1 00:00:08,480 --> 00:00:11,840 Speaker 1: Hey, Jorgey, are you good at navigating? Depends on what 2 00:00:11,920 --> 00:00:13,920 Speaker 1: do you mean by navigating? Do you mean navigating the 3 00:00:13,920 --> 00:00:17,599 Speaker 1: complex issues of how to lead a good life? Then no, 4 00:00:17,720 --> 00:00:19,239 Speaker 1: I haven't figured that one out. But if you mean 5 00:00:19,320 --> 00:00:22,040 Speaker 1: like getting somewhere, I have a phone with GPS, so 6 00:00:22,239 --> 00:00:24,600 Speaker 1: I guess i'm pretty good. Well, what have you lost 7 00:00:24,600 --> 00:00:27,720 Speaker 1: your phone? Like? Or civilization crumbled? Do you know how 8 00:00:27,760 --> 00:00:31,680 Speaker 1: to oriente yourself in the woods? Well? I imagine I 9 00:00:31,680 --> 00:00:33,640 Speaker 1: could use a map and a compass, right, do you 10 00:00:33,680 --> 00:00:36,960 Speaker 1: mean like a basic old school compass or the compass 11 00:00:36,960 --> 00:00:39,080 Speaker 1: app on your phone? Okay, yeah, that's a good point. 12 00:00:39,800 --> 00:00:42,839 Speaker 1: I only have the compass on my phone. But I 13 00:00:42,880 --> 00:00:45,960 Speaker 1: guess you could probably find a low tech original you know, 14 00:00:46,040 --> 00:00:48,600 Speaker 1: og compass. Yeah, that would let you get low tech 15 00:00:48,680 --> 00:00:53,400 Speaker 1: original lost. I guess there's civilization crumbles were all lost. 16 00:01:08,760 --> 00:01:11,840 Speaker 1: I am morehammy cartoonist and the creator of PhD comics. Hi, 17 00:01:11,920 --> 00:01:14,400 Speaker 1: I'm Daniel. I'm a particle physicist and a professor at 18 00:01:14,480 --> 00:01:19,039 Speaker 1: UC Irvine, and I've never honestly been lost in the woods. Well, well, yeah, 19 00:01:19,040 --> 00:01:20,959 Speaker 1: I think that's self evident, because you're talking to us 20 00:01:21,040 --> 00:01:23,840 Speaker 1: right now. If you were lost in the woods, I'm 21 00:01:23,880 --> 00:01:26,280 Speaker 1: not sure we would have from you again. Maybe I'm 22 00:01:26,280 --> 00:01:28,800 Speaker 1: calling you from my secret woods hideout, or even I 23 00:01:28,800 --> 00:01:31,720 Speaker 1: don't know where it is, although if you have Wi 24 00:01:31,760 --> 00:01:35,040 Speaker 1: Fi there and are able to record, I'm not sure 25 00:01:35,040 --> 00:01:38,399 Speaker 1: you're that lost. Yeah, that's true. But I've often gone 26 00:01:38,400 --> 00:01:41,120 Speaker 1: on long backpacking trips and wonder if I really could 27 00:01:41,160 --> 00:01:43,959 Speaker 1: get myself out of the woods if I had to. Yeah, 28 00:01:44,000 --> 00:01:46,479 Speaker 1: it's pretty tricky because I guess it's hard to see 29 00:01:46,520 --> 00:01:48,360 Speaker 1: above the trees and know where you are right. I 30 00:01:48,400 --> 00:01:50,960 Speaker 1: can't see the forest for the tree. It's definitely a 31 00:01:50,960 --> 00:01:53,960 Speaker 1: particular skill of figuring out how the map represents the 32 00:01:54,000 --> 00:01:56,080 Speaker 1: world you're seeing around you, and how to figure out 33 00:01:56,120 --> 00:01:58,600 Speaker 1: where on the map you are. Well, I'm glad you're 34 00:01:58,640 --> 00:02:00,320 Speaker 1: not lost in the woods, Daniel, it's what of my 35 00:02:00,480 --> 00:02:03,520 Speaker 1: recurring nightmares. Welcome to our podcast Daniel and Jorge Explain 36 00:02:03,600 --> 00:02:06,160 Speaker 1: the Universe, a production of our Heart Radio in which 37 00:02:06,160 --> 00:02:09,160 Speaker 1: we try to avoid being lost in the woods of physics. 38 00:02:09,440 --> 00:02:11,800 Speaker 1: We try to navigate our way through all of the 39 00:02:11,880 --> 00:02:16,080 Speaker 1: confusing issues about this incredible universe, figure out how we 40 00:02:16,160 --> 00:02:18,960 Speaker 1: can actually understand it, what we can make sense of, 41 00:02:19,120 --> 00:02:22,799 Speaker 1: how big our map of the intellectual cosmos. We really 42 00:02:22,840 --> 00:02:25,040 Speaker 1: can illuminate it. So I think of this podcast as 43 00:02:25,080 --> 00:02:28,760 Speaker 1: your GPS for the entire universe, helping you know where 44 00:02:28,800 --> 00:02:31,800 Speaker 1: things are and how to get there. Because slowly, over 45 00:02:31,960 --> 00:02:34,919 Speaker 1: hundreds or thousands of years, we have started to build 46 00:02:34,960 --> 00:02:37,960 Speaker 1: a map of how the universe works. We have a 47 00:02:38,000 --> 00:02:41,359 Speaker 1: literal map of like what's physically out there in the universe, 48 00:02:41,639 --> 00:02:44,440 Speaker 1: but we also have a conceptual map one that tells 49 00:02:44,520 --> 00:02:47,560 Speaker 1: us how things work, how they explain the experience we see, 50 00:02:47,600 --> 00:02:50,240 Speaker 1: and what they predict about what is to come. Yeah, 51 00:02:50,240 --> 00:02:52,360 Speaker 1: because it is a pretty big universe and there's a 52 00:02:52,360 --> 00:02:54,919 Speaker 1: lot out there for us to explore and to check out, 53 00:02:54,960 --> 00:02:56,959 Speaker 1: and so having a map is a really good thing. 54 00:02:57,040 --> 00:02:58,960 Speaker 1: Do you know where we sit in the universe? And 55 00:02:59,000 --> 00:03:00,560 Speaker 1: it turns out that, we say it in a very 56 00:03:00,560 --> 00:03:03,400 Speaker 1: small corner of one tiny galaxy that's part of a 57 00:03:03,480 --> 00:03:06,600 Speaker 1: giant supercluster. And it's amazing we've been able to figure 58 00:03:06,639 --> 00:03:08,640 Speaker 1: that out just looking at the night sky from this 59 00:03:08,720 --> 00:03:11,680 Speaker 1: little piece of rock. Why do you call our galaxy tiny? 60 00:03:11,760 --> 00:03:13,639 Speaker 1: I think it's pretty impressive. Well, you know, it could 61 00:03:13,680 --> 00:03:15,760 Speaker 1: be bigger. You know, always use a bigger house, right, 62 00:03:16,800 --> 00:03:18,280 Speaker 1: I don't know. I have friends that moved into a 63 00:03:18,280 --> 00:03:21,040 Speaker 1: bigger house, and they found themselves just screaming at each 64 00:03:21,040 --> 00:03:23,560 Speaker 1: other from opposite ends of the house all the time. 65 00:03:23,800 --> 00:03:26,320 Speaker 1: I think they were happier in their tiny, little cramp department. 66 00:03:27,160 --> 00:03:30,360 Speaker 1: Sounds like they needed an intercom, which is like technology 67 00:03:30,440 --> 00:03:33,000 Speaker 1: from the eighties seventies. Yeah, exactly. And so if we 68 00:03:33,080 --> 00:03:35,880 Speaker 1: lived in Andromeda, we'd have an even bigger galaxy to 69 00:03:36,000 --> 00:03:38,640 Speaker 1: explore to find those aliens unless we had some sort 70 00:03:38,640 --> 00:03:41,480 Speaker 1: of like alien galactic intercom where we could just talk 71 00:03:41,520 --> 00:03:44,000 Speaker 1: to everybody. Yeah, you could have like a quantum warp 72 00:03:44,080 --> 00:03:49,680 Speaker 1: tunnel the intercom. But the universe is quite vast, even 73 00:03:49,720 --> 00:03:53,480 Speaker 1: beyond our tiny or large galaxy, depending on how you 74 00:03:53,520 --> 00:03:55,440 Speaker 1: see it. And it's incredible that we have been able 75 00:03:55,480 --> 00:03:57,880 Speaker 1: to figure out what's out there. Remember when you look 76 00:03:57,880 --> 00:04:00,720 Speaker 1: at a map of the superclusters or our galaxy, that 77 00:04:00,800 --> 00:04:05,040 Speaker 1: those are constructed from painstaking work to figure out where 78 00:04:05,120 --> 00:04:08,320 Speaker 1: everything is. We don't have cameras above the Milky Way 79 00:04:08,400 --> 00:04:11,760 Speaker 1: or outside of the galaxy. We've basically only ever observed 80 00:04:11,840 --> 00:04:15,200 Speaker 1: things from Earth or from very very close to Earth, 81 00:04:15,480 --> 00:04:18,440 Speaker 1: and those technological eyeballs we have built have allowed us 82 00:04:18,480 --> 00:04:22,240 Speaker 1: to piece together this concept of where we are in 83 00:04:22,279 --> 00:04:24,719 Speaker 1: the cosmos. Yeah, it's amazing what we've been able to 84 00:04:24,720 --> 00:04:28,400 Speaker 1: piece together just from our little viewpoint using basically like 85 00:04:28,440 --> 00:04:31,599 Speaker 1: two pieces of glass. Right, the original telescopes were che 86 00:04:32,240 --> 00:04:34,800 Speaker 1: tube and two pieces of glass. I mean they're a 87 00:04:34,839 --> 00:04:38,600 Speaker 1: little fastier now, but essentially the same thing. Yeah. I 88 00:04:38,600 --> 00:04:41,640 Speaker 1: think you're glossing over a couple of crucial details, like 89 00:04:41,680 --> 00:04:43,880 Speaker 1: the shape of that glass, but yeah, those are the 90 00:04:43,920 --> 00:04:47,120 Speaker 1: basic ingredients. Yeah, and so we've been able to look 91 00:04:47,120 --> 00:04:49,760 Speaker 1: at the stars and other galaxies from our point or 92 00:04:49,760 --> 00:04:51,480 Speaker 1: an Earth, but we've also been able to look at 93 00:04:51,520 --> 00:04:54,400 Speaker 1: the sky from the sky. We now have more than 94 00:04:54,400 --> 00:04:57,600 Speaker 1: a few space telescopes out there in orbit and beyond 95 00:04:57,720 --> 00:05:00,520 Speaker 1: orbit looking at the rest of the universe. Yeah, we 96 00:05:00,560 --> 00:05:04,640 Speaker 1: have two really awesome sets of technology ground based telescopes 97 00:05:04,680 --> 00:05:07,560 Speaker 1: that can get really really big tens of meters across 98 00:05:07,800 --> 00:05:10,440 Speaker 1: for the primary mirrors, but those can be obscured by 99 00:05:10,520 --> 00:05:13,400 Speaker 1: all the air that's between us and space. That air 100 00:05:13,440 --> 00:05:16,760 Speaker 1: wiggles and shimmys and makes a little bit unclear to 101 00:05:16,800 --> 00:05:19,480 Speaker 1: see what's out there. So we have this other awesome 102 00:05:19,600 --> 00:05:22,000 Speaker 1: set of eyeballs we built that are actually out there 103 00:05:22,120 --> 00:05:26,279 Speaker 1: in space above the atmosphere and can see much more clearly, 104 00:05:26,320 --> 00:05:29,320 Speaker 1: although they can't yet be quite as large, So it's 105 00:05:29,320 --> 00:05:33,400 Speaker 1: a complementary set of eyeballs. Now, these are not literal eyeballs, Like, 106 00:05:33,440 --> 00:05:35,920 Speaker 1: we didn't send eyeballs into space, did we. Well, it 107 00:05:35,920 --> 00:05:39,000 Speaker 1: depends on your definition of eyeballs. Right, they're not human 108 00:05:39,200 --> 00:05:43,200 Speaker 1: biological eyeballs, but they're more like cameras. Right. They take 109 00:05:43,240 --> 00:05:46,400 Speaker 1: pictures which are then transmitted to your eyes. Are they 110 00:05:46,440 --> 00:05:49,280 Speaker 1: in the shape of a ball at least there are 111 00:05:49,279 --> 00:05:51,839 Speaker 1: definitely some balls on them, right, we'll talk about it 112 00:05:51,880 --> 00:05:55,160 Speaker 1: in the podcast. But they have spinning wheels and spinning balls, 113 00:05:55,240 --> 00:05:58,720 Speaker 1: which are crucial elements of their operation. Oh all right, well, 114 00:05:58,800 --> 00:06:02,960 Speaker 1: so technically there are they are eye and balls. But 115 00:06:03,040 --> 00:06:05,880 Speaker 1: it is amazing that we have space telescodes. It's pretty cool. 116 00:06:05,880 --> 00:06:08,920 Speaker 1: It's like, literally we build spaceships that are nothing but 117 00:06:09,560 --> 00:06:12,760 Speaker 1: or spacecraft that are nothing but a telescope. Right, that's 118 00:06:12,800 --> 00:06:15,800 Speaker 1: their only function, and they're out there in space doing 119 00:06:15,800 --> 00:06:20,040 Speaker 1: their job. They're sort of like robotic space telescope spacecraft. Yeah, 120 00:06:20,040 --> 00:06:23,520 Speaker 1: they're sort of like distant robot eyeballs that we connect 121 00:06:23,600 --> 00:06:26,599 Speaker 1: to our own minds. It is really incredible. And you know, 122 00:06:26,680 --> 00:06:29,480 Speaker 1: the telescopes here on Earth. That makes sense how they work. 123 00:06:29,560 --> 00:06:32,240 Speaker 1: You want to look at something, you can turn the telescope, 124 00:06:32,240 --> 00:06:34,760 Speaker 1: you point it at that thing that you want to watch. 125 00:06:35,000 --> 00:06:37,040 Speaker 1: But the telescopes that are out there in space, it's 126 00:06:37,080 --> 00:06:40,000 Speaker 1: a little harder to understand, like how those work, how 127 00:06:40,040 --> 00:06:42,120 Speaker 1: they keep track of where they are, how you can 128 00:06:42,200 --> 00:06:44,960 Speaker 1: turn and telescope in space? And a bunch of listeners 129 00:06:45,000 --> 00:06:47,039 Speaker 1: wrote in and ask me how does that work? So 130 00:06:47,120 --> 00:06:49,080 Speaker 1: do they end the program? We'll be tackling the question 131 00:06:53,880 --> 00:06:58,080 Speaker 1: how do space telescopes point themselves? Now? I guess, Daniel, 132 00:06:58,080 --> 00:07:00,720 Speaker 1: The question I guess is like, if you telescope here 133 00:07:00,720 --> 00:07:03,440 Speaker 1: on Earth, you're grounded to the Earth, so you sort 134 00:07:03,440 --> 00:07:05,080 Speaker 1: of know where you are and which way you're pointing. 