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Speaker 3: Terms apply. Hey, Jorge, are you good at navigating? Depends

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Speaker 3: on what you mean by navigating. Do you mean navigating

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Speaker 3: the complex issues of how to lead a good life?

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Speaker 3: Then no, I haven't figured that one out. But if

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Speaker 3: you mean like getting somewhere, I have a phone with GPS,

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Speaker 3: so I guess I'm pretty good.

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Speaker 1: Well, what have you lost your phone?

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Speaker 5: Like?

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Speaker 1: Or civilization crumbled? Do you know how to oriente yourself

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Speaker 1: in the woods?

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Speaker 3: Well, I imagine I could use a map and a compass, right.

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Speaker 1: You mean like a basic old school compass or the

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Speaker 1: compass app on your phone.

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Speaker 3: Okay, yeah, that's a good point. I only have the

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Speaker 3: compass on my phone. But I guess you could probably

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Speaker 3: find our low tech original you know, og compass.

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Speaker 1: Yeah, that would let you get low tech original lost.

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Speaker 3: I guess there's civilization crumbles were all lost. I am

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Speaker 3: or Hammer, cartoonist and the creator of PhD comics.

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Speaker 1: Hi, I'm Daniel. I'm a particle physicist and a professor

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Speaker 1: at UC Irvine, and I've never honestly been lost in

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Speaker 1: the woods.

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Speaker 3: Well, yeah, I think that's self evident because you're talking

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Speaker 3: to us right now. If you were lost in the woods,

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Speaker 3: I'm not sure we would have heard from you.

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Speaker 1: Again, maybe I'm calling you from my secret woods hideout

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Speaker 1: or even I don't know where it.

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Speaker 3: Is, although if you have Wi Fi there and are

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Speaker 3: able to record, I'm not sure you're that lost.

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Speaker 1: Yeah, that's true. But I've often gone on long backpacking

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Speaker 1: trips and wondered if I really could get myself out

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Speaker 1: of the woods if I had to.

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Speaker 3: Yeah, it's pretty tricky because I guess it's hard to

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Speaker 3: see above the trees and know where you are right,

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Speaker 3: can't see the forest for the tree.

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Speaker 1: It's definitely a particular skill of figuring out how the

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Speaker 1: map represents the world you're seeing around you, and now

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Speaker 1: to figure out where on the map you are.

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Speaker 3: Well, I'm glad you're not lost in the woods, Daniel.

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Speaker 1: It's one of my recurring nightmares.

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Speaker 3: Welcome to our podcast, Daniel and Jorge Explain the Universe,

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Speaker 3: a production of iHeartRadio.

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Speaker 1: In which we try to avoid being lost in the woods.

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Speaker 1: Of physics, we try to navigate our way through all

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Speaker 1: of the confusing issues about this incredible universe, figure out

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Speaker 1: how we can actually understand it, what we can make

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Speaker 1: sense of, how big our map of the intellectual cosmos

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Speaker 1: we really can illuminate.

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Speaker 3: So I think of this podcast as your GPS for

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Speaker 3: the entire universe, helping you know where things are and

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Speaker 3: how to get there.

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Speaker 1: Because slowly, over hundreds or thousands of years, we have

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Speaker 1: started to build a map of how the universe works.

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Speaker 1: We have a literal map of like what's physically out

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Speaker 1: there in the universe, but we also have a conceptual

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Speaker 1: map one that tells us how things work, how they

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Speaker 1: explain the experiments we see, and what they predict about

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Speaker 1: what is to come.

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Speaker 3: Yeah, because it is a pretty big universe and there's

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Speaker 3: a lot out there for us to explore and to

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Speaker 3: check out, and so having a map is a really

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Speaker 3: good thing to you know, where we sit in the universe.

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Speaker 3: And it turns out that we sit in a very

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Speaker 3: small corner of one tiny galaxy that's part of a

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Speaker 3: giant supercluster. And it's amazing we've been able to figure

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Speaker 3: that out just looking at the night sky from this

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Speaker 3: little piece of rock.

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Speaker 1: Why do you call our galaxy tiny. I think it's

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Speaker 1: pretty impressive.

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Speaker 3: Well, you know, it could be bigger. You know's use

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Speaker 3: a bigger house.

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Speaker 1: Right, I don't know. I had friends that moved into

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Speaker 1: a bigger house and they found themselves just screaming at

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Speaker 1: each other from opposite ends of the house all the time.

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Speaker 1: I think they were happier in their tiny, little cramp department.

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Speaker 3: M sounds like they needed an intercom, which is like

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Speaker 3: technology from the eighties seventies.

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Speaker 1: Yeah, exactly. And so if we lived in Andromeda, we'd

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Speaker 1: have an even bigger galaxy to explore to find those

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Speaker 1: unless we had some sort of like alien galactic intercom

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Speaker 1: where we could just talk to everybody.

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Speaker 3: Yeah, you could have like a quantum warp tunnel intercom.

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Speaker 1: But the universe is quite vast, even beyond our tiny

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Speaker 1: or large galaxy, depending on how you see it. And

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Speaker 1: it's incredible that we have been able to figure out

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Speaker 1: what's out there. Remember when you look at a map

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Speaker 1: of the superclusters or our galaxy, that those are constructed

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Speaker 1: from painstaking work to figure out where everything is. We

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Speaker 1: don't have cameras above the Milky Way or outside of

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Speaker 1: the galaxy. We basically only ever observed things from Earth

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Speaker 1: or from very very close to Earth, and those technological

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Speaker 1: eyeballs we have built have allowed us to piece together

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Speaker 1: this concept of where we are in the cosmos.

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Speaker 3: Yeah, it's amazing what we've been able to piece together

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Speaker 3: just from our little viewpoint using basically like two pieces

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Speaker 3: of glass. Right, the original telescopes were juice, a tube

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Speaker 3: and two pieces of glass. I mean they're a little

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Speaker 3: faster now, but essentially the same thing.

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Speaker 6: Yeah.

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Speaker 1: I think you're glossing over a couple of crucial details,

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Speaker 1: like the shape of that glass, but yeah, those are

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Speaker 1: the basic ingredients.

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Speaker 3: Yeah, and so we've been able to look at the

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Speaker 3: stars and other galaxies from our point here on Earth,

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Speaker 3: but we've also been able to look at the sky

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Speaker 3: from the sky. We now have more than a few

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Speaker 3: space telescopes out there in orbit and beyond orbit looking

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Speaker 3: at the rest of the universe.

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Speaker 1: Yeah, we have two really awesome sets of technology ground

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Speaker 1: based telescopes that can get really really big, tens of

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Speaker 1: meters across for the primary mirrors, but those can be

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Speaker 1: obscured by all the air that's between us and space.

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Speaker 1: That air wiggles and shimmys and makes it a little

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Speaker 1: bit unclear to see what's out there. So we have

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Speaker 1: this other awesome set of eyeballs we built that are

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Speaker 1: actually out there in space above the atmosphere and can

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Speaker 1: see much more clearly, although they can't yet be quite

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Speaker 1: as large. So it's a complementary set of eyeballs.

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Speaker 3: Now, these are not literal eyeballs, Like, we didn't send

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Speaker 3: eyeballs into space, did.

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Speaker 1: We, Well, depends on your definition of eyeballs. Right, they're

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Speaker 1: not human biological eyeballs, but they're more like cameras, right.

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Speaker 1: They take pictures which are then transmitted to your eyes.

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Speaker 3: Are they in the shape of a ball?

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Speaker 1: At least there are definitely some balls on them, right,

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Speaker 1: we'll talk about it in the podcast. But they have

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Speaker 1: spinning wheels and spinning balls, which are crucial elements of

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Speaker 1: their operation.

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Speaker 3: Oh all right, Well, so technically they are eye and balls.

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Speaker 3: But it is amazing that we have space telescopes. It's

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Speaker 3: pretty cool. It's like, literally, we build spaceships that are

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Speaker 3: nothing but or spacecraft that are nothing but a telescope, right,

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Speaker 3: that's their only function, and they're out there in space

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Speaker 3: doing their job. They're sort of like robotic space telescope spacecraft.

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Speaker 1: Yeah, they're sort of like distant robot eyeballs that we

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Speaker 1: connect to our own minds. It is really incredible. And

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Speaker 1: you know, the telescopes here on Earth, that makes sense

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Speaker 1: how they work. You want to look at something, you

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Speaker 1: can turn the telescope, you point it at that thing

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Speaker 1: that you want to watch. But the telescopes that are

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Speaker 1: out there in space a little harder to understand, like

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Speaker 1: how those work, how they keep track of where they are,

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Speaker 1: how you can turn a telescope in space. And a

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Speaker 1: bunch of listeners wrote in and asked me how does

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Speaker 1: that work?

