WEBVTT - How do space telescopes point themselves? 0:00:08.480 --> 0:00:11.840 Hey, Jorgey, are you good at navigating? Depends on what 0:00:11.920 --> 0:00:13.920 do you mean by navigating? Do you mean navigating the 0:00:13.920 --> 0:00:17.599 complex issues of how to lead a good life? Then no, 0:00:17.720 --> 0:00:19.239 I haven't figured that one out. But if you mean 0:00:19.320 --> 0:00:22.040 like getting somewhere, I have a phone with GPS, so 0:00:22.239 --> 0:00:24.600 I guess i'm pretty good. Well, what have you lost 0:00:24.600 --> 0:00:27.720 your phone? Like? Or civilization crumbled? Do you know how 0:00:27.760 --> 0:00:31.680 to oriente yourself in the woods? Well? I imagine I 0:00:31.680 --> 0:00:33.640 could use a map and a compass, right, do you 0:00:33.680 --> 0:00:36.960 mean like a basic old school compass or the compass 0:00:36.960 --> 0:00:39.080 app on your phone? Okay, yeah, that's a good point. 0:00:39.800 --> 0:00:42.839 I only have the compass on my phone. But I 0:00:42.880 --> 0:00:45.960 guess you could probably find a low tech original you know, 0:00:46.040 --> 0:00:48.600 og compass. Yeah, that would let you get low tech 0:00:48.680 --> 0:00:53.400 original lost. I guess there's civilization crumbles were all lost. 0:01:08.760 --> 0:01:11.840 I am morehammy cartoonist and the creator of PhD comics. Hi, 0:01:11.920 --> 0:01:14.400 I'm Daniel. I'm a particle physicist and a professor at 0:01:14.480 --> 0:01:19.039 UC Irvine, and I've never honestly been lost in the woods. Well, well, yeah, 0:01:19.040 --> 0:01:20.959 I think that's self evident, because you're talking to us 0:01:21.040 --> 0:01:23.840 right now. If you were lost in the woods, I'm 0:01:23.880 --> 0:01:26.280 not sure we would have from you again. Maybe I'm 0:01:26.280 --> 0:01:28.800 calling you from my secret woods hideout, or even I 0:01:28.800 --> 0:01:31.720 don't know where it is, although if you have Wi 0:01:31.760 --> 0:01:35.040 Fi there and are able to record, I'm not sure 0:01:35.040 --> 0:01:38.399 you're that lost. Yeah, that's true. But I've often gone 0:01:38.400 --> 0:01:41.120 on long backpacking trips and wonder if I really could 0:01:41.160 --> 0:01:43.959 get myself out of the woods if I had to. Yeah, 0:01:44.000 --> 0:01:46.479 it's pretty tricky because I guess it's hard to see 0:01:46.520 --> 0:01:48.360 above the trees and know where you are right. I 0:01:48.400 --> 0:01:50.960 can't see the forest for the tree. It's definitely a 0:01:50.960 --> 0:01:53.960 particular skill of figuring out how the map represents the 0:01:54.000 --> 0:01:56.080 world you're seeing around you, and how to figure out 0:01:56.120 --> 0:01:58.600 where on the map you are. Well, I'm glad you're 0:01:58.640 --> 0:02:00.320 not lost in the woods, Daniel, it's what of my 0:02:00.480 --> 0:02:03.520 recurring nightmares. Welcome to our podcast Daniel and Jorge Explain 0:02:03.600 --> 0:02:06.160 the Universe, a production of our Heart Radio in which 0:02:06.160 --> 0:02:09.160 we try to avoid being lost in the woods of physics. 0:02:09.440 --> 0:02:11.800 We try to navigate our way through all of the 0:02:11.880 --> 0:02:16.080 confusing issues about this incredible universe, figure out how we 0:02:16.160 --> 0:02:18.960 can actually understand it, what we can make sense of, 0:02:19.120 --> 0:02:22.799 how big our map of the intellectual cosmos. We really 0:02:22.840 --> 0:02:25.040 can illuminate it. So I think of this podcast as 0:02:25.080 --> 0:02:28.760 your GPS for the entire universe, helping you know where 0:02:28.800 --> 0:02:31.800 things are and how to get there. Because slowly, over 0:02:31.960 --> 0:02:34.919 hundreds or thousands of years, we have started to build 0:02:34.960 --> 0:02:37.960 a map of how the universe works. We have a 0:02:38.000 --> 0:02:41.359 literal map of like what's physically out there in the universe, 0:02:41.639 --> 0:02:44.440 but we also have a conceptual map one that tells 0:02:44.520 --> 0:02:47.560 us how things work, how they explain the experience we see, 0:02:47.600 --> 0:02:50.240 and what they predict about what is to come. Yeah, 0:02:50.240 --> 0:02:52.360 because it is a pretty big universe and there's a 0:02:52.360 --> 0:02:54.919 lot out there for us to explore and to check out, 0:02:54.960 --> 0:02:56.959 and so having a map is a really good thing. 