135 00:07:05,800 --> 00:07:08,479 Speaker 1: But maybe the question that the listeners were wondering is like, 136 00:07:08,480 --> 00:07:10,320 Speaker 1: if you have a telescope out there in space, like, 137 00:07:10,400 --> 00:07:11,640 Speaker 1: how do you know where you are? And how do 138 00:07:11,680 --> 00:07:14,120 Speaker 1: you know which way you're pointing? Yeah, I think there's 139 00:07:14,160 --> 00:07:16,360 Speaker 1: two different parts to it, right, is how do you 140 00:07:16,400 --> 00:07:19,760 Speaker 1: know which direction you are pointing? And then also how 141 00:07:19,760 --> 00:07:22,680 Speaker 1: do you change your direction? Right? How do you actually 142 00:07:22,720 --> 00:07:25,880 Speaker 1: turn something that's up in space? Because here on the 143 00:07:25,920 --> 00:07:28,480 Speaker 1: ground you can push against the ground it's like connected 144 00:07:28,480 --> 00:07:31,720 Speaker 1: to something that you can push against. But up in space, right, 145 00:07:31,800 --> 00:07:34,640 Speaker 1: it's harder to move things around, especially if you wanted 146 00:07:34,720 --> 00:07:37,880 Speaker 1: to last four decades. M I see, because I guess 147 00:07:37,920 --> 00:07:41,680 Speaker 1: anything that you do, like if you have jets or anything, 148 00:07:41,720 --> 00:07:45,080 Speaker 1: then that means that you're expending energy. Yeah, and more 149 00:07:45,120 --> 00:07:48,480 Speaker 1: specifically mass, right, jets have to push out something. You 150 00:07:48,520 --> 00:07:50,840 Speaker 1: have to throw something out the back of the jet 151 00:07:51,160 --> 00:07:53,640 Speaker 1: in order to get the momentum. You mean, we count 152 00:07:53,680 --> 00:07:56,680 Speaker 1: to throw something at them from here, like to you know, 153 00:07:57,040 --> 00:07:59,520 Speaker 1: knock them into the linement. That was definitely one of 154 00:07:59,520 --> 00:08:01,480 Speaker 1: the plans, So I think it was pretty far down 155 00:08:01,520 --> 00:08:04,440 Speaker 1: on the list. Maybe zap them from Earth with lasers 156 00:08:04,480 --> 00:08:06,800 Speaker 1: also was pretty far down on the list. Oh, but 157 00:08:06,880 --> 00:08:10,480 Speaker 1: that would be pretty good, wouldn't it. That's what our 158 00:08:10,520 --> 00:08:13,240 Speaker 1: strategies for turning asteroids that are coming towards Earth. So 159 00:08:13,280 --> 00:08:16,240 Speaker 1: maybe we would also work for spacecraft. Yeah, you know, 160 00:08:16,600 --> 00:08:21,960 Speaker 1: it would indowd used lasers. Actually, I think that would 161 00:08:22,000 --> 00:08:24,520 Speaker 1: work if you had like sales on the telescope and 162 00:08:24,520 --> 00:08:26,880 Speaker 1: you could just push it from Earth with lasers. That 163 00:08:26,880 --> 00:08:29,080 Speaker 1: would be really cool. I can't imagine what could go 164 00:08:29,160 --> 00:08:31,600 Speaker 1: wrong or why there might be an issue with building 165 00:08:31,640 --> 00:08:36,560 Speaker 1: an enormous space laser. They should high NASA obviously because 166 00:08:36,600 --> 00:08:39,480 Speaker 1: we have good ideas. I'll be expecting an email as 167 00:08:39,480 --> 00:08:41,200 Speaker 1: soon as we're done with this podcast. Well, as usually, 168 00:08:41,200 --> 00:08:43,000 Speaker 1: we were wondering how many people had there had thought 169 00:08:43,040 --> 00:08:46,080 Speaker 1: about the space telescopes out there in space and how 170 00:08:46,120 --> 00:08:49,439 Speaker 1: they turned themselves to point at different stars. So thanks 171 00:08:49,440 --> 00:08:52,319 Speaker 1: to everybody who answered these questions for the podcast. If 172 00:08:52,360 --> 00:08:54,840 Speaker 1: you would like to participate for our future episodes, please 173 00:08:54,840 --> 00:08:57,880 Speaker 1: please please do right to me two questions at Daniel 174 00:08:57,920 --> 00:09:00,760 Speaker 1: and Jorhey dot com. We'd love to hear a huge 175 00:09:00,840 --> 00:09:03,560 Speaker 1: variety of voices from all over the world. So think 176 00:09:03,559 --> 00:09:05,920 Speaker 1: about it for a second. If you earned space pointing 177 00:09:05,920 --> 00:09:09,280 Speaker 1: a telescope, how would you turn yourself. Here's what people 178 00:09:09,320 --> 00:09:14,080 Speaker 1: had to say. I haven't thought about it. Maybe by 179 00:09:14,240 --> 00:09:20,400 Speaker 1: using some geroscopes, either this cameramount that you pointed at 180 00:09:20,440 --> 00:09:28,439 Speaker 1: the North Star and then it's basically calibrated to turn 181 00:09:29,240 --> 00:09:32,360 Speaker 1: to compensate for the rotation of the Earth, which is 182 00:09:32,400 --> 00:09:37,720 Speaker 1: like very consistent. So I'm assuming that space telescopes would 183 00:09:37,720 --> 00:09:41,360 Speaker 1: do the same. I would guess that the space telescopes 184 00:09:41,600 --> 00:09:46,680 Speaker 1: point themselves the same way that Alon Musk's SpaceX rockets 185 00:09:46,679 --> 00:09:50,200 Speaker 1: do with the air pressure thing, I don't know, maybe 186 00:09:50,240 --> 00:09:53,240 Speaker 1: either that or like a ion engine, I don't know. 187 00:09:53,760 --> 00:09:56,400 Speaker 1: I learned that the James Webb telescope has a set 188 00:09:56,480 --> 00:10:01,600 Speaker 1: of wheels that spin and apply some torque, so the 189 00:10:01,600 --> 00:10:05,000 Speaker 1: whole thing making the twist a little okay, I think 190 00:10:05,040 --> 00:10:08,040 Speaker 1: I actually remember this one from a previous episode in 191 00:10:08,080 --> 00:10:10,880 Speaker 1: which we said that it was actually very hard to 192 00:10:10,920 --> 00:10:14,320 Speaker 1: orient yourself in space, with the exception of being able 193 00:10:14,360 --> 00:10:18,240 Speaker 1: to use pulsars, which you described as sort of like 194 00:10:18,400 --> 00:10:24,960 Speaker 1: celestial guiding points that flash very consistently and can therefore 195 00:10:25,240 --> 00:10:31,360 Speaker 1: somehow be used to triangulate your location, assuming that you 196 00:10:31,760 --> 00:10:35,760 Speaker 1: already have the known location of two or more pulsars. 197 00:10:36,360 --> 00:10:41,439 Speaker 1: I believe they use gyroscopes in order to orient themselves, 198 00:10:41,559 --> 00:10:45,960 Speaker 1: or perhaps they off gas, you know, shooting little jets 199 00:10:46,040 --> 00:10:48,920 Speaker 1: in particular directions in order to orient themselves in order 200 00:10:48,960 --> 00:10:52,040 Speaker 1: to point themselves in a particular direction, and they use 201 00:10:52,120 --> 00:10:58,080 Speaker 1: the background stars to orient themselves correctly. All right, pretty 202 00:10:59,120 --> 00:11:02,680 Speaker 1: technical answer here, but pretty imaginative. Yeah, our listeners have 203 00:11:02,800 --> 00:11:05,360 Speaker 1: thought about flying through space, how to get around, how 204 00:11:05,400 --> 00:11:08,079 Speaker 1: to turn, how to know where you're pointing. We got 205 00:11:08,120 --> 00:11:11,080 Speaker 1: some pretty smart folks listening to the podcast. Yeah, let's 206 00:11:12,040 --> 00:11:16,800 Speaker 1: flatter our audience. You guys are awesome, beautiful and brilliant. 207 00:11:16,920 --> 00:11:19,079 Speaker 1: But I feel like the answer is here, and we're 208 00:11:19,120 --> 00:11:22,320 Speaker 1: also a little confused about what we're asking in the question, 209 00:11:22,400 --> 00:11:25,600 Speaker 1: like are we asking like how does a space telescope 210 00:11:26,000 --> 00:11:28,280 Speaker 1: orient itself? Like how do we how does it know 211 00:11:28,400 --> 00:11:31,000 Speaker 1: which way it's pointing? And also how does it turn 212 00:11:31,120 --> 00:11:33,720 Speaker 1: to point at something it wants to look at. Yeah, 213 00:11:33,760 --> 00:11:37,119 Speaker 1: I think we're asking both questions and have different answers, 214 00:11:37,120 --> 00:11:39,480 Speaker 1: both of which are really fascinating. So I think all 215 00:11:39,520 --> 00:11:41,640 Speaker 1: of that is involved. I mean, you have your eyeball 216 00:11:41,640 --> 00:11:44,040 Speaker 1: out in space, you wanted to look at something in particular, 217 00:11:44,120 --> 00:11:46,680 Speaker 1: you got to solve both problems. You gotta know where 218 00:11:46,720 --> 00:11:49,199 Speaker 1: it is now and how to change its position. M 219 00:11:50,120 --> 00:11:52,160 Speaker 1: do you think there's a there's like a joystick somewhere 220 00:11:52,160 --> 00:11:55,840 Speaker 1: in NASA or Houston Control Center that points these telescopes? 221 00:11:56,360 --> 00:11:58,880 Speaker 1: Like who gets to move that joysting? And I wonder 222 00:11:59,000 --> 00:12:00,559 Speaker 1: if there's a red button on the top of that 223 00:12:00,640 --> 00:12:03,720 Speaker 1: joystick and if it actually fires something or if it 224 00:12:03,760 --> 00:12:07,840 Speaker 1: just has a little like sound effect peo pew, or 225 00:12:07,840 --> 00:12:09,880 Speaker 1: maybe if you press the button like a flag pops 226 00:12:09,920 --> 00:12:12,880 Speaker 1: out at the end of Hubble boom, or I wonder 227 00:12:12,880 --> 00:12:15,360 Speaker 1: if anyone that NASA has never been tempted to turn 228 00:12:15,440 --> 00:12:18,840 Speaker 1: the telescope around and point it at Earth, like, what 229 00:12:18,920 --> 00:12:21,160 Speaker 1: could it look at? What could it see? You could 230 00:12:21,200 --> 00:12:24,080 Speaker 1: take a selfie with Hubble? Right? Yeah, oh man, do 231 00:12:24,120 --> 00:12:27,520 Speaker 1: you probably find all of NASA selling those selfie opportunities. 232 00:12:28,720 --> 00:12:31,520 Speaker 1: Hubble is quite delicate, and if too much light enters 233 00:12:31,600 --> 00:12:33,800 Speaker 1: its aperture it could damage it. They have to be 234 00:12:33,920 --> 00:12:36,520 Speaker 1: very careful about not pointing it, for example, towards the Sun. 235 00:12:36,840 --> 00:12:39,120 Speaker 1: And I wonder if even the Earth might be too 236 00:12:39,200 --> 00:12:41,880 Speaker 1: bright a source for Hubble. Well, I guess it would 237 00:12:41,880 --> 00:12:44,880 Speaker 1: have to be night selfies. Then all right, well, let's 238 00:12:44,880 --> 00:12:48,160 Speaker 1: dig into this question of how based telescopes orient themselves, 239 00:12:48,200 --> 00:12:50,160 Speaker 1: how they know which way they're pointing at, and then 240 00:12:50,160 --> 00:12:52,240 Speaker 1: if they want to point somewhere in particular, how do 241 00:12:52,320 --> 00:12:55,240 Speaker 1: they move themselves to point in that direction. So, first 242 00:12:55,240 --> 00:12:58,040 Speaker 1: of all, Daniel stepped us through this. Why this is 243 00:12:58,480 --> 00:13:02,040 Speaker 1: important and heart wells important because we want to choose 244 00:13:02,280 --> 00:13:05,400 Speaker 1: what we are seeing. Remember that the telescopes don't see 245 00:13:05,480 --> 00:13:08,199 Speaker 1: all of space, right, It's not like when you look 246 00:13:08,200 --> 00:13:09,680 Speaker 1: out of the night sky and you stare up and 247 00:13:09,720 --> 00:13:11,679 Speaker 1: you basically see the whole sky, or at least the 248 00:13:11,720 --> 00:13:14,559 Speaker 1: part that's not blocked by the earth. A telescope is 249 00:13:14,720 --> 00:13:18,520 Speaker 1: very very narrow aperture in comparison, and so you're only 250 00:13:18,520 --> 00:13:21,679 Speaker 1: really looking at a small portion of the sky, and 251 00:13:21,720 --> 00:13:23,720 Speaker 1: you want to get to pick which portion of the 252 00:13:23,760 --> 00:13:26,199 Speaker 1: sky you are looking at. Are we studying this galaxy, 253 00:13:26,200 --> 00:13:28,760 Speaker 1: are we studying that star over there? Are we tracking 254 00:13:28,840 --> 00:13:32,079 Speaker 1: something that's moving? So you definitely want to have control 255 00:13:32,200 --> 00:13:35,200 Speaker 1: over where your telescope is pointed. Yeah, it's sort of 256 00:13:35,200 --> 00:13:37,160 Speaker 1: like you say, it has a very narrow field of view. 257 00:13:37,200 --> 00:13:40,120 Speaker 1: I imagine it's sort of like walking around your neighborhood 258 00:13:40,200 --> 00:13:43,600 Speaker 1: looking through a straw or something like that. Right, that's 259 00:13:43,640 --> 00:13:45,240 Speaker 1: what it means to have a narrow field of view. 260 00:13:45,320 --> 00:13:47,440 Speaker 1: Like if you close one eye and the other eye 261 00:13:47,600 --> 00:13:51,719 Speaker 1: could only look through a drinking straw, your field of 262 00:13:51,760 --> 00:13:54,160 Speaker 1: view moop be super narrow, and it'd be pretty hard 263 00:13:54,200 --> 00:13:57,520 Speaker 1: to know where you are. And anybody who looked through 264 00:13:57,520 --> 00:14:01,440 Speaker 1: a telescope has that experience. Your telescope sort of towards 265 00:14:01,480 --> 00:14:02,880 Speaker 1: the thing you're looking for, and then you look through 266 00:14:02,880 --> 00:14:05,040 Speaker 1: the telescope and you don't see it and show wiggle 267 00:14:05,080 --> 00:14:07,520 Speaker 1: the telescope around and try to find the object. It's 268 00:14:07,559 --> 00:14:10,120 Speaker 1: not easy when you're looking through a telescope to find 269 00:14:10,160 --> 00:14:12,920 Speaker 1: that particular object has to be pointed very very close 270 00:14:13,200 --> 00:14:15,160 Speaker 1: for you to even see it. And a straw is 271 00:14:15,160 --> 00:14:18,080 Speaker 1: a great example, but it's actually not even dramatic enough. 