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Speaker 3: So to the end of the program, mobly tackling the

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Speaker 3: question how do space telescopes point themselves? Now? I guess, Daniel,

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Speaker 3: The question I guess is like, if you have a

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Speaker 3: telescope here on Earth, you're grounded to the Earth, so

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Speaker 3: you sort of know where you are and which way

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Speaker 3: you're pointing. But maybe the question that the listeners were

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Speaker 3: wondering is like, if you have a telescope out there

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Speaker 3: in space, like, how do you know where you are?

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Speaker 3: And how do you know which way you're pointing?

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Speaker 1: Yeah, I think there's two different parts to it, right,

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Speaker 1: is how do you know which direction you are? Pointing.

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Speaker 1: And then also how do you change your direction? Right?

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Speaker 1: How do you actually turn something that's up in space?

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Speaker 1: Because here on the ground you can push against the ground,

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Speaker 1: it's like connected to something that you can push against.

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Speaker 1: But up in space, right, it's harder to move things around,

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Speaker 1: especially if you wanted to last four decades.

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Speaker 3: See, because I guess anything that you do, like if

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Speaker 3: you have jets or anything, then that means that you're

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Speaker 3: expending energy.

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Speaker 1: Yeah, and more specifically mass, right, jets have to push

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Speaker 1: out something. You have to throw something out the back

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Speaker 1: of the jet in order to get the momentum.

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Speaker 3: M you mean we kint to throw something at them

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Speaker 3: from here, like to you know, knock them into the lignment.

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Speaker 1: That was definitely one of the plans, So I think

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Speaker 1: it was pretty far down on the list. Maybe zap

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Speaker 1: them from Earth with lasers also was pretty far down

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Speaker 1: on the list.

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Speaker 3: Oh, but that would be pretty good, wouldn't it.

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Speaker 1: That's what our strategies for turning asteroids that are coming

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Speaker 1: towards Earth. So maybe it would also work for spacecraft.

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Speaker 3: Yeah, you know when endowed used lasers.

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Speaker 1: Actually, I think that would work if you had like

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Speaker 1: sales on the telescope and you could just push it

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Speaker 1: from Earth with lasers. That would be really cool. I

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Speaker 1: can't imagine what could go wrong or why there might

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Speaker 1: be an issue with building an enormous space laser.

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Speaker 3: They should hire us NASA obviously, because we have good.

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Speaker 1: I'll be expecting an email as soon as we're done

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Speaker 1: with this podcast.

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Speaker 3: Well, as usually, we're wondering how many people had there.

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Speaker 3: I had thought about the space telescopes out there in

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Speaker 3: space and how they turned themselves to point at different stars.

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Speaker 1: So thanks to everybody who answered these questions for the podcast.

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Speaker 1: If you would like to participate for our future episodes,

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Speaker 1: please please please do right to me two questions at

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Speaker 1: danieland Jorge dot com. We'd love to hear a huge

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Speaker 1: variety of voices from all over the world.

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Speaker 3: So think about it for a second. If you earn

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Speaker 3: space pointing a telescope, how would you turn yourself. Here's

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Speaker 3: what people had to say.

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Speaker 1: I haven't thought about it. Maybe by using some geroscopes.

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Speaker 7: By this camera mount that you pointed at the North

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Speaker 7: Star and then it's basically calibrated to turn to compensate

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Speaker 7: for the rotation of the Earth, which is like very consistent.

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Speaker 7: So I'm assuming that the space telescope would do the same.

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Speaker 6: I would guess that the space telescopes point themselves the

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Speaker 6: same way that Elon Musk's Space six rockets do with

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Speaker 6: the air pressure thing. I don't know, maybe either that

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Speaker 6: or like a ion engine.

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Speaker 3: I don't know. I learned that the James Webb telescope

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Speaker 3: has a set of wheels that spin and apply some

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Speaker 3: torque to the whole thing, making the twist.

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Speaker 8: A little Okay, I think I actually remember this one

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Speaker 8: from a previous episode in which we said that it

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Speaker 8: was actually very hard to orient yourself in space, with

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Speaker 8: the exception of being able to use pulsars, which you

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Speaker 8: described as sort of like celestial guiding points that flash

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Speaker 8: very consistently and can therefore somehow be used to triangulate

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Speaker 8: your location, assuming that you already have the known location

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Speaker 8: of two or more pulsars.

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Speaker 9: I believe they use gyroscopes in order to orient themselves,

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Speaker 9: or perhaps they off gas, you know, shooting little jets

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Speaker 9: in particular directions in order to orient themselves in order

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Speaker 9: to point themselves in a particular direction, and they use

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Speaker 9: the background stars to orient themselves correctly.

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Speaker 3: All right, some pretty technical answers here but pretty imaginative.

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Speaker 1: Yeah, our listeners have thought about flying through space, how

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Speaker 1: to get around, how to turn, how to know where

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Speaker 1: you're pointing. We've got some pretty smart folks listening to

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Speaker 1: the podcast.

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Speaker 3: Yeah, let's flatter our audience. You guys are awesome, beautiful

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Speaker 3: and brilliant. But I feel like the answers here and

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Speaker 3: we're also a little confused about what we're asking in

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Speaker 3: the question, Like are we asking like how does a

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Speaker 3: space telescope orient itself? Like how does it know which

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Speaker 3: way's pointing? And also how does it turn to point

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Speaker 3: that something it wants to look at.

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Speaker 1: Yeah, I think we're asking both questions and have different answers,

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Speaker 1: both of which are really fascinating. So I think all

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Speaker 1: of that is involved. I mean, you have your eyeball

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Speaker 1: out in space, you wanted to look at something in particular,

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Speaker 1: you got to solve both problems. You got to know

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Speaker 1: where it is now and how to change its position.

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Speaker 3: Mmm. Do you think there's a there's like a joystick

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Speaker 3: somewhere in NASA or Houston Control Center that points these

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Speaker 3: telescopes and who gets to move that joystick?

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Speaker 1: And I wonder if there's a red button on the

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Speaker 1: top of that joystick and if it actually fires something.

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Speaker 3: Mm, or if it just has a little like sound effect.

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Speaker 1: Peo pew, or maybe if you press the button like

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Speaker 1: a flag pops out at the end of hubble.

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Speaker 3: Boom, or I wonder if anyone in NASA has ever

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Speaker 3: been tempted to turn the telescope around and point it

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Speaker 3: at Earth, like what could it look at? What could

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Speaker 3: it see?

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Speaker 1: You could take a selfie with Hubble?

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Speaker 3: Right yeah, oh man, you could probably find all of

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Speaker 3: NASA selling those selfie opportunities.

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Speaker 1: Hubble is quite delicate, and if too much light enters

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Speaker 1: its aperture it could damage it. They have to be

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Speaker 1: very careful but not pointing it, for example, towards the Sun.

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Speaker 1: And I I wonder if even the Earth might be

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Speaker 1: too bright a source for hovel m.

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Speaker 3: Well, I guess it would have to be night selfies.

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Speaker 1: Then all right, Well, let's.

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Speaker 3: Dig into this question of how spased telescopes orient themselves,

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Speaker 3: how they know which way they're pointing at, and then

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Speaker 3: if they want to point somewhere in particular, how do

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Speaker 3: they move themselves point in that direction. So, first of all,

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Speaker 3: Daniel step us through this, Why this is important and hard?

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Speaker 1: Well, it's important because we want to choose what we

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Speaker 1: are seeing. Remember that the telescopes don't see all of space, right,

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Speaker 1: It's not like when you look out of the night

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Speaker 1: sky and you stare up and you basically see the

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Speaker 1: whole sky, or at least the part that's not blocked

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Speaker 1: by the Earth. A telescope is very very narrow aperture

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Speaker 1: in comparison, so you're only really looking at a small

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Speaker 1: portion of the sky, and you want to get to

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Speaker 1: pick which portion of the sky you are looking at.

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Speaker 1: Are we studying this galaxy, Are we studying that star

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Speaker 1: over there? Are we tracking something that's moving? So you

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Speaker 1: definitely want to have control over where your telescope is pointed.

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Speaker 3: Yeah, it's sort of like you say, it has a

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Speaker 3: very narrow field of view. I imagine it's sort of

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Speaker 3: like walking around your neighborhood looking through a straw or

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Speaker 3: something like that. Right, that's what it means to have

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Speaker 3: a narrow field of view. Like if you close one

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Speaker 3: eye and the other eye could only look through a

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Speaker 3: drinking straw, your field of view would be super narrow

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Speaker 3: and it'd be pretty hard to know where you are.

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Speaker 1: And anybody who looked through a telescope has that experience.

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Speaker 1: You point your telescope sorted towards the thing you're looking for,

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Speaker 1: and then you look through the telescope and you don't

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Speaker 1: see it, and show wiggle the telescope around and try

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Speaker 1: to find the object. It's not easy when you're looking

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Speaker 1: through a telescope to find that particular object has to

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Speaker 1: be pointed very very close for you to even see it.

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Speaker 1: And a straw is a great example, but it's actually

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Speaker 1: not even dramatic enough. Some of these telescopes, their field

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Speaker 1: of view is so small. It's more like looking at

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Speaker 1: a grain of sand you hold at arm's length. That's

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Speaker 1: the fraction of the sky these telescopes can look at

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Speaker 1: at one time.