0:02:57.040 --> 0:02:58.960 Do you know where we sit in the universe? And 0:02:59.000 --> 0:03:00.560 it turns out that, we say it in a very 0:03:00.560 --> 0:03:03.400 small corner of one tiny galaxy that's part of a 0:03:03.480 --> 0:03:06.600 giant supercluster. And it's amazing we've been able to figure 0:03:06.639 --> 0:03:08.640 that out just looking at the night sky from this 0:03:08.720 --> 0:03:11.680 little piece of rock. Why do you call our galaxy tiny? 0:03:11.760 --> 0:03:13.639 I think it's pretty impressive. Well, you know, it could 0:03:13.680 --> 0:03:15.760 be bigger. You know, always use a bigger house, right, 0:03:16.800 --> 0:03:18.280 I don't know. I have friends that moved into a 0:03:18.280 --> 0:03:21.040 bigger house, and they found themselves just screaming at each 0:03:21.040 --> 0:03:23.560 other from opposite ends of the house all the time. 0:03:23.800 --> 0:03:26.320 I think they were happier in their tiny, little cramp department. 0:03:27.160 --> 0:03:30.360 Sounds like they needed an intercom, which is like technology 0:03:30.440 --> 0:03:33.000 from the eighties seventies. Yeah, exactly. And so if we 0:03:33.080 --> 0:03:35.880 lived in Andromeda, we'd have an even bigger galaxy to 0:03:36.000 --> 0:03:38.640 explore to find those aliens unless we had some sort 0:03:38.640 --> 0:03:41.480 of like alien galactic intercom where we could just talk 0:03:41.520 --> 0:03:44.000 to everybody. Yeah, you could have like a quantum warp 0:03:44.080 --> 0:03:49.680 tunnel the intercom. But the universe is quite vast, even 0:03:49.720 --> 0:03:53.480 beyond our tiny or large galaxy, depending on how you 0:03:53.520 --> 0:03:55.440 see it. And it's incredible that we have been able 0:03:55.480 --> 0:03:57.880 to figure out what's out there. Remember when you look 0:03:57.880 --> 0:04:00.720 at a map of the superclusters or our galaxy, that 0:04:00.800 --> 0:04:05.040 those are constructed from painstaking work to figure out where 0:04:05.120 --> 0:04:08.320 everything is. We don't have cameras above the Milky Way 0:04:08.400 --> 0:04:11.760 or outside of the galaxy. We've basically only ever observed 0:04:11.840 --> 0:04:15.200 things from Earth or from very very close to Earth, 0:04:15.480 --> 0:04:18.440 and those technological eyeballs we have built have allowed us 0:04:18.480 --> 0:04:22.240 to piece together this concept of where we are in 0:04:22.279 --> 0:04:24.719 the cosmos. Yeah, it's amazing what we've been able to 0:04:24.720 --> 0:04:28.400 piece together just from our little viewpoint using basically like 0:04:28.440 --> 0:04:31.599 two pieces of glass. Right, the original telescopes were che 0:04:32.240 --> 0:04:34.800 tube and two pieces of glass. I mean they're a 0:04:34.839 --> 0:04:38.600 little fastier now, but essentially the same thing. Yeah. I 0:04:38.600 --> 0:04:41.640 think you're glossing over a couple of crucial details, like 0:04:41.680 --> 0:04:43.880 the shape of that glass, but yeah, those are the 0:04:43.920 --> 0:04:47.120 basic ingredients. Yeah, and so we've been able to look 0:04:47.120 --> 0:04:49.760 at the stars and other galaxies from our point or 0:04:49.760 --> 0:04:51.480 an Earth, but we've also been able to look at 0:04:51.520 --> 0:04:54.400 the sky from the sky. We now have more than 0:04:54.400 --> 0:04:57.600 a few space telescopes out there in orbit and beyond 0:04:57.720 --> 0:05:00.520 orbit looking at the rest of the universe. Yeah, we 0:05:00.560 --> 0:05:04.640 have two really awesome sets of technology ground based telescopes 0:05:04.680 --> 0:05:07.560 that can get really really big tens of meters across 0:05:07.800 --> 0:05:10.440 for the primary mirrors, but those can be obscured by 0:05:10.520 --> 0:05:13.400 all the air that's between us and space. That air 0:05:13.440 --> 0:05:16.760 wiggles and shimmys and makes a little bit unclear to 0:05:16.800 --> 0:05:19.480 see