272 00:14:18,320 --> 00:14:20,720 Speaker 1: Some of these telescopes, their field of view is so small. 273 00:14:20,760 --> 00:14:23,240 Speaker 1: It's more like looking at a grain of saying you 274 00:14:23,320 --> 00:14:26,160 Speaker 1: hold at arm's length, right, that's the fraction of the 275 00:14:26,200 --> 00:14:29,480 Speaker 1: sky these telescopes can look at at one time. It's 276 00:14:29,480 --> 00:14:31,840 Speaker 1: like looking at a straw. That's the width of a 277 00:14:31,880 --> 00:14:34,480 Speaker 1: grain of salt, and a meter lungs what you're saying, Yeah, 278 00:14:34,640 --> 00:14:37,600 Speaker 1: that's exactly right. So some recent images, for example from 279 00:14:37,680 --> 00:14:40,520 Speaker 1: James Webb, where they focus on the deep, deep sky, 280 00:14:40,600 --> 00:14:43,440 Speaker 1: they point at one particular place in the sky and 281 00:14:43,480 --> 00:14:46,400 Speaker 1: they take a bunch of pictures of that one spot. 282 00:14:46,560 --> 00:14:48,280 Speaker 1: And the reason you want to hold it there for 283 00:14:48,320 --> 00:14:50,600 Speaker 1: a long time is that the things that they're looking 284 00:14:50,640 --> 00:14:53,680 Speaker 1: at are quite dim. You know, these distant galaxies don't 285 00:14:53,720 --> 00:14:56,360 Speaker 1: send a whole lot of photons per second, so you 286 00:14:56,400 --> 00:14:58,520 Speaker 1: want to build up a crisp image of them. You've 287 00:14:58,520 --> 00:15:00,960 Speaker 1: got to wait as many seconds as possible to get 288 00:15:01,000 --> 00:15:03,480 Speaker 1: as many photons as possible. So you have to keep 289 00:15:03,480 --> 00:15:07,200 Speaker 1: pointing in the same direction for as long as possible. Yeah, 290 00:15:07,200 --> 00:15:10,000 Speaker 1: and I imagine that's extra hard because first of all, 291 00:15:10,120 --> 00:15:12,320 Speaker 1: like that thing that you're looking at might be moving, 292 00:15:12,960 --> 00:15:15,360 Speaker 1: but also like the space telescope is moving, right, and 293 00:15:15,440 --> 00:15:19,400 Speaker 1: like these space telescopes are usually an orbit around something, 294 00:15:19,480 --> 00:15:21,880 Speaker 1: either the Earth or I guess mostly the Earth, but 295 00:15:22,080 --> 00:15:25,360 Speaker 1: either a near orbit or far orbit. Yeah, we're always 296 00:15:25,400 --> 00:15:27,920 Speaker 1: moving relative to the Sun. And even if these distant 297 00:15:27,920 --> 00:15:31,400 Speaker 1: objects aren't effectively moving relative to our galaxy, You're right, 298 00:15:31,480 --> 00:15:33,360 Speaker 1: our position is moving, and so you have to do 299 00:15:33,440 --> 00:15:36,640 Speaker 1: something to stay on target. You can't just turn it 300 00:15:36,720 --> 00:15:39,440 Speaker 1: and point and take pictures. The things you're looking at 301 00:15:39,480 --> 00:15:42,080 Speaker 1: will change as you orbit the Sun, and so you 302 00:15:42,080 --> 00:15:43,800 Speaker 1: have to do work. I have to do something to 303 00:15:43,960 --> 00:15:47,240 Speaker 1: keep pointing in the same direction. M okay. So then, 304 00:15:47,280 --> 00:15:50,720 Speaker 1: and that's hard to do to move your space telescope 305 00:15:50,760 --> 00:15:54,280 Speaker 1: because basically there's nothing to push against in space. Exactly, 306 00:15:54,360 --> 00:15:56,160 Speaker 1: if you're swimming in a swimming pool and you want 307 00:15:56,160 --> 00:15:57,840 Speaker 1: to turn, what do you do. You hold your arms 308 00:15:57,840 --> 00:16:00,480 Speaker 1: out and you push against the water. Right, You're pushing 309 00:16:00,600 --> 00:16:03,840 Speaker 1: against something, and so you turn. But in space, what 310 00:16:04,080 --> 00:16:06,360 Speaker 1: is there, right, There's no air, there's no water, there's 311 00:16:06,400 --> 00:16:10,000 Speaker 1: nothing to push against, and so turning yourself is much 312 00:16:10,040 --> 00:16:13,880 Speaker 1: harder because there's nothing immediately there for you to push against, 313 00:16:13,880 --> 00:16:16,440 Speaker 1: for you to like boost off of right. And but 314 00:16:16,600 --> 00:16:20,520 Speaker 1: usually satellites and spacecraft the way they navigate and turn 315 00:16:20,600 --> 00:16:24,800 Speaker 1: and move around, they have rockets, right, or at least 316 00:16:24,800 --> 00:16:28,400 Speaker 1: some sort of like a listener suggested, like an ion engine. 317 00:16:28,840 --> 00:16:32,000 Speaker 1: And the crucial thing here is conservation of momentum. If 318 00:16:32,040 --> 00:16:34,800 Speaker 1: you're stationary and you want to get moving, then to 319 00:16:34,880 --> 00:16:37,960 Speaker 1: conserve momentum, you have to throw something going the other direction. 320 00:16:38,080 --> 00:16:40,480 Speaker 1: That requires mass right the same way that like if 321 00:16:40,520 --> 00:16:43,320 Speaker 1: you fire a bullet, you feel a recoil. If you're 322 00:16:43,320 --> 00:16:46,560 Speaker 1: out in space you turn on a rocket, then basically 323 00:16:46,560 --> 00:16:49,800 Speaker 1: the motion of your ship is the recoil from firing 324 00:16:49,840 --> 00:16:52,640 Speaker 1: the rocket, because it's basically shooting a bunch of tiny 325 00:16:52,680 --> 00:16:55,360 Speaker 1: bullets out the back of the rocket. The rocket is 326 00:16:55,360 --> 00:16:58,480 Speaker 1: not just flames, it's throwing mass out the back of it. 327 00:16:58,640 --> 00:17:00,640 Speaker 1: So you don't just need fuel to run the rocket. 328 00:17:00,680 --> 00:17:03,400 Speaker 1: You need some sort of propellant something to throw out 329 00:17:03,480 --> 00:17:06,120 Speaker 1: of the rocket to move your ship. And that's true 330 00:17:06,160 --> 00:17:09,480 Speaker 1: both for motion and for rotation. And so if you 331 00:17:09,560 --> 00:17:11,879 Speaker 1: need a mass to do it, then eventually you're going 332 00:17:11,920 --> 00:17:14,119 Speaker 1: to run out because you can only bring a limited 333 00:17:14,119 --> 00:17:16,640 Speaker 1: amount of mass. So the goal is to figure out 334 00:17:16,640 --> 00:17:20,040 Speaker 1: a way to turn your telescope without using some kind 335 00:17:20,040 --> 00:17:23,080 Speaker 1: of propellant, right, because I guess if you're using a propellant, 336 00:17:23,280 --> 00:17:27,840 Speaker 1: even if there are like ion atoms or molecules, you're 337 00:17:27,880 --> 00:17:30,000 Speaker 1: going to run out eventually, right, You are going to 338 00:17:30,080 --> 00:17:32,680 Speaker 1: run out eventually. And if you spend billions of dollars 339 00:17:32,720 --> 00:17:35,000 Speaker 1: and decades to develop this thing, then you want it 340 00:17:35,040 --> 00:17:37,080 Speaker 1: to last as long as possible. So you're going to 341 00:17:37,119 --> 00:17:39,920 Speaker 1: try to avoid at all costs having things that run out. 342 00:17:40,040 --> 00:17:43,760 Speaker 1: Can you make it electric like an electric car? Yeah, 343 00:17:43,840 --> 00:17:46,280 Speaker 1: you can make it electric, and an ion engine essentially 344 00:17:46,359 --> 00:17:48,840 Speaker 1: is electric, but it still has to throw something out 345 00:17:48,880 --> 00:17:51,600 Speaker 1: of the back, right, it's throwing ions which have been 346 00:17:51,640 --> 00:17:55,040 Speaker 1: accelerated by electric fields. And just bring like a really 347 00:17:55,040 --> 00:17:58,639 Speaker 1: big gas tank, like one that will last one hundred years, right, 348 00:17:58,640 --> 00:18:03,240 Speaker 1: Because these missions usually don't have like an unlimited lifespan, right, 349 00:18:03,240 --> 00:18:05,840 Speaker 1: They usually come with like an expiration date. You can't 350 00:18:05,840 --> 00:18:07,720 Speaker 1: do that. But then the gas tank is big, which 351 00:18:07,760 --> 00:18:09,800 Speaker 1: means it's heavy, which means you need more gas to 352 00:18:09,880 --> 00:18:11,720 Speaker 1: launch it. And usually you want to use all of 353 00:18:11,720 --> 00:18:14,240 Speaker 1: your available space and mass to design it for science 354 00:18:14,359 --> 00:18:16,400 Speaker 1: rather than having a huge fuel tank on the back 355 00:18:16,440 --> 00:18:18,479 Speaker 1: of it. I see. So I guess if you can 356 00:18:18,520 --> 00:18:22,159 Speaker 1: figure out a smarter way to turn out there in space, 357 00:18:22,320 --> 00:18:24,760 Speaker 1: then you could have more science than your rugget bigger 358 00:18:24,800 --> 00:18:28,800 Speaker 1: telescope exactly, more science and more years of science because 359 00:18:28,840 --> 00:18:31,199 Speaker 1: you wouldn't run out of something. Then you need to 360 00:18:31,240 --> 00:18:33,800 Speaker 1: turn the thing also be greener, I imagine, right for 361 00:18:33,960 --> 00:18:39,480 Speaker 1: the space ecosystem, you'd be less pollution. That's true exactly, 362 00:18:39,840 --> 00:18:41,720 Speaker 1: and so for all of our neighbors out there, we 363 00:18:41,720 --> 00:18:44,080 Speaker 1: should be consider it. All right, Well, that's why it's 364 00:18:44,119 --> 00:18:47,560 Speaker 1: important and hard to turn a space telescope and orient 365 00:18:47,640 --> 00:18:49,560 Speaker 1: it out there in space. And so let's get into 366 00:18:49,760 --> 00:18:51,800 Speaker 1: how you would actually do this and how you would 367 00:18:51,800 --> 00:18:55,480 Speaker 1: find yourself if you were lost in space. So let's 368 00:18:55,480 --> 00:18:57,800 Speaker 1: dig into that. But first let's take a quick right, 369 00:19:10,359 --> 00:19:14,000 Speaker 1: all right, we're talking about space telescopes, which are telescopes 370 00:19:14,000 --> 00:19:20,520 Speaker 1: in space basically finally a well named physics object. Well, 371 00:19:20,560 --> 00:19:24,440 Speaker 1: I know, right, and we're talking about how they point 372 00:19:24,480 --> 00:19:26,960 Speaker 1: themselves out there in space. So let's tackle maybe the 373 00:19:27,000 --> 00:19:29,919 Speaker 1: first question is, if you're on telescope out there in space, 374 00:19:30,200 --> 00:19:31,480 Speaker 1: how do you know where you are? And how do 375 00:19:31,480 --> 00:19:33,800 Speaker 1: you know where you're pointing? So these telescopes typically have 376 00:19:34,080 --> 00:19:36,160 Speaker 1: multiple ways to figure out where they are pointing. First 377 00:19:36,160 --> 00:19:38,159 Speaker 1: of all, they just have a bunch of sensors. Like 378 00:19:38,200 --> 00:19:41,280 Speaker 1: the Hubble, for example, has several different kinds of sensors. 379 00:19:41,560 --> 00:19:43,960 Speaker 1: It has a sensor that tells it where the Sun is, 380 00:19:44,359 --> 00:19:47,080 Speaker 1: which helps it know where it's pointing, but also helps 381 00:19:47,080 --> 00:19:50,440 Speaker 1: it avoid pointing into the Sun accidentally. It also has 382 00:19:50,480 --> 00:19:52,919 Speaker 1: sensors for magnetic field, so that you can use the 383 00:19:52,960 --> 00:19:55,720 Speaker 1: Earth's magnetic field to help figure out where it is. 384 00:19:56,040 --> 00:19:58,639 Speaker 1: And then there are sensors that look at stars, and 385 00:19:58,680 --> 00:20:01,320 Speaker 1: there's like a known star map and helps it get 386 00:20:01,320 --> 00:20:04,600 Speaker 1: an orientation roughly for where it is, So to get 387 00:20:04,640 --> 00:20:07,040 Speaker 1: a rough idea for where it is and orient itself, 388 00:20:07,200 --> 00:20:10,560 Speaker 1: it has essentially maps the Sun, the magnetic field, and 389 00:20:10,640 --> 00:20:13,400 Speaker 1: the stars that give it a sense for where it is. Yeah, 390 00:20:13,440 --> 00:20:15,240 Speaker 1: that's usually how they do it in science fiction, Like 391 00:20:15,280 --> 00:20:17,280 Speaker 1: if you're in a spaceship and you land in a 392 00:20:17,359 --> 00:20:19,960 Speaker 1: place you're not quite sure where you are. Usually the 393 00:20:20,000 --> 00:20:22,720 Speaker 1: way you orient yourself is by looking at the stars 394 00:20:22,760 --> 00:20:25,120 Speaker 1: around you, and if you sort of know where they're 395 00:20:25,119 --> 00:20:26,800 Speaker 1: supposed to be, you can figure out where you are 396 00:20:26,840 --> 00:20:29,320 Speaker 1: relative to them. That's the idea, right Basically, they're looking 397 00:20:29,320 --> 00:20:32,399 Speaker 1: at the constellations. They're looking at the constellations, and Hubble 398 00:20:32,680 --> 00:20:35,800 Speaker 1: is not a traveling spacecraft, so it will never appear 399 00:20:35,840 --> 00:20:38,199 Speaker 1: in Andromeda and have to figure out where it is. 400 00:20:38,640 --> 00:20:40,600 Speaker 1: It's always going to be orbiting the Earth, and so 401 00:20:40,760 --> 00:20:43,479 Speaker 1: we know what the stars look like when you're orbiting 402 00:20:43,480 --> 00:20:46,240 Speaker 1: the Earth, and so you just need a few examples 403 00:20:46,320 --> 00:20:49,320 Speaker 1: of particular known stars and you can roughly figure out 404 00:20:49,520 --> 00:20:51,679 Speaker 1: where you are. So those are the sort of lower 405 00:20:51,760 --> 00:20:55,120 Speaker 1: precision instruments, sort of baseline that Hubble uses to figure 406 00:20:55,160 --> 00:20:57,840 Speaker 1: out where it's pointing. But it also has much more 407 00:20:57,920 --> 00:21:01,040 Speaker 1: precise way to measure how it's so not just like 408 00:21:01,240 --> 00:21:02,960 Speaker 1: look at the map and figure out where you are, 409 00:21:03,240 --> 00:21:06,320 Speaker 1: but also understand how far you have turned right. And 410 00:21:06,400 --> 00:21:10,240 Speaker 1: so in internal to Hubble and almost all of these spacecraft, 411 00:21:10,480 --> 00:21:13,760 Speaker 1: they have gyroscopes. Gyroscopes are these balls that's been really 412 00:21:13,760 --> 00:21:16,600 Speaker 1: really fast, and so they're insensitive to the motion of Hubble, 413 00:21:16,880 --> 00:21:19,439 Speaker 1: and they can measure sort of how far it's turned. 