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Speaker 3: It's like looking at a straw. That's the width of

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Speaker 3: a grain of salt and a meter lungs. What you're saying, Yeah,

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Speaker 3: that's exactly right. So some recent images, for from James

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Speaker 3: Web where they focus on the deep, deep sky, they

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Speaker 3: point at one particular place in the sky and they

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Speaker 3: take a bunch of pictures of that one spot. And

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Speaker 3: the reason you want to hold it there for a

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Speaker 3: long time is that the things that they're looking at

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Speaker 3: are quite dim. You know, these distant galaxies don't send

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Speaker 3: a whole lot of photons per second, so you want

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Speaker 3: to build up a crisp image of them, You've got

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Speaker 3: to have weight as many seconds as possible to get

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Speaker 3: as many photons as possible. So you have to keep

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Speaker 3: pointing in the same direction for as long as possible. Yeah,

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Speaker 3: and imagine that's extra hard because first of all, like

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Speaker 3: that thing that you're looking at might be moving, but

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Speaker 3: also like the space telescope is moving, right, and like

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Speaker 3: these space telescopes are usually an orbit around something, either

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Speaker 3: the Earth or or I guess mostly the Earth, but

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Speaker 3: either in near orbit or far orbit.

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Speaker 1: Yeah, we're always moving relative to the Sun. And even

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Speaker 1: if these distant objects aren't effectively moving relative to our galaxy,

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Speaker 1: you're right, our position is moving, and so you have

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Speaker 1: to do something to stay on target. You can't just

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Speaker 1: turn it and point and take pictures. The things you're

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Speaker 1: looking at will change as you orbit the Sun, and

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Speaker 1: so you have to do work. You have to do

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Speaker 1: something to keep pointing in the same direction.

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Speaker 3: Okay, So then, and that's hard to do, to like

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Speaker 3: move your space telescope because basically there's nothing to push

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Speaker 3: against in space.

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Speaker 1: Exactly If you're swimming in a swimming pool and you

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Speaker 1: want to turn, what do you do? You hold your

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Speaker 1: arms out and you push against the water. Right, you're

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Speaker 1: pushing against something, and so you turn. But in space,

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Speaker 1: what is there, right, There's no air, there's no water,

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Speaker 1: there's nothing to push against, and so turning yourself is

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Speaker 1: much harder because there's nothing immediately there for you to

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Speaker 1: push against, for you to like boost off of.

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Speaker 3: Right and so. But usually satellites and spacecraft the way

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Speaker 3: they navigate and turn and move around is they have rockets, right,

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Speaker 3: or at least some sort of like as a listener

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Speaker 3: suggests it, like an ion engine mm hm.

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Speaker 1: And the crucial thing here is conservation of momentum. If

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Speaker 1: you're stationary and you want to get moving, then to

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Speaker 1: conserve momentum you have to throw something going beyond other

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Speaker 1: direction that requires mass, right the same way that like,

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Speaker 1: if you fire a bullet, you feel a recoil. If

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Speaker 1: you're out in space you turn on a rocket, then

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Speaker 1: basically the motion of your ship is the recoil from

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Speaker 1: firing the rocket, because it's basically shooting a bunch of

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Speaker 1: tiny bullets out the back of the rocket. The rocket

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Speaker 1: is not just flames. It's throwing mass out the back

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Speaker 1: of it. So you don't just need fuel to run

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Speaker 1: the rocket. You need some sort of propellant something to

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Speaker 1: throw out of the rocket to move your ship. And

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Speaker 1: that's true both for motion and for rotation. And so

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Speaker 1: if you need mass to do it, then eventually you're

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Speaker 1: going to run out because you can only bring a

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Speaker 1: limited amount of mass. So the goal is to figure

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Speaker 1: out a way to turn your telescope without using some

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Speaker 1: kind of propellant.

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Speaker 3: Right, because I guess if you're using a propellant, even

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Speaker 3: if there are like ion atoms or molecules, you're going

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Speaker 3: to run out eventually, Right.

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Speaker 1: You are going to run out eventually. And if you

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Speaker 1: spend billions of dollars and decades to develop this thing,

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Speaker 1: then you want it to last as long as possible.

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Speaker 1: So you're going to try how to avoid at all

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Speaker 1: costs having things that run out.

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Speaker 3: Can just make it electric like an electric.

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Speaker 1: Car, Yeah, you can make it electric, and an ion

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Speaker 1: engine essentially is electric, but it still has to throw

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Speaker 1: something out of the back. It's throwing ions which have

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Speaker 1: been accelerated by electric fields.

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Speaker 3: It just brings like a really big gas tank like

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Speaker 3: one that will last one hundred years, right, because these

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Speaker 3: missions usually don't have like an unlimited lifespan, right, They

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Speaker 3: usually come with like an expiration date.

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Speaker 1: Mmm. You can't do that. But then the gas tank

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Speaker 1: is big, which means it's heavy, which means you need

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Speaker 1: more gas to launch it. And usually you want to

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Speaker 1: use all of your available space and masks to design

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Speaker 1: it for science rather than having a huge fuel tank

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Speaker 1: on the back of it.

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Speaker 3: Mmm. I see. So I guess if you can figure

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Speaker 3: out a smarter way to turn out there in space,

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Speaker 3: then you could have more science in your rugget, bigger.

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Speaker 1: Telescope exactly, more science and more years of science because

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Speaker 1: you wouldn't run out of something. Then you need to

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Speaker 1: turn the.

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Speaker 3: Thing also be greener, I imagine, right for the space ecosystem,

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Speaker 3: you'd be less pollution.

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Speaker 1: That's true exactly, And so for all of our neighbors

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Speaker 1: out there, we should be considerate.

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Speaker 3: All right. Well, that's why it's important and hard to

441
00:21:08,760 --> 00:21:10,920
Speaker 3: turn a space teles come and orient it out there

442
00:21:10,920 --> 00:21:13,080
Speaker 3: in space. And so let's get into how you would

443
00:21:13,119 --> 00:21:15,480
Speaker 3: actually do this and how you would find yourself if

444
00:21:15,520 --> 00:21:18,879
Speaker 3: you were lost in space. So let's dig into that.

445
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446
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470
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Speaker 1: When you pop a piece of cheese into your mouth

487
00:23:28,359 --> 00:23:31,520
Speaker 1: or enjoy a rich spoonful of Greek yogurt, you're probably

488
00:23:31,560 --> 00:23:35,600
Speaker 1: not thinking about the environmental impact of each and every bite.

489
00:23:35,640 --> 00:23:38,240
Speaker 1: But the people in the dairy industry are. US Dairy

490
00:23:38,280 --> 00:23:42,600
Speaker 1: has set themselves some ambitious sustainability goals, including being greenhouse

491
00:23:42,600 --> 00:23:45,200
Speaker 1: gas neutral by twenty to fifty. That's why they're working

492
00:23:45,200 --> 00:23:47,560
Speaker 1: hard every day to find new ways to reduce waste,

493
00:23:47,640 --> 00:23:51,840
Speaker 1: conserve natural resources, and drive down greenhouse gas emissions. Take water,

494
00:23:51,880 --> 00:23:54,960
Speaker 1: for example, most dairy farms reuse water up to four

495
00:23:55,040 --> 00:23:58,480
Speaker 1: times the same water cools the milk, cleans equipment, washes

496
00:23:58,520 --> 00:24:01,320
Speaker 1: the barn, and irrigates the c How is US dairy

497
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Speaker 1: tackling greenhouse gases? Many farms use anaerobic digestors that turn

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499
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500
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501
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502
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503
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504
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505
00:24:26,240 --> 00:24:29,720
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506
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Speaker 10: from the California Office of Traffic Safety and Caltrans.

510
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Speaker 3: All right, we're talking about space telescopes, which are telescopes

511
00:24:52,320 --> 00:24:52,960
Speaker 3: and space.

512
00:24:52,800 --> 00:24:58,520
Speaker 1: Basically finally a well named physics object.

513
00:24:58,800 --> 00:25:02,720
Speaker 3: I know, right, And we're talking about how they point

514
00:25:02,760 --> 00:25:05,240
Speaker 3: themselves out there in space. So let's tackle Maybe the

515
00:25:05,280 --> 00:25:07,760
Speaker 3: first question is, if you're on a telescope out there

516
00:25:07,800 --> 00:25:09,679
Speaker 3: in space, how do you know where you are? How

517
00:25:09,720 --> 00:25:10,560
Speaker 3: do you know where you're pointing?

