1 00:00:07,320 --> 00:00:10,800 Speaker 1: You know, Daniel, sometimes I think how far is everything 2 00:00:10,960 --> 00:00:14,680 Speaker 1: from us? Like how alone are we? We are nowhere 3 00:00:14,760 --> 00:00:17,759 Speaker 1: in the universe exactly, or maybe right on the edge 4 00:00:17,800 --> 00:00:19,919 Speaker 1: of the middle of nowhere. You mean, we're like in 5 00:00:19,960 --> 00:00:22,800 Speaker 1: the suburbs. That's right. You have to drive pretty far 6 00:00:22,840 --> 00:00:25,240 Speaker 1: to get somewhere excitings from where we are in the universe. 7 00:00:25,520 --> 00:00:26,960 Speaker 1: You know, if you look at into the night skuy, 8 00:00:27,360 --> 00:00:30,240 Speaker 1: it just looks black with little pinpoints, you know, Like, 9 00:00:30,320 --> 00:00:33,160 Speaker 1: how do we know how far away these things are? Yeah, 10 00:00:33,200 --> 00:00:35,120 Speaker 1: it's amazing. Some of these things we look at, the 11 00:00:35,200 --> 00:00:37,880 Speaker 1: nice guy are pretty close by, you know, planets, other 12 00:00:37,960 --> 00:00:42,000 Speaker 1: things are incredibly distant, you know, billions of light years away. 13 00:00:42,479 --> 00:00:45,159 Speaker 1: We are sitting on this little ball of rock floating 14 00:00:45,159 --> 00:00:48,640 Speaker 1: through space, and we are making these huge a statements 15 00:00:48,680 --> 00:00:51,960 Speaker 1: about the structure of the rest of the entire universe, 16 00:00:53,560 --> 00:00:55,920 Speaker 1: Like how could we possibly know all this? She's sitting 17 00:00:55,960 --> 00:01:16,800 Speaker 1: on this little tiny rock. Hi am Jorge, and I'm Daniel, 18 00:01:16,959 --> 00:01:20,640 Speaker 1: am my cartoonist. I'm a particle physicist. And this is 19 00:01:20,680 --> 00:01:24,640 Speaker 1: our podcast called Daniel and Jorge Explain the Universe, in 20 00:01:24,640 --> 00:01:27,520 Speaker 1: which we talk about all the things in the universe 21 00:01:27,720 --> 00:01:31,440 Speaker 1: and how we understand them. Or if we understand them. 22 00:01:31,440 --> 00:01:34,360 Speaker 1: Were actually most of the things that we don't understand 23 00:01:34,680 --> 00:01:36,400 Speaker 1: to be on the podcast, we're going to answer a 24 00:01:36,520 --> 00:01:39,880 Speaker 1: question from a listener. That's right. Listener Ryan Lynn wrote 25 00:01:39,880 --> 00:01:42,720 Speaker 1: in with a really interesting question. He said, how do 26 00:01:42,800 --> 00:01:45,520 Speaker 1: we know what we know? A lot of times in 27 00:01:45,560 --> 00:01:48,360 Speaker 1: science you hear about an amazing discovery or something science 28 00:01:48,360 --> 00:01:51,200 Speaker 1: has figured out. But this listener, Ryan always wondered, how 29 00:01:51,200 --> 00:01:53,480 Speaker 1: do they know that? How they figure that out? How 30 00:01:53,520 --> 00:01:56,560 Speaker 1: is it possible to know such crazy facts about the 31 00:01:56,640 --> 00:01:59,520 Speaker 1: universe given that we're stuck on this tiny rock in 32 00:01:59,600 --> 00:02:02,040 Speaker 1: one the will spot around the in the universe. Yeah, 33 00:02:02,080 --> 00:02:03,760 Speaker 1: and just for the record, we may or may not 34 00:02:03,840 --> 00:02:08,720 Speaker 1: have changed his name to protect his identity, and he 35 00:02:08,800 --> 00:02:14,079 Speaker 1: may or may not live at one two three Question Drive, Atlanta, Georgia, 36 00:02:14,200 --> 00:02:16,720 Speaker 1: And that's obviously made up. But yeah, if you have 37 00:02:16,760 --> 00:02:19,560 Speaker 1: any questions at listeners, please send them to us. You 38 00:02:19,560 --> 00:02:22,600 Speaker 1: can always write us at questions at Daniel and Jorge 39 00:02:22,760 --> 00:02:25,640 Speaker 1: dot com. So this is a very broad question, how 40 00:02:25,680 --> 00:02:27,080 Speaker 1: do we know what we know? But he had a 41 00:02:27,160 --> 00:02:34,040 Speaker 1: very specific example, right, He asked, how do we know 42 00:02:34,160 --> 00:02:37,200 Speaker 1: how far away the stars are? Yeah, which is a 43 00:02:37,280 --> 00:02:40,359 Speaker 1: great question because as you look up with the night sky. 44 00:02:40,400 --> 00:02:42,480 Speaker 1: A lot of the stars look similar, right, they're just 45 00:02:42,720 --> 00:02:45,760 Speaker 1: pinpoints in the sky. Yeah, And so you might ask, like, 46 00:02:45,800 --> 00:02:47,480 Speaker 1: how can you tell which ones are close by and 47 00:02:47,520 --> 00:02:50,120 Speaker 1: which ones are are far away? In fact, your eyes 48 00:02:50,160 --> 00:02:52,400 Speaker 1: sort of looks like they're all just painted on a 49 00:02:52,520 --> 00:02:54,920 Speaker 1: ceiling right to your eye, to your brain, they just 50 00:02:54,960 --> 00:02:58,240 Speaker 1: look like they're painted on a huge dome roof. Yeah, 51 00:02:58,240 --> 00:03:00,799 Speaker 1: And I think for many thousand and some years that's 52 00:03:00,840 --> 00:03:03,320 Speaker 1: what people thought. They thought they were looking up essentially 53 00:03:03,400 --> 00:03:06,560 Speaker 1: the ceiling of their living room, right, and that the 54 00:03:06,600 --> 00:03:08,960 Speaker 1: stars were painted on them. There's like a show and 55 00:03:09,000 --> 00:03:12,520 Speaker 1: it's very uh, you know, anthrocentric that suggests that there's 56 00:03:12,560 --> 00:03:15,600 Speaker 1: something created for us to experience, when in fact, of course, 57 00:03:15,840 --> 00:03:19,120 Speaker 1: it's a mostly cold, empty universe that ignores and ignores us. 58 00:03:19,480 --> 00:03:21,480 Speaker 1: I'd love to live in that house where your living 59 00:03:21,560 --> 00:03:25,440 Speaker 1: room is the size of the cosmos. Right. But that's 60 00:03:25,440 --> 00:03:27,440 Speaker 1: the thing. They had no idea how big it was, right. 61 00:03:27,480 --> 00:03:29,919 Speaker 1: They thought the sky was, you know, a few miles 62 00:03:30,000 --> 00:03:31,960 Speaker 1: or a a few hundred miles up there. They had no 63 00:03:32,240 --> 00:03:34,800 Speaker 1: concept at the scale of the thing they we're looking at, 64 00:03:34,880 --> 00:03:37,440 Speaker 1: you know. And that's the crux of the issue, is 65 00:03:37,440 --> 00:03:38,800 Speaker 1: that when you look up in the night sky, you 66 00:03:38,840 --> 00:03:41,440 Speaker 1: can't tell if something is really far away and huge 67 00:03:41,680 --> 00:03:44,400 Speaker 1: or really close by and not actually that big, right, 68 00:03:44,560 --> 00:03:46,920 Speaker 1: because like if you look out into a landscape, you 69 00:03:46,920 --> 00:03:49,080 Speaker 1: can see a mountain, and you sort of know how 70 00:03:49,320 --> 00:03:51,920 Speaker 1: big mountains are, so just kind of by the size 71 00:03:51,960 --> 00:03:54,120 Speaker 1: of how it looks, you can sort of guess how 72 00:03:54,160 --> 00:03:56,840 Speaker 1: far away it is, right, But a star is it's 73 00:03:56,880 --> 00:03:58,600 Speaker 1: like you don't even see it as a circle or 74 00:03:58,640 --> 00:04:01,480 Speaker 1: a ball or nothing. It's just like a pinpoint of light, 75 00:04:01,800 --> 00:04:04,040 Speaker 1: that's right. And that applies even for closer up stuff. 76 00:04:04,080 --> 00:04:07,440 Speaker 1: Like I was talking with my kids about this question yesterday, 77 00:04:07,840 --> 00:04:10,080 Speaker 1: and I told my daughter, you know that the sun 78 00:04:10,240 --> 00:04:12,280 Speaker 1: is much much bigger than the Earth, it just looks 79 00:04:12,320 --> 00:04:15,240 Speaker 1: small because it's far away, And she was surprised. She 80 00:04:15,280 --> 00:04:17,520 Speaker 1: didn't realize that the Sun was bigger than the Earth. 