what's out there. So we have this other awesome 0:05:19.600 --> 0:05:22.000 set of eyeballs we built that are actually out there 0:05:22.120 --> 0:05:26.279 in space above the atmosphere and can see much more clearly, 0:05:26.320 --> 0:05:29.320 although they can't yet be quite as large, So it's 0:05:29.320 --> 0:05:33.400 a complementary set of eyeballs. Now, these are not literal eyeballs, Like, 0:05:33.440 --> 0:05:35.920 we didn't send eyeballs into space, did we. Well, it 0:05:35.920 --> 0:05:39.000 depends on your definition of eyeballs. Right, they're not human 0:05:39.200 --> 0:05:43.200 biological eyeballs, but they're more like cameras. Right. They take 0:05:43.240 --> 0:05:46.400 pictures which are then transmitted to your eyes. Are they 0:05:46.440 --> 0:05:49.280 in the shape of a ball at least there are 0:05:49.279 --> 0:05:51.839 definitely some balls on them, right, we'll talk about it 0:05:51.880 --> 0:05:55.160 in the podcast. But they have spinning wheels and spinning balls, 0:05:55.240 --> 0:05:58.720 which are crucial elements of their operation. Oh all right, well, 0:05:58.800 --> 0:06:02.960 so technically there are they are eye and balls. But 0:06:03.040 --> 0:06:05.880 it is amazing that we have space telescodes. It's pretty cool. 0:06:05.880 --> 0:06:08.920 It's like, literally we build spaceships that are nothing but 0:06:09.560 --> 0:06:12.760 or spacecraft that are nothing but a telescope. Right, that's 0:06:12.800 --> 0:06:15.800 their only function, and they're out there in space doing 0:06:15.800 --> 0:06:20.040 their job. They're sort of like robotic space telescope spacecraft. Yeah, 0:06:20.040 --> 0:06:23.520 they're sort of like distant robot eyeballs that we connect 0:06:23.600 --> 0:06:26.599 to our own minds. It is really incredible. And you know, 0:06:26.680 --> 0:06:29.480 the telescopes here on Earth. That makes sense how they work. 0:06:29.560 --> 0:06:32.240 You want to look at something, you can turn the telescope, 0:06:32.240 --> 0:06:34.760 you point it at that thing that you want to watch. 0:06:35.000 --> 0:06:37.040 But the telescopes that are out there in space, it's 0:06:37.080 --> 0:06:40.000 a little harder to understand, like how those work, how 0:06:40.040 --> 0:06:42.120 they keep track of where they are, how you can 0:06:42.200 --> 0:06:44.960 turn and telescope in space? And a bunch of listeners 0:06:45.000 --> 0:06:47.039 wrote in and ask me how does that work? So 0:06:47.120 --> 0:06:49.080 do they end the program? We'll be tackling the question 0:06:53.880 --> 0:06:58.080 how do space telescopes point themselves? Now? I guess, Daniel, 0:06:58.080 --> 0:07:00.720 The question I guess is like, if you telescope here 0:07:00.720 --> 0:07:03.440 on Earth, you're grounded to the Earth, so you sort 0:07:03.440 --> 0:07:05.080 of know where you are and which way you're pointing. 0:07:05.800 --> 0:07:08.479 But maybe the question that the listeners were wondering is like, 0:07:08.480 --> 0:07:10.320 if you have a telescope out there in space, like, 0:07:10.400 --> 0:07:11.640 how do you know where you are? And how do 0:07:11.680 --> 0:07:14.120 you know which way you're pointing? Yeah, I think there's 0:07:14.160 --> 0:07:16.360 two different parts to it, right, is how do you 0:07:16.400 --> 0:07:19.760 know which direction you are pointing? And then also how 0:07:19.760 --> 0:07:22.680 do you change your direction? Right? How do you actually 0:07:22.720 --> 0:07:25.880 turn something that's up in space? Because here on the 0:07:25.920 --> 0:07:28.480 ground you can push against the ground it's like connected 0:07:28.480 --> 0:07:31.720 to something that you can push against. But up in space, right, 0:07:31.800 --> 0:07:34.640 it's harder to move things around, especially if you wanted 0:07:34.720 --> 0:07:37.880 to last four decades. M I see, because I guess 0:07:37.920 --> 0:07:41.680 anything that you do, like if you have jets or anything, 0:07:41.720 --> 0:07:45.080 then that means that you're expending energy. Yeah, and more 0:07:45.120 --> 0:07:48.480 specifically mass, right, jets have to push out something. You 