518
00:25:10,600 --> 00:25:13,320
Speaker 1: So these telescopes typically have multiple ways to figure out

519
00:25:13,320 --> 00:25:15,040
Speaker 1: where they are pointing. First of all, they just have

520
00:25:15,080 --> 00:25:17,800
Speaker 1: a bunch of sensors. Like the Hubble, for example, has

521
00:25:17,840 --> 00:25:20,760
Speaker 1: several different kinds of sensors. It has a sensor that

522
00:25:20,840 --> 00:25:23,479
Speaker 1: tells it where the sun is, which helps it know

523
00:25:23,560 --> 00:25:26,640
Speaker 1: where it's pointing, but also helps it avoid pointing into

524
00:25:26,640 --> 00:25:30,320
Speaker 1: the sun accidentally. It also has sensors for magnetic field

525
00:25:30,400 --> 00:25:32,480
Speaker 1: so that you can use the Earth's magnetic field to

526
00:25:32,480 --> 00:25:35,040
Speaker 1: help figure out where it is. And then there are

527
00:25:35,040 --> 00:25:37,800
Speaker 1: sensors that look at stars, and there's like a known

528
00:25:37,960 --> 00:25:41,199
Speaker 1: star map and helps it get an orientation roughly for

529
00:25:41,440 --> 00:25:43,639
Speaker 1: where it is. So to get a rough idea for

530
00:25:43,680 --> 00:25:46,840
Speaker 1: where it is and orient itself. It has essentially maps

531
00:25:47,160 --> 00:25:50,120
Speaker 1: the Sun, the magnetic field, and the stars. They give

532
00:25:50,160 --> 00:25:51,320
Speaker 1: it a sense for where it is.

533
00:25:51,480 --> 00:25:53,359
Speaker 3: Yeah, that's usually how they did it in science fiction.

534
00:25:53,480 --> 00:25:55,359
Speaker 3: Like if you're in a space ship and you land

535
00:25:55,359 --> 00:25:57,560
Speaker 3: in a place you're not quite sure where you are.

536
00:25:57,840 --> 00:26:00,280
Speaker 3: Usually the way you orient yourself is by looking at

537
00:26:00,600 --> 00:26:02,719
Speaker 3: the stars around you, and if you sort of know

538
00:26:02,960 --> 00:26:04,920
Speaker 3: where they're supposed to be, you can figure out where

539
00:26:04,920 --> 00:26:07,119
Speaker 3: you are relative to them. That's the idea, right, Basically,

540
00:26:07,160 --> 00:26:08,480
Speaker 3: they're looking at the constellations.

541
00:26:08,520 --> 00:26:11,280
Speaker 1: They're looking at the constellations, and Hubble is not a

542
00:26:11,359 --> 00:26:15,000
Speaker 1: traveling spacecraft, so it will never appear in Andromeda and

543
00:26:15,080 --> 00:26:17,560
Speaker 1: have to figure out where it is. It's always going

544
00:26:17,600 --> 00:26:19,680
Speaker 1: to be orbiting the Earth, and so we know what

545
00:26:19,720 --> 00:26:22,520
Speaker 1: the stars look like when you're orbiting the Earth, and

546
00:26:22,600 --> 00:26:25,680
Speaker 1: so you just need a few examples of particular known

547
00:26:25,800 --> 00:26:28,560
Speaker 1: stars and you can roughly figure out where you are.

548
00:26:28,760 --> 00:26:31,119
Speaker 1: So those are the sort of lower precision instruments, the

549
00:26:31,160 --> 00:26:33,800
Speaker 1: sort of baseline that Hubble uses to figure out where

550
00:26:33,800 --> 00:26:36,920
Speaker 1: it's pointing, but it also has much more precise way

551
00:26:36,960 --> 00:26:39,720
Speaker 1: to measure how it's turning, so not just like look

552
00:26:39,760 --> 00:26:41,600
Speaker 1: at the map and figure out where you are, but

553
00:26:41,720 --> 00:26:44,800
Speaker 1: also understand how far you have turned right and so

554
00:26:45,000 --> 00:26:48,920
Speaker 1: internal to Hubble and almost all of these spacecraft they

555
00:26:48,960 --> 00:26:52,679
Speaker 1: have gyroscopes. Gyroscopes are these balls that's been really really fast,

556
00:26:52,760 --> 00:26:55,280
Speaker 1: and so they're insensitive to the motion of Hubble and

557
00:26:55,359 --> 00:26:57,760
Speaker 1: they can measure sort of how far it's turned.

558
00:26:58,640 --> 00:27:02,119
Speaker 3: Yeah, that's pretty cool. Use gyroscopes here on Earth all

559
00:27:02,160 --> 00:27:05,480
Speaker 3: the time also to measure how things turn. But I

560
00:27:05,520 --> 00:27:07,679
Speaker 3: guess you know as an engineer, the triggering thing with

561
00:27:07,800 --> 00:27:10,359
Speaker 3: gyroscopes is that they tell you how much, if whether

562
00:27:10,480 --> 00:27:13,720
Speaker 3: you've turned and how much. But over time, they're sort

563
00:27:13,720 --> 00:27:17,720
Speaker 3: of not calibrated to something fixed like the sun for example, exactly.

564
00:27:17,760 --> 00:27:20,280
Speaker 1: And so if you're holding a gyroscope and you turn,

565
00:27:20,400 --> 00:27:23,000
Speaker 1: the gyroscope states pointing in its original direction, and so

566
00:27:23,080 --> 00:27:25,640
Speaker 1: you can measure, oh, I've turned thirty six point two degrees,

567
00:27:25,840 --> 00:27:28,240
Speaker 1: so it's a relative measurement. As you say, it tells

568
00:27:28,240 --> 00:27:30,120
Speaker 1: you how far you have turned, doesn't tell you where

569
00:27:30,119 --> 00:27:33,840
Speaker 1: you're actually pointing. That's why Hubble has this combination of

570
00:27:34,000 --> 00:27:37,280
Speaker 1: having the rough sensors to tell it the absolute measurements

571
00:27:37,280 --> 00:27:39,080
Speaker 1: like on pointing in this part of the sky or

572
00:27:39,080 --> 00:27:40,840
Speaker 1: that part of the sky or this part relative to

573
00:27:40,880 --> 00:27:44,240
Speaker 1: the sun, plus these gyroscopes to measure very precisely how

574
00:27:44,280 --> 00:27:46,919
Speaker 1: far it has turned. So it needs a combination of

575
00:27:46,960 --> 00:27:49,639
Speaker 1: these sensors to get an absolute sense for where it

576
00:27:49,800 --> 00:27:51,120
Speaker 1: is pointing in the sky.

577
00:27:51,600 --> 00:27:54,720
Speaker 3: Because I guess if you're using a sensor to track

578
00:27:54,760 --> 00:27:58,359
Speaker 3: where the sun is, you're basically talking about a camera, right,

579
00:27:59,080 --> 00:28:01,679
Speaker 3: and so maybe a camera is not that accurate.

580
00:28:01,720 --> 00:28:04,160
Speaker 1: Yeah, it's basically a low tech camera. Then the precision

581
00:28:04,160 --> 00:28:06,479
Speaker 1: of that is limited by like the pixels of the

582
00:28:06,520 --> 00:28:09,600
Speaker 1: camera and also basically the width of the object you're

583
00:28:09,640 --> 00:28:12,879
Speaker 1: looking at. And so the gyroscopes give you the most

584
00:28:13,000 --> 00:28:16,200
Speaker 1: precise measurement of how far you have turned. And these

585
00:28:16,200 --> 00:28:19,520
Speaker 1: things need to be again super duper precise. Like when

586
00:28:19,560 --> 00:28:21,879
Speaker 1: Hubble is focusing on something and trying to keep it

587
00:28:21,920 --> 00:28:24,920
Speaker 1: in its field of view, it's like holding a laser

588
00:28:25,000 --> 00:28:29,239
Speaker 1: beam focused on a dime two hundred miles away. That's

589
00:28:29,280 --> 00:28:30,560
Speaker 1: how precise we're trying to be.

590
00:28:30,680 --> 00:28:32,760
Speaker 3: You mean, like how steady your hand needs to be

591
00:28:32,840 --> 00:28:33,720
Speaker 3: basically right.

592
00:28:33,840 --> 00:28:36,680
Speaker 1: Yeah, exactly, And so you're focusing on a dime that's

593
00:28:36,720 --> 00:28:40,440
Speaker 1: two hundred miles away, plus you're moving relative to that dime,

594
00:28:40,480 --> 00:28:42,560
Speaker 1: and so it's not just about being steady, it's about

595
00:28:42,600 --> 00:28:46,040
Speaker 1: slowly tracking. It's about turning your telescope so you can

596
00:28:46,120 --> 00:28:49,040
Speaker 1: keep on it. So these gyroscopes are super duper important

597
00:28:49,040 --> 00:28:51,640
Speaker 1: to the operation of these based telescopes. And Hubble has

598
00:28:51,680 --> 00:28:54,280
Speaker 1: been going for decades and because these things are so important,

599
00:28:54,320 --> 00:28:56,000
Speaker 1: they actually went up in two thousand and nine and

600
00:28:56,040 --> 00:28:59,320
Speaker 1: replaced all six of them. Hubble has six of these

601
00:28:59,360 --> 00:29:03,040
Speaker 1: things to me, six gyroscopes, yeah, and each one spins

602
00:29:03,080 --> 00:29:06,560
Speaker 1: at like twenty thousand rpm. Why do they need to

603
00:29:06,560 --> 00:29:09,600
Speaker 1: be replaced, Well, eventually they degrade. You know, there's always

604
00:29:09,600 --> 00:29:12,360
Speaker 1: some amount of friction in those things, so they'll rub

605
00:29:12,360 --> 00:29:15,440
Speaker 1: against each other, they'll slow down, they'll heat up, and

606
00:29:15,600 --> 00:29:19,040
Speaker 1: nothing is a perpetual motion machine, right, and so eventually

607
00:29:19,080 --> 00:29:20,760
Speaker 1: these things do need to be replaced.