81 00:04:17,560 --> 00:04:19,960 Speaker 1: And of course we know now it's much much bigger 82 00:04:19,960 --> 00:04:21,880 Speaker 1: than the Earth. But in the sky it seems a 83 00:04:21,880 --> 00:04:24,680 Speaker 1: lot smaller than the Earth, which is huge right in 84 00:04:24,680 --> 00:04:27,160 Speaker 1: our perspective, But it only looks that way because it's 85 00:04:27,240 --> 00:04:29,800 Speaker 1: far away. And if you didn't know, like, well, how 86 00:04:29,839 --> 00:04:32,039 Speaker 1: big is it, then you would have no idea is 87 00:04:32,040 --> 00:04:35,560 Speaker 1: it enormous and far away or kind of small and 88 00:04:35,600 --> 00:04:38,679 Speaker 1: close up. Right. Yeah, so this is a good question, 89 00:04:38,800 --> 00:04:40,960 Speaker 1: and it's not an easy question, right, and it's taken 90 00:04:41,040 --> 00:04:42,680 Speaker 1: us a while to figure out how to tell how 91 00:04:42,680 --> 00:04:45,560 Speaker 1: far away stars are. But before we talk about how 92 00:04:45,680 --> 00:04:47,839 Speaker 1: scientists have done it, we thought we'd ask people on 93 00:04:47,839 --> 00:04:50,200 Speaker 1: the street if they hadn't in any ideas. Do people 94 00:04:50,320 --> 00:04:53,159 Speaker 1: know how the distance to far away stars is measured? 95 00:04:53,560 --> 00:04:56,200 Speaker 1: Or do they just take scientists at their word. Think 96 00:04:56,240 --> 00:04:57,920 Speaker 1: about it for a moment. You know, how would you 97 00:04:58,040 --> 00:05:01,120 Speaker 1: tell how far away a star is? Well, here's what 98 00:05:01,160 --> 00:05:03,640 Speaker 1: people around the U See Irvine campus had to say. 99 00:05:04,040 --> 00:05:05,960 Speaker 1: I have no idea how to tell that. No, I 100 00:05:06,000 --> 00:05:11,599 Speaker 1: don't know that at all. You use the telescope, I 101 00:05:11,640 --> 00:05:17,760 Speaker 1: don't know. Stressed out but sorry, um by some scientific 102 00:05:18,360 --> 00:05:22,320 Speaker 1: TV show something like that. Okay, yeah, I think so 103 00:05:22,440 --> 00:05:24,440 Speaker 1: I don't know, like who count we metch with that? 104 00:05:24,920 --> 00:05:29,760 Speaker 1: I don't know? Actually, okay, okay, So most people had 105 00:05:29,839 --> 00:05:32,560 Speaker 1: no idea how this is done, which I love, right, 106 00:05:32,640 --> 00:05:34,760 Speaker 1: And I could see in their faces when I asked 107 00:05:34,760 --> 00:05:37,279 Speaker 1: them they're all of a sudden they thought, what, wait, 108 00:05:37,320 --> 00:05:39,839 Speaker 1: that's a good question. I have no idea, not only 109 00:05:39,880 --> 00:05:41,960 Speaker 1: how you would how scientists do it, but how you 110 00:05:42,080 --> 00:05:44,880 Speaker 1: would even do it right? Most of the people reacted 111 00:05:44,960 --> 00:05:47,240 Speaker 1: that way. It's all familiar words. You know, how far 112 00:05:47,800 --> 00:05:50,600 Speaker 1: away something? Stars? Who know stars? But when you think 113 00:05:50,600 --> 00:05:53,599 Speaker 1: about it, like, it's really not that intuitive to know 114 00:05:53,680 --> 00:05:56,160 Speaker 1: how far away stars? Yeah, it's not that easy, though. 115 00:05:56,200 --> 00:05:58,320 Speaker 1: I love that some people had ideas, like one guy's like, well, 116 00:05:58,400 --> 00:06:01,560 Speaker 1: just watch scientific television shows and we'll tell you. Just 117 00:06:01,680 --> 00:06:04,840 Speaker 1: listen to a podcast. I mean, that's what scientists do, right, 118 00:06:04,839 --> 00:06:06,640 Speaker 1: you wanted the answer to question, just just turn on 119 00:06:06,800 --> 00:06:09,599 Speaker 1: science TV and listen for the answer. Then you write 120 00:06:09,600 --> 00:06:11,919 Speaker 1: it up in the paper. It's like a snake eating 121 00:06:11,960 --> 00:06:15,240 Speaker 1: its own tail. That's how all science has done. But 122 00:06:15,279 --> 00:06:17,560 Speaker 1: the point is that it's not an easy problem and 123 00:06:17,600 --> 00:06:23,640 Speaker 1: that most people don't know the answer. Yeah, maybe we 124 00:06:23,680 --> 00:06:25,760 Speaker 1: should start by talking about things that are close up, 125 00:06:25,839 --> 00:06:28,800 Speaker 1: Like how do we tell how far away things are? Well, 126 00:06:28,839 --> 00:06:31,839 Speaker 1: we have two eyes, right, So say, for example, Uh, 127 00:06:32,240 --> 00:06:34,840 Speaker 1: somebody's throwing a basketball at you. How do you know 128 00:06:34,960 --> 00:06:37,080 Speaker 1: how far away the basketball is? Well, one thing is 129 00:06:37,160 --> 00:06:40,560 Speaker 1: you know how big a basketball should be, So as 130 00:06:40,600 --> 00:06:43,520 Speaker 1: it gets bigger, you're imagining it's getting closer. But say 131 00:06:43,520 --> 00:06:45,720 Speaker 1: somebody throws something at you you've never seen before, you're 132 00:06:45,760 --> 00:06:48,479 Speaker 1: not familiar with. Right, has your brain know how far 133 00:06:48,520 --> 00:06:50,839 Speaker 1: away it is? The key is that you have two 134 00:06:50,839 --> 00:06:53,720 Speaker 1: eyeballs and not just one. Yeah, so you you your 135 00:06:53,720 --> 00:06:56,120 Speaker 1: brain looks at the difference between what your left eye 136 00:06:56,360 --> 00:06:59,000 Speaker 1: and your right eye are seeing. Right. Yeah, you have 137 00:06:59,080 --> 00:07:01,839 Speaker 1: to do this experiment. Hold out one finger in front 138 00:07:01,880 --> 00:07:04,720 Speaker 1: of your face and then look at it with your 139 00:07:04,800 --> 00:07:07,719 Speaker 1: left eye only and then your right eye only, and 140 00:07:07,760 --> 00:07:10,320 Speaker 1: you'll see it move right. You get two different images, 141 00:07:10,360 --> 00:07:12,120 Speaker 1: and you see a little bit different. You see a 142 00:07:12,160 --> 00:07:13,880 Speaker 1: little bit more of one side of the finger with 143 00:07:13,920 --> 00:07:15,240 Speaker 1: one eye and a little bit more of the other 144 00:07:15,280 --> 00:07:17,360 Speaker 1: side of the finger with the other eye. Right, so 145 00:07:17,520 --> 00:07:20,840 Speaker 1: you get its binocular vision right binocular meaning two eyes. 146 00:07:21,520 --> 00:07:24,760 Speaker 1: You get binocular vision, and your brain compares these two pictures. 147 00:07:25,200 --> 00:07:27,920 Speaker 1: And if these two pictures are really different, that means 148 00:07:27,960 --> 00:07:30,680 Speaker 1: the thing is pretty close, right, because you're looking at 149 00:07:30,680 --> 00:07:33,800 Speaker 1: the thing from very two very different angles. Um, only 150 00:07:33,840 --> 00:07:37,200 Speaker 1: if it's really close. But now move your finger as 151 00:07:37,240 --> 00:07:39,800 Speaker 1: far away as your arm will allow. Right. Please don't 152 00:07:39,880 --> 00:07:41,680 Speaker 1: chop off your finger and throw a bast room or 153 00:07:45,720 --> 00:07:48,640 Speaker 1: over driving. Then you do this as a mental exercise. 154 00:07:48,760 --> 00:07:51,560 Speaker 1: Please or pull over. Yeah, So now with your finger 155 00:07:51,600 --> 00:07:54,040 Speaker 1: further away, do the same thing where you look at 156 00:07:54,040 --> 00:07:55,720 Speaker 1: it only with one eye or the other, and you'll 157 00:07:55,800 --> 00:07:59,080 Speaker 1: you'll notice that the two images look more similar. And 158 00:07:59,160 --> 00:08:01,400 Speaker 1: as your finger gets further and further away, the two 159 00:08:01,400 --> 00:08:04,520 Speaker 1: images look more and more similar. Something that's really really 160 00:08:04,520 --> 00:08:07,720 Speaker 1: far away looks the same to both eyes, right, because 161 00:08:07,760 --> 00:08:11,080 Speaker 1: the distance between your eyes gets really small compared to 162 00:08:11,120 --> 00:08:15,080 Speaker 1: the distance to the object. Yeah, and it's more noticeable 163 00:08:15,120 --> 00:08:17,640 Speaker 1: if you switch eyes very quickly, right, Like, if you 164 00:08:17,680 --> 00:08:20,200 Speaker 1: go blink blink, blink, blink, blink, switch between eyes, you 165 00:08:20,200 --> 00:08:22,840 Speaker 1: can really see how things change the closer they are too, 166 00:08:23,280 --> 00:08:24,720 Speaker 1: that's right. It also kind of makes you look like 167 00:08:24,720 --> 00:08:27,640 Speaker 1: a crazy person. So if you're listening to this podcast 168 00:08:27,680 --> 00:08:29,800 Speaker 1: out in public, you know, maybe get a little privacy. 