0:07:48.520 --> 0:07:50.840 have to throw something out the back of the jet 0:07:51.160 --> 0:07:53.640 in order to get the momentum. You mean, we count 0:07:53.680 --> 0:07:56.680 to throw something at them from here, like to you know, 0:07:57.040 --> 0:07:59.520 knock them into the linement. That was definitely one of 0:07:59.520 --> 0:08:01.480 the plans, So I think it was pretty far down 0:08:01.520 --> 0:08:04.440 on the list. Maybe zap them from Earth with lasers 0:08:04.480 --> 0:08:06.800 also was pretty far down on the list. Oh, but 0:08:06.880 --> 0:08:10.480 that would be pretty good, wouldn't it. That's what our 0:08:10.520 --> 0:08:13.240 strategies for turning asteroids that are coming towards Earth. So 0:08:13.280 --> 0:08:16.240 maybe we would also work for spacecraft. Yeah, you know, 0:08:16.600 --> 0:08:21.960 it would indowd used lasers. Actually, I think that would 0:08:22.000 --> 0:08:24.520 work if you had like sales on the telescope and 0:08:24.520 --> 0:08:26.880 you could just push it from Earth with lasers. That 0:08:26.880 --> 0:08:29.080 would be really cool. I can't imagine what could go 0:08:29.160 --> 0:08:31.600 wrong or why there might be an issue with building 0:08:31.640 --> 0:08:36.560 an enormous space laser. They should high NASA obviously because 0:08:36.600 --> 0:08:39.480 we have good ideas. I'll be expecting an email as 0:08:39.480 --> 0:08:41.200 soon as we're done with this podcast. Well, as usually, 0:08:41.200 --> 0:08:43.000 we were wondering how many people had there had thought 0:08:43.040 --> 0:08:46.080 about the space telescopes out there in space and how 0:08:46.120 --> 0:08:49.439 they turned themselves to point at different stars. So thanks 0:08:49.440 --> 0:08:52.319 to everybody who answered these questions for the podcast. If 0:08:52.360 --> 0:08:54.840 you would like to participate for our future episodes, please 0:08:54.840 --> 0:08:57.880 please please do right to me two questions at Daniel 0:08:57.920 --> 0:09:00.760 and Jorhey dot com. We'd love to hear a huge 0:09:00.840 --> 0:09:03.560 variety of voices from all over the world. So think 0:09:03.559 --> 0:09:05.920 about it for a second. If you earned space pointing 0:09:05.920 --> 0:09:09.280 a telescope, how would you turn yourself. Here's what people 0:09:09.320 --> 0:09:14.080 had to say. I haven't thought about it. Maybe by 0:09:14.240 --> 0:09:20.400 using some geroscopes, either this cameramount that you pointed at 0:09:20.440 --> 0:09:28.439 the North Star and then it's basically calibrated to turn 0:09:29.240 --> 0:09:32.360 to compensate for the rotation of the Earth, which is 0:09:32.400 --> 0:09:37.720 like very consistent. So I'm assuming that space telescopes would 0:09:37.720 --> 0:09:41.360 do the same. I would guess that the space telescopes 0:09:41.600 --> 0:09:46.680 point themselves the same way that Alon Musk's SpaceX rockets 0:09:46.679 --> 0:09:50.200 do with the air pressure thing, I don't know, maybe 0:09:50.240 --> 0:09:53.240 either that or like a ion engine, I don't know. 0:09:53.760 --> 0:09:56.400 I learned that the James Webb telescope has a set 0:09:56.480 --> 0:10:01.600 of wheels that spin and apply some torque, so the 0:10:01.600 --> 0:10:05.000 whole thing making the twist a little okay, I think 0:10:05.040 --> 0:10:08.040 I actually remember this one from a previous episode in 0:10:08.080 --> 0:10:10.880 which we said that it was actually very hard to 0:10:10.920 --> 0:10:14.320 orient yourself in space, with the exception of being able 0:10:14.360 --> 0:10:18.240 to use pulsars, which you described as sort of like 0:10:18.400 --> 0:10:24.960 celestial guiding points that flash very consistently and can therefore 0:10:25.240 --> 0:10:31.360 somehow be used to triangulate your location, assuming that you 0:10:31.760 --> 0:10:35.760 already have the known location of two or more pulsars. 