608
00:29:21,360 --> 00:29:24,040
Speaker 3: Now, when you say it needs to be accurate to

609
00:29:24,080 --> 00:29:26,360
Speaker 3: the point where you can spot a din two hundred

610
00:29:26,440 --> 00:29:29,800
Speaker 3: miles away. Is that when you're tracking something, you know,

611
00:29:29,920 --> 00:29:32,800
Speaker 3: when you're trying to stay focused on a star or

612
00:29:32,920 --> 00:29:37,000
Speaker 3: is that more for finding stars and things like that.

613
00:29:37,600 --> 00:29:40,520
Speaker 3: So I imagine the gyroscopes maybe don't really help you to

614
00:29:40,600 --> 00:29:41,320
Speaker 3: find a star.

615
00:29:41,720 --> 00:29:44,200
Speaker 1: Yeah, the gyroscopes don't tell you what's out there at all.

616
00:29:44,280 --> 00:29:46,840
Speaker 1: They just tell you how far you have turned. And

617
00:29:46,880 --> 00:29:49,479
Speaker 1: the scientists need to decide where they want to look.

618
00:29:49,840 --> 00:29:52,640
Speaker 1: So maybe they've seen something already in the sky near

619
00:29:52,680 --> 00:29:55,480
Speaker 1: another object and they want to appear more closely, or

620
00:29:55,520 --> 00:29:58,040
Speaker 1: they seen it maybe in the infrared using Spitzer and

621
00:29:58,040 --> 00:30:00,600
Speaker 1: how they want to get optical images. So they have

622
00:30:00,640 --> 00:30:03,080
Speaker 1: to already know where in the sky to look, so

623
00:30:03,120 --> 00:30:06,400
Speaker 1: they have like galactic coordinate systems they used to orient

624
00:30:06,480 --> 00:30:09,560
Speaker 1: to say where something is in the sky relative to

625
00:30:09,600 --> 00:30:11,920
Speaker 1: the plane of the galaxy, for example, And so you

626
00:30:11,960 --> 00:30:14,000
Speaker 1: have to know basically where something is and then go

627
00:30:14,040 --> 00:30:15,160
Speaker 1: look at it.

628
00:30:15,200 --> 00:30:17,440
Speaker 3: Is there like a galactic coordinate system.

629
00:30:17,640 --> 00:30:20,000
Speaker 1: Oh absolutely. When you look at the maps, for example,

630
00:30:20,000 --> 00:30:23,160
Speaker 1: of the cosmic microwave background, those are relative to the

631
00:30:23,160 --> 00:30:25,840
Speaker 1: plane of the galaxy. So the galaxy runs through the

632
00:30:25,880 --> 00:30:28,200
Speaker 1: middle of those like a line through the middle of

633
00:30:28,240 --> 00:30:30,760
Speaker 1: that oval and then you go above and below the

634
00:30:30,760 --> 00:30:33,760
Speaker 1: galactic plane. It's arbitrary, right, you could pick an axis

635
00:30:33,800 --> 00:30:36,600
Speaker 1: anywhere in space, and so we pick it relative to

636
00:30:36,760 --> 00:30:38,040
Speaker 1: the Milky Way center.

637
00:30:37,960 --> 00:30:41,720
Speaker 3: To the basically the main axis of the Milky Way.

638
00:30:41,840 --> 00:30:43,480
Speaker 1: Yeah, and if you are out camping and lost in

639
00:30:43,480 --> 00:30:44,960
Speaker 1: the woods and you look up at the sky, you

640
00:30:45,000 --> 00:30:47,720
Speaker 1: see the sort of Milky Way of stars across the

641
00:30:47,840 --> 00:30:50,959
Speaker 1: night sky, and that is the plane of the galaxy. Right,

642
00:30:51,040 --> 00:30:53,320
Speaker 1: if you're looking above it or below it, you're looking

643
00:30:53,400 --> 00:30:55,760
Speaker 1: out from the galaxy. Because remember our galaxy is kind

644
00:30:55,760 --> 00:30:57,680
Speaker 1: of like a disk. And if you're looking at that

645
00:30:57,760 --> 00:31:00,520
Speaker 1: line and you're looking through the galaxy, which is why

646
00:31:00,520 --> 00:31:02,960
Speaker 1: it looks so milky, because there's so many more stars

647
00:31:03,000 --> 00:31:05,000
Speaker 1: and gas and dust and all that kind of stuff.

648
00:31:05,040 --> 00:31:07,480
Speaker 1: So that's the galactic coordinate system. We used to talk

649
00:31:07,480 --> 00:31:09,040
Speaker 1: about where things are in space.

650
00:31:09,120 --> 00:31:11,600
Speaker 3: Well, that's that gives you the direction, But like, where's

651
00:31:11,640 --> 00:31:12,840
Speaker 3: the origin of this cord?

652
00:31:12,840 --> 00:31:15,239
Speaker 1: And it's at the center of the Milky Way. If

653
00:31:15,280 --> 00:31:16,880
Speaker 1: you look at that oval, for example, and you put

654
00:31:16,920 --> 00:31:19,120
Speaker 1: a dot in the very very center of it, that's

655
00:31:19,120 --> 00:31:20,120
Speaker 1: where the black hole is.

656
00:31:20,680 --> 00:31:23,000
Speaker 3: But then when we look at our night sky, it's

657
00:31:23,040 --> 00:31:24,560
Speaker 3: going to be a little different than that, right.

658
00:31:24,440 --> 00:31:26,520
Speaker 1: That's right, we don't see that entire thing, but you

659
00:31:26,560 --> 00:31:28,880
Speaker 1: can map the sphere of things that we can see

660
00:31:29,200 --> 00:31:30,560
Speaker 1: onto that coordinate system.

661
00:31:30,920 --> 00:31:32,480
Speaker 3: You have to like a little bit of an angle

662
00:31:32,520 --> 00:31:34,800
Speaker 3: change because we're not at the center of the galaxy, right.

663
00:31:34,720 --> 00:31:36,800
Speaker 1: Exactly, We're not at the center of the galaxy. And

664
00:31:36,840 --> 00:31:39,560
Speaker 1: also our solar system is tilted a little bit, so

665
00:31:39,600 --> 00:31:41,920
Speaker 1: you have to know where the Sun is relative to

666
00:31:41,960 --> 00:31:43,840
Speaker 1: the center of the galaxy in order to map that on.

667
00:31:44,680 --> 00:31:46,880
Speaker 3: Cool. But then then you said it uses sort of

668
00:31:46,880 --> 00:31:50,120
Speaker 3: a cameras to see the constellations in a way, or

669
00:31:50,200 --> 00:31:53,120
Speaker 3: a map of the stars. Does it actually do that?

670
00:31:53,160 --> 00:31:56,240
Speaker 3: Does it actually like track certain stars or constellations? And

671
00:31:56,320 --> 00:31:57,800
Speaker 3: is that one of those maps you can buy in

672
00:31:58,040 --> 00:32:01,760
Speaker 3: Hollywood Boulevard the Map to the Stars?

673
00:32:02,000 --> 00:32:04,479
Speaker 1: Yeah. So Hubble has a bunch of these different systems, right,

674
00:32:04,560 --> 00:32:07,840
Speaker 1: has the coarse sun sensors, has the magnetic sensing system.

675
00:32:08,120 --> 00:32:11,960
Speaker 1: Then it has star trackers, right, and the star trackers

676
00:32:12,040 --> 00:32:15,440
Speaker 1: determines Hubble's altitude by looking at the location and brightness

677
00:32:15,480 --> 00:32:17,560
Speaker 1: of stars that it sees, so has a broader field

678
00:32:17,560 --> 00:32:20,000
Speaker 1: of view than Hubble sort of main camera, and this

679
00:32:20,120 --> 00:32:24,080
Speaker 1: lets it like identify unique patterns throughout the sky, which

680
00:32:24,120 --> 00:32:27,400
Speaker 1: a computer then maps to star maps internal to Hubble

681
00:32:27,400 --> 00:32:29,400
Speaker 1: and lets it figure out like if there's a correction

682
00:32:29,760 --> 00:32:31,960
Speaker 1: or if it's slightly pointed in the wrong direction, and

683
00:32:32,000 --> 00:32:35,880
Speaker 1: then the fine guidance system uses the gyroscopes and everything

684
00:32:35,880 --> 00:32:37,760
Speaker 1: else to sort of fine tune everything.