169 00:08:29,960 --> 00:08:32,640 Speaker 1: I'd love to imagine there's some some car pulled over 170 00:08:32,679 --> 00:08:35,959 Speaker 1: by this side of the road with a person blinking 171 00:08:36,000 --> 00:08:40,640 Speaker 1: back and forth, and somebody is now calling Homeland Security 172 00:08:40,800 --> 00:08:45,040 Speaker 1: saying because of somebody's suspicious behavior. Right, let's take a 173 00:08:45,120 --> 00:09:00,839 Speaker 1: quick break. So yeah, that's called parallel right, which is 174 00:09:01,160 --> 00:09:05,000 Speaker 1: is not a comic book villain. It's like an actually, 175 00:09:06,360 --> 00:09:08,839 Speaker 1: oh man, this should totally be a comic book villain 176 00:09:08,880 --> 00:09:12,440 Speaker 1: with like lots of sets of eyeballs or something. Parallax. Yeah, 177 00:09:12,440 --> 00:09:16,319 Speaker 1: that's um, that's called binocular vision, right end, or parallax. 178 00:09:16,600 --> 00:09:18,280 Speaker 1: And the idea there is that you see from different 179 00:09:18,320 --> 00:09:20,640 Speaker 1: angles if you have two views of it. So that 180 00:09:20,760 --> 00:09:24,199 Speaker 1: works for your eyeballs because they're spaced, um fairly, there 181 00:09:24,280 --> 00:09:27,319 Speaker 1: is space fairly wide. Right, It's kind of like a triangle, right, 182 00:09:27,320 --> 00:09:29,680 Speaker 1: Like if you draw a line between your eyes and 183 00:09:29,720 --> 00:09:32,760 Speaker 1: then another line from each of your eyes to the object, 184 00:09:32,880 --> 00:09:35,360 Speaker 1: you form a triangle, right, And that's how you it's 185 00:09:35,400 --> 00:09:39,160 Speaker 1: called triangulation for because then with the triangle, you can 186 00:09:39,200 --> 00:09:41,000 Speaker 1: tell how far away it is, that's right. And that's 187 00:09:41,000 --> 00:09:43,000 Speaker 1: why if you lose an eye or close an eye, 188 00:09:43,360 --> 00:09:46,480 Speaker 1: you don't have very good depth perception, right, because you 189 00:09:46,520 --> 00:09:48,640 Speaker 1: need both of those views to see how far away 190 00:09:48,640 --> 00:09:50,800 Speaker 1: things are. So people with one eye or people with 191 00:09:50,800 --> 00:09:53,160 Speaker 1: an eye Patriot ever, you know, they stumble more often 192 00:09:53,200 --> 00:09:55,480 Speaker 1: for this reason, and they have developed other techniques for 193 00:09:55,559 --> 00:09:59,520 Speaker 1: knowing how far away things are. So that also works 194 00:09:59,640 --> 00:10:02,120 Speaker 1: for the stars, right, and maybe you're thinking a whole 195 00:10:02,120 --> 00:10:05,040 Speaker 1: lot of second, the stars are super duper far away, right, 196 00:10:05,800 --> 00:10:08,600 Speaker 1: My eyes can't measure the distance to a mountain. How 197 00:10:08,600 --> 00:10:11,560 Speaker 1: can my eyes measure the distance to the stars? It 198 00:10:11,600 --> 00:10:13,960 Speaker 1: seems almost impossible. Well, what's happening when I look at 199 00:10:14,000 --> 00:10:16,880 Speaker 1: the stars with my naked eye? Like, why can't I 200 00:10:16,960 --> 00:10:20,440 Speaker 1: just resolve the use the same technique? Right? And the 201 00:10:20,480 --> 00:10:22,880 Speaker 1: reason is that the distance to the stars compared to 202 00:10:23,000 --> 00:10:26,680 Speaker 1: the distance between your eyes is almost infinite. Right, that 203 00:10:26,720 --> 00:10:30,360 Speaker 1: triangle you talked about a tiny little side which is 204 00:10:30,400 --> 00:10:33,440 Speaker 1: the distance between your eyes, and then you know the 205 00:10:33,480 --> 00:10:36,080 Speaker 1: other two sides that extend all the way to the stars. 206 00:10:36,200 --> 00:10:38,439 Speaker 1: It's like light years and light years and light years. 207 00:10:38,760 --> 00:10:41,920 Speaker 1: So basically those photons are parallel to each other, right, 208 00:10:42,480 --> 00:10:45,720 Speaker 1: And do you see the same image? Technically your eyes 209 00:10:45,760 --> 00:10:48,440 Speaker 1: see different images. It's just that maybe the difference is 210 00:10:48,520 --> 00:10:52,760 Speaker 1: so small your brain and your eyeball can't tell the 211 00:10:52,800 --> 00:10:56,880 Speaker 1: difference exactly. So in theory, if you had super duper vision, 212 00:10:57,280 --> 00:11:00,360 Speaker 1: then maybe you could use that information to tell the 213 00:11:00,400 --> 00:11:02,640 Speaker 1: distance to the stars. Or if your eyes were really 214 00:11:02,679 --> 00:11:05,960 Speaker 1: really far apart exactly, if your eyes are really far apart, 215 00:11:06,640 --> 00:11:08,600 Speaker 1: or you have really really good vision, those are two 216 00:11:08,640 --> 00:11:11,600 Speaker 1: ways to make this distance measurement measurement more possible. So 217 00:11:11,640 --> 00:11:14,640 Speaker 1: that's exactly what we do to make our eyes further apart. 218 00:11:14,960 --> 00:11:17,200 Speaker 1: We don't just look at the star up at the 219 00:11:17,280 --> 00:11:20,240 Speaker 1: night sky. We wait for the Earth to go around 220 00:11:20,240 --> 00:11:22,280 Speaker 1: the Sun, and we look at the star from both 221 00:11:22,320 --> 00:11:24,840 Speaker 1: sides of the Sun. So, you know, you look at 222 00:11:24,840 --> 00:11:27,480 Speaker 1: the star in in June and you're one side of 223 00:11:27,480 --> 00:11:30,160 Speaker 1: the Sun, and then the Earth goes around the Sun. 224 00:11:30,280 --> 00:11:33,080 Speaker 1: You look at the same star in December. Now you're 225 00:11:33,120 --> 00:11:36,920 Speaker 1: looking at the star from two astronomical units apart, right, 226 00:11:37,160 --> 00:11:41,280 Speaker 1: as if your eyeballs were two astronomical units apart, right 227 00:11:41,760 --> 00:11:45,560 Speaker 1: opposite sides of the Sun. So that's pretty good distance. Yeah, 228 00:11:45,559 --> 00:11:48,160 Speaker 1: it's like in December you open your right eye and 229 00:11:48,200 --> 00:11:50,120 Speaker 1: you look at the star, and in June you open 230 00:11:50,160 --> 00:11:51,520 Speaker 1: your left eye and you look at the star, and 231 00:11:51,520 --> 00:11:54,200 Speaker 1: you compare how those two images are different. That's right. 232 00:11:54,240 --> 00:11:56,240 Speaker 1: And I hope that you have things to do between 233 00:11:56,280 --> 00:11:58,960 Speaker 1: December and June other than just standing outside waiting for 234 00:11:59,040 --> 00:12:02,360 Speaker 1: six months to open and the other isn't that? I thought? 