414 00:21:19,760 --> 00:21:23,080 Speaker 1: M Yeah, that's pretty cool. We use gyroscopes here on 415 00:21:23,400 --> 00:21:26,400 Speaker 1: Earth all the time also to measure how things turn. 416 00:21:27,000 --> 00:21:29,040 Speaker 1: But I guess you know as an engineer, the trickling 417 00:21:29,119 --> 00:21:31,480 Speaker 1: thing with gyroscopes is that they tell you how much, 418 00:21:31,560 --> 00:21:34,960 Speaker 1: if whether you've turned and how much, But over time 419 00:21:34,960 --> 00:21:37,840 Speaker 1: they're sort of not calibrated to something fixed like the 420 00:21:37,880 --> 00:21:40,800 Speaker 1: sun for example, exactly. And so if you're holding a 421 00:21:40,880 --> 00:21:43,680 Speaker 1: gyroscope and you turn, the gyroscope stays pointing in its 422 00:21:43,680 --> 00:21:46,240 Speaker 1: original direction, and so you can measure I turned thirty 423 00:21:46,240 --> 00:21:49,280 Speaker 1: six point two degrees. So it's a relative measurement, as 424 00:21:49,320 --> 00:21:50,960 Speaker 1: you say, it tells you how far you have turned, 425 00:21:51,000 --> 00:21:54,040 Speaker 1: doesn't tell you where you're actually pointing. That's why Hubble 426 00:21:54,080 --> 00:21:57,560 Speaker 1: has this combination of having the rough sensors to tell 427 00:21:57,600 --> 00:22:00,280 Speaker 1: it the absolute measurements like on pointing and is part 428 00:22:00,320 --> 00:22:01,720 Speaker 1: of the sky or that part of the sky or 429 00:22:01,720 --> 00:22:04,399 Speaker 1: this part relative to the sun, plus these gyroscopes to 430 00:22:04,440 --> 00:22:07,520 Speaker 1: measure very precisely how far it has turned. So it 431 00:22:07,560 --> 00:22:10,520 Speaker 1: needs a combination of these sensors to get an absolute 432 00:22:10,520 --> 00:22:13,560 Speaker 1: sense for where it is pointing in the sky. Because 433 00:22:13,600 --> 00:22:16,680 Speaker 1: I guess if you're using a sensor to track where 434 00:22:16,720 --> 00:22:20,080 Speaker 1: the sun is. You're basically talking about a camera, right, 435 00:22:20,760 --> 00:22:23,600 Speaker 1: and so maybe a camera is not that accurate. Yeah, 436 00:22:23,600 --> 00:22:25,960 Speaker 1: it's basically a low tech camera, and the precision of 437 00:22:25,960 --> 00:22:28,600 Speaker 1: that is limited by like the pixels of the camera 438 00:22:28,920 --> 00:22:31,880 Speaker 1: and also basically the width of the object you're looking at. 439 00:22:32,119 --> 00:22:35,800 Speaker 1: And so the gyroscopes give you the most precise measurement 440 00:22:35,880 --> 00:22:38,400 Speaker 1: of how far you have turned. And these things need 441 00:22:38,440 --> 00:22:41,720 Speaker 1: to be again, super duper precise. Like when Hubble is 442 00:22:41,720 --> 00:22:43,920 Speaker 1: focusing on something and trying to keep it in its 443 00:22:43,960 --> 00:22:47,720 Speaker 1: field of view, it's like holding a laser beam focused 444 00:22:47,760 --> 00:22:51,600 Speaker 1: on a dime two hundred miles away. That's how precise 445 00:22:51,640 --> 00:22:53,399 Speaker 1: we're trying to be. You mean, like how stead of 446 00:22:53,440 --> 00:22:56,479 Speaker 1: your hand needs to be basically right, Yeah, exactly, And 447 00:22:56,520 --> 00:22:59,760 Speaker 1: so you're focusing on a dime that's two hundred miles away, 448 00:23:00,080 --> 00:23:02,640 Speaker 1: plus you're moving relative to that dime, and so it's 449 00:23:02,680 --> 00:23:05,639 Speaker 1: not just about being steady, it's about slowly tracking, it's 450 00:23:05,680 --> 00:23:08,400 Speaker 1: about turning your telescope so you can keep on it. 451 00:23:08,480 --> 00:23:11,400 Speaker 1: So these gyroscopes are super duper important to the operation 452 00:23:11,440 --> 00:23:14,440 Speaker 1: of these based telescopes, and Hubble has been going for decades, 453 00:23:14,640 --> 00:23:16,560 Speaker 1: and because these things are so important, they actually went 454 00:23:16,640 --> 00:23:19,200 Speaker 1: up in two thousand and nine and replaced all six 455 00:23:19,240 --> 00:23:22,119 Speaker 1: of them. Hobble has six of these things, six gyroscopes. 456 00:23:22,119 --> 00:23:24,920 Speaker 1: I met six gyroscopes. Yeah, and each one spins at 457 00:23:24,960 --> 00:23:29,120 Speaker 1: like twenty thousand rpm. Why do they need to be replaced, Well, 458 00:23:29,119 --> 00:23:32,199 Speaker 1: eventually they degrade. You know, there's always some amount of 459 00:23:32,200 --> 00:23:34,800 Speaker 1: friction in those things, so they'll rub against each other, 460 00:23:35,200 --> 00:23:37,919 Speaker 1: they'll slow down, they'll heat up, and nothing is a 461 00:23:37,960 --> 00:23:41,399 Speaker 1: perpetual motion machine, right, and so eventually these things do 462 00:23:41,520 --> 00:23:44,440 Speaker 1: need to be replaced. No, when you say it needs 463 00:23:44,440 --> 00:23:47,159 Speaker 1: to be accurate to the point where you can spot 464 00:23:47,160 --> 00:23:50,280 Speaker 1: a dime two hundred miles away, is that when you're 465 00:23:50,320 --> 00:23:53,479 Speaker 1: tracking something, you know, when you're trying to stay focus 466 00:23:53,560 --> 00:23:57,960 Speaker 1: on a star? Or is that more for finding stars 467 00:23:58,000 --> 00:24:01,120 Speaker 1: and things like that? I imagine in the gyroscopes maybe 468 00:24:01,200 --> 00:24:03,720 Speaker 1: don't really help you to find a star. Yeah, the 469 00:24:03,760 --> 00:24:06,160 Speaker 1: gyroscopes don't tell you what's out there at all. They 470 00:24:06,200 --> 00:24:08,679 Speaker 1: just tell you how far you have turned. And the 471 00:24:08,720 --> 00:24:11,720 Speaker 1: scientists need to decide where they want to look. So 472 00:24:11,760 --> 00:24:15,080 Speaker 1: maybe they've seen something already in the sky near another object, 473 00:24:15,080 --> 00:24:17,640 Speaker 1: then they want to appear more closely, or they've seen 474 00:24:17,680 --> 00:24:20,040 Speaker 1: it maybe in the infrared using Spitzer, and now they 475 00:24:20,080 --> 00:24:22,320 Speaker 1: want to get optical images of it. So they have 476 00:24:22,359 --> 00:24:24,800 Speaker 1: to already know where in the sky to look. So 477 00:24:24,840 --> 00:24:28,119 Speaker 1: they have like galactic coordinate systems they used to orient 478 00:24:28,200 --> 00:24:31,280 Speaker 1: to say where something is in the sky relative to 479 00:24:31,320 --> 00:24:33,639 Speaker 1: the plane of the galaxy, for example, And so you 480 00:24:33,680 --> 00:24:35,639 Speaker 1: have to know basically where something is and then go 481 00:24:35,760 --> 00:24:40,119 Speaker 1: look at it. Is there like a galactic coordinate system. Oh. Absolutely. 482 00:24:40,280 --> 00:24:41,879 Speaker 1: When you look at the maps, for example, of the 483 00:24:41,920 --> 00:24:45,240 Speaker 1: cosmic microwave background, those are relative to the plane of 484 00:24:45,320 --> 00:24:48,000 Speaker 1: the galaxy. So the galaxy runs through the middle of 485 00:24:48,040 --> 00:24:50,520 Speaker 1: those like a line through the middle of that oval. 486 00:24:50,680 --> 00:24:53,359 Speaker 1: And then you go above and below the galactic plane. 487 00:24:53,520 --> 00:24:56,679 Speaker 1: It's arbitrary, right, You could pick an access anywhere in space, 488 00:24:56,840 --> 00:24:59,160 Speaker 1: and so we pick it relative to the Milky Way 489 00:24:59,240 --> 00:25:02,879 Speaker 1: center to the like basically the main axis of the 490 00:25:02,920 --> 00:25:04,840 Speaker 1: Milky Way. Yeah. And if you are out camping and 491 00:25:04,880 --> 00:25:06,440 Speaker 1: lost in the woods and you look at the sky, 492 00:25:06,640 --> 00:25:09,280 Speaker 1: you see the sort of Milky Way of stars across 493 00:25:09,359 --> 00:25:12,720 Speaker 1: the night sky, and that is the plane of the galaxy, right, 494 00:25:12,760 --> 00:25:15,359 Speaker 1: if you're looking above it or below, you're looking out 495 00:25:15,520 --> 00:25:17,560 Speaker 1: from the galaxy, because remember, our galaxy is kind of 496 00:25:17,560 --> 00:25:19,720 Speaker 1: like a disc, and if you're looking at that line 497 00:25:19,760 --> 00:25:22,320 Speaker 1: and you're looking through the galaxy, which is why it 498 00:25:22,320 --> 00:25:24,720 Speaker 1: looks so milky, because there's so many more stars and 499 00:25:24,920 --> 00:25:26,879 Speaker 1: gas and dust and all that kind of stuff. So 500 00:25:27,000 --> 00:25:29,440 Speaker 1: that's the galactic coordinate system. We used to talk about 501 00:25:29,480 --> 00:25:32,600 Speaker 1: where things are in space. Well, that gives you the direction, 502 00:25:32,680 --> 00:25:35,280 Speaker 1: but like, where's the origin of this coordinate system. It's 503 00:25:35,280 --> 00:25:37,240 Speaker 1: at the center of the Milky Way. If you look 504 00:25:37,240 --> 00:25:38,920 Speaker 1: at that oval, for example, and you put a dot 505 00:25:38,920 --> 00:25:41,119 Speaker 1: in the very very center of it, that's where the 506 00:25:41,160 --> 00:25:43,600 Speaker 1: black hole is. But then when we look at our 507 00:25:43,720 --> 00:25:46,119 Speaker 1: night sky, it's going to be a little different than that. Right, 508 00:25:46,160 --> 00:25:48,239 Speaker 1: that's right, we don't see that entire thing. But you 509 00:25:48,280 --> 00:25:50,800 Speaker 1: can map the sphere of things that we can see 510 00:25:50,880 --> 00:25:53,399 Speaker 1: onto that coordinate system. But you have to like a 511 00:25:53,400 --> 00:25:55,080 Speaker 1: little bit of an angle change because we're not at 512 00:25:55,119 --> 00:25:57,159 Speaker 1: the center of the galaxy, right exactly, we're not at 513 00:25:57,200 --> 00:25:59,760 Speaker 1: the center of the galaxy. And also our solar system 514 00:25:59,840 --> 00:26:01,840 Speaker 1: is filted a little bit, so you have to know 515 00:26:01,920 --> 00:26:04,119 Speaker 1: where the Sun is relative to the center of the 516 00:26:04,160 --> 00:26:07,199 Speaker 1: galaxy in order to map that on cool But then 517 00:26:07,520 --> 00:26:09,919 Speaker 1: you said it uses sort of a cameras to see 518 00:26:09,960 --> 00:26:13,080 Speaker 1: the constellations in a way or a map of the stars. 519 00:26:13,680 --> 00:26:15,600 Speaker 1: Does it actually do that, like does it actually like 520 00:26:15,680 --> 00:26:18,520 Speaker 1: track certain stars or constellations? And is that one of 521 00:26:18,560 --> 00:26:23,920 Speaker 1: those maps you can buy in Hollywood Boulevard to the Stars. Yeah. 522 00:26:23,960 --> 00:26:26,199 Speaker 1: So Hubble has a bunch of these different systems, right, 523 00:26:26,280 --> 00:26:29,560 Speaker 1: has the course sun sensors, has a magnetic sensing system. 524 00:26:29,840 --> 00:26:33,720 Speaker 1: Then it has star trackers, right, and the star trackers 525 00:26:33,760 --> 00:26:37,120 Speaker 1: determines Hubble's altitude by looking at the location and brightness 526 00:26:37,160 --> 00:26:39,040 Speaker 1: of stars that it sees, So it has a broader 527 00:26:39,040 --> 00:26:41,440 Speaker 1: field of view than Hubble sort of main camera. And 528 00:26:41,600 --> 00:26:45,360 Speaker 1: this lets it like identify unique patterns throughout the sky, 529 00:26:45,520 --> 00:26:48,680 Speaker 1: which a computer then maps to star maps internal to 530 00:26:48,800 --> 00:26:50,679 Speaker 1: Hubble and lets it figure out like if there's a 531 00:26:50,680 --> 00:26:53,360 Speaker 1: correction or if it's slightly pointed in the wrong direction. 532 00:26:53,560 --> 00:26:57,199 Speaker 1: And then the fine guidance system uses the gyroscopes and 533 00:26:57,240 --> 00:27:02,200 Speaker 1: everything else to sort of fine tune everything. Now that's interesting. 