:05:11.680 --> 0:05:13.760 wind resistance? And then we get to turn around and 0:05:13.760 --> 0:05:15.640 be like, well, why does this work? What does that 0:05:15.720 --> 0:05:17.880 tell us it? Lets us do something which I think 0:05:17.920 --> 0:05:20.640 is really awesome. We just peel back that layer of 0:05:20.680 --> 0:05:22.960 intuitive reality and say, hey, we thought the universe was 0:05:23.000 --> 0:05:25.520 like this, Actually it turns out it works like that. 0:05:25.800 --> 0:05:28.320 The universe is different from the way we thought it was, 0:05:28.400 --> 0:05:31.640 and that's wonderful. That's the incredible experience we're going for 0:05:31.760 --> 0:05:33.840 in physics. We want to pull the veil from our 0:05:33.839 --> 0:05:37.000 eyes and figure out how the universe actually is. I 0:05:37.040 --> 0:05:39.280 think what we'll discover today is that, wow, we really 0:05:39.320 --> 0:05:42.679 just don't know that the universe works. But it's important 0:05:42.680 --> 0:05:44.839 that everybody understand what we do know and what we 0:05:44.920 --> 0:05:48.360 don't know about these really basic questions about the nature. 0:05:48.160 --> 0:05:50.560 Of the universe, right And if you stop asking the questions, 0:05:50.600 --> 0:05:52.680 then you never get to the answer. So it's important 0:05:52.680 --> 0:05:53.159 to keep. 0:05:53.040 --> 0:05:55.279 Going exactly and that thing. It might be helpful for 0:05:55.320 --> 0:05:57.920 people when we're talking about something as fuzzy and difficult 0:05:57.920 --> 0:06:00.440 to grapple with a space to think about like what 0:06:00.520 --> 0:06:02.880 kind of question we're asking and what kind of answers 0:06:02.880 --> 0:06:05.400 are satisfactory? You know, because when we ask a vague 0:06:05.440 --> 0:06:08.560 question like what is space? What are we really asking 0:06:08.640 --> 0:06:11.320 when we say that? Even so often in philosophy, I 0:06:11.360 --> 0:06:14.240 replace a confusing word with something familiar, like replace the 0:06:14.240 --> 0:06:16.760 confusing word with an elephant, and think, what does the 0:06:16.839 --> 0:06:19.039 question mean if I'm talking about an elephant? You know, 0:06:19.080 --> 0:06:21.960 So if somebody asks you, hey, what is an elephant. 0:06:22.320 --> 0:06:23.880 You know, what kind of question is that? What kind 0:06:23.920 --> 0:06:26.320 of answers do we expect to that kind of question? 0:06:26.400 --> 0:06:28.240 When I was reading through our outline today, one of 0:06:28.240 --> 0:06:30.520 the things that got me excited was thinking back to 0:06:30.520 --> 0:06:32.479 grad school and when we would talk about behavior and 0:06:32.480 --> 0:06:34.520 we'd be like, well, what is the behavior? And there's 0:06:34.600 --> 0:06:36.960 like at least four different ways to think about it, 0:06:37.000 --> 0:06:39.520 you know, like how did it evolve? What neurotransmitters make 0:06:39.560 --> 0:06:43.440 this behavior happen? What things that happened beforehands initiate the behavior? 0:06:43.520 --> 0:06:45.320 And so in the case of behavior, there's a lot 0:06:45.400 --> 0:06:48.039 of different answers you could have for that question. Is 0:06:48.080 --> 0:06:50.440 it the same for space? Are we looking for like 0:06:50.480 --> 0:06:53.120 an equation? So yeah, like what would make a satisfying 0:06:53.160 --> 0:06:55.320 answer for something like this? Or are there lots? 0:06:55.600 --> 0:06:57.839 No, You're right, what we're looking for our answers to 0:06:57.920 --> 0:06:59.760 questions like well what can space do? 0:07:00.360 --> 0:07:00.520 Right? 