0:10:36.360 --> 0:10:41.439 I believe they use gyroscopes in order to orient themselves, 0:10:41.559 --> 0:10:45.960 or perhaps they off gas, you know, shooting little jets 0:10:46.040 --> 0:10:48.920 in particular directions in order to orient themselves in order 0:10:48.960 --> 0:10:52.040 to point themselves in a particular direction, and they use 0:10:52.120 --> 0:10:58.080 the background stars to orient themselves correctly. All right, pretty 0:10:59.120 --> 0:11:02.680 technical answer here, but pretty imaginative. Yeah, our listeners have 0:11:02.800 --> 0:11:05.360 thought about flying through space, how to get around, how 0:11:05.400 --> 0:11:08.079 to turn, how to know where you're pointing. We got 0:11:08.120 --> 0:11:11.080 some pretty smart folks listening to the podcast. Yeah, let's 0:11:12.040 --> 0:11:16.800 flatter our audience. You guys are awesome, beautiful and brilliant. 0:11:16.920 --> 0:11:19.079 But I feel like the answer is here, and we're 0:11:19.120 --> 0:11:22.320 also a little confused about what we're asking in the question, 0:11:22.400 --> 0:11:25.600 like are we asking like how does a space telescope 0:11:26.000 --> 0:11:28.280 orient itself? Like how do we how does it know 0:11:28.400 --> 0:11:31.000 which way it's pointing? And also how does it turn 0:11:31.120 --> 0:11:33.720 to point at something it wants to look at. Yeah, 0:11:33.760 --> 0:11:37.119 I think we're asking both questions and have different answers, 0:11:37.120 --> 0:11:39.480 both of which are really fascinating. So I think all 0:11:39.520 --> 0:11:41.640 of that is involved. I mean, you have your eyeball 0:11:41.640 --> 0:11:44.040 out in space, you wanted to look at something in particular, 0:11:44.120 --> 0:11:46.680 you got to solve both problems. You gotta know where 0:11:46.720 --> 0:11:49.199 it is now and how to change its position. M 0:11:50.120 --> 0:11:52.160 do you think there's a there's like a joystick somewhere 0:11:52.160 --> 0:11:55.840 in NASA or Houston Control Center that points these telescopes? 0:11:56.360 --> 0:11:58.880 Like who gets to move that joysting? And I wonder 0:11:59.000 --> 0:12:00.559 if there's a red button on the top of that 0:12:00.640 --> 0:12:03.720 joystick and if it actually fires something or if it 0:12:03.760 --> 0:12:07.840 just has a little like sound effect peo pew, or 0:12:07.840 --> 0:12:09.880 maybe if you press the button like a flag pops 0:12:09.920 --> 0:12:12.880 out at the end of Hubble boom, or I wonder 0:12:12.880 --> 0:12:15.360 if anyone that NASA has never been tempted to turn 0:12:15.440 --> 0:12:18.840 the telescope around and point it at Earth, like, what 0:12:18.920 --> 0:12:21.160 could it look at? What could it see? You could 0:12:21.200 --> 0:12:24.080 take a selfie with Hubble? Right? Yeah, oh man, do 0:12:24.120 --> 0:12:27.520 you probably find all of NASA selling those selfie opportunities. 0:12:28.720 --> 0:12:31.520 Hubble is quite delicate, and if too much light enters 0:12:31.600 --> 0:12:33.800 its aperture it could damage it. They have to be 0:12:33.920 --> 0:12:36.520 very careful about not pointing it, for example, towards the Sun. 0:12:36.840 --> 0:12:39.120 And I wonder if even the Earth might be too 0:12:39.200 --> 0:12:41.880 bright a source for Hubble. Well, I guess it would 0:12:41.880 --> 0:12:44.880 have to be night selfies. Then all right, well, let's 0:12:44.880 --> 0:12:48.160 dig into this question of how based telescopes orient themselves, 0:12:48.200 --> 0:12:50.160 how they know which way they're pointing at, and then 0:12:50.160 --> 0:12:52.240 if they want to point somewhere in particular, how do 0:12:52.320 --> 0:12:55.240 they move themselves to point in that direction. So, first 0:12:55.240 --> 0:12:58.040 of all, Daniel stepped us through this. Why this is 0:12:58.480 --> 0:13:02.040 important and heart wells important because we want to choose 0:13:02.280 --> 0:13:05.400 what we are seeing. Remember that the telescopes don't see 0:13:05.480 --> 0:13:08.199 all of space, right, It's not like when you look 0:13:08.200 --> 0:13:09.680 out of the night sky and you stare up and 0:13:09.720 --> 0:13:11.679 you basically see the whole sky, or at least the 0:13:11.720 --> 0:13:14.559 part that's not blocked by the earth. A telescope is 0:13:14.720 --> 0:13:18.520 very very narrow aperture in comparison, and so you're