534 00:27:02,240 --> 00:27:04,879 Speaker 1: They had to go and replace those gyroscopes. Is that 535 00:27:04,960 --> 00:27:08,040 Speaker 1: something we can do pretty easily? Like how do we 536 00:27:08,080 --> 00:27:09,960 Speaker 1: do that? We need to send a rocket with people 537 00:27:10,040 --> 00:27:12,119 Speaker 1: or do we send robots it's not something we can 538 00:27:12,160 --> 00:27:14,800 Speaker 1: do very easily. We have to send astronauts up there 539 00:27:14,880 --> 00:27:17,800 Speaker 1: because it's a complicated job, and so it was done 540 00:27:17,840 --> 00:27:19,640 Speaker 1: in two thousand and nine, but that was the last time, 541 00:27:19,880 --> 00:27:21,920 Speaker 1: and it's not something that we can do for James 542 00:27:22,000 --> 00:27:25,240 Speaker 1: Webb for example. James Webb. Remember it's not in Earth orbit, 543 00:27:25,280 --> 00:27:28,359 Speaker 1: it's out at a Lagarrange point. It's much much further away, 544 00:27:28,480 --> 00:27:30,640 Speaker 1: and it's not a place where we can send humans. 545 00:27:31,040 --> 00:27:34,480 Speaker 1: So either we have to develop robotic repair people or 546 00:27:34,640 --> 00:27:36,879 Speaker 1: we just can't replace it. So James Webb actually has 547 00:27:36,880 --> 00:27:41,000 Speaker 1: a slightly different technology than Hubble does. M what does 548 00:27:41,000 --> 00:27:44,240 Speaker 1: the James Webb telescope do? So Hubble has these spinning balls. 549 00:27:44,240 --> 00:27:47,320 Speaker 1: They're like mechanical, right, But James Webb tried to look 550 00:27:47,320 --> 00:27:50,240 Speaker 1: for something that was less mechanical, that didn't require something 551 00:27:50,320 --> 00:27:53,120 Speaker 1: spinning a really high speed, because that seems like sort 552 00:27:53,160 --> 00:27:55,159 Speaker 1: of easy to mess up, like a little grain in 553 00:27:55,240 --> 00:27:57,440 Speaker 1: there can really mess it up. So James Webb actually 554 00:27:57,560 --> 00:28:00,960 Speaker 1: uses this weird technology. It's a quartzemisp fear that resonates 555 00:28:00,960 --> 00:28:03,000 Speaker 1: in a particular way, sort of like if you have 556 00:28:03,040 --> 00:28:05,520 Speaker 1: a wine glass and you rub your finger around it. 557 00:28:05,520 --> 00:28:08,439 Speaker 1: It resonates and it makes like a ringing sound. That's 558 00:28:08,480 --> 00:28:11,240 Speaker 1: that wine glass like flexing a little bit. You can't 559 00:28:11,280 --> 00:28:14,679 Speaker 1: see flexing, but it's actually shaking a little bit. And 560 00:28:14,800 --> 00:28:17,959 Speaker 1: if you like rotated the wine glass, then the sound 561 00:28:18,000 --> 00:28:20,760 Speaker 1: would rotate with it. So what happens in the gyroscope 562 00:28:20,800 --> 00:28:24,040 Speaker 1: inside James Webb is that the quartz hemisphere resonates in 563 00:28:24,040 --> 00:28:26,920 Speaker 1: this very particular way. It's surrounded by electrodes that are 564 00:28:26,960 --> 00:28:30,160 Speaker 1: like driving the resonance. They can also detect any slight 565 00:28:30,240 --> 00:28:34,000 Speaker 1: change in its orientation, Like if James Webb rotates around 566 00:28:34,160 --> 00:28:37,879 Speaker 1: this quartz hemisphere, they will hear the resonance impacting the 567 00:28:37,880 --> 00:28:41,360 Speaker 1: telescope at a different location. Well, it's pretty fascinating and 568 00:28:41,360 --> 00:28:43,880 Speaker 1: so I guess those don't wear out. The hope is 569 00:28:43,880 --> 00:28:46,360 Speaker 1: that they don't wear out as fast. Right, everything will 570 00:28:46,400 --> 00:28:49,360 Speaker 1: wear out eventually. This is still moving. Every time James 571 00:28:49,440 --> 00:28:53,080 Speaker 1: Webb moves, it moves relative to these gyroscopes, and so 572 00:28:53,120 --> 00:28:55,680 Speaker 1: there's a potential for friction there. But you don't have 573 00:28:55,760 --> 00:28:58,920 Speaker 1: a spinning mass, right, and so it's less kinetic energy, 574 00:28:58,960 --> 00:29:01,040 Speaker 1: it's less mechanical, and so the hope is that it 575 00:29:01,080 --> 00:29:05,120 Speaker 1: will last longer. And so that's how it orients itself. 576 00:29:05,160 --> 00:29:06,800 Speaker 1: And so if you wanted to point to like a 577 00:29:06,840 --> 00:29:10,200 Speaker 1: particular galaxy out there that you know about, um, do 578 00:29:10,240 --> 00:29:12,560 Speaker 1: you still have to kind of like tan around you think, like, 579 00:29:12,600 --> 00:29:14,600 Speaker 1: do you think there's someone and NASA with the joystick 580 00:29:14,640 --> 00:29:17,480 Speaker 1: going back and forth, back and forth, opened out, Oh 581 00:29:17,520 --> 00:29:19,520 Speaker 1: there it is. Or do you think they can just 582 00:29:19,560 --> 00:29:23,920 Speaker 1: go like point to here, boom, it's pointing there. I 583 00:29:23,960 --> 00:29:26,280 Speaker 1: don't know the details, but I'm pretty sure it's not 584 00:29:26,360 --> 00:29:29,200 Speaker 1: a joystick. I think they type in the coordinates and 585 00:29:29,320 --> 00:29:32,959 Speaker 1: Hubble like pans over. This thing happens very slowly, like 586 00:29:33,000 --> 00:29:35,640 Speaker 1: when Hubble turns, it turns about as fast as a 587 00:29:35,720 --> 00:29:39,120 Speaker 1: clock does. It's a hubble, for example, can turn ninety 588 00:29:39,160 --> 00:29:42,960 Speaker 1: degrees and about fifteen minutes. This is not something you 589 00:29:43,000 --> 00:29:45,760 Speaker 1: want to spin around very quickly. I see, So it 590 00:29:45,800 --> 00:29:48,840 Speaker 1: just takes a while with the joystick. I hold the 591 00:29:48,920 --> 00:29:54,120 Speaker 1: joystick for a while. Yes, it takes patience with a joystick. 592 00:29:54,680 --> 00:29:57,280 Speaker 1: Probably they do have a joystick that's not actually doing anything. 593 00:29:57,280 --> 00:29:59,640 Speaker 1: It's just connected like the large change on collider and 594 00:29:59,680 --> 00:30:01,600 Speaker 1: the the center. They have a big red button you 595 00:30:01,600 --> 00:30:04,040 Speaker 1: can press that sets off lots of alarm bells and 596 00:30:04,120 --> 00:30:07,640 Speaker 1: flashing lights, but doesn't actually shut anything down. Wow, that 597 00:30:07,800 --> 00:30:12,120 Speaker 1: sounds like something the fire department did not approve. All right, well, 598 00:30:12,120 --> 00:30:15,080 Speaker 1: that's how space telescopes orient themselves. How they know where 599 00:30:15,080 --> 00:30:17,200 Speaker 1: they're looking at in the night sky or I guess. 600 00:30:17,240 --> 00:30:19,160 Speaker 1: And if you're if you're in space, every every night 601 00:30:19,240 --> 00:30:21,280 Speaker 1: is the night sky. It's always night in space. Yeah, 602 00:30:21,360 --> 00:30:23,360 Speaker 1: unless you're looking at the Sun, I guess. But now 603 00:30:23,440 --> 00:30:26,600 Speaker 1: let's talk about how space telescopes move, how they actually 604 00:30:26,600 --> 00:30:30,520 Speaker 1: turn to look at a particular star or galaxy or nebula. 605 00:30:30,720 --> 00:30:32,880 Speaker 1: So let's get into that, but first let's take another 606 00:30:33,000 --> 00:30:50,320 Speaker 1: quick break. Or we're talking about how space telescopes point themselves. 607 00:30:50,840 --> 00:30:53,400 Speaker 1: That's that seems very like self accusatory. I mean, like, 608 00:30:53,520 --> 00:30:56,400 Speaker 1: what's the point of space telescopes? No, like they have 609 00:30:56,440 --> 00:30:59,680 Speaker 1: to point at them they're pointing themselves at themselves. I mean, 610 00:30:59,760 --> 00:31:02,120 Speaker 1: some you've got to do it, right. How introspective are 611 00:31:02,160 --> 00:31:05,360 Speaker 1: space telescopes? I guess they're not really pointing themselves. We 612 00:31:05,440 --> 00:31:09,880 Speaker 1: are pointing them, right, somebody is doing it. Yeah yeah, right, 613 00:31:10,000 --> 00:31:12,160 Speaker 1: the joystick. It's not like they're up there just deciding 614 00:31:12,160 --> 00:31:14,800 Speaker 1: on their own. Hey I'm going to look at Andromeda today. 615 00:31:15,280 --> 00:31:19,920 Speaker 1: Yeah yeah, I'm sure there's the NASA joystick person listening 616 00:31:19,920 --> 00:31:22,840 Speaker 1: to this brain now going, hey, I point the space 617 00:31:22,920 --> 00:31:28,719 Speaker 1: tells cooes. Do you think space telescodes point themselves? That's right? 618 00:31:28,720 --> 00:31:30,680 Speaker 1: What do you think the garbage takes itself out just 619 00:31:30,720 --> 00:31:33,160 Speaker 1: because you're not doing that well? We talked about how 620 00:31:33,320 --> 00:31:36,680 Speaker 1: space telescopes can know which way they're pointing out out 621 00:31:36,680 --> 00:31:40,040 Speaker 1: there in space, because I guess it's pretty disorient can 622 00:31:40,080 --> 00:31:42,080 Speaker 1: be disorient thing. If you're out there in space, you're 623 00:31:42,120 --> 00:31:43,640 Speaker 1: sort of it's hard to know which way is up 624 00:31:43,640 --> 00:31:47,080 Speaker 1: and down exactly. And so the second question now is 625 00:31:47,120 --> 00:31:49,760 Speaker 1: how do they actually turn? How do they like if 626 00:31:49,760 --> 00:31:52,000 Speaker 1: you're looking in one way looking at a star and 627 00:31:52,040 --> 00:31:53,880 Speaker 1: you want to look at the star over there, how 628 00:31:53,880 --> 00:31:55,840 Speaker 1: do you make that term? Because, as we talked about, 629 00:31:55,960 --> 00:31:59,080 Speaker 1: you don't want to rely on propellants or rockets or 630 00:31:59,120 --> 00:32:03,920 Speaker 1: ion engines because those are kind of costly. They maybe 631 00:32:04,160 --> 00:32:06,320 Speaker 1: you might run out at some point in the future. Yeah, 632 00:32:06,360 --> 00:32:08,400 Speaker 1: and those would be nice, right, you'd like to do that. 633 00:32:08,440 --> 00:32:10,920 Speaker 1: It's sort of an easy solution because it lets you 634 00:32:10,960 --> 00:32:13,320 Speaker 1: have a net force. Right, you have your space telescope, 635 00:32:13,360 --> 00:32:15,880 Speaker 1: you throw something off the side, you're applying a force 636 00:32:15,920 --> 00:32:18,680 Speaker 1: to that object. That object applies to force back to you. 637 00:32:18,680 --> 00:32:21,440 Speaker 1: You turn or you move and make some sort of sense. 638 00:32:21,680 --> 00:32:24,160 Speaker 1: But as we said, that requires some mass, and so 639 00:32:24,240 --> 00:32:26,840 Speaker 1: now we need a solution that doesn't have any net 640 00:32:26,880 --> 00:32:30,000 Speaker 1: force or no net torque on the object. Right, you 641 00:32:30,000 --> 00:32:32,640 Speaker 1: have to figure out how to turn the telescope without 642 00:32:32,680 --> 00:32:35,560 Speaker 1: applying an overall force to it. Oh, I see what 643 00:32:35,560 --> 00:32:38,720 Speaker 1: you're saying. Because if you are applying an overall net 644 00:32:38,880 --> 00:32:42,760 Speaker 1: force or torque, that means you're expending energy in the universe, right, yeah, 645 00:32:42,760 --> 00:32:45,680 Speaker 1: and not just energy momentum. Right. So if you're going 646 00:32:45,720 --> 00:32:48,800 Speaker 1: to turn this thing from the outside, you're like, put 647 00:32:48,800 --> 00:32:51,360 Speaker 1: your hand on it and turn it, then you're applying 648 00:32:51,360 --> 00:32:54,080 Speaker 1: a force to it, right, Or if you're on the 649 00:32:54,080 --> 00:32:56,520 Speaker 1: telescope and you're throwing a rock off the side of it, 650 00:32:56,680 --> 00:32:59,920 Speaker 1: you're using some mass. You're expending momentum. So what we 651 00:33:00,080 --> 00:33:02,720 Speaker 1: want is a way to turn the telescope without changing 652 00:33:02,760 --> 00:33:07,080 Speaker 1: its total momentum, because changing its total momentum, by Newton's laws, 653 00:33:07,400 --> 00:33:10,240 Speaker 1: requires something else to balance that momentum, which means something 654 00:33:10,280 --> 00:33:12,520 Speaker 1: else with mass, and there's nothing else out there. It's 655 00:33:12,520 --> 00:33:14,800 Speaker 1: just floating out in space. How do you turn the 656 00:33:14,880 --> 00:33:18,200 Speaker 1: telescope without applying some overall force to it. That's the 657 00:33:18,240 --> 00:33:22,160 Speaker 1: physics puzzle, Like how do you change your absolute orientation 658 00:33:22,480 --> 00:33:27,280 Speaker 1: without changing your overall angular momentum? Kind of Yeah, imagine, 659 00:33:27,320 --> 00:33:29,520 Speaker 1: for example, you're on ice skates and you're on a 660 00:33:29,520 --> 00:33:32,680 Speaker 1: super duper slippery surface. How do you turn? Or you 661 00:33:32,680 --> 00:33:35,080 Speaker 1: can't push against the ice because you're on ice skates 662 00:33:35,080 --> 00:33:37,760 Speaker 1: in a super slippery So how do you turn your direction? 663 00:33:37,760 --> 00:33:40,680 Speaker 1: How do you change which way you are pointing? That's 664 00:33:40,720 --> 00:33:43,440 Speaker 1: basically the puzzle, right, So if you could push against 665 00:33:43,480 --> 00:33:45,840 Speaker 1: the side, that'd be great, but there is no side. 666 00:33:45,960 --> 00:33:48,360 Speaker 1: If you could like throw a rock, then that'd be great, 667 00:33:48,360 --> 00:33:50,440 Speaker 1: but you can't do that. So the question is how 668 00:33:50,480 --> 00:33:52,960 Speaker 1: do you turn on this slippery surface? Right? Or I 669 00:33:53,000 --> 00:33:54,720 Speaker 1: was thinking it's more like, you know, if you were 670 00:33:54,760 --> 00:33:57,000 Speaker 1: stuck out there in space, like if you're an astronaut. 