235 00:12:03,559 --> 00:12:05,920 Speaker 1: It depends on how devoted you are to science, you know, 236 00:12:06,200 --> 00:12:08,760 Speaker 1: like people, if you really care about this stuff. No, 237 00:12:08,880 --> 00:12:10,959 Speaker 1: that's exactly what it's like. And um, so you take 238 00:12:11,000 --> 00:12:12,760 Speaker 1: one piece of data in one part of the year, 239 00:12:12,760 --> 00:12:14,079 Speaker 1: and the other piece of dating the other part of 240 00:12:14,120 --> 00:12:17,880 Speaker 1: the year, and that's effectively like making your head you 241 00:12:17,920 --> 00:12:20,280 Speaker 1: know the size of the solar system, and so that's 242 00:12:20,320 --> 00:12:24,440 Speaker 1: a huge additional leverage Toto seeing things that are really 243 00:12:24,440 --> 00:12:27,320 Speaker 1: far away. I wonder if that's how they measured how 244 00:12:27,360 --> 00:12:29,240 Speaker 1: far the moon was, do you know what I mean? 245 00:12:29,280 --> 00:12:32,959 Speaker 1: Like maybe not waiting, waited until a whole half year, 246 00:12:33,000 --> 00:12:36,120 Speaker 1: but just kind of like looked at the moon, talk 247 00:12:36,160 --> 00:12:38,280 Speaker 1: to somebody who was a couple of miles away and 248 00:12:38,320 --> 00:12:40,360 Speaker 1: see what the what the difference between what he saw 249 00:12:40,400 --> 00:12:42,120 Speaker 1: and you saw That would tell you how far away 250 00:12:42,160 --> 00:12:44,120 Speaker 1: the moon is. Right, Well, there's a couple of things there. 251 00:12:44,160 --> 00:12:47,079 Speaker 1: One is them waiting part of the year won't help 252 00:12:47,080 --> 00:12:49,360 Speaker 1: you with the moon because the moon moves with the Earth, right, 253 00:12:49,840 --> 00:12:51,880 Speaker 1: we don't leave the moon behind. And the Moon is 254 00:12:51,880 --> 00:12:53,920 Speaker 1: actually so close up that you can do cool stuff 255 00:12:53,920 --> 00:12:56,640 Speaker 1: like bounce a laser off the moon or bounce radio 256 00:12:56,679 --> 00:12:59,640 Speaker 1: waves off the moon, and to measure the distance, that's 257 00:12:59,640 --> 00:13:01,920 Speaker 1: actually the best way to measure the distance to the moon. 258 00:13:02,960 --> 00:13:05,560 Speaker 1: And what they've discovered actually is that the Moon is 259 00:13:05,559 --> 00:13:08,880 Speaker 1: getting further and further every every year. We're losing the moon, 260 00:13:09,000 --> 00:13:12,040 Speaker 1: like the Moon is orbiting the Earth. But what orbit 261 00:13:12,120 --> 00:13:15,120 Speaker 1: grows very gradually? Yeah, when when are we going to 262 00:13:15,200 --> 00:13:17,439 Speaker 1: lose the moon? Let's see what time is it now? 263 00:13:18,240 --> 00:13:20,319 Speaker 1: You know, um, it's gonna be a long time. We're 264 00:13:20,320 --> 00:13:21,680 Speaker 1: gonna have the Moon around for a while. You don't 265 00:13:21,679 --> 00:13:23,400 Speaker 1: have to worry about it. And if you bought real 266 00:13:23,480 --> 00:13:26,160 Speaker 1: estate on the Moon, you're fine. But I think by 267 00:13:26,200 --> 00:13:28,920 Speaker 1: a centimeter of years is the number. I remember. The 268 00:13:29,360 --> 00:13:31,480 Speaker 1: distance from the Earth to the Moon is growing. That's 269 00:13:31,520 --> 00:13:34,360 Speaker 1: not nothing. That's not nothing. But also the astronauts put 270 00:13:34,440 --> 00:13:36,800 Speaker 1: mirrors on the Moon when they landed there so that 271 00:13:36,840 --> 00:13:39,439 Speaker 1: we can shine lasers at those mirrors and do cool 272 00:13:39,440 --> 00:13:45,480 Speaker 1: tests stuff like a global selfie. That's exactly right. Yeah, 273 00:13:45,800 --> 00:13:47,960 Speaker 1: And so so we're saying, if you want to get 274 00:13:48,000 --> 00:13:51,040 Speaker 1: better measurements of UM using this parallax system, you either 275 00:13:51,120 --> 00:13:53,000 Speaker 1: need to have your eyes further apart and when you 276 00:13:53,040 --> 00:13:55,400 Speaker 1: do that is so the June and December, or you 277 00:13:55,440 --> 00:13:57,680 Speaker 1: need better eyes. So, of course we don't just use 278 00:13:58,040 --> 00:14:01,160 Speaker 1: my eyeballs or Jorges eyeballs or my students eyeballs. We 279 00:14:01,240 --> 00:14:04,960 Speaker 1: use telescopes and telescopes out in space that can tell 280 00:14:05,000 --> 00:14:08,200 Speaker 1: the difference between really really small images, right, that can 281 00:14:08,240 --> 00:14:12,240 Speaker 1: look really really far away and measure very precisely where 282 00:14:12,280 --> 00:14:14,679 Speaker 1: these stars are at different times of the year. Yeah, 283 00:14:15,120 --> 00:14:18,040 Speaker 1: I just think it's amazing that you can see something 284 00:14:18,120 --> 00:14:19,960 Speaker 1: so far away. You know, like here on Earth, you're 285 00:14:20,040 --> 00:14:24,360 Speaker 1: used to far away things looking blurry or faded or faint. 286 00:14:24,800 --> 00:14:27,720 Speaker 1: But just the idea that you know, millions trillions of 287 00:14:27,800 --> 00:14:30,840 Speaker 1: light years away, you know, a photon left the star, 288 00:14:31,400 --> 00:14:35,920 Speaker 1: traveled throughout the entire cosmos and then arrived into your eyeball, 289 00:14:36,040 --> 00:14:37,960 Speaker 1: right when you're looking at the night sky. That's one 290 00:14:37,960 --> 00:14:39,760 Speaker 1: of my favorite things of the night sky is that 291 00:14:39,840 --> 00:14:43,960 Speaker 1: it's the world's greatest view. It's the universe is greatest view. 292 00:14:44,120 --> 00:14:46,640 Speaker 1: You know, you are seeing across billions of light years 293 00:14:46,640 --> 00:14:49,120 Speaker 1: of space. It's it's amazing to me. I totally agree 294 00:14:49,520 --> 00:14:52,240 Speaker 1: that those photons traveled unimpeded for so long and then 295 00:14:52,240 --> 00:14:54,320 Speaker 1: finally just get absorbed by your eyeball and then you 296 00:14:54,400 --> 00:14:57,280 Speaker 1: just a little a glance away, you know. Okay, So 297 00:14:57,360 --> 00:14:59,960 Speaker 1: then what are other ways? How do we tell how 298 00:15:00,000 --> 00:15:03,640 Speaker 1: are weight things are beyond a few thousand light years? Well, 299 00:15:03,640 --> 00:15:06,000 Speaker 1: that's really the best method we have, is this parallax method. 300 00:15:06,080 --> 00:15:08,360 Speaker 1: And so science has been working on that really hard, 301 00:15:08,440 --> 00:15:11,880 Speaker 1: and it's actually cool because our ability to do this 302 00:15:12,000 --> 00:15:14,680 Speaker 1: is improving pretty rapidly. It used to be we could 303 00:15:14,680 --> 00:15:16,760 Speaker 1: only see things to like maybe a thousand of thousand 304 00:15:16,840 --> 00:15:19,080 Speaker 1: light years away, and then we've got better telescopes and 305 00:15:19,160 --> 00:15:22,080 Speaker 1: navigate they see things pretty reliably up to several thousand 306 00:15:22,120 --> 00:15:25,440 Speaker 1: light years, And now that we have even better telescopes, 307 00:15:25,720 --> 00:15:28,520 Speaker 1: we're seeing some things up to like ten fifteen thousand 308 00:15:28,600 --> 00:15:31,320 Speaker 1: light years away. So as we get better and better telescopes, 309 00:15:31,320 --> 00:15:33,240 Speaker 1: we're gonna get better and better measurements of this than 310 00:15:33,360 --> 00:15:36,840 Speaker 1: Parallax is really the crux. That's the way that we 311 00:15:36,920 --> 00:15:40,160 Speaker 1: really believe that it gives us the most reliable estimates 312 00:15:40,160 --> 00:15:43,480 Speaker 1: of distance, so everything is built on that. Beyond that, 313 00:15:43,760 --> 00:15:48,119 Speaker 1: when things are further away, then there's you know, fuzziness, 314 00:15:48,120 --> 00:15:50,120 Speaker 1: there's questions and people out there might get a little 315 00:15:50,120 --> 00:15:51,920 Speaker 1: skeptical and how do we know some of these things? 316 00:15:52,360 --> 00:15:54,320 Speaker 1: But essentially what you need to do is what we 317 00:15:54,320 --> 00:15:57,320 Speaker 1: talked about earlier, is find something that's a reference point. 