only 0:13:18.520 --> 0:13:21.679 really looking at a small portion of the sky, and 0:13:21.720 --> 0:13:23.720 you want to get to pick which portion of the 0:13:23.760 --> 0:13:26.199 sky you are looking at. Are we studying this galaxy, 0:13:26.200 --> 0:13:28.760 are we studying that star over there? Are we tracking 0:13:28.840 --> 0:13:32.079 something that's moving? So you definitely want to have control 0:13:32.200 --> 0:13:35.200 over where your telescope is pointed. Yeah, it's sort of 0:13:35.200 --> 0:13:37.160 like you say, it has a very narrow field of view. 0:13:37.200 --> 0:13:40.120 I imagine it's sort of like walking around your neighborhood 0:13:40.200 --> 0:13:43.600 looking through a straw or something like that. Right, that's 0:13:43.640 --> 0:13:45.240 what it means to have a narrow field of view. 0:13:45.320 --> 0:13:47.440 Like if you close one eye and the other eye 0:13:47.600 --> 0:13:51.719 could only look through a drinking straw, your field of 0:13:51.760 --> 0:13:54.160 view moop be super narrow, and it'd be pretty hard 0:13:54.200 --> 0:13:57.520 to know where you are. And anybody who looked through 0:13:57.520 --> 0:14:01.440 a telescope has that experience. Your telescope sort of towards 0:14:01.480 --> 0:14:02.880 the thing you're looking for, and then you look through 0:14:02.880 --> 0:14:05.040 the telescope and you don't see it and show wiggle 0:14:05.080 --> 0:14:07.520 the telescope around and try to find the object. It's 0:14:07.559 --> 0:14:10.120 not easy when you're looking through a telescope to find 0:14:10.160 --> 0:14:12.920 that particular object has to be pointed very very close 0:14:13.200 --> 0:14:15.160 for you to even see it. And a straw is 0:14:15.160 --> 0:14:18.080 a great example, but it's actually not even dramatic enough. 0:14:18.320 --> 0:14:20.720 Some of these telescopes, their field of view is so small. 0:14:20.760 --> 0:14:23.240 It's more like looking at a grain of saying you 0:14:23.320 --> 0:14:26.160 hold at arm's length, right, that's the fraction of the 0:14:26.200 --> 0:14:29.480 sky these telescopes can look at at one time. It's 0:14:29.480 --> 0:14:31.840 like looking at a straw. That's the width of a 0:14:31.880 --> 0:14:34.480 grain of salt, and a meter lungs what you're saying, Yeah, 0:14:34.640 --> 0:14:37.600 that's exactly right. So some recent images, for example from 0:14:37.680 --> 0:14:40.520 James Webb, where they focus on the deep, deep sky, 0:14:40.600 --> 0:14:43.440 they point at one particular place in the sky and 0:14:43.480 --> 0:14:46.400 they take a bunch of pictures of that one spot. 0:14:46.560 --> 0:14:48.280 And the reason you want to hold it there for 0:14:48.320 --> 0:14:50.600 a long time is that the things that they're looking 0:14:50.640 --> 0:14:53.680 at are quite dim. You know, these distant galaxies don't 0:14:53.720 --> 0:14:56.360 send a whole lot of photons per second, so you 0:14:56.400 --> 0:14:58.520 want to build up a crisp image of them. You've 0:14:58.520 --> 0:15:00.960 got to wait as many seconds as possible to get 0:15:01.000 --> 0:15:03.480 as many photons as possible. So you have to keep 0:15:03.480 --> 0:15:07.200 pointing in the same direction for as long as possible. Yeah, 0:15:07.200 --> 0:15:10.000 and I imagine that's extra hard because first of all, 0:15:10.120 --> 0:15:12.320 like that thing that you're looking at might be moving, 0:15:12.960 --> 0:15:15.360 but also like the space telescope is moving, right, and 0:15:15.440 --> 0:15:19.400 like these space telescopes are usually an orbit around something, 0:15:19.480 --> 0:15:21.880 either the Earth or I guess mostly the Earth, but 0:15:22.080 --> 0:15:25.360 either a near orbit or far orbit. Yeah, we're always 0:15:25.400 --> 0:15:27.920 moving relative to the Sun. And even if these distant 0:15:27.920 --> 0:15:31.400 objects aren't effectively moving relative to our galaxy, You're right, 0:15:31.480 --> 0:15:33.360 our position is moving, and so you have to do 0:15:33.440 --> 0:15:36.640 something to stay on target. You can't just turn it 0:15:36.720 --> 0:15:39.440 and point and take pictures. The