0:07:00.520 --> 0:07:02.800 Like what is an elephant? Well, an elephant has big ears, 0:07:02.839 --> 0:07:04.560 it does this thing? Right, you can describe it, You 0:07:04.600 --> 0:07:07.120 can describe what it does. You can also ask like, well, 0:07:07.120 --> 0:07:09.360 why is there space? You know the same way you 0:07:09.400 --> 0:07:11.080 can be like why do we have elephants? You know, 0:07:11.200 --> 0:07:13.960 there's a story there that tells us something about elephants 0:07:14.040 --> 0:07:17.840 the relationship to other living things. Right, we can also ask, well, 0:07:18.160 --> 0:07:20.760 what is space made out of? Is it itself the 0:07:20.840 --> 0:07:23.560 fundamental thing in the universe where like you just got 0:07:23.600 --> 0:07:25.520 to have it, you don't have universe without it? Or 0:07:25.560 --> 0:07:28.840 somehow like elephants and ice cream, does it emerge from 0:07:29.000 --> 0:07:32.080 the workings of other little bits deeper inside it that 0:07:32.240 --> 0:07:35.800 somehow weave themselves together to make this experience we call space. 0:07:35.960 --> 0:07:38.360 That's what I was referring to earlier, where in that scenario, 0:07:38.400 --> 0:07:41.600 you're like pulling back a layer of reality understanding what's 0:07:41.640 --> 0:07:44.760 going on underneath. So you discover that your experience is 0:07:44.760 --> 0:07:47.640 not like fundamental, it's just sort of like one thing 0:07:47.680 --> 0:07:49.920 that the universe can do. It can make elephants, it 0:07:49.920 --> 0:07:51.880 can make ice cream, it can also not. So those 0:07:51.880 --> 0:07:53.600 are the kind of questions I want to know the 0:07:53.640 --> 0:07:56.760 answers to about space, like what can it do? Why 0:07:56.760 --> 0:07:59.880 do we have it? Is it itself made us something smaller? 0:08:00.120 --> 0:08:02.840 Or is it fundamental? Is it a requirement for the universe. 0:08:03.240 --> 0:08:04.680 So one of the things that I was worried about 0:08:04.680 --> 0:08:06.960 when we started talking about this question was the word 0:08:07.040 --> 0:08:10.920 space has been used by so many other fields that 0:08:11.000 --> 0:08:13.560 now it's not confusing from a physics perspective, it's just 0:08:13.680 --> 0:08:16.480 confusing because humans use that word for lots of different things. 0:08:16.640 --> 0:08:20.000 But I think I was definitely proved wrong there because 0:08:20.040 --> 0:08:22.880 when you asked the audience to tell us what they 0:08:22.880 --> 0:08:26.120 thought space was, nobody was like, well, space is the 0:08:26.360 --> 0:08:30.320 literature on space, and like everyone got it. I guess 0:08:30.360 --> 0:08:32.080 they know us well enough to know what we were 0:08:32.080 --> 0:08:34.800 probably talking about. So let's hear what the listeners had 0:08:34.800 --> 0:08:35.199 to say. 0:08:35.280 --> 0:08:37.280 That's right, And if you would like to participate in 0:08:37.320 --> 0:08:41.000 the audience participation segments of this podcast, please write to 0:08:41.080 --> 0:08:44.960 us to questions at Danielankelly dot org. We will set 0:08:45.000 --> 0:08:47.920 you up and you can hear your voice speculating basistly 0:08:48.160 --> 0:08:50.400 on the podcast. Here's a bunch of people answering the 0:08:50.480 --> 0:08:52.240 question what is space. 0:08:53.120 --> 0:08:54.880 I don't think that space is a real thing. 0:08:54.960 --> 0:08:56.720 I think that space is just an abstraction. 0:08:56.880 --> 0:09:02.319 Perhaps space is a medium in which fields can exist, 0:09:02.679 --> 0:09:10.280 that has shape and perhaps has density and can change 0:09:10.480 --> 0:09:17.160 in its form. Space is like an invisible lattice, geometric framework. 0:09:17.480 --> 0:09:21.160 Or other diffuse concept that is just a name we 0:09:21.240 --> 0:09:22.520 give our experience. 0:09:22.760 --> 0:09:28.840 The composite of all energy fields, gravitational fields, and dimensions. 0:09:28.360 --> 0:09:31.560 The medium that we are traveling through. It's like combining 0:09:31.600 --> 0:09:35.000 the trajectory of the Earth of some galaxy. 0:09:35.400 --> 0:09:41.240 Universe. Space is that which matter can move within. 0:09:41.600 --> 0:09:45.280 Space is the background fabric of the entire universe. 