318 00:15:57,600 --> 00:16:00,440 Speaker 1: Find something where you know how bright it is, so 319 00:16:00,520 --> 00:16:02,640 Speaker 1: you can tell like a mountain, like, you know how 320 00:16:02,680 --> 00:16:07,040 Speaker 1: big amountain typically is. Yeah exactly. Um, yeah, So if 321 00:16:07,080 --> 00:16:09,560 Speaker 1: you if somebody was, for example, standing on a mountain 322 00:16:09,880 --> 00:16:12,600 Speaker 1: and shining a really bright light, and you knew how 323 00:16:12,640 --> 00:16:15,760 Speaker 1: bright that light was at the source, then you could 324 00:16:15,760 --> 00:16:17,960 Speaker 1: measure how dim it is where you are, and you 325 00:16:17,960 --> 00:16:20,880 Speaker 1: could tell the distance, right, because the brightness falls like 326 00:16:21,000 --> 00:16:24,040 Speaker 1: one over the distance squared, because the photons go out 327 00:16:24,040 --> 00:16:26,920 Speaker 1: in every direction, and the surface area of a sphere 328 00:16:27,200 --> 00:16:30,800 Speaker 1: around the star goes like radius squared, and so the 329 00:16:30,880 --> 00:16:34,080 Speaker 1: same amount of light is spread over more and more areas. 330 00:16:34,120 --> 00:16:36,520 Speaker 1: You just get fewer of those photons the further away 331 00:16:36,520 --> 00:16:39,640 Speaker 1: you are, even if with no atmosphere, no air between you, 332 00:16:39,880 --> 00:16:42,000 Speaker 1: that's right, things just spread out. And so, as you said, 333 00:16:42,160 --> 00:16:44,680 Speaker 1: we get just a little stream of those photons. Most 334 00:16:44,720 --> 00:16:47,400 Speaker 1: of the photons from stars are going somewhere else, right, 335 00:16:47,680 --> 00:16:50,080 Speaker 1: something somewhere else in the universe, and eyeball, we hope 336 00:16:50,280 --> 00:16:52,760 Speaker 1: is picking up one of those photons. So we're only 337 00:16:52,880 --> 00:16:55,480 Speaker 1: seeing a tiny little slice of the photons that come 338 00:16:55,520 --> 00:16:58,200 Speaker 1: from that star. So, as we were saying, if you 339 00:16:58,240 --> 00:16:59,880 Speaker 1: want to know how far aways something is, you have 340 00:17:00,040 --> 00:17:02,120 Speaker 1: to know how bright it was originally, how bright it 341 00:17:02,240 --> 00:17:04,080 Speaker 1: is at the source, and then compare that to the 342 00:17:04,119 --> 00:17:07,639 Speaker 1: brightness you're measuring on Earth. That's pretty tricky because the 343 00:17:07,720 --> 00:17:10,760 Speaker 1: universe is filled with weird stuff that we don't understand, right, 344 00:17:10,800 --> 00:17:12,680 Speaker 1: and so it's sort of chicken and egg, Right, you 345 00:17:12,720 --> 00:17:14,800 Speaker 1: want to know how far away is that stuff? When 346 00:17:14,800 --> 00:17:17,040 Speaker 1: what is it? Well, you don't know either one. You're 347 00:17:17,080 --> 00:17:18,919 Speaker 1: you're sort of in a in a pinch. It just 348 00:17:18,920 --> 00:17:21,160 Speaker 1: looks like little dots. It just looks like little dots. 349 00:17:21,480 --> 00:17:23,560 Speaker 1: But we found a few things that we can use 350 00:17:23,760 --> 00:17:26,119 Speaker 1: for reference points. But maybe let's take a break and 351 00:17:26,119 --> 00:17:40,399 Speaker 1: we can dig into that in a moment. Okay, So 352 00:17:40,440 --> 00:17:42,000 Speaker 1: what are the other ways we can tell how far 353 00:17:42,040 --> 00:17:44,720 Speaker 1: away stars are? So one of the ways is with 354 00:17:44,800 --> 00:17:47,960 Speaker 1: these really weird kind of stars that are variable stars 355 00:17:48,000 --> 00:17:50,920 Speaker 1: that don't shine the same amount of brightness all the time. 356 00:17:51,520 --> 00:17:54,360 Speaker 1: And the reason is that, well, there's some really complicated 357 00:17:54,359 --> 00:17:57,439 Speaker 1: astrophysics that's beyond me, frankly. But the thing that's important 358 00:17:57,440 --> 00:18:02,159 Speaker 1: to know these stars, which are called sapid's um, they pulsate, 359 00:18:02,520 --> 00:18:05,520 Speaker 1: and the rate at which they pulsate is very closely 360 00:18:05,560 --> 00:18:09,640 Speaker 1: connected to their brightness. So if you can measure how 361 00:18:09,680 --> 00:18:13,160 Speaker 1: fast they are pulsating, you can know their brightness. It's 362 00:18:13,200 --> 00:18:16,600 Speaker 1: got this internal layer that stores and releases energy so 363 00:18:16,640 --> 00:18:20,119 Speaker 1: that the whole star expands and contracts, and that's what 364 00:18:20,200 --> 00:18:22,760 Speaker 1: makes it pulsate, kind of like a lighthouse. Yeah, just 365 00:18:22,800 --> 00:18:26,200 Speaker 1: like a lighthouse exactly. Um, it's just like a lighthouse. 366 00:18:26,240 --> 00:18:28,840 Speaker 1: So these things are like lighthouses out there in in 367 00:18:28,920 --> 00:18:32,080 Speaker 1: our galaxy and in other galaxies. And people figured out 368 00:18:32,080 --> 00:18:35,040 Speaker 1: by using parallax that the ones that are pretty close 369 00:18:35,160 --> 00:18:38,240 Speaker 1: up that there's a relationship between how bright they are 370 00:18:38,440 --> 00:18:42,200 Speaker 1: and how fast they pulsate. And that's really cool because 371 00:18:42,240 --> 00:18:44,320 Speaker 1: then there are ones that are really far away where 372 00:18:44,359 --> 00:18:47,080 Speaker 1: we can't use parallax to tell how far away they are, 373 00:18:47,440 --> 00:18:50,320 Speaker 1: but we can tell how fast they are pulsating. Right, 374 00:18:50,359 --> 00:18:52,320 Speaker 1: that's not hard to measure. You just watch it and 375 00:18:52,320 --> 00:18:55,280 Speaker 1: you see blink on and off. You can then say, 376 00:18:55,320 --> 00:18:58,199 Speaker 1: you know how bright it is at the source. You 377 00:18:58,240 --> 00:19:00,119 Speaker 1: know how bright it is at the source, and you 378 00:19:00,160 --> 00:19:02,080 Speaker 1: know how bright it is here on Earth. Then you 379 00:19:02,080 --> 00:19:04,640 Speaker 1: can do some simple math to figure out how far 380 00:19:04,680 --> 00:19:07,080 Speaker 1: away it must be. Like it's telling you using Morse 381 00:19:07,160 --> 00:19:10,600 Speaker 1: code how bright it is, right, Like it's like I'm 382 00:19:10,600 --> 00:19:13,880 Speaker 1: really right, I'm really dim yeah, and so and that's 383 00:19:13,920 --> 00:19:16,800 Speaker 1: the key. These things are called standard candles, and they're 384 00:19:16,840 --> 00:19:19,800 Speaker 1: just ways to know how bright something is at the 385 00:19:19,880 --> 00:19:22,560 Speaker 1: source without knowing how far away it is, right, that's 386 00:19:22,600 --> 00:19:24,560 Speaker 1: the key. You have to have some other way of 387 00:19:24,600 --> 00:19:27,560 Speaker 1: knowing how bright they are. And so these were discovered, 388 00:19:27,600 --> 00:19:30,080 Speaker 1: you know, almost a hundred years ago, and it was 389 00:19:30,160 --> 00:19:33,600 Speaker 1: Hubble himself, Edwin Hubble, who used these and found them, 390 00:19:33,880 --> 00:19:36,119 Speaker 1: a bunch of them that were surprisingly far away. He 391 00:19:36,160 --> 00:19:38,480 Speaker 1: looked up in the night sky, and back then people 392 00:19:38,480 --> 00:19:41,200 Speaker 1: thought the whole universe was just the Milky Way Galaxy. 