671 00:33:57,200 --> 00:33:59,360 Speaker 1: So imagine you're an astronaut and your space suit and 672 00:33:59,360 --> 00:34:02,080 Speaker 1: you're out there and base whether you're looking away from 673 00:34:02,120 --> 00:34:03,960 Speaker 1: your spaceshipe or away from the Earth, and you want 674 00:34:03,960 --> 00:34:06,480 Speaker 1: to turn around to look at your spaceship or Earth, 675 00:34:06,520 --> 00:34:09,280 Speaker 1: but you've run out of fuel and maybe in your jetpack, 676 00:34:09,640 --> 00:34:11,680 Speaker 1: how do you turn yourself around, Like, you can't just 677 00:34:11,760 --> 00:34:14,479 Speaker 1: like grab something and pull yourself to look the other way. 678 00:34:14,520 --> 00:34:17,400 Speaker 1: And you can't just like flail your arms because it 679 00:34:17,400 --> 00:34:19,799 Speaker 1: would be hard to sort of change your orientation. Yeah, 680 00:34:19,840 --> 00:34:22,279 Speaker 1: even just flailing your arms won't do it, right. You 681 00:34:22,320 --> 00:34:26,080 Speaker 1: can't by flailing your arms apply any overall force to yourself. 682 00:34:26,360 --> 00:34:28,640 Speaker 1: So this seems like an unsolvable problem, and the way 683 00:34:28,640 --> 00:34:31,839 Speaker 1: to solve it is to find a loophole is to say, well, 684 00:34:31,840 --> 00:34:34,799 Speaker 1: what if I don't want to turn the whole telescope. 685 00:34:34,960 --> 00:34:37,440 Speaker 1: What if I only want to turn part of the telescope. 686 00:34:37,480 --> 00:34:40,120 Speaker 1: So imagine like an invisible dividing line. You say, this 687 00:34:40,200 --> 00:34:42,080 Speaker 1: part of the telescope I want to turn because it's 688 00:34:42,080 --> 00:34:43,960 Speaker 1: got the cameras on it, and this other part of 689 00:34:43,960 --> 00:34:46,720 Speaker 1: the telescope has the electronics and all the other stuff. 690 00:34:46,719 --> 00:34:48,920 Speaker 1: They can't see anything, so I don't really care about 691 00:34:48,960 --> 00:34:51,400 Speaker 1: that one. So instead of turning the whole telescope, what 692 00:34:51,480 --> 00:34:53,239 Speaker 1: if you just want to turn part of the telescope 693 00:34:53,280 --> 00:34:55,520 Speaker 1: one way? You can do that by turning the other 694 00:34:55,560 --> 00:34:58,440 Speaker 1: part the other way. I imagine, for example, having two 695 00:34:58,520 --> 00:35:01,440 Speaker 1: ice skaters that are ski getting together. One of them 696 00:35:01,480 --> 00:35:04,439 Speaker 1: can start spinning if they push against the other one. Right, 697 00:35:04,560 --> 00:35:06,840 Speaker 1: So instead of turning the whole telescope, just turn the 698 00:35:06,880 --> 00:35:09,319 Speaker 1: part of the telescope you want to actually use to 699 00:35:09,360 --> 00:35:12,239 Speaker 1: look at the universe by pushing it against another part 700 00:35:12,320 --> 00:35:15,440 Speaker 1: of the telescope, or maybe instead of iceicators. You can 701 00:35:15,480 --> 00:35:19,200 Speaker 1: imagine our stranded astronaut out there in space. You know, 702 00:35:19,239 --> 00:35:21,239 Speaker 1: they can't look in a particular way by themselves, but 703 00:35:21,280 --> 00:35:23,880 Speaker 1: if they had a buddy or a friend, like, one 704 00:35:23,960 --> 00:35:26,920 Speaker 1: of them could push against the other one and at 705 00:35:27,000 --> 00:35:28,799 Speaker 1: least one of them can look back at Earth or 706 00:35:28,800 --> 00:35:30,879 Speaker 1: at their spaceship. Exactly. If you don't care what your 707 00:35:30,920 --> 00:35:33,279 Speaker 1: buddy gets to see, then you can turn in one 708 00:35:33,280 --> 00:35:37,120 Speaker 1: direction by pushing against him or her. And that's exactly 709 00:35:37,120 --> 00:35:39,359 Speaker 1: what they do. On the space telescopes. They have a 710 00:35:39,360 --> 00:35:42,960 Speaker 1: little part of it called at a buddy. It's got 711 00:35:42,960 --> 00:35:46,600 Speaker 1: a little space telescope. Buddy, it's got the important part 712 00:35:46,640 --> 00:35:48,919 Speaker 1: and the not important part, and the non important part 713 00:35:49,040 --> 00:35:51,600 Speaker 1: is just there to help the other part turn. It's 714 00:35:51,600 --> 00:35:55,840 Speaker 1: at the buddy, the sidekick, right, and so on a 715 00:35:55,880 --> 00:35:59,600 Speaker 1: space telescope, this is called a reaction wheel. Essentially, it's 716 00:35:59,600 --> 00:36:02,719 Speaker 1: a little piece which turns the opposite direction that the 717 00:36:02,760 --> 00:36:05,680 Speaker 1: spacecraft does, so spacecraft says, I want to go that way. 718 00:36:06,040 --> 00:36:08,839 Speaker 1: Then the reaction wheel turns the other way in order 719 00:36:08,840 --> 00:36:12,160 Speaker 1: to balance it. So you're not changing the overall angular 720 00:36:12,200 --> 00:36:14,920 Speaker 1: momentum of this thing at all. You're only changing the 721 00:36:14,920 --> 00:36:17,279 Speaker 1: angle momentum of the part that you care about and 722 00:36:17,280 --> 00:36:19,400 Speaker 1: the part you don't care about. The sidekick gets the 723 00:36:19,440 --> 00:36:23,120 Speaker 1: opposite angular momentum, so physics is happy and you get 724 00:36:23,120 --> 00:36:25,280 Speaker 1: to point the part that you want in the right direction. 725 00:36:25,480 --> 00:36:29,200 Speaker 1: M So I'm imagining like inside of the space telescope, 726 00:36:29,239 --> 00:36:33,000 Speaker 1: there's basically like a just a big disc maybe right, 727 00:36:33,400 --> 00:36:35,840 Speaker 1: or like a big donut or cylinder that's that you 728 00:36:35,840 --> 00:36:38,920 Speaker 1: can spin. Is that the idea? That's exactly the idea. 729 00:36:39,040 --> 00:36:41,120 Speaker 1: So if you want to turn like clockwise, you would 730 00:36:41,120 --> 00:36:45,360 Speaker 1: turn the donut or the disc counterclockwise. M Imagine you 731 00:36:45,480 --> 00:36:47,880 Speaker 1: two astronauts. One of them ones to turn clockwise, so 732 00:36:47,920 --> 00:36:50,239 Speaker 1: he pushes against the other one and one of them 733 00:36:50,239 --> 00:36:52,080 Speaker 1: turns one way, the other one turns the other way. 734 00:36:52,239 --> 00:36:54,400 Speaker 1: Now on the space telescope, you don't want like a 735 00:36:54,480 --> 00:36:57,719 Speaker 1: second telescope to push against, so you shrink the other 736 00:36:57,760 --> 00:37:00,760 Speaker 1: part down as much as you can make it massive 737 00:37:00,800 --> 00:37:03,359 Speaker 1: and make it spin really, really fast, so it can 738 00:37:03,360 --> 00:37:05,880 Speaker 1: store a lot of angular momentum. And so the space 739 00:37:05,880 --> 00:37:08,719 Speaker 1: telescope has one of these for each direction it might 740 00:37:08,880 --> 00:37:13,000 Speaker 1: need to turn interesting like up and down, the side 741 00:37:13,040 --> 00:37:14,920 Speaker 1: to side, in front, the back exactly. So you need 742 00:37:15,040 --> 00:37:18,320 Speaker 1: three of these to control your direction complete the in space. 743 00:37:18,560 --> 00:37:21,240 Speaker 1: Usually they have extras just in case one of them breaks. 744 00:37:21,440 --> 00:37:24,040 Speaker 1: But they're called reaction wheels or momentum wheels, and they 745 00:37:24,080 --> 00:37:25,719 Speaker 1: are fixed in place on the sort of on the 746 00:37:25,760 --> 00:37:29,160 Speaker 1: side of the telescope. They spin many many times, like 747 00:37:29,200 --> 00:37:32,439 Speaker 1: a thousand or four thousand times a minute. M Now, 748 00:37:32,640 --> 00:37:36,120 Speaker 1: I guess maybe I have two questions. One is okay, 749 00:37:36,120 --> 00:37:37,920 Speaker 1: so I'm out there and floating a space, and I 750 00:37:37,960 --> 00:37:41,360 Speaker 1: want to turn clockwise, So I spin my little wheel counterclockwise, 751 00:37:42,080 --> 00:37:46,480 Speaker 1: and that gets me to turn clockwise while the spinning 752 00:37:46,480 --> 00:37:49,360 Speaker 1: wheel is spinning inside of me. Now, let's say I 753 00:37:49,360 --> 00:37:51,760 Speaker 1: want to stop because I certainly I got some angular 754 00:37:51,840 --> 00:37:55,279 Speaker 1: momentum turning. How do I stop turning? Do I just 755 00:37:55,320 --> 00:37:57,520 Speaker 1: spin the wheel the other way? Just spin the wheel 756 00:37:57,560 --> 00:38:00,360 Speaker 1: the other way exactly, And so you can apply whatever 757 00:38:00,440 --> 00:38:02,560 Speaker 1: torque you want to yourself as long as you're applying 758 00:38:02,560 --> 00:38:05,279 Speaker 1: the opposite torque to the wheel and that works in 759 00:38:05,320 --> 00:38:08,279 Speaker 1: both directions, and so the wheel isn't like ever stationary. 760 00:38:08,320 --> 00:38:10,319 Speaker 1: What you're doing is you're speeding the wheel up or 761 00:38:10,400 --> 00:38:12,840 Speaker 1: slowing the wheel down, and I do that with a 762 00:38:12,840 --> 00:38:16,200 Speaker 1: little electric motor which is solar powered. So it is 763 00:38:16,320 --> 00:38:18,359 Speaker 1: sort of like your Tesla as you said earlier, yeah, 764 00:38:18,440 --> 00:38:21,160 Speaker 1: or like the Prios, right, or any any car with battery. 765 00:38:21,200 --> 00:38:23,960 Speaker 1: Like when you break, you're putting energy into the battery, 766 00:38:24,440 --> 00:38:26,240 Speaker 1: and then when you need to accelerate, you take energy 767 00:38:26,280 --> 00:38:29,560 Speaker 1: from the battery. So basically the same concept, right, Basically 768 00:38:29,560 --> 00:38:32,800 Speaker 1: the same concept exactly. So you want to change your orientation, 769 00:38:32,880 --> 00:38:34,759 Speaker 1: you have to change the speed of the wheel to 770 00:38:34,800 --> 00:38:37,040 Speaker 1: create a torque on the rest of the object. And 771 00:38:37,080 --> 00:38:39,160 Speaker 1: so this thing spins really really fast, so it can 772 00:38:39,200 --> 00:38:41,040 Speaker 1: store a lot of ing the momentum, but it's still 773 00:38:41,120 --> 00:38:44,759 Speaker 1: really small and low mass compared to the actual telescope, 774 00:38:45,040 --> 00:38:47,799 Speaker 1: which means you can't turn the telescope very quickly. But 775 00:38:47,840 --> 00:38:50,840 Speaker 1: that's good, right, you don't want this thing jerking around. 776 00:38:51,239 --> 00:38:53,560 Speaker 1: They're not super dupe or powerful, but you don't ever 777 00:38:53,600 --> 00:38:57,080 Speaker 1: need to ever change the telescope's direction really really quickly. 778 00:38:57,680 --> 00:38:59,760 Speaker 1: It sort of feels like you got something for free 779 00:38:59,840 --> 00:39:01,719 Speaker 1: or something for nothing, you know, do you know what 780 00:39:01,719 --> 00:39:03,640 Speaker 1: I mean? Like that was pointing one way and then 781 00:39:03,680 --> 00:39:05,719 Speaker 1: I did something, and now I'm pointing it another way. 782 00:39:05,760 --> 00:39:08,479 Speaker 1: But I didn't lose really any energy. Yeah, there's two 783 00:39:08,520 --> 00:39:12,719 Speaker 1: different aspects of this, energy and momentum. So momentum conservation 784 00:39:12,840 --> 00:39:15,560 Speaker 1: is satisfied. Because part of U spunum one way, the 785 00:39:15,640 --> 00:39:17,640 Speaker 1: other part supund the other way, so it adds up 786 00:39:17,640 --> 00:39:20,319 Speaker 1: to zero. Just like your two astronauts, they could also 787 00:39:20,360 --> 00:39:22,640 Speaker 1: split apart if they push against each other, right, they 788 00:39:22,640 --> 00:39:25,040 Speaker 1: could float away in space when you could get back 789 00:39:25,080 --> 00:39:26,960 Speaker 1: to the spaceship, and the other one could be lost 790 00:39:27,040 --> 00:39:30,080 Speaker 1: to infinity, and that would satisfy conservation momentum. There'd be 791 00:39:30,120 --> 00:39:32,080 Speaker 1: no net force on the pair of them, even though 792 00:39:32,160 --> 00:39:35,360 Speaker 1: there is a force relative between them, So momentum is satisfied. 793 00:39:35,400 --> 00:39:37,920 Speaker 1: But you're right, we are using energy, so this is 794 00:39:37,960 --> 00:39:40,840 Speaker 1: not for free. You need to speed up that reaction 795 00:39:40,880 --> 00:39:45,040 Speaker 1: wheel or slow down that reaction wheel. That requires some energy, 796 00:39:45,080 --> 00:39:46,920 Speaker 1: and so this thing is not for free. It does 797 00:39:47,000 --> 00:39:50,279 Speaker 1: use some energy, but it doesn't need any propellant. Right. 798 00:39:50,520 --> 00:39:53,880 Speaker 1: A rocket uses both energy and propellant, has to have 799 00:39:53,920 --> 00:39:56,800 Speaker 1: some math to throw at the side. This doesn't require 800 00:39:56,800 --> 00:39:59,360 Speaker 1: any propellant, though it does use some energy. Yeah, I 801 00:39:59,360 --> 00:40:02,200 Speaker 1: guess what I mean. Like in the two astronaut example, 802 00:40:02,520 --> 00:40:06,000 Speaker 1: if you and I are in space and I'm like, Daniel, 803 00:40:06,040 --> 00:40:08,400 Speaker 1: save yourself. I'm going to push you towards the spaceship 804 00:40:09,360 --> 00:40:11,719 Speaker 1: to save yourself, and I push you. You're moving towards 805 00:40:11,760 --> 00:40:14,920 Speaker 1: the spaceship, but I'm not. I'm moving away from the spaceship. 