0:09:45.600 --> 0:09:48.240 I think to think of space as a huge collection 0:09:48.320 --> 0:09:52.280 of spots that can have multiple states of excitement, and 0:09:52.320 --> 0:09:55.679 the excitement of a spot interferes with its neighbors. 0:09:55.240 --> 0:09:58.520 The replacement or nothing. 0:09:58.840 --> 0:10:03.319 A physical meta that we can experience and move around 0:10:03.840 --> 0:10:06.679 and in which events occur that we can observe and 0:10:06.880 --> 0:10:07.680 try to understand. 0:10:08.480 --> 0:10:14.400 Space is this kind of thing in which everything happens, 0:10:14.760 --> 0:10:17.680 but we can't see or feel it. We can only 0:10:17.760 --> 0:10:19.400 see the evidence of it. 0:10:20.120 --> 0:10:22.120 I think this is outdated now, but I still just 0:10:22.160 --> 0:10:24.560 think of spice as a volume that we can put 0:10:24.559 --> 0:10:25.160 stuff into. 0:10:25.679 --> 0:10:27.760 I think space used to be seen as like a 0:10:27.800 --> 0:10:31.880 substrate where everything happened on or within, But I believe 0:10:32.000 --> 0:10:34.920 now space is kind of understood to be the thing 0:10:35.040 --> 0:10:36.000 that is happening. 0:10:36.480 --> 0:10:39.440 So none of the people who answered the question were 0:10:39.520 --> 0:10:43.160 like Daniel, I hate you, or like Daniel go away, 0:10:43.440 --> 0:10:46.400 So it seems like everybody was, you know, enjoying thinking 0:10:46.440 --> 0:10:48.439 it through and giving you an answer, and we got 0:10:48.440 --> 0:10:50.920 some pretty good answers. So maybe the world is not 0:10:51.000 --> 0:10:53.800 filled with angry young versions of Kelly, which is great, 0:10:53.840 --> 0:10:56.320 would be better. I was also like a goth chick 0:10:56.400 --> 0:10:58.760 covered in black all the time. I've cheered up a 0:10:58.760 --> 0:10:59.120 bit too. 0:10:59.280 --> 0:11:01.000 I want to see when those pictures at some point. 0:11:01.160 --> 0:11:02.680 All right, I'll share one with you, but not with 0:11:02.720 --> 0:11:06.000 everyone else. So, yeah, what did you think of these answers? 0:11:06.280 --> 0:11:06.480 Yeah? 0:11:06.520 --> 0:11:08.360 I thought it was good. And I also love hearing 0:11:08.360 --> 0:11:09.959 people grapple with a hard question. 0:11:10.080 --> 0:11:10.240 You know. 0:11:10.280 --> 0:11:12.120 It's the kind of thing, as you say, everybody's got 0:11:12.120 --> 0:11:15.040 some intuition about what space is because we live in it, right, 0:11:15.200 --> 0:11:18.280 and yet it's difficult to say, like exactly what is 0:11:18.320 --> 0:11:20.320 it and where it comes from a lot of people 0:11:20.480 --> 0:11:23.800 described what it can do, right, or it can hold, 0:11:23.960 --> 0:11:26.559 you can have things in space. So I think those 0:11:26.600 --> 0:11:29.080 are all fine ways to approach this problem. But I 0:11:29.120 --> 0:11:30.839 hope by the end of the podcast we give people 0:11:30.880 --> 0:11:33.800 a really comprehensive view of like what physics says about 0:11:33.840 --> 0:11:37.840 space and all the different, confusing, contradictory things the physics 0:11:37.840 --> 0:11:39.480 says about what space might be. 0:11:39.960 --> 0:11:42.200 All right, So then what do you think is the 0:11:42.240 --> 0:11:45.240 best place to start. So to me, I'm just like 0:11:45.400 --> 0:11:47.240 I don't know space. It's like there's like stuff in 0:11:47.240 --> 0:11:49.319 front of me. But if my table is there, it 0:11:49.360 --> 0:11:51.480 still counts as space because my table's just like in 0:11:51.600 --> 0:11:55.040 the space. And to be honest, that I think is 0:11:55.280 --> 0:11:57.880 most everything I've thought about this question. So where do 0:11:57.960 --> 0:11:58.800 we go from here? 0:12:00.120 --> 0:12:02.080 Maybe the best place to start is to try to answer, 0:12:02.160 --> 0:12:04.920 like what is we're asking about? You know, when we 0:12:04.960 --> 0:12:06.840 say space, what do we even mean by it before 0:12:06.880 --> 0:12:08.559 we talk about like where it comes from and how 0:12:08.600 --> 0:12:10.320 it works and what the rules are and what physics 0:12:10.360 --> 0:12:13.360 has learned, Like what is the thing we're asking about? 