685
00:32:39,720 --> 00:32:42,880
Speaker 3: Now that's interesting. They had to go and replace those gyroscopes.

686
00:32:42,960 --> 00:32:46,080
Speaker 3: Is that something we can do pretty easily? Like how

687
00:32:46,080 --> 00:32:47,440
Speaker 3: do we do that? Do we need to send a

688
00:32:47,560 --> 00:32:49,240
Speaker 3: rocket with people or do we send robots?

689
00:32:49,320 --> 00:32:51,400
Speaker 1: It's not something we can do very easily. We have

690
00:32:51,480 --> 00:32:54,640
Speaker 1: to send astronauts up there because it's a complicated job.

691
00:32:55,160 --> 00:32:56,920
Speaker 1: And so it was done in two thousand and nine

692
00:32:56,960 --> 00:32:59,080
Speaker 1: and that was the last time, and it's not something

693
00:32:59,160 --> 00:33:01,640
Speaker 1: that we can do for James Webb, for example. James Webb,

694
00:33:01,680 --> 00:33:04,080
Speaker 1: remember is not in Earth orbit. It's out at a

695
00:33:04,120 --> 00:33:07,160
Speaker 1: Lagarannge point. It's much much further away, and it's not

696
00:33:07,240 --> 00:33:10,000
Speaker 1: a place where we can send humans. So either we

697
00:33:10,080 --> 00:33:13,600
Speaker 1: have to develop robotic repair people or we just can't

698
00:33:13,600 --> 00:33:16,120
Speaker 1: replace it. So James Webb actually has a slightly different

699
00:33:16,160 --> 00:33:18,000
Speaker 1: technology than Hubble does.

700
00:33:18,480 --> 00:33:20,480
Speaker 3: M what does the James Webb telescope do.

701
00:33:20,720 --> 00:33:23,880
Speaker 1: So Hubble has these spinning balls. They're like mechanical, right,

702
00:33:24,280 --> 00:33:26,280
Speaker 1: But James Webb tried to look for something that was

703
00:33:26,400 --> 00:33:29,440
Speaker 1: less mechanical. It didn't require something spinning at a really

704
00:33:29,480 --> 00:33:31,960
Speaker 1: high speed because that seems like sort of easy to

705
00:33:32,000 --> 00:33:34,160
Speaker 1: mess up, like a little grain in there can really

706
00:33:34,160 --> 00:33:36,600
Speaker 1: mess it up. So James Webb actually uses this weird

707
00:33:36,680 --> 00:33:40,240
Speaker 1: technology is a quartz hemisphere that resonates in a particular way,

708
00:33:40,440 --> 00:33:42,520
Speaker 1: sort of like if you have a wine glass and

709
00:33:42,560 --> 00:33:44,960
Speaker 1: you rub your finger around it, it resonates and makes

710
00:33:45,000 --> 00:33:48,360
Speaker 1: like a ringing sound. That's that wine glass like flexing

711
00:33:48,440 --> 00:33:50,960
Speaker 1: a little bit. You can't see flexing, but it's actually

712
00:33:51,040 --> 00:33:54,400
Speaker 1: shaking a little bit. And if you like rotated the

713
00:33:54,440 --> 00:33:57,680
Speaker 1: wine glass, then the sound would rotate with it. So

714
00:33:57,760 --> 00:34:00,520
Speaker 1: what happens with the gyroscope inside James Webb is that

715
00:34:00,560 --> 00:34:03,680
Speaker 1: the quartz hemisphere resonates in this very particular way. It's

716
00:34:03,720 --> 00:34:07,040
Speaker 1: surrounded by electrodes that are like driving the resonance. They

717
00:34:07,040 --> 00:34:10,279
Speaker 1: can also detect any slight change in its orientation, Like

718
00:34:10,280 --> 00:34:14,279
Speaker 1: if James Web rotates around this quartz hemisphere, they will

719
00:34:14,320 --> 00:34:17,600
Speaker 1: hear the resonance impacting the telescope at a different location.

720
00:34:17,920 --> 00:34:20,640
Speaker 3: Hmmm, well, it's pretty fascinating and so I guess those

721
00:34:20,719 --> 00:34:21,439
Speaker 3: don't wear out.

722
00:34:21,600 --> 00:34:24,000
Speaker 1: The hope is that they don't wear out as fast, right,

723
00:34:24,080 --> 00:34:27,200
Speaker 1: everything will wear out eventually. This is still moving every

724
00:34:27,200 --> 00:34:30,880
Speaker 1: time James Web moves, it moves relative to these gyroscopes,

725
00:34:31,160 --> 00:34:33,840
Speaker 1: and so there's potential for friction there. But you don't

726
00:34:33,840 --> 00:34:37,200
Speaker 1: have a spinning mass, right, and so it's less kinetic energy,

727
00:34:37,239 --> 00:34:39,319
Speaker 1: it's less mechanical, and so the hope is that it

728
00:34:39,320 --> 00:34:40,200
Speaker 1: will last longer.

729
00:34:41,719 --> 00:34:43,880
Speaker 3: And so that's how it orients itself. And so if

730
00:34:43,880 --> 00:34:46,600
Speaker 3: you wanted to point to a particular galaxy out there

731
00:34:46,719 --> 00:34:49,319
Speaker 3: that you know about, do you still have to kind

732
00:34:49,320 --> 00:34:51,200
Speaker 3: of like pan around? You think, like, do you think

733
00:34:51,239 --> 00:34:53,560
Speaker 3: there's someone and nasaid with a joystick going like back

734
00:34:53,600 --> 00:34:57,040
Speaker 3: and forth, back and forth. Oh, there it is, Or

735
00:34:57,080 --> 00:34:59,160
Speaker 3: do you think they can just go like point to here,

736
00:34:59,320 --> 00:35:00,520
Speaker 3: boom pointing there.

737
00:35:02,120 --> 00:35:04,319
Speaker 1: I don't know the details, but I'm pretty sure it's

738
00:35:04,400 --> 00:35:07,440
Speaker 1: not a joystick. I think they type in the coordinates

739
00:35:07,480 --> 00:35:10,800
Speaker 1: and Hubble like pans over. This thing happens very slowly,

740
00:35:11,160 --> 00:35:13,879
Speaker 1: Like when hubble turns, it turns about as fast as

741
00:35:13,880 --> 00:35:16,560
Speaker 1: a clock does. So a hubble, for example, can turn

742
00:35:17,040 --> 00:35:21,040
Speaker 1: ninety degrees in about fifteen minutes. This is not something

743
00:35:21,160 --> 00:35:22,680
Speaker 1: you want to spin around very quickly.

744
00:35:23,280 --> 00:35:25,239
Speaker 3: I see, So it just takes a while to with

745
00:35:25,320 --> 00:35:27,959
Speaker 3: the joystick. I'll hold the joystick for a while.

746
00:35:30,360 --> 00:35:33,600
Speaker 1: Yes, it takes patience with a joystick. Probably, they do

747
00:35:33,680 --> 00:35:36,320
Speaker 1: have a joystick that's not actually doing anything. It's just connected.

748
00:35:36,640 --> 00:35:38,719
Speaker 1: Like at the large Adron collider and the visitor center,

749
00:35:38,760 --> 00:35:40,759
Speaker 1: they have a big red button you can press. It

750
00:35:40,840 --> 00:35:43,080
Speaker 1: sets off lots of alarm bells and flashing lights, but

751
00:35:43,120 --> 00:35:44,719
Speaker 1: doesn't actually shut anything down.

752
00:35:44,960 --> 00:35:49,000
Speaker 3: Wow, that sounds like something that fire department did not approve.

753
00:35:49,840 --> 00:35:52,799
Speaker 3: All right, Well, that's how space telescopes orient themselves. How

754
00:35:52,880 --> 00:35:54,799
Speaker 3: they know where they're looking at in the night sky

755
00:35:55,160 --> 00:35:57,440
Speaker 3: or I guess if if you're in space, every night

756
00:35:57,520 --> 00:35:57,640
Speaker 3: is the.

757
00:35:57,680 --> 00:35:59,320
Speaker 1: Night sky, it's always night in space.

758
00:35:59,400 --> 00:36:01,879
Speaker 3: Yeah, looking at the sun, I guess. But now let's

759
00:36:01,920 --> 00:36:05,160
Speaker 3: talk about how space telescopes move, how they actually turn

760
00:36:05,400 --> 00:36:08,800
Speaker 3: to look at a particular star or galaxy or nebula.

761
00:36:09,040 --> 00:36:11,200
Speaker 3: So let's get into that. But first, let's take another

762
00:36:11,280 --> 00:36:11,759
Speaker 3: quick break.