806 00:40:14,920 --> 00:40:17,080 Speaker 1: But then I'm what if? And then but then suddenly 807 00:40:17,200 --> 00:40:19,040 Speaker 1: it's like I changed my mind. I'm like, wait, wait, wait, no, 808 00:40:19,120 --> 00:40:21,759 Speaker 1: that was a terrible idea, and I pull on the 809 00:40:21,840 --> 00:40:26,400 Speaker 1: rope that was attached between us to bring us back together. Technically, 810 00:40:26,400 --> 00:40:28,640 Speaker 1: we would not, like, our center of mask would not 811 00:40:28,680 --> 00:40:31,440 Speaker 1: have moved. That's right, right. Our center of masks cannot 812 00:40:31,440 --> 00:40:34,480 Speaker 1: move without some external force. Right. So even if you 813 00:40:34,480 --> 00:40:36,960 Speaker 1: don't change your mind and I drift back to the spaceship, 814 00:40:37,239 --> 00:40:40,200 Speaker 1: you're drifting away from the spaceships. Our center of mass 815 00:40:40,280 --> 00:40:43,440 Speaker 1: is not changing, right, right. But on the spinning example 816 00:40:43,480 --> 00:40:45,640 Speaker 1: with the space telescope, I kind of it sort of 817 00:40:45,680 --> 00:40:48,160 Speaker 1: feels like you did get away with something, right. It's 818 00:40:48,160 --> 00:40:50,799 Speaker 1: like you spun the mass one way and then you 819 00:40:50,800 --> 00:40:52,640 Speaker 1: spun it the other way and now you're you're in 820 00:40:52,640 --> 00:40:56,479 Speaker 1: a different spot. Your total orientation change direction. Well, part 821 00:40:56,480 --> 00:40:59,680 Speaker 1: of the spaceship changes direction and another part changes direction 822 00:40:59,719 --> 00:41:03,440 Speaker 1: in the opposite way. So the total angle momentum hasn't changed. Right. 823 00:41:03,480 --> 00:41:05,640 Speaker 1: But then when you slow down to stop, you spin 824 00:41:05,719 --> 00:41:07,960 Speaker 1: it the other way, and presumably it's the same amount 825 00:41:07,960 --> 00:41:10,160 Speaker 1: of momentum that you need to take out or put 826 00:41:10,239 --> 00:41:12,239 Speaker 1: back in. And so you and the wheel are in 827 00:41:12,280 --> 00:41:14,719 Speaker 1: the same spot you started with, but both of you 828 00:41:14,719 --> 00:41:16,960 Speaker 1: are pointing in a different direction. Though you're both pointing 829 00:41:17,000 --> 00:41:20,080 Speaker 1: in a different direction, but the angular momentum hasn't changed. 830 00:41:20,120 --> 00:41:23,799 Speaker 1: You've expended some energy, but the angular momentum isn't different. Yeah, right, 831 00:41:23,840 --> 00:41:26,200 Speaker 1: it sort of feels like you're getting something for free. Well, 832 00:41:26,239 --> 00:41:28,239 Speaker 1: it's sort of like if the astronauts push against each 833 00:41:28,280 --> 00:41:30,680 Speaker 1: other and they're further away, it costs some energy to 834 00:41:30,800 --> 00:41:34,080 Speaker 1: change that configuration, but it didn't change the overall momentum. Yeah, 835 00:41:34,160 --> 00:41:36,960 Speaker 1: but in the astronaut example, they didn't move if they 836 00:41:37,040 --> 00:41:40,080 Speaker 1: come back together. But in the wheel case, do you 837 00:41:40,120 --> 00:41:41,920 Speaker 1: do sort of like move, You're not pointing in a 838 00:41:41,920 --> 00:41:44,200 Speaker 1: different direction, right, Well, in the astronaut a case, imagine 839 00:41:44,200 --> 00:41:46,799 Speaker 1: we're connected by ropes and you push against me, so 840 00:41:46,800 --> 00:41:48,839 Speaker 1: that I drifted back towards the ship, and you drift 841 00:41:48,840 --> 00:41:50,520 Speaker 1: away from the ship. And then you change your mind, 842 00:41:50,560 --> 00:41:53,040 Speaker 1: and so you tug on the rope to stop my motion, 843 00:41:53,080 --> 00:41:56,600 Speaker 1: which also stops you. Now we're further apart than where 844 00:41:56,640 --> 00:41:58,960 Speaker 1: we were, but we have no change in our center 845 00:41:58,960 --> 00:42:01,799 Speaker 1: of mass, no change in our overall momentum. We've lost 846 00:42:01,920 --> 00:42:04,359 Speaker 1: is you spend some energy pushing me away and then 847 00:42:04,360 --> 00:42:06,640 Speaker 1: pulling me back, So in the same way, when you're 848 00:42:06,640 --> 00:42:11,160 Speaker 1: orienting the telescope, you've changed its overall configuration, but there's 849 00:42:11,160 --> 00:42:13,480 Speaker 1: no change in its overall angle momentum. That you have 850 00:42:13,640 --> 00:42:16,880 Speaker 1: spent some energy to change the directions of both parts, 851 00:42:16,920 --> 00:42:20,640 Speaker 1: the telescope and the reaction wheel. Interesting, so well, well, 852 00:42:20,680 --> 00:42:22,759 Speaker 1: I feel also that the other part question I had 853 00:42:22,840 --> 00:42:25,759 Speaker 1: is it isn't spinning a little wheel basically the same 854 00:42:25,800 --> 00:42:28,000 Speaker 1: as flailing your arms, Like if I was stuck out 855 00:42:28,040 --> 00:42:30,600 Speaker 1: there in space, could I also just like gonna spin 856 00:42:30,680 --> 00:42:33,520 Speaker 1: my arm and that would reorient myself? If you could 857 00:42:33,560 --> 00:42:36,839 Speaker 1: turn your arm effectively into a reaction wheel, then yes, 858 00:42:37,520 --> 00:42:39,200 Speaker 1: I don't know if you really could get your arm 859 00:42:39,239 --> 00:42:42,640 Speaker 1: to spin independently along the same access though I had 860 00:42:42,680 --> 00:42:44,920 Speaker 1: to think about the biomechanics of it. Actually, you're an 861 00:42:44,920 --> 00:42:47,360 Speaker 1: expert in that, aren't you. I'm not sure if you 862 00:42:47,480 --> 00:42:50,080 Speaker 1: really can have it spinned independently, or if when you're 863 00:42:50,120 --> 00:42:52,480 Speaker 1: moving in or way, if you're moving in a circle, 864 00:42:52,680 --> 00:42:55,520 Speaker 1: if you're effectively pushing back on your body. But yes, 865 00:42:55,520 --> 00:42:58,200 Speaker 1: if you, for example, ripped your arm off and attached 866 00:42:58,239 --> 00:43:01,520 Speaker 1: it via mechanical axle to your body, then by spinning 867 00:43:01,520 --> 00:43:06,560 Speaker 1: it you could change your direction. That seems a little dramatic, 868 00:43:06,600 --> 00:43:09,080 Speaker 1: but I think the answer, since you say that I'm 869 00:43:09,120 --> 00:43:11,239 Speaker 1: the expert, I think the answer is yes, I think 870 00:43:11,280 --> 00:43:13,239 Speaker 1: you could do that. It's kind of the reason why 871 00:43:13,320 --> 00:43:15,880 Speaker 1: when you jump off a cliff into the water, for example, 872 00:43:16,040 --> 00:43:19,640 Speaker 1: or of a diving board, people flail their arms. They 873 00:43:19,719 --> 00:43:22,640 Speaker 1: sort of like moving like a windmill, and that because 874 00:43:22,640 --> 00:43:25,319 Speaker 1: they're trying not to fall on their face in the water. Yeah. Well, 875 00:43:25,320 --> 00:43:28,440 Speaker 1: I'll trust you whether that's possible. I prefer the cleaner 876 00:43:28,560 --> 00:43:31,200 Speaker 1: physics but more gory example where you actually pull the 877 00:43:31,320 --> 00:43:33,640 Speaker 1: arm off, but I trust you that it's possible even 878 00:43:33,680 --> 00:43:36,840 Speaker 1: without filling your arms. All right, we're in space. You 879 00:43:36,840 --> 00:43:40,200 Speaker 1: can rip your arm out, but they don't have to 880 00:43:40,239 --> 00:43:43,080 Speaker 1: look back at the spaceship, although I'm not sure what 881 00:43:43,080 --> 00:43:44,880 Speaker 1: you're going to do once you get the spaceship. Are 882 00:43:44,920 --> 00:43:48,239 Speaker 1: you going to open the door? And I'll do my 883 00:43:48,360 --> 00:43:50,120 Speaker 1: way and we'll see how that goes? All right, Well, 884 00:43:50,160 --> 00:43:51,919 Speaker 1: we'll see if the door was designed to be opened 885 00:43:51,960 --> 00:43:57,600 Speaker 1: one handed, just space was designed for arm removal. I'm 886 00:43:57,600 --> 00:43:59,960 Speaker 1: not saying it's more practical. I'm just saying the physics 887 00:44:00,080 --> 00:44:02,279 Speaker 1: of it is clearer. I see, I see, And that's 888 00:44:02,320 --> 00:44:05,920 Speaker 1: more important than your arm. I guess in this scenario, 889 00:44:05,960 --> 00:44:07,560 Speaker 1: if it's just hypothetical and I want to give the 890 00:44:07,600 --> 00:44:11,160 Speaker 1: accurate physics answer, then yes, I prefer the more gruesome 891 00:44:11,200 --> 00:44:14,320 Speaker 1: but clear physics scenario, right right. I think as an engineer, 892 00:44:14,320 --> 00:44:18,319 Speaker 1: I would try my way first if it works, rather 893 00:44:18,400 --> 00:44:23,239 Speaker 1: than getting to the physics dogma here. All right, but 894 00:44:23,280 --> 00:44:26,040 Speaker 1: you can be expending valuable oxygen as you do your experiment. 895 00:44:26,040 --> 00:44:28,279 Speaker 1: All right? So then is this how the James Webb 896 00:44:28,320 --> 00:44:30,719 Speaker 1: space does coupe orient itself? Do they have? Does it 897 00:44:30,840 --> 00:44:33,919 Speaker 1: have these spinning wheels? Do the Hubble also do this? Yeah? 898 00:44:33,920 --> 00:44:37,640 Speaker 1: So basically every spacecraft does this. James Webb has six 899 00:44:37,719 --> 00:44:40,160 Speaker 1: of these reaction wheels that are spinning that help it 900 00:44:40,280 --> 00:44:43,520 Speaker 1: turn Hubble has these things. Kepler has these things, and 901 00:44:43,640 --> 00:44:47,520 Speaker 1: Kepler is a fascinating story because these things failed on Kepler, 902 00:44:47,680 --> 00:44:49,960 Speaker 1: which made it very, very difficult for Kepler to do 903 00:44:50,040 --> 00:44:54,439 Speaker 1: its mission. What happened? So Kepler launched two thousand and nine, 904 00:44:54,520 --> 00:44:57,360 Speaker 1: had four of these reaction wheels you only nearly need three, 905 00:44:57,400 --> 00:45:00,239 Speaker 1: but it had a spare just for good measure. And remember, 906 00:45:00,320 --> 00:45:03,880 Speaker 1: Kepler is a telescope that's looking for planets to eclipse 907 00:45:03,920 --> 00:45:05,840 Speaker 1: their stars. So you got to watch a star for 908 00:45:05,880 --> 00:45:08,759 Speaker 1: a while, for a long time to see it's one 909 00:45:08,880 --> 00:45:12,360 Speaker 1: ten thousands drop in brightness as a planet goes across 910 00:45:12,400 --> 00:45:14,839 Speaker 1: the star, so you really got to be focused on it. 911 00:45:15,000 --> 00:45:17,360 Speaker 1: A few years into itsmission, in two thousand and twelve, 912 00:45:17,600 --> 00:45:20,240 Speaker 1: one of these things failed and they didn't understand why. 913 00:45:20,280 --> 00:45:22,480 Speaker 1: But that's okay. They were had four, so they had 914 00:45:22,480 --> 00:45:24,719 Speaker 1: one spare. They're okay with three, and then the next 915 00:45:24,800 --> 00:45:27,080 Speaker 1: year they lost weight. I have a question, like, you 916 00:45:27,120 --> 00:45:29,600 Speaker 1: need one for every direction, right up, down, left, and 917 00:45:29,680 --> 00:45:32,920 Speaker 1: right from the back. Which one is your spare? Like? 918 00:45:33,239 --> 00:45:36,040 Speaker 1: Can you spur point in all three directions? Yeah? Good question. 919 00:45:36,080 --> 00:45:38,080 Speaker 1: I don't know the answer. I guess the engineers have 920 00:45:38,160 --> 00:45:41,279 Speaker 1: probably figured that out. Okay, So then Kepler lost one 921 00:45:41,320 --> 00:45:43,560 Speaker 1: and they activated to spare and then what happened, And 922 00:45:43,600 --> 00:45:46,480 Speaker 1: then they lost another one in twenty thirteen, so now 923 00:45:46,480 --> 00:45:50,040 Speaker 1: they only had two, which limits how the spacecraft can 924 00:45:50,080 --> 00:45:52,600 Speaker 1: turn right. And this thing has to be able to 925 00:45:52,640 --> 00:45:55,799 Speaker 1: turn in three D to track an arbitrary star. So 926 00:45:55,920 --> 00:45:57,919 Speaker 1: people were pretty bummed. They spent a lot of time 927 00:45:57,960 --> 00:46:00,760 Speaker 1: and money on this spacecraft, and it also cost money 928 00:46:00,800 --> 00:46:02,880 Speaker 1: to operate. It's not like once you have it up 929 00:46:02,880 --> 00:46:05,560 Speaker 1: there in space it's free, it's saying, costs millions of 930 00:46:05,600 --> 00:46:08,360 Speaker 1: dollars to operate the deep space network and the people 931 00:46:08,440 --> 00:46:11,400 Speaker 1: and all electronics and everything. So it's a real question 932 00:46:11,440 --> 00:46:13,680 Speaker 1: of like you just shut the thing down or do 933 00:46:13,680 --> 00:46:17,120 Speaker 1: you try to figure out another way to operate this telescope. 934 00:46:17,800 --> 00:46:21,040 Speaker 1: I wonder I'm guessing the answers no, because otherwise it 935 00:46:21,080 --> 00:46:22,440 Speaker 1: would have figured that out. But I wonder if you 936 00:46:22,480 --> 00:46:25,400 Speaker 1: can just use two to orient yourself in any direction 937 00:46:25,400 --> 00:46:28,560 Speaker 1: in space? You know what I mean, because orientations in 938 00:46:28,560 --> 00:46:31,920 Speaker 1: space are these kinds of weird transformations where you can, like, 939 00:46:31,960 --> 00:46:34,600 Speaker 1: if you wanted to point to the right, you could, 940 00:46:35,400 --> 00:46:37,040 Speaker 1: but you don't have something that turns you to the right. 