0:12:13.520 --> 0:12:16.640 You know, let's at least pinpoint the elephant here. And 0:12:16.880 --> 0:12:19.720 you know, in my mind, space is not about the 0:12:19.760 --> 0:12:23.559 stuff in the universe, It's about what's underneath it. It's 0:12:23.559 --> 0:12:26.200 about the underlying fabric. So like, take a chunk of 0:12:26.320 --> 0:12:29.959 universe wherever it is, and remove everything you can remove, 0:12:30.360 --> 0:12:32.400 so it maybe there's a peanut in the universe, toss 0:12:32.480 --> 0:12:35.040 that out, Maybe there's a planet there, toss that out, 0:12:35.280 --> 0:12:37.800 Maybe there's a galaxy whatever, pushed out all to the side. 0:12:37.880 --> 0:12:40.960 Empty it as much as possible, right, because the thing 0:12:41.000 --> 0:12:43.679 we're not talking about is like particles and matter and 0:12:43.720 --> 0:12:47.200 photons and stuff. Let's talk about what's underneath it. That's 0:12:47.240 --> 0:12:49.800 really what's exciting to me about this question is that 0:12:49.840 --> 0:12:52.800 we're like digging under the carpet of the universe, right, 0:12:53.160 --> 0:12:55.880 And so to me, space is what's left when you 0:12:55.960 --> 0:12:59.920 remove everything that you could remove from a portion of 0:13:00.040 --> 0:13:00.680 the universe. 0:13:00.920 --> 0:13:03.200 So, like in my office right now, and if we 0:13:03.200 --> 0:13:05.560 were to try to figure out what space is in 0:13:05.640 --> 0:13:07.680 terms of my office, we'd turn it into a vacuum. 0:13:07.760 --> 0:13:09.400 So I should leave my office if we're going to 0:13:09.440 --> 0:13:12.559 do this experiment, like we take everything out, and now 0:13:12.600 --> 0:13:14.920 we're asking what are we left with? 0:13:15.160 --> 0:13:17.320 Yeah, well we'd have to take you out because you're 0:13:17.320 --> 0:13:20.800 not space right your stuff? Yeah, so yeah, remove all 0:13:20.800 --> 0:13:24.120 the stuff what is left? And that opens up immediately like, 0:13:24.160 --> 0:13:26.719 well is there anything left? Does it mean anything to 0:13:26.800 --> 0:13:29.040 have space there without stuff in it? Is space just 0:13:29.080 --> 0:13:31.760 defined to be the place between stuff? Or is it 0:13:31.800 --> 0:13:36.560 a thing itself? Right? Is space a kind of stuff? Right? 0:13:37.160 --> 0:13:39.120 I Mean, I know we're getting like really banana pels 0:13:39.120 --> 0:13:41.600 behind the gym over here, but these are the questions 0:13:41.640 --> 0:13:43.600 we're grappling with, and to me, this is what's exciting 0:13:43.600 --> 0:13:46.920 about physics is that these questions are really fuzzy, and yeah, 0:13:47.080 --> 0:13:49.040 you could you know, smoke banana peels and talk about 0:13:49.040 --> 0:13:51.600 them all afternoon and really make no progress, or for 0:13:51.720 --> 0:13:54.560 thousands of years and make no progress. But physics gives 0:13:54.559 --> 0:13:57.800 you a way forward. Physics gives you this method to 0:13:58.000 --> 0:14:01.360 like understand your intuitive experience and make it make sense 0:14:01.559 --> 0:14:04.080 by asking, like, can we build a model that describes 0:14:04.120 --> 0:14:05.760 what he can do? And then can we look at 0:14:05.760 --> 0:14:07.760 that model and say, like, what does that mean about 0:14:07.760 --> 0:14:10.160 what it is? So to me, the reason I'm a 0:14:10.160 --> 0:14:12.920 physicist and not a philosopher is that we can't actually 0:14:13.000 --> 0:14:16.040 make some progress if we think about it like mathematically 0:14:16.280 --> 0:14:17.559 and systematically. 0:14:17.880 --> 0:14:20.280 Okay, so we've now gotten to like you've removed everything, 0:14:20.320 --> 0:14:22.520 so you've got a vacuum, and now I feel like 0:14:22.520 --> 0:14:24.000 there's a vacuum in my brain and I'm like, well, 0:14:24.040 --> 0:14:26.440 where do you go from there? How does physics tackle 0:14:26.480 --> 0:14:27.000 this question? 