763
00:36:16,000 --> 00:36:17,759
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764
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765
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766
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768
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769
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770
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821
00:39:15,080 --> 00:39:15,279
Speaker 1: Orright.

822
00:39:15,360 --> 00:39:19,560
Speaker 3: We're talking about how space telescopes point themselves. That's that

823
00:39:19,600 --> 00:39:21,239
Speaker 3: seems very like self accusatory.

824
00:39:21,320 --> 00:39:23,320
Speaker 1: I mean, like, what's the point of space telescopes?

825
00:39:23,520 --> 00:39:25,920
Speaker 3: No, like they have to point at them They're pointing

826
00:39:25,960 --> 00:39:27,120
Speaker 3: themselves at themselves.

827
00:39:27,760 --> 00:39:29,239
Speaker 1: I mean, somebody's got to do it right.

828
00:39:29,360 --> 00:39:31,280
Speaker 3: How introspective are space telescopes.

829
00:39:31,600 --> 00:39:35,319
Speaker 1: I guess they're not really pointing themselves. We are pointing them, right,

830
00:39:35,600 --> 00:39:36,880
Speaker 1: somebody is doing.

831
00:39:36,680 --> 00:39:38,880
Speaker 3: It, yeah, right, the joystick.

832
00:39:38,960 --> 00:39:41,160
Speaker 1: It's not like they're up there just deciding on their own. Hey,

833
00:39:41,200 --> 00:39:43,200
Speaker 1: I'm going to look at Andromeda today.

834
00:39:43,600 --> 00:39:47,720
Speaker 3: Yeah. Yeah, I'm sure there's some the NASA joystick person

835
00:39:47,920 --> 00:39:50,880
Speaker 3: listening to this right now, going, Hey, I point the

836
00:39:50,920 --> 00:39:53,840
Speaker 3: space teles clothed. You think space telescopes point themselves?

837
00:39:56,640 --> 00:39:58,640
Speaker 1: That's right? What do you think the garbage takes itself

838
00:39:58,680 --> 00:40:00,560
Speaker 1: out just because you're not doing it well?

839
00:40:00,600 --> 00:40:03,839
Speaker 3: We talked about how space telescopes can know which way

840
00:40:03,880 --> 00:40:07,160
Speaker 3: they're pointing out out there in space, because I guess

841
00:40:07,160 --> 00:40:09,440
Speaker 3: it's pretty disorient can be disorient thing. If you're out

842
00:40:09,440 --> 00:40:11,279
Speaker 3: there in space, you're sort of it's hard to know

843
00:40:11,320 --> 00:40:13,960
Speaker 3: which ways up and down mm hmm exactly. And so

844
00:40:14,000 --> 00:40:16,760
Speaker 3: the second question now is how do they actually turn?

845
00:40:17,320 --> 00:40:19,399
Speaker 3: How do they like if you're looking in one way

846
00:40:19,480 --> 00:40:20,880
Speaker 3: looking at a star, and you want to look at

847
00:40:20,880 --> 00:40:23,439
Speaker 3: the star over there, how do you make that turn? Because,

848
00:40:23,440 --> 00:40:25,680
Speaker 3: as we talked about, you don't want to rely on

849
00:40:25,800 --> 00:40:30,440
Speaker 3: propellants or rockets or ion engines because those are kind

850
00:40:30,440 --> 00:40:33,520
Speaker 3: of costly. They maybe you might run out at some

851
00:40:33,520 --> 00:40:34,280
Speaker 3: point in the future.

852
00:40:34,440 --> 00:40:36,480
Speaker 1: Yeah, and those would be nice, right, you'd like to

853
00:40:36,520 --> 00:40:38,840
Speaker 1: do that. It's sort of an easy solution because it

854
00:40:38,920 --> 00:40:41,680
Speaker 1: lets you have a net force. You have your space telescope,

855
00:40:41,719 --> 00:40:44,200
Speaker 1: you throw something off the side, you're applying a force

856
00:40:44,239 --> 00:40:47,000
Speaker 1: to that object. That object applies a force back to you.

857
00:40:47,000 --> 00:40:49,720
Speaker 1: You turn or you move. It makes some sort of sense.

858
00:40:50,000 --> 00:40:52,719
Speaker 1: But as we said, that requires some mass. So now

859
00:40:52,719 --> 00:40:55,520
Speaker 1: we need a solution that doesn't have any net force

860
00:40:55,640 --> 00:40:58,400
Speaker 1: or no net torque on the object. Right, you have

861
00:40:58,440 --> 00:41:00,320
Speaker 1: to figure out how to turn the tell Us scope

862
00:41:00,640 --> 00:41:03,120
Speaker 1: without applying an overall force to it.

863
00:41:03,400 --> 00:41:05,120
Speaker 3: Oh, I see what you're saying. Because if you are

864
00:41:05,239 --> 00:41:08,520
Speaker 3: applying an overall net force or torque, that means you're

865
00:41:08,600 --> 00:41:10,680
Speaker 3: expending energy in the universe, right.

866
00:41:10,840 --> 00:41:13,880
Speaker 1: Yeah, and not just energy momentum. Right. So if you're

867
00:41:13,880 --> 00:41:16,640
Speaker 1: going to turn this thing from the outside, you're like

868
00:41:16,920 --> 00:41:19,279
Speaker 1: put your hand on it and turn it, then you're

869
00:41:19,280 --> 00:41:22,239
Speaker 1: applying a force to it, right, Or if you're on

870
00:41:22,320 --> 00:41:24,560
Speaker 1: the telescope and you're throwing a rock off the side

871
00:41:24,600 --> 00:41:28,000
Speaker 1: of it, you're using some mass. You're expending momentum. So

872
00:41:28,080 --> 00:41:30,160
Speaker 1: what we want is a way to turn the telescope

873
00:41:30,200 --> 00:41:34,040
Speaker 1: without changing its total momentum, because changing is total momentum

874
00:41:34,280 --> 00:41:37,799
Speaker 1: by Newton's laws, requires something else to balance that momentum,

875
00:41:37,840 --> 00:41:40,359
Speaker 1: which means something else with mass, and there's nothing else

876
00:41:40,360 --> 00:41:42,560
Speaker 1: out there. It's just floating out in space. How do

877
00:41:42,600 --> 00:41:45,920
Speaker 1: you turn the telescope without applying some overall force to it?

878
00:41:46,200 --> 00:41:47,320
Speaker 1: That's the physics puzzle.

879
00:41:47,560 --> 00:41:51,320
Speaker 3: M Like, how do you change your absolute orientation without

880
00:41:51,680 --> 00:41:54,320
Speaker 3: changing your overall angular momentum?

881
00:41:54,400 --> 00:41:57,440
Speaker 1: Kind of yeah, imagine, for example, you're on ice skates

882
00:41:57,440 --> 00:41:59,759
Speaker 1: and you're on a super duper slippery surface. How do

883
00:41:59,800 --> 00:42:02,879
Speaker 1: you or you can't push against the ice because you're

884
00:42:02,880 --> 00:42:05,080
Speaker 1: on ice skates in a super slippery so how do

885
00:42:05,120 --> 00:42:07,839
Speaker 1: you turn your direction? How do you change which way

886
00:42:07,880 --> 00:42:10,880
Speaker 1: you are pointing? That's basically the puzzle. Right, So if

887
00:42:10,920 --> 00:42:13,200
Speaker 1: you could push against the side, that'd be great, but

888
00:42:13,239 --> 00:42:15,640
Speaker 1: there is no side. If you could like throw a rock,

889
00:42:15,880 --> 00:42:18,000
Speaker 1: then that'd be great, but you can't do that. So

890
00:42:18,040 --> 00:42:20,800
Speaker 1: the question is how do you turn on this slippery surface?

891
00:42:20,880 --> 00:42:21,040
Speaker 6: Right?

892
00:42:21,120 --> 00:42:22,719
Speaker 3: Or I was thinking it's more like, you know, if

893
00:42:22,719 --> 00:42:24,520
Speaker 3: you were stuck out there in space, like if you're

894
00:42:24,560 --> 00:42:27,359
Speaker 3: an astronaut, So imagine you're an astronaut in your space

895
00:42:27,400 --> 00:42:29,720
Speaker 3: suit and you're out there in space, whether you're looking

896
00:42:29,760 --> 00:42:31,879
Speaker 3: away from your space ship or away from the Earth,

897
00:42:31,920 --> 00:42:34,040
Speaker 3: and you want to turn around to look at your

898
00:42:34,040 --> 00:42:36,080
Speaker 3: space ship or Earth, but you've run out of fuel

899
00:42:36,160 --> 00:42:39,319
Speaker 3: and maybe in your jetpack. How do you turn yourself around? Like,

900
00:42:39,360 --> 00:42:42,040
Speaker 3: you can't just like grab something and pull yourself to

901
00:42:42,080 --> 00:42:44,080
Speaker 3: look the other way. And you can't just like flail

902
00:42:44,440 --> 00:42:46,719
Speaker 3: your arms because it would be hard to sort of

903
00:42:46,920 --> 00:42:47,840
Speaker 3: change your orientation.