941 00:46:37,120 --> 00:46:40,920 Speaker 1: You could maybe point down, turn left, or you know, 942 00:46:40,960 --> 00:46:43,319 Speaker 1: turn the other way and then switch back and do 943 00:46:43,480 --> 00:46:46,200 Speaker 1: some weird complicated maneuver to get you to point right. Well, 944 00:46:46,200 --> 00:46:49,320 Speaker 1: these things are orthogonal from each other, and so having 945 00:46:49,360 --> 00:46:53,000 Speaker 1: only two basically only lets you map out a plane 946 00:46:53,560 --> 00:46:56,120 Speaker 1: in a three D space. But like it, used one 947 00:46:56,160 --> 00:46:59,520 Speaker 1: to turn one way, then that reorients the other one, 948 00:46:59,560 --> 00:47:01,759 Speaker 1: doesn't it, So you essentially kind of can point in 949 00:47:01,800 --> 00:47:04,080 Speaker 1: any direction. No, yeah, that's a really good point, and 950 00:47:04,120 --> 00:47:06,080 Speaker 1: I think that that's essentially what they tried to do. 951 00:47:06,120 --> 00:47:08,640 Speaker 1: But you still need help in that third direction because 952 00:47:08,680 --> 00:47:10,480 Speaker 1: you don't want to drift right. You don't want to 953 00:47:10,560 --> 00:47:13,160 Speaker 1: drift in that third direction. And once you've turned and 954 00:47:13,200 --> 00:47:16,040 Speaker 1: pointed at the star, now you've used your two reaction 955 00:47:16,040 --> 00:47:19,359 Speaker 1: wheels along those two planes, which means you're susceptible. You're 956 00:47:19,360 --> 00:47:22,359 Speaker 1: always susceptible to moving in that third dimension. And so 957 00:47:22,400 --> 00:47:24,280 Speaker 1: in order to correct, you would then need to turn 958 00:47:24,760 --> 00:47:27,680 Speaker 1: twice basically in order to correct, which you'd bring you 959 00:47:27,760 --> 00:47:29,880 Speaker 1: off of the star. So they actually came up with 960 00:47:29,880 --> 00:47:33,160 Speaker 1: an ingenious way to try to prevent that from happening. Oh, 961 00:47:33,200 --> 00:47:35,160 Speaker 1: I see what you're saying is that if you could 962 00:47:35,880 --> 00:47:39,880 Speaker 1: point anywhere you want with maybe two reaction wheels active, 963 00:47:40,000 --> 00:47:44,200 Speaker 1: but you wouldn't be able to maybe track a star smoothly. Yeah, 964 00:47:44,239 --> 00:47:46,239 Speaker 1: you might have to take like zig zags, right, and 965 00:47:46,280 --> 00:47:48,439 Speaker 1: which means you couldn't keep it in your field of view. 966 00:47:49,200 --> 00:47:50,880 Speaker 1: So then what did they do? So they came up 967 00:47:50,880 --> 00:47:54,000 Speaker 1: with this really cool scheme to use the sun. Right, 968 00:47:54,000 --> 00:47:56,680 Speaker 1: the Sun is actually pushing on these things. Remember our 969 00:47:56,680 --> 00:47:59,880 Speaker 1: conversation earlier about like zapping a solar sail attached to 970 00:48:00,080 --> 00:48:02,799 Speaker 1: telescope with lasers from Earth. They basically are doing that, 971 00:48:02,840 --> 00:48:05,920 Speaker 1: except they're using sunlight instead of lasers from Earth. So 972 00:48:05,960 --> 00:48:08,360 Speaker 1: as it moves around the Sun, the solar wind and 973 00:48:08,400 --> 00:48:12,080 Speaker 1: the photons push against the solar panels on Kepler, and 974 00:48:12,120 --> 00:48:15,759 Speaker 1: so now instead of compensating for that, they're using that 975 00:48:15,840 --> 00:48:19,919 Speaker 1: to help keep it stable. Interest in using the solar wind, Yeah, 976 00:48:19,920 --> 00:48:23,200 Speaker 1: they're actually using the photon pressure, right, not just the 977 00:48:23,280 --> 00:48:25,400 Speaker 1: solar wind, but the actual photon pressure. It's like a 978 00:48:25,440 --> 00:48:27,880 Speaker 1: solar sale. So the solar panels are in sort of 979 00:48:27,880 --> 00:48:31,600 Speaker 1: like a hexagon around Kepler. And if the pointy part 980 00:48:31,640 --> 00:48:34,080 Speaker 1: where the solar panels meet, if that thing is oriented 981 00:48:34,160 --> 00:48:36,719 Speaker 1: right along the direction of the photons, then it sort 982 00:48:36,719 --> 00:48:39,640 Speaker 1: of stays stable and it's turned a little bit, then 983 00:48:39,680 --> 00:48:42,640 Speaker 1: it's unstable. So they can use that orientation to help 984 00:48:42,680 --> 00:48:45,720 Speaker 1: either push on the spacecraft or to keep it stable, 985 00:48:46,600 --> 00:48:49,160 Speaker 1: but would that help it track a start? It really 986 00:48:49,200 --> 00:48:51,080 Speaker 1: limits what they can do. They can only look at 987 00:48:51,120 --> 00:48:53,319 Speaker 1: sort of a couple different places in the sky, but 988 00:48:53,400 --> 00:48:56,400 Speaker 1: for a couple of spots and its orbit around the Sun, 989 00:48:56,719 --> 00:48:59,479 Speaker 1: they can use the Sun to compensate for the lack 990 00:48:59,560 --> 00:49:02,319 Speaker 1: of the third reaction wheel and keep it stable and 991 00:49:02,440 --> 00:49:04,359 Speaker 1: keep a tract on a planet for a little while. 992 00:49:04,600 --> 00:49:07,080 Speaker 1: So it's not a complete recovery of its abilities by 993 00:49:07,080 --> 00:49:09,960 Speaker 1: any means, but it's a partial recovery of the science 994 00:49:10,000 --> 00:49:14,560 Speaker 1: mission cool. Well, that's a pretty clever technology, I guess, 995 00:49:14,920 --> 00:49:16,640 Speaker 1: although I feel like they should change the name from 996 00:49:16,680 --> 00:49:21,240 Speaker 1: reaction wheels to flailing arms. It's a really big bummer 997 00:49:21,280 --> 00:49:23,920 Speaker 1: that these things went bad. They've been trying to understand 998 00:49:23,960 --> 00:49:27,400 Speaker 1: what happened, and in twenty seventeen there's a paper that 999 00:49:27,520 --> 00:49:31,280 Speaker 1: came out that suggests that it's due to geomagnetic storms 1000 00:49:31,360 --> 00:49:34,080 Speaker 1: from the Sun. Basically, the Sun has like some big 1001 00:49:34,200 --> 00:49:37,080 Speaker 1: energetic event, it dumps out a bunch of plasma and 1002 00:49:37,120 --> 00:49:40,719 Speaker 1: a coronal mass ejection and as this passes through the spacecraft, 1003 00:49:40,800 --> 00:49:45,080 Speaker 1: it interferes with the operation of the reaction wheel. Wow. Yeah, 1004 00:49:45,120 --> 00:49:49,960 Speaker 1: that's pretty cool and also a pretty convenient story to 1005 00:49:51,040 --> 00:49:53,640 Speaker 1: make up for the fact that era the thing you 1006 00:49:53,760 --> 00:49:57,080 Speaker 1: design did not last as much as you thought it would. Yeah, 1007 00:49:57,120 --> 00:50:00,640 Speaker 1: and these reaction wheels are very specialized technology. This one 1008 00:50:00,680 --> 00:50:03,919 Speaker 1: manufacturer that has been putting these things out it's called Ithaco, 1009 00:50:03,960 --> 00:50:06,400 Speaker 1: and their reaction wheels have failed not just on Kepler 1010 00:50:06,480 --> 00:50:10,279 Speaker 1: but also on other spacecraft. So James Webb actually went 1011 00:50:10,320 --> 00:50:13,680 Speaker 1: to a different manufacturer to produce these things. So we're 1012 00:50:13,680 --> 00:50:16,520 Speaker 1: hoping that James Webb's reaction wheels lasts a lot longer. 1013 00:50:17,680 --> 00:50:19,919 Speaker 1: And so that is a pretty clever way to turn 1014 00:50:19,960 --> 00:50:23,160 Speaker 1: yourself in space to have these reaction wheels. And so 1015 00:50:23,239 --> 00:50:26,920 Speaker 1: basically the space teal skills use them. Do other spacecraft 1016 00:50:27,000 --> 00:50:29,440 Speaker 1: use them like the voyage you're used at, or do 1017 00:50:29,520 --> 00:50:32,120 Speaker 1: some of these like the Parker Solar Probe does it 1018 00:50:32,200 --> 00:50:34,920 Speaker 1: use that too? Some other spacecraft do use these kind 1019 00:50:34,960 --> 00:50:37,520 Speaker 1: of things, But remember they're very slow, so they're not 1020 00:50:37,600 --> 00:50:40,479 Speaker 1: great for navigation. They're really just great for like very 1021 00:50:40,640 --> 00:50:44,680 Speaker 1: gentle orientation. Another example is light Sale Light Sale is 1022 00:50:44,719 --> 00:50:46,680 Speaker 1: one of these things that's testing out the ability to 1023 00:50:46,840 --> 00:50:49,799 Speaker 1: sail on sunlight. There's a huge solar sale that it's 1024 00:50:49,880 --> 00:50:53,000 Speaker 1: using to gather momentum and navigate around the solar system. 1025 00:50:53,320 --> 00:50:55,439 Speaker 1: But they also want to be able to steer this thing, 1026 00:50:55,840 --> 00:50:57,960 Speaker 1: and so they have a reaction wheel on it to 1027 00:50:58,040 --> 00:51:00,440 Speaker 1: try to turn it sort of towards an away from 1028 00:51:00,480 --> 00:51:03,160 Speaker 1: the sun to change how it's sailing. So then it 1029 00:51:03,160 --> 00:51:05,759 Speaker 1: only needs one wheel. It only needs one wheel. Yeah, 1030 00:51:05,760 --> 00:51:07,840 Speaker 1: though it's also sort of experimental craft, and so I 1031 00:51:07,840 --> 00:51:10,919 Speaker 1: think they're trying to be simpler and cheaper. Everybody would 1032 00:51:10,920 --> 00:51:12,880 Speaker 1: love to have more of these wheels, and a lot 1033 00:51:12,920 --> 00:51:15,919 Speaker 1: of the spacecraft have a combination of reaction wheels and 1034 00:51:16,120 --> 00:51:19,640 Speaker 1: chemical thrusters. Chemical thrusters are for when you've like saturated 1035 00:51:19,640 --> 00:51:22,320 Speaker 1: your reaction wheel you can't turn anymore because it's already 1036 00:51:22,320 --> 00:51:24,759 Speaker 1: spinning in it's max rpm, or when you need to 1037 00:51:24,760 --> 00:51:27,719 Speaker 1: turn faster than you can with your reaction wheels, that 1038 00:51:27,840 --> 00:51:30,200 Speaker 1: you want to use your chemical thrusters very sparingly because 1039 00:51:30,360 --> 00:51:33,040 Speaker 1: you just use up the mass and then eventually you're 1040 00:51:33,080 --> 00:51:37,560 Speaker 1: run out cool Well overall, a pretty clever solution to 1041 00:51:37,640 --> 00:51:40,879 Speaker 1: move yourself, at least in orientation in space. Yeah, it's 1042 00:51:40,880 --> 00:51:43,120 Speaker 1: a very clever idea. And when I think we'll be 1043 00:51:43,200 --> 00:51:44,840 Speaker 1: using for a long time in the future, if we 1044 00:51:44,880 --> 00:51:47,520 Speaker 1: can make these things more reliable and if they don't 1045 00:51:47,560 --> 00:51:51,680 Speaker 1: require tearing your arm off, yes, let's try that solution. Second, 1046 00:51:54,239 --> 00:51:57,719 Speaker 1: So first zapping with lasers, second tearing your arm off. 1047 00:51:57,840 --> 00:52:03,080 Speaker 1: Kind that's right, I'm gonna be up up there is 1048 00:52:03,080 --> 00:52:05,920 Speaker 1: space going yes, season, go ahead and shoot the lasers 1049 00:52:06,040 --> 00:52:09,320 Speaker 1: at Daniel and let me know if that works. And 1050 00:52:09,480 --> 00:52:11,480 Speaker 1: if it does, then you can shoot them in me. 1051 00:52:11,800 --> 00:52:13,799 Speaker 1: But I'm going to be flailing my arms out here 1052 00:52:14,280 --> 00:52:15,759 Speaker 1: and I'll see you back at the space ship. I 1053 00:52:15,760 --> 00:52:18,640 Speaker 1: wonder if that big earth laser for zapping astronauts also 1054 00:52:18,680 --> 00:52:20,839 Speaker 1: has a joystick? And who gets to run that one? 1055 00:52:21,160 --> 00:52:24,200 Speaker 1: Oh man? Yeah? Yeah, And what kind of training the 1056 00:52:24,360 --> 00:52:26,880 Speaker 1: prison needs to do? You know, play a lot of 1057 00:52:26,880 --> 00:52:31,000 Speaker 1: asteroids maybe, or a lot of Halo. Perhaps you want 1058 00:52:31,040 --> 00:52:33,439 Speaker 1: someone who can get a good head shot the first 1059 00:52:33,480 --> 00:52:36,279 Speaker 1: try Fortnite experts. All right, Well, hopefully you did not 1060 00:52:36,400 --> 00:52:39,960 Speaker 1: get lost in this discussion, and we navigated your brain 1061 00:52:40,040 --> 00:52:43,600 Speaker 1: to understanding how space tells coopes move and orient themselves 1062 00:52:43,680 --> 00:52:45,880 Speaker 1: to look at the universe out there and This is 1063 00:52:45,880 --> 00:52:48,480 Speaker 1: crucial to our ability to understand what is out there 1064 00:52:48,520 --> 00:52:51,600 Speaker 1: in the universe and to continue to build that physical 1065 00:52:51,719 --> 00:52:55,320 Speaker 1: and conceptual map of how the universe works. Thanks for 1066 00:52:55,480 --> 00:53:05,960 Speaker 1: joining us, See you next time. Thanks for listening, and 1067 00:53:06,000 --> 00:53:08,759 Speaker 1: remember that Daniel and Jorge Explain the Universe is a 1068 00:53:08,760 --> 00:53:12,839 Speaker 1: production of iHeartRadio. Or more podcast from my heart Radio 1069 00:53:13,000 --> 00:53:17,160 Speaker 1: visit the iHeartRadio app, Apple Podcasts, or wherever you listen 1070 00:53:17,239 --> 00:53:18,360 Speaker 1: to your favorite shows.