things you're looking at 0:15:39.480 --> 0:15:42.080 will change as you orbit the Sun, and so you 0:15:42.080 --> 0:15:43.800 have to do work. I have to do something to 0:15:43.960 --> 0:15:47.240 keep pointing in the same direction. M okay. So then, 0:15:47.280 --> 0:15:50.720 and that's hard to do to move your space telescope 0:15:50.760 --> 0:15:54.280 because basically there's nothing to push against in space. Exactly, 0:15:54.360 --> 0:15:56.160 if you're swimming in a swimming pool and you want 0:15:56.160 --> 0:15:57.840 to turn, what do you do. You hold your arms 0:15:57.840 --> 0:16:00.480 out and you push against the water. Right, You're pushing 0:16:00.600 --> 0:16:03.840 against something, and so you turn. But in space, what 0:16:04.080 --> 0:16:06.360 is there, right, There's no air, there's no water, there's 0:16:06.400 --> 0:16:10.000 nothing to push against, and so turning yourself is much 0:16:10.040 --> 0:16:13.880 harder because there's nothing immediately there for you to push against, 0:16:13.880 --> 0:16:16.440 for you to like boost off of right. And but 0:16:16.600 --> 0:16:20.520 usually satellites and spacecraft the way they navigate and turn 0:16:20.600 --> 0:16:24.800 and move around, they have rockets, right, or at least 0:16:24.800 --> 0:16:28.400 some sort of like a listener suggested, like an ion engine. 0:16:28.840 --> 0:16:32.000 And the crucial thing here is conservation of momentum. If 0:16:32.040 --> 0:16:34.800 you're stationary and you want to get moving, then to 0:16:34.880 --> 0:16:37.960 conserve momentum, you have to throw something going the other direction. 0:16:38.080 --> 0:16:40.480 That requires mass right the same way that like if 0:16:40.520 --> 0:16:43.320 you fire a bullet, you feel a recoil. If you're 0:16:43.320 --> 0:16:46.560 out in space you turn on a rocket, then basically 0:16:46.560 --> 0:16:49.800 the motion of your ship is the recoil from firing 0:16:49.840 --> 0:16:52.640 the rocket, because it's basically shooting a bunch of tiny 0:16:52.680 --> 0:16:55.360 bullets out the back of the rocket. The rocket is 0:16:55.360 --> 0:16:58.480 not just flames, it's throwing mass out the back of it. 0:16:58.640 --> 0:17:00.640 So you don't just need fuel to run the rocket. 0:17:00.680 --> 0:17:03.400 You need some sort of propellant something to throw out 0:17:03.480 --> 0:17:06.120 of the rocket to move your ship. And that's true 0:17:06.160 --> 0:17:09.480 both for motion and for rotation. And so if you 0:17:09.560 --> 0:17:11.879 need a mass to do it, then eventually you're going 0:17:11.920 --> 0:17:14.119 to run out because you can only bring a limited 0:17:14.119 --> 0:17:16.640 amount of mass. So the goal is to figure out 0:17:16.640 --> 0:17:20.040 a way to turn your telescope without using some kind 0:17:20.040 --> 0:17:23.080 of propellant, right, because I guess if you're using a propellant, 0:17:23.280 --> 0:17:27.840 even if there are like ion atoms or molecules, you're 0:17:27.880 --> 0:17:30.000 going to run out eventually, right, You are going to 0:17:30.080 --> 0:17:32.680 run out eventually. And if you spend billions of dollars 0:17:32.720 --> 0:17:35.000 and decades to develop this thing, then you want it 0:17:35.040 --> 0:17:37.080 to last as long as possible. So you're going to 0:17:37.119 --> 0:17:39.920 try to avoid at all costs having things that run out. 0:17:40.040 --> 0:17:43.760 Can you make it electric like an electric car? Yeah, 0:17:43.840 --> 0:17:46.280 you can make it electric, and an ion engine essentially 0:17:46.359 --> 0:17:48.840 is electric, but it still has to throw something out 0:17:48.880 --> 0:17:51.600 of the back, right, it's throwing ions which have been 0:17:51.640 --> 0:17:55.040 accelerated by electric fields. And just bring like a really 0:17:55.040 --> 0:17:58.639 big gas tank, like one that will last one hundred years, right, 0:17:58.640 --> 0:18:03.240 Because these missions usually don't have like an unlimited lifespan, right, 0:18:03.240 --> 0:18:05.840 They usually come with like an expiration date. You can't 0:18:05.840 --> 0:18:07.720 do that. But then the