393 00:19:41,920 --> 00:19:43,600 Speaker 1: That was it. You know, there was just a bunch 394 00:19:43,600 --> 00:19:46,160 Speaker 1: of stars and we are galaxy and nothing else right 395 00:19:46,320 --> 00:19:49,240 Speaker 1: like there was it was all concentrated around us. Yeah, 396 00:19:49,240 --> 00:19:50,919 Speaker 1: they thought that was the whole universe. And you know, 397 00:19:50,960 --> 00:19:53,000 Speaker 1: even that was mind blowing to people. Right If if 398 00:19:53,000 --> 00:19:55,120 Speaker 1: all you thought was, oh, it's just just the Earth 399 00:19:55,160 --> 00:19:57,320 Speaker 1: and a few other planets and everything else is sort 400 00:19:57,320 --> 00:19:59,720 Speaker 1: of painted on the living room of the sky, then 401 00:19:59,720 --> 00:20:02,119 Speaker 1: it's mind blowing to think, what, there's a whole galaxy 402 00:20:02,160 --> 00:20:04,840 Speaker 1: of zillions of stars, right. So people were just are 403 00:20:05,320 --> 00:20:09,320 Speaker 1: slowly accepting that. And then Hubble he looked to try 404 00:20:09,359 --> 00:20:12,120 Speaker 1: to measure these these syfids and see how far away 405 00:20:12,119 --> 00:20:14,119 Speaker 1: they were, and he got some really weird results. He 406 00:20:14,200 --> 00:20:18,280 Speaker 1: got results that suggested that these things were crazy far away, 407 00:20:18,280 --> 00:20:21,720 Speaker 1: far away than any star anybody has seen before, and 408 00:20:21,760 --> 00:20:24,720 Speaker 1: so we thought, well, maybe these things are not just 409 00:20:24,840 --> 00:20:27,640 Speaker 1: like weird nebula or weird other stars. Maybe there are 410 00:20:27,720 --> 00:20:30,479 Speaker 1: other galaxies. And that must have been a mind blowing 411 00:20:30,520 --> 00:20:33,320 Speaker 1: moment for him, Right, Wow, It's like, it's not just 412 00:20:33,480 --> 00:20:38,400 Speaker 1: us in our living room, there's other houses around us, exactly, exactly. 413 00:20:38,440 --> 00:20:41,359 Speaker 1: And that's what I love about this question is figuring 414 00:20:41,359 --> 00:20:44,000 Speaker 1: out how far away the stars is, gives us a 415 00:20:44,119 --> 00:20:47,560 Speaker 1: three D map of the universe, right, tells us where 416 00:20:47,560 --> 00:20:50,080 Speaker 1: everything is, what is the structure where we living, Like, 417 00:20:50,200 --> 00:20:52,040 Speaker 1: are we in the suburbs? Are we in the exciting 418 00:20:52,080 --> 00:20:55,639 Speaker 1: downtown hip area of the universe? Right? So it's so important, 419 00:20:55,760 --> 00:20:59,119 Speaker 1: and it's exactly what's led to these moments of realization 420 00:20:59,160 --> 00:21:02,080 Speaker 1: where you discover or that the universe is totally different 421 00:21:02,080 --> 00:21:03,960 Speaker 1: from the way you thought it was. I hope to 422 00:21:04,000 --> 00:21:05,600 Speaker 1: I hope to have one of those moments myself in 423 00:21:05,600 --> 00:21:08,640 Speaker 1: my science career. It's it's let us map the universe 424 00:21:08,800 --> 00:21:11,280 Speaker 1: and where we are in exactly. That's a big exactly, 425 00:21:11,840 --> 00:21:14,600 Speaker 1: that's a huge deal. And that really was the birth 426 00:21:14,640 --> 00:21:18,119 Speaker 1: of modern cosmology. You know, knowing there were other galaxies 427 00:21:18,119 --> 00:21:20,000 Speaker 1: and wondering how many are there and how did this 428 00:21:20,040 --> 00:21:23,359 Speaker 1: all come together? And you know, and obviously if there 429 00:21:23,359 --> 00:21:25,640 Speaker 1: are other galaxies, then maybe we're not the most important 430 00:21:25,640 --> 00:21:28,120 Speaker 1: one or at the center of anything or all those 431 00:21:28,200 --> 00:21:30,840 Speaker 1: questions were created just at that moment when we discovered 432 00:21:30,840 --> 00:21:37,680 Speaker 1: that there were other galaxies. Okay, so that's a really 433 00:21:37,680 --> 00:21:42,159 Speaker 1: cool trick is find an astronomical object that somehow tells 434 00:21:42,200 --> 00:21:44,840 Speaker 1: you how bright it is, not by how bright it is, 435 00:21:44,880 --> 00:21:48,280 Speaker 1: but through some other information. Yeah, exactly, and so you 436 00:21:48,320 --> 00:21:50,800 Speaker 1: have to really know the astrophysics of it. And the 437 00:21:50,840 --> 00:21:55,200 Speaker 1: cepheids were calibrated by comparing to the parallax scale, So 438 00:21:55,320 --> 00:21:57,760 Speaker 1: parallax works up to you know, maybe ten tho light years, 439 00:21:57,960 --> 00:22:00,320 Speaker 1: and in that sphere there are some of these stars, 440 00:22:00,359 --> 00:22:03,680 Speaker 1: these variable stars. Once you know that, then you can 441 00:22:03,720 --> 00:22:06,320 Speaker 1: look at the ones even further out using this technique 442 00:22:06,320 --> 00:22:10,440 Speaker 1: exactly exactly. An astronomers call this the cosmic distance ladder. 443 00:22:10,480 --> 00:22:12,840 Speaker 1: Because there's a bunch of different techniques that use for 444 00:22:12,880 --> 00:22:15,240 Speaker 1: things at different distances, and then you try to overlap 445 00:22:15,280 --> 00:22:17,920 Speaker 1: them and stitch them together. There's no one technique that 446 00:22:17,960 --> 00:22:20,359 Speaker 1: will work for everything really close up stuff. You've got 447 00:22:20,400 --> 00:22:23,520 Speaker 1: parallax for stuff that's a little further away. You got 448 00:22:23,520 --> 00:22:26,159 Speaker 1: these these variable stars, the cfids, and then after that 449 00:22:26,280 --> 00:22:30,000 Speaker 1: you have to use GPS. After that you just watch 450 00:22:30,000 --> 00:22:34,639 Speaker 1: a science TV show that you have to do everything. Um, 451 00:22:34,800 --> 00:22:37,639 Speaker 1: the problem is that cefids are just stars, and so 452 00:22:37,720 --> 00:22:39,800 Speaker 1: they're bright, but they're not that bright and you want 453 00:22:39,840 --> 00:22:42,280 Speaker 1: to see something like in another galaxy or really really 454 00:22:42,320 --> 00:22:46,320 Speaker 1: far away galaxies. You can't resolve individual stars in super 455 00:22:46,400 --> 00:22:49,520 Speaker 1: duper far away galaxies, so that has a limit to Yeah, 456 00:22:50,119 --> 00:22:53,600 Speaker 1: so then they needed something super crazy bright to serve 457 00:22:53,640 --> 00:22:55,560 Speaker 1: as a standard candle for the rest of the universe 458 00:22:56,680 --> 00:23:00,560 Speaker 1: because these stars, even though they blink, they get lost 459 00:23:00,600 --> 00:23:04,760 Speaker 1: in the light from the rest of the galaxy they're in. Yeah, exactly, 460 00:23:04,760 --> 00:23:07,920 Speaker 1: they're not particularly bright kind of stars, and so that's 461 00:23:07,960 --> 00:23:11,480 Speaker 1: why the end of the cosmic distance Ladder is dominated 462 00:23:11,520 --> 00:23:15,360 Speaker 1: by supernova. Supernova is when a star goes boom, right 463 00:23:15,760 --> 00:23:17,920 Speaker 1: when it's time to check out. It's had all of 464 00:23:18,000 --> 00:23:20,560 Speaker 1: its fun and it's decided we're done with all this 465 00:23:20,680 --> 00:23:23,840 Speaker 1: fusion stuff. Let's just blow it on one last big party. 