0:14:27.080 --> 0:14:27.280 Then? 0:14:27.760 --> 0:14:32.120 Physics thinks about space in terms of location and motion, 0:14:32.480 --> 0:14:35.080 because what do you have left once you've emptied your office? 0:14:35.480 --> 0:14:39.040 There's just space there, which means the possibility to put 0:14:39.040 --> 0:14:40.760 something in it. Right, you can put a proton in it, 0:14:40.840 --> 0:14:43.240 But The interesting thing is you can choose where to 0:14:43.280 --> 0:14:45.680 put the proton. You can put the proton where Kelly's 0:14:45.720 --> 0:14:47.520 desk used to be, or you could put the proton 0:14:47.560 --> 0:14:51.000 where Kelly's head used to be. Those in principle are different, right, 0:14:51.040 --> 0:14:54.240 And so space offers us these choices. You can be here, 0:14:54.520 --> 0:14:57.200 you can be there. Space seems to have inherent in 0:14:57.240 --> 0:15:02.440 it this like location, right, and and those locations can change. So, like, 0:15:02.800 --> 0:15:05.360 very very early on, before we were doing science, the 0:15:05.360 --> 0:15:07.320 way we think about it science, you know, the Greeks, 0:15:07.760 --> 0:15:11.040 they were thinking about space in terms of change, like 0:15:11.200 --> 0:15:14.640 motion and change. So the way physics begins attacking this 0:15:14.720 --> 0:15:17.680 problem is like why are there locations? And what are 0:15:17.680 --> 0:15:20.040 the rules about locations? Like how do things go from 0:15:20.080 --> 0:15:22.160 here to there? And why is here different from there? 0:15:22.200 --> 0:15:24.200 And can you tell the difference between here and there? 0:15:24.960 --> 0:15:27.040 In my head? Right now, I've got like a three 0:15:27.080 --> 0:15:32.200 dimensional graph, and you identify space as like a point 0:15:32.240 --> 0:15:36.080 on that graph, and does it stay there forever? Or 0:15:36.120 --> 0:15:39.080 does space move? Or have you just jumped to a 0:15:39.120 --> 0:15:40.440 different point on the graph? 0:15:40.680 --> 0:15:44.240 Yeah? Right, great questions right, like are we moving relative 0:15:44.360 --> 0:15:48.120 to space? Can you measure our motion relative to space? 0:15:48.360 --> 0:15:50.800 Or can we only measure our motion relative to like 0:15:51.160 --> 0:15:54.920 other things in space. Right, that's an early basic question, 0:15:55.200 --> 0:15:57.760 and this is the kind of thing Aristotle was thinking about. 0:15:57.920 --> 0:16:00.000 Aristotle was like, well, you know, why do things move 0:16:00.080 --> 0:16:02.640 move at all? Wasn't everything just like stay the same 0:16:02.720 --> 0:16:05.440 place you put a proton? Wasn't it just stay there forever? 0:16:05.720 --> 0:16:07.360 And of course he was working on the surface of 0:16:07.360 --> 0:16:10.400 the Earth, and so he noticed like, hey, things fall down, right, 0:16:10.560 --> 0:16:12.480 Why do things fall down? Why do things seem to 0:16:12.560 --> 0:16:15.280 move through this space? And so you see that, like 0:16:15.400 --> 0:16:17.520 very early on, the questions of space and motion were 0:16:17.560 --> 0:16:19.840 tied together. And you know, Aristotle didn't have like a 0:16:19.840 --> 0:16:23.800 mathematical picture of how the universe worked or how anything happened. 0:16:24.000 --> 0:16:25.880 He was sort of like words based, you know, it 0:16:25.920 --> 0:16:29.360 was like vibes based signs. And he just basically said, look, 0:16:29.480 --> 0:16:32.600 things fall down because things move according to their nature. 0:16:32.840 --> 0:16:35.200 Matter tends to fall down. That's just it's sort of 0:16:35.240 --> 0:16:37.960 like a descriptive. It's not really explanatory. He's just like, 0:16:38.080 --> 0:16:40.240 stuff falls down because it's in the nature of things 0:16:40.280 --> 0:16:44.200 to fall down. Such a circular answer. I don't even 0:16:44.240 --> 0:16:45.760 know why it was ever satisfactory. 