gas tank is big, which 0:18:07.760 --> 0:18:09.800 means it's heavy, which means you need more gas to 0:18:09.880 --> 0:18:11.720 launch it. And usually you want to use all of 0:18:11.720 --> 0:18:14.240 your available space and mass to design it for science 0:18:14.359 --> 0:18:16.400 rather than having a huge fuel tank on the back 0:18:16.440 --> 0:18:18.479 of it. I see. So I guess if you can 0:18:18.520 --> 0:18:22.159 figure out a smarter way to turn out there in space, 0:18:22.320 --> 0:18:24.760 then you could have more science than your rugget bigger 0:18:24.800 --> 0:18:28.800 telescope exactly, more science and more years of science because 0:18:28.840 --> 0:18:31.199 you wouldn't run out of something. Then you need to 0:18:31.240 --> 0:18:33.800 turn the thing also be greener, I imagine, right for 0:18:33.960 --> 0:18:39.480 the space ecosystem, you'd be less pollution. That's true exactly, 0:18:39.840 --> 0:18:41.720 and so for all of our neighbors out there, we 0:18:41.720 --> 0:18:44.080 should be consider it. All right, Well, that's why it's 0:18:44.119 --> 0:18:47.560 important and hard to turn a space telescope and orient 0:18:47.640 --> 0:18:49.560 it out there in space. And so let's get into 0:18:49.760 --> 0:18:51.800 how you would actually do this and how you would 0:18:51.800 --> 0:18:55.480 find yourself if you were lost in space. So let's 0:18:55.480 --> 0:18:57.800 dig into that. But first let's take a quick right, 0:19:10.359 --> 0:19:14.000 all right, we're talking about space telescopes, which are telescopes 0:19:14.000 --> 0:19:20.520 in space basically finally a well named physics object. Well, 0:19:20.560 --> 0:19:24.440 I know, right, and we're talking about how they point 0:19:24.480 --> 0:19:26.960 themselves out there in space. So let's tackle maybe the 0:19:27.000 --> 0:19:29.919 first question is, if you're on telescope out there in space, 0:19:30.200 --> 0:19:31.480 how do you know where you are? And how do 0:19:31.480 --> 0:19:33.800 you know where you're pointing? So these telescopes typically have 0:19:34.080 --> 0:19:36.160 multiple ways to figure out where they are pointing. First 0:19:36.160 --> 0:19:38.159 of all, they just have a bunch of sensors. Like 0:19:38.200 --> 0:19:41.280 the Hubble, for example, has several different kinds of sensors. 0:19:41.560 --> 0:19:43.960 It has a sensor that tells it where the Sun is, 0:19:44.359 --> 0:19:47.080 which helps it know where it's pointing, but also helps 0:19:47.080 --> 0:19:50.440 it avoid pointing into the Sun accidentally. It also has 0:19:50.480 --> 0:19:52.919 sensors for magnetic field, so that you can use the 0:19:52.960 --> 0:19:55.720 Earth's magnetic field to help figure out where it is. 0:19:56.040 --> 0:19:58.639 And then there are sensors that look at stars, and 0:19:58.680 --> 0:20:01.320 there's like a known star map and helps it get 0:20:01.320 --> 0:20:04.600 an orientation roughly for where it is, So to get 0:20:04.640 --> 0:20:07.040 a rough idea for where it is and orient itself, 0:20:07.200 --> 0:20:10.560 it has essentially maps the Sun, the magnetic field, and 0:20:10.640 --> 0:20:13.400 the stars that give it a sense for where it is. Yeah, 0:20:13.440 --> 0:20:15.240 that's usually how they do it in science fiction, Like 0:20:15.280 --> 0:20:17.280 if you're in a spaceship and you land in a 0:20:17.359 --> 0:20:19.960 place you're not quite sure where you are. Usually the 0:20:20.000 --> 0:20:22.720 way you orient yourself is by looking at the stars 0:20:22.760 --> 0:20:25.120 around you, and if you sort of know where they're 0:20:25.119 --> 0:20:26.800 supposed to be, you can figure out where you are 0:20:26.840 --> 0:20:29.320 relative to them. That's the idea, right Basically, they're looking 0:20:29.320 --> 0:20:32.399 at the constellations. They're looking at the constellations, and Hubble 0:20:32.680 --> 0:20:35.800 is not a traveling spacecraft, so it will never appear 0:20:35.840 --> 0:20:38.199 in Andromeda and have to figure out where it is. 0:20:38.640 --> 0:20:40.600 It's always going to be orbiting the Earth, and so 0:20:40.760 --> 0:20:43.479