466 00:23:23,880 --> 00:23:26,120 Speaker 1: It collapses basically right like it runs out of fuel 467 00:23:26,320 --> 00:23:29,359 Speaker 1: and then it just yeah, and we did a whole 468 00:23:29,359 --> 00:23:32,800 Speaker 1: fun podcast episode on house stars and their lives um 469 00:23:32,920 --> 00:23:34,560 Speaker 1: which you should go out and listen to you're interested 470 00:23:34,560 --> 00:23:36,760 Speaker 1: in that kind of detail. But the critical thing is 471 00:23:36,800 --> 00:23:40,000 Speaker 1: that one kind of star ends in a very particular way, 472 00:23:40,040 --> 00:23:42,600 Speaker 1: and it's called a type one a supernova, and the 473 00:23:42,720 --> 00:23:45,840 Speaker 1: supernova are extraordinarily bright. The thing you have to understand 474 00:23:45,920 --> 00:23:48,640 Speaker 1: is that the stars like using up all of its 475 00:23:48,680 --> 00:23:51,760 Speaker 1: fuel in a very short amount of time, and so 476 00:23:51,840 --> 00:23:55,080 Speaker 1: it's extremely bright, and a single supernova can be brighter 477 00:23:55,119 --> 00:23:57,879 Speaker 1: than the entire galaxy that it's in. So that's how 478 00:23:57,920 --> 00:23:59,800 Speaker 1: we can see it. I mean, if you look at 479 00:23:59,800 --> 00:24:02,280 Speaker 1: the night sky, you can see these these little fuzzy 480 00:24:02,400 --> 00:24:04,960 Speaker 1: things that are the other galaxies, but you can't really 481 00:24:04,960 --> 00:24:07,520 Speaker 1: resolve any particular star in it right. Well, for the 482 00:24:07,520 --> 00:24:10,000 Speaker 1: close up ones you can, like for Andromeda, which is 483 00:24:10,000 --> 00:24:11,879 Speaker 1: whe of the nearest galaxies, you can see the shape 484 00:24:11,880 --> 00:24:13,719 Speaker 1: of it, you can see individual stars, but you're right. 485 00:24:13,760 --> 00:24:16,639 Speaker 1: For the furthest ones, they're just little smudges and you 486 00:24:16,680 --> 00:24:20,320 Speaker 1: can't resolve individual stars except when one of them goes boom, 487 00:24:20,480 --> 00:24:22,360 Speaker 1: and then you can see it and it's brighter than 488 00:24:22,400 --> 00:24:26,879 Speaker 1: the hundred billion stars combined. Right. That's it's incredible to 489 00:24:26,960 --> 00:24:29,320 Speaker 1: me how bright these supernov are. And you don't want 490 00:24:29,359 --> 00:24:31,360 Speaker 1: to be close to any of these things, right, any 491 00:24:31,440 --> 00:24:35,440 Speaker 1: Anybody near these things gets instantly sterilized. So we would 492 00:24:35,440 --> 00:24:37,040 Speaker 1: see it as a like a little dot in the 493 00:24:37,320 --> 00:24:39,960 Speaker 1: inside of a galaxy which is flash like it will 494 00:24:40,040 --> 00:24:43,199 Speaker 1: just yeah, And in the night sky you see it 495 00:24:43,200 --> 00:24:45,280 Speaker 1: as maybe a new star. Right. There could be like 496 00:24:45,320 --> 00:24:47,520 Speaker 1: a little smudge there you never noticed from a really 497 00:24:47,520 --> 00:24:49,639 Speaker 1: far away galaxy, and all of a sudden, there's a 498 00:24:49,640 --> 00:24:52,640 Speaker 1: bright star there. And you can look back in history 499 00:24:52,680 --> 00:24:55,960 Speaker 1: and see the record where ancient people's saw these things 500 00:24:55,960 --> 00:24:57,600 Speaker 1: in the night sky. Right, we have a history of 501 00:24:57,640 --> 00:25:00,119 Speaker 1: supernov explosions that goes back more than a thou and 502 00:25:00,200 --> 00:25:04,160 Speaker 1: years because like Chinese astronomers are noticed, hey, on this date, 503 00:25:04,200 --> 00:25:06,160 Speaker 1: a new star appeared in this guy and the only 504 00:25:06,240 --> 00:25:08,400 Speaker 1: lasted for three weeks and then it was gone. Boy, 505 00:25:08,480 --> 00:25:11,480 Speaker 1: that was weird. And the trick is that these supernova 506 00:25:11,520 --> 00:25:14,639 Speaker 1: are always the same, right, It's not like do you 507 00:25:14,640 --> 00:25:17,480 Speaker 1: have small supernovas and big supernovas. It's like, if you're 508 00:25:17,480 --> 00:25:21,280 Speaker 1: gonna have a supernova, it's always this bright. Well, there 509 00:25:21,320 --> 00:25:23,240 Speaker 1: are a lot of different kinds of supernova. But this 510 00:25:23,440 --> 00:25:26,600 Speaker 1: one kind, called Type one A always has the same 511 00:25:26,600 --> 00:25:28,880 Speaker 1: sort of curve, this light curve when we talk about 512 00:25:28,920 --> 00:25:30,880 Speaker 1: how bright it gets and then it hits a peak 513 00:25:30,920 --> 00:25:34,520 Speaker 1: brightness and then dims away, and the whole process last days. 514 00:25:34,520 --> 00:25:37,400 Speaker 1: But it always has the same shape and always has 515 00:25:37,400 --> 00:25:39,919 Speaker 1: the same peak brightness. Now, for those of you who 516 00:25:40,000 --> 00:25:42,240 Speaker 1: know a lot about this, there are some technical details 517 00:25:42,280 --> 00:25:44,680 Speaker 1: and in the variation of the peak brightness, but that 518 00:25:44,720 --> 00:25:47,080 Speaker 1: can get calibrated away, and we can talk about that 519 00:25:47,119 --> 00:25:49,760 Speaker 1: another time. But the basic version of the story is 520 00:25:49,960 --> 00:25:52,200 Speaker 1: that they always have the same peak brightness because it's 521 00:25:52,200 --> 00:25:54,840 Speaker 1: always the same kind of process. It's always the same 522 00:25:55,080 --> 00:25:58,639 Speaker 1: size star with the same amount of fuel in it. 523 00:25:58,640 --> 00:26:01,800 Speaker 1: It's not like every star those supernova. It's like only 524 00:26:01,840 --> 00:26:04,120 Speaker 1: once with a particular size and stuff, and it will 525 00:26:04,320 --> 00:26:06,960 Speaker 1: collapse at some point right in a very particular way. 526 00:26:07,200 --> 00:26:09,520 Speaker 1: That's exactly right. There's lots of different kinds of supernova, 527 00:26:09,640 --> 00:26:13,040 Speaker 1: but one kind which comes from binary star systems, in 528 00:26:13,040 --> 00:26:16,320 Speaker 1: which one of them is a white dwarf that leads 529 00:26:16,359 --> 00:26:19,119 Speaker 1: to Type one A supernova, and which just happens to 530 00:26:19,240 --> 00:26:21,480 Speaker 1: be very regular, and it happens to be very little 531 00:26:21,560 --> 00:26:26,240 Speaker 1: variation between the brightness of different type one A supernova. 532 00:26:26,320 --> 00:26:29,480 Speaker 1: And this is something people realized, you know, like twenty 533 00:26:29,600 --> 00:26:32,159 Speaker 1: thirty years ago, but it took some work. You know, 534 00:26:32,240 --> 00:26:35,600 Speaker 1: people are constantly out there looking for new ways to 535 00:26:35,960 --> 00:26:38,399 Speaker 1: find distance metrics, new ways to figure out how far 536 00:26:38,440 --> 00:26:41,719 Speaker 1: away things are. And people we're working on Type one 537 00:26:41,720 --> 00:26:44,119 Speaker 1: A supernova and other people working on this kind of thing. 538 00:26:44,160 --> 00:26:46,159 Speaker 1: So people work on the other kind of thing. People 539 00:26:46,200 --> 00:26:48,600 Speaker 1: today right now are working on new ways to measure 540 00:26:48,600 --> 00:26:51,600 Speaker 1: distances because we always want to know more precise information. 541 00:26:51,680 --> 00:26:55,560 Speaker 1: So behind the scenes, grad students were slogging away, can 542 00:26:55,600 --> 00:26:57,840 Speaker 1: we figure out how far away type and supernova are? 543 00:26:57,960 --> 00:27:00,479 Speaker 1: Can we calibrate they're they're like her, so that they 544 00:27:00,480 --> 00:27:03,520 Speaker 1: all look the same. And then about in the late nineties, 545 00:27:04,160 --> 00:27:06,320 Speaker 1: people figured out how to do it, and the technology 546 00:27:06,320 --> 00:27:09,960 Speaker 1: became possible and they started collecting this information, right, and 547 00:27:10,000 --> 00:27:12,200 Speaker 1: so all of a sudden, a whole new window into 548 00:27:12,240 --> 00:27:14,480 Speaker 1: the universe. We could tell how far away things that 549 00:27:14,560 --> 00:27:18,480 Speaker 1: are super far away we're because the supernova are so bright. Right, 550 00:27:18,560 --> 00:27:20,480 Speaker 1: But it's sort of interesting because it came from kind 551 00:27:20,480 --> 00:27:23,000 Speaker 1: of a random occurrence in the universe, right, Like people 552 00:27:23,119 --> 00:27:27,520 Speaker 1: just cataloging and observing supernova just for the sake of science. 