0:16:46.320 --> 0:16:49.240 So we were talking about the absence of stuff, and 0:16:49.320 --> 0:16:53.360 now we're talking about the movement of stuff, and so 0:16:53.400 --> 0:16:56.120 the connection to space is that space is standing still 0:16:56.160 --> 0:16:59.120 while the stuff is moving, or just that this is 0:16:59.160 --> 0:17:01.840 the first time people have thought about the relationship between 0:17:01.880 --> 0:17:02.920 space and stuff. 0:17:03.120 --> 0:17:05.360 Yeah, I think all of that early on people trying 0:17:05.359 --> 0:17:08.080 to figure out what space is by understanding how things 0:17:08.160 --> 0:17:10.719 move through space, like what does it mean to go 0:17:10.760 --> 0:17:12.600 from here to there? What does it mean to fall down? 0:17:12.720 --> 0:17:15.200 And why do things fall down? Anyway, and it gives 0:17:15.200 --> 0:17:17.960 you a handle like what does speed mean? But you know, 0:17:18.040 --> 0:17:21.280 Aristotle's view of what this meant was basically the way 0:17:21.320 --> 0:17:25.080 people thought about it for thousands of years until around Galileo. 0:17:25.760 --> 0:17:28.520 And Galileo was the first person to think like, well, 0:17:28.640 --> 0:17:30.840 what do you really mean? Aristotle like, what are you 0:17:30.880 --> 0:17:35.040 talking about things fall down? Because down seems to kind 0:17:35.040 --> 0:17:37.679 of depend on who you are. And he had this 0:17:37.720 --> 0:17:41.879 famous thought experiment way before Einstein was thinking about stuff. 0:17:41.960 --> 0:17:44.280 He was like, say you're on a boat and you're 0:17:44.359 --> 0:17:46.360 inside the boat, so you can't see the outside. You're 0:17:46.400 --> 0:17:49.760 like below decks, and you drop a ball. What's going 0:17:49.800 --> 0:17:52.639 to happen? Well, Aristotle says, the ball's going to fall down. 0:17:52.720 --> 0:17:54.840 Anybody who dropped. Anything on a boat knows the ball 0:17:54.880 --> 0:17:58.960 falls down. Cool, But now what happens if there's somebody 0:17:58.960 --> 0:18:02.440 on the ground and they're watching your experiment somehow does 0:18:02.480 --> 0:18:05.479 the ball fall down according to the person on the boat, 0:18:05.680 --> 0:18:08.200 which means it's then moving with the boat, or does 0:18:08.240 --> 0:18:10.720 the ball fall down according to the person on the ground, 0:18:11.080 --> 0:18:14.120 in which case it would be left behind. Right, there's 0:18:14.119 --> 0:18:17.280 actually different predictions there. If the ball falls down according 0:18:17.320 --> 0:18:19.680 to the person on the dock, it falls like sort 0:18:19.720 --> 0:18:22.639 of straight down, then as the boat keeps moving, the 0:18:22.680 --> 0:18:25.080 ball gets left behind and the person on the boat 0:18:25.080 --> 0:18:28.399 should see the ball like weirdly fall backwards. Whereas if 0:18:28.440 --> 0:18:30.439 the ball falls down according to the person on the 0:18:30.520 --> 0:18:33.800 boat right, then it falls down for them, but the 0:18:33.800 --> 0:18:36.520 person on the dock sees it moving forward with the boat, 0:18:36.800 --> 0:18:39.240 So you can't have it fall straight down for both people. 0:18:39.280 --> 0:18:40.760 This is what Galleo realized. 0:18:41.200 --> 0:18:44.320 Okay, so my brain is now again trying to so 0:18:44.400 --> 0:18:47.159 it feels like we're talking about stuff, but we're not 0:18:47.200 --> 0:18:52.400 talking about space. And so the connection is the stuff 0:18:52.440 --> 0:18:55.719 is moving through space, and by understanding the movement of 0:18:55.800 --> 0:18:58.480 the stuff, we can understand the space better. 0:18:58.960 --> 0:19:01.480 Exactly because galle is experiment helps us think about what 0:19:01.560 --> 0:19:05.400 speed means. Right, what is velocity? Are you moving relative 0:19:05.440 --> 0:19:08.560 to space? Are you only moving relative to other things? 0:19:09.000 --> 0:19:12.560