553 00:27:27,680 --> 00:27:31,159 Speaker 1: Suddenly they realized that this gives us a tool for 554 00:27:31,400 --> 00:27:34,600 Speaker 1: mapping the universe exactly. And that's what astronomy is all about. 555 00:27:34,600 --> 00:27:36,600 Speaker 1: It is like, let's figure out how to use the 556 00:27:36,640 --> 00:27:41,000 Speaker 1: idiosyncrasies of the universe to give ourselves clues, right, And 557 00:27:41,080 --> 00:27:43,199 Speaker 1: so yeah, it's just luck, right, I mean, I mean 558 00:27:43,240 --> 00:27:46,560 Speaker 1: it's luck. What is it revealing that we underneed the 559 00:27:46,560 --> 00:27:49,480 Speaker 1: surface exactly? That is that is pure science right there. 560 00:27:49,520 --> 00:27:53,600 Speaker 1: It's like, let's nail down facts about the universe by 561 00:27:53,680 --> 00:27:56,080 Speaker 1: things that accidentally reveals to us. I mean, everything the 562 00:27:56,160 --> 00:27:59,240 Speaker 1: universe tells us is an accident, right, nobody's purposely sending 563 00:27:59,320 --> 00:28:04,600 Speaker 1: us information. We're just a sit unless we're living in 564 00:28:04,640 --> 00:28:07,960 Speaker 1: a simulation, in which case everything is on purpose. Um. Yeah, 565 00:28:08,000 --> 00:28:10,680 Speaker 1: So Type one A supernova stand out really really far. 566 00:28:10,760 --> 00:28:13,400 Speaker 1: The best distance measurements we have come from type one 567 00:28:13,400 --> 00:28:16,320 Speaker 1: A supernova. So this sort of three step louder there. 568 00:28:16,320 --> 00:28:19,480 Speaker 1: There's the parallax for close up stuff, the cepids for 569 00:28:19,680 --> 00:28:22,399 Speaker 1: medium range stuff, and then the type one A supernova 570 00:28:22,440 --> 00:28:24,840 Speaker 1: for super far away stuff. And you know they overlap, 571 00:28:24,880 --> 00:28:28,800 Speaker 1: which allows us to calibrate. And it's built one on 572 00:28:28,840 --> 00:28:30,680 Speaker 1: top of the other, right, like what we know from 573 00:28:30,680 --> 00:28:34,840 Speaker 1: supernovas is built on what we know from these blinking stars, 574 00:28:34,880 --> 00:28:37,520 Speaker 1: which is built on what we know about from parallax, 575 00:28:38,160 --> 00:28:41,640 Speaker 1: which is built on our eyeballs. That's right, exactly, it's 576 00:28:41,640 --> 00:28:47,920 Speaker 1: built on our listeners eyeballs. And now we actually have 577 00:28:47,960 --> 00:28:50,360 Speaker 1: a new way to measure distance, which is really cool, 578 00:28:50,400 --> 00:28:53,520 Speaker 1: which has only been possible recently, and that's um from 579 00:28:53,560 --> 00:28:58,240 Speaker 1: gravitational waves. Gravitational waves are these ripples in space time 580 00:28:58,720 --> 00:29:02,760 Speaker 1: that we can measure by seeing how these observatories shrink 581 00:29:02,880 --> 00:29:07,520 Speaker 1: and expand by my new distances as the gravitational wave passes. 582 00:29:08,120 --> 00:29:11,760 Speaker 1: And just like with type one A supernova or with cepheids, 583 00:29:12,040 --> 00:29:16,520 Speaker 1: we know something about the strength of the gravitational wave 584 00:29:16,640 --> 00:29:19,160 Speaker 1: based on what it looks like here, based on not 585 00:29:19,320 --> 00:29:21,840 Speaker 1: on its brightness, but like on how fast it's wiggling, 586 00:29:22,080 --> 00:29:25,520 Speaker 1: because because gravitational waves wiggle right there waves of space, 587 00:29:26,040 --> 00:29:28,480 Speaker 1: so something about how they're wiggling gives you a clue 588 00:29:28,480 --> 00:29:31,440 Speaker 1: as to how bright, how intense they were at the source. 589 00:29:31,880 --> 00:29:34,360 Speaker 1: And then we can by measuring how the intense they 590 00:29:34,400 --> 00:29:36,360 Speaker 1: are here, we can tell how far away things were. 591 00:29:36,440 --> 00:29:39,240 Speaker 1: So this is a whole new handle. We only recently 592 00:29:39,280 --> 00:29:43,400 Speaker 1: added to our cosmic distance ladder. You sound pretty excited 593 00:29:43,440 --> 00:29:48,240 Speaker 1: about gravitational waves. Um, I am, I am. It's a 594 00:29:48,480 --> 00:29:52,280 Speaker 1: it's a heavy topic. Um, but it's sort of cool. 595 00:29:52,360 --> 00:29:54,280 Speaker 1: I guess just taking a step back just to think 596 00:29:54,280 --> 00:29:56,280 Speaker 1: that we went from like a two D v of 597 00:29:56,280 --> 00:29:58,600 Speaker 1: the universe just looking at these things that we thought 598 00:29:58,640 --> 00:30:01,480 Speaker 1: we're painting on the ceiling, to this now really sort 599 00:30:01,480 --> 00:30:06,840 Speaker 1: of incredibly rich and deep three D conception of the 600 00:30:07,000 --> 00:30:10,360 Speaker 1: entire cosmics. Right, It's absolutely incredible, and it's more than 601 00:30:10,440 --> 00:30:12,720 Speaker 1: three D. Actually, it's actually kind of like four D 602 00:30:13,560 --> 00:30:16,120 Speaker 1: because when we look out into space, we don't just 603 00:30:16,120 --> 00:30:18,120 Speaker 1: look at it where things are. We look at where 604 00:30:18,120 --> 00:30:20,960 Speaker 1: things used to be, right, so we see things in 605 00:30:21,080 --> 00:30:23,680 Speaker 1: sort of these spheres, like the things that are nearby 606 00:30:23,800 --> 00:30:26,560 Speaker 1: are recent, things that are far away are old. And 607 00:30:26,600 --> 00:30:29,520 Speaker 1: so we're not just looking out at where we are 608 00:30:29,520 --> 00:30:31,840 Speaker 1: in the universe like a three D map. We're looking 609 00:30:31,880 --> 00:30:35,479 Speaker 1: at these shells that get further and further back in time, 610 00:30:35,560 --> 00:30:38,320 Speaker 1: and so this allows us to see what the universe 611 00:30:38,440 --> 00:30:40,640 Speaker 1: used to be like, so absolutely gives us a sense 612 00:30:40,680 --> 00:30:42,520 Speaker 1: for the structure the universe, but also gives us a 613 00:30:42,560 --> 00:30:45,479 Speaker 1: sense for how that structure is changing, and why you 614 00:30:45,520 --> 00:30:48,480 Speaker 1: cannot get more rich information about the formation of the 615 00:30:48,600 --> 00:30:51,160 Speaker 1: universe in our context and why we're here and all 616 00:30:51,200 --> 00:30:54,840 Speaker 1: that crazy important stuff. Then understanding how the universe came 617 00:30:54,920 --> 00:30:58,000 Speaker 1: to be the way it is, right, all that just 618 00:30:58,080 --> 00:31:01,880 Speaker 1: from looking up. That's right. So next time you're looking 619 00:31:01,920 --> 00:31:04,840 Speaker 1: at the night sky, wonder is there more information there 620 00:31:04,840 --> 00:31:08,560 Speaker 1: that I'm seeing? If they're more information than even scientists know. Bobile, 621 00:31:08,600 --> 00:31:11,800 Speaker 1: future scientists laugh at us for missing what's going to 622 00:31:11,880 --> 00:31:14,360 Speaker 1: be in those futures science shows what's going to be 623 00:31:14,600 --> 00:31:17,479 Speaker 1: on a future science podcast. All right, thank you very 624 00:31:17,560 --> 00:31:19,480 Speaker 1: much for listening, and thank you to Ryan for sending 625 00:31:19,480 --> 00:31:30,120 Speaker 1: this question. Thanks for listening, See you next time. If 626 00:31:30,200 --> 00:31:33,280 Speaker 1: you still have a question after listening to all these explanations, 627 00:31:33,320 --> 00:31:36,280 Speaker 1: please drop us a line. We'd love to hear from you. 628 00:31:36,280 --> 00:31:39,120 Speaker 1: You can find us at Facebook, Twitter, and Instagram at 629 00:31:39,440 --> 00:31:42,560 Speaker 1: Daniel and Jorge that's one word, or email us at 630 00:31:42,840 --> 00:31:54,360 Speaker 1: Feedback at Daniel and Jorge dot com.