904
00:42:47,920 --> 00:42:50,360
Speaker 1: Yeah, even just flailing your arms won't do it right.

905
00:42:50,520 --> 00:42:53,480
Speaker 1: You can't by flailing your arms apply any overall force

906
00:42:53,640 --> 00:42:56,640
Speaker 1: to yourself. So this seems like an unsolvable problem, and

907
00:42:56,680 --> 00:42:59,320
Speaker 1: the way to solve it is to find a loophole

908
00:42:59,560 --> 00:43:01,200
Speaker 1: is to say, well, what if I don't want to

909
00:43:01,239 --> 00:43:04,080
Speaker 1: turn the whole telescope? What if I only want to

910
00:43:04,120 --> 00:43:06,960
Speaker 1: turn part of the telescope. So imagine like an invisible

911
00:43:06,960 --> 00:43:09,440
Speaker 1: dividing line. You say, this part of the telescope I

912
00:43:09,440 --> 00:43:11,359
Speaker 1: want to turn because it's got the cameras on it,

913
00:43:11,440 --> 00:43:14,280
Speaker 1: and this other part of the telescope has the electronics

914
00:43:14,280 --> 00:43:16,160
Speaker 1: and all the other stuff. They can't see anything, so

915
00:43:16,160 --> 00:43:18,480
Speaker 1: I don't really care about that one. So instead of

916
00:43:18,480 --> 00:43:20,360
Speaker 1: turning the whole telescope. What if you just want to

917
00:43:20,360 --> 00:43:22,719
Speaker 1: turn part of the telescope one way, you could do

918
00:43:22,760 --> 00:43:25,880
Speaker 1: that by turning the other part the other way. I imagine,

919
00:43:25,920 --> 00:43:28,960
Speaker 1: for example, having two ice skaters that are skating together.

920
00:43:29,320 --> 00:43:31,440
Speaker 1: One of them can start spinning if they push against

921
00:43:31,440 --> 00:43:34,640
Speaker 1: the other one. Right, So instead of turning the whole telescope,

922
00:43:34,680 --> 00:43:36,880
Speaker 1: just turn the part of the telescope you want to

923
00:43:36,960 --> 00:43:39,520
Speaker 1: actually use to look at the universe by pushing it

924
00:43:39,560 --> 00:43:41,400
Speaker 1: against another part of the telescope.

925
00:43:41,480 --> 00:43:44,200
Speaker 3: M or maybe instead of ice skaters, you can imagine

926
00:43:44,600 --> 00:43:47,719
Speaker 3: our stranded astronaut out there in space. You know, they

927
00:43:47,760 --> 00:43:49,680
Speaker 3: can't look in a particular way by themselves, but if

928
00:43:49,719 --> 00:43:52,319
Speaker 3: they had a buddy or a friend, like, one of

929
00:43:52,360 --> 00:43:55,520
Speaker 3: them could push against the other one and at least

930
00:43:55,520 --> 00:43:57,239
Speaker 3: one of them can look back at Earth or at

931
00:43:57,280 --> 00:43:57,800
Speaker 3: their spaceship.

932
00:43:57,840 --> 00:44:00,240
Speaker 1: Exactly. If you don't care what your buddy gets to see,

933
00:44:00,480 --> 00:44:03,040
Speaker 1: then you can turn in one direction by pushing against

934
00:44:03,320 --> 00:44:05,960
Speaker 1: him or her. And that's exactly what they do on

935
00:44:06,000 --> 00:44:08,400
Speaker 1: the space telescopes. They have a little part of it

936
00:44:08,440 --> 00:44:09,120
Speaker 1: called a react.

937
00:44:09,160 --> 00:44:12,280
Speaker 3: Got a buddy space telescope.

938
00:44:12,280 --> 00:44:16,160
Speaker 1: Buddy, it's got the important part and the not important part,

939
00:44:16,200 --> 00:44:18,279
Speaker 1: and the non important part is just there to help

940
00:44:18,320 --> 00:44:23,319
Speaker 1: the other part turn. It's the buddy, the sidekick, right,

941
00:44:23,480 --> 00:44:25,560
Speaker 1: and so. On a space telescope, this is called a

942
00:44:25,600 --> 00:44:29,640
Speaker 1: reaction wheel. Essentially, it's a little piece which turns the

943
00:44:29,719 --> 00:44:32,960
Speaker 1: opposite direction that the spacecraft does. So spacecraft says, I

944
00:44:33,040 --> 00:44:35,720
Speaker 1: want to go that way. Then the reaction wheel turns

945
00:44:35,760 --> 00:44:38,399
Speaker 1: the other way in order to balance it. So you're

946
00:44:38,440 --> 00:44:42,000
Speaker 1: not changing the overall angular momentum of this thing at all.

947
00:44:42,200 --> 00:44:44,719
Speaker 1: You're only changing the angle momentum of the part you

948
00:44:44,840 --> 00:44:46,640
Speaker 1: care about, and the part you don't care about. The

949
00:44:46,640 --> 00:44:50,400
Speaker 1: sidekick gets the opposite angular momentum, so physics is happy

950
00:44:50,800 --> 00:44:52,600
Speaker 1: and you get to point the part that you want

951
00:44:52,760 --> 00:44:53,560
Speaker 1: in the right direction.

952
00:44:53,800 --> 00:44:57,520
Speaker 3: M So I'm imagining like inside of the space telescope,

953
00:44:57,560 --> 00:45:01,839
Speaker 3: there's basically like just a big disc maybe right, or

954
00:45:01,880 --> 00:45:04,600
Speaker 3: like a big doughnut or cylinder that's that you can spin.

955
00:45:05,120 --> 00:45:05,760
Speaker 3: Is that the idea?

956
00:45:06,160 --> 00:45:07,240
Speaker 1: That's exactly the idea.

957
00:45:07,360 --> 00:45:09,439
Speaker 3: So if you want to turn like clockwise, you would

958
00:45:09,440 --> 00:45:12,200
Speaker 3: turn the doughnut or the disc counterclockwise.

959
00:45:13,200 --> 00:45:15,880
Speaker 1: Imagine you two astronauts. One of the ones to turn clockwise,

960
00:45:16,080 --> 00:45:18,400
Speaker 1: so he pushes against the other one and one of

961
00:45:18,400 --> 00:45:20,799
Speaker 1: them turns one way, the other one turns the other way. Now,

962
00:45:20,880 --> 00:45:23,200
Speaker 1: on the space telescope, you don't want like a second

963
00:45:23,239 --> 00:45:26,279
Speaker 1: telescope to push against, so you shrink the other part

964
00:45:26,320 --> 00:45:29,080
Speaker 1: down as much as you can. You make it massive

965
00:45:29,120 --> 00:45:31,640
Speaker 1: and make it spin really really fast, so it can

966
00:45:31,680 --> 00:45:34,160
Speaker 1: store a lot of angular momentum. And so the space

967
00:45:34,200 --> 00:45:37,040
Speaker 1: telescope has one of these for each direction it might

968
00:45:37,200 --> 00:45:38,120
Speaker 1: need to turn.

969
00:45:38,520 --> 00:45:41,719
Speaker 3: Hmmm, interesting, like up and down the side to side

970
00:45:41,719 --> 00:45:42,800
Speaker 3: in front of the back exactly.

971
00:45:42,840 --> 00:45:45,000
Speaker 1: So you need three of these to control your direction

972
00:45:45,440 --> 00:45:48,520
Speaker 1: complete the in space. Usually they have extras just in

973
00:45:48,560 --> 00:45:51,120
Speaker 1: case one of them breaks. But they're called reaction wheels

974
00:45:51,200 --> 00:45:53,480
Speaker 1: or momentum wheels, and they are fixed in place on

975
00:45:53,520 --> 00:45:55,640
Speaker 1: the sort of on the side of the telescope. They

976
00:45:55,680 --> 00:45:58,840
Speaker 1: spin many many times, like one thousand or four thousand

977
00:45:58,880 --> 00:45:59,840
Speaker 1: times a minute.

978
00:46:00,520 --> 00:46:04,440
Speaker 3: Now, I guess maybe I have two questions. One is, okay,

979
00:46:04,440 --> 00:46:06,239
Speaker 3: so I'm out there and floating a space and I

980
00:46:06,239 --> 00:46:09,720
Speaker 3: want to turn clockwise. So I spin my little wheel counterclockwise,

981
00:46:10,400 --> 00:46:14,800
Speaker 3: and that gets me to turn clockwise while the spinning

982
00:46:14,800 --> 00:46:17,640
Speaker 3: wheel is spinning inside of me. Now, let's say I

983
00:46:17,640 --> 00:46:20,120
Speaker 3: want to stop because I certainly I got some angular

984
00:46:20,160 --> 00:46:23,600
Speaker 3: momentum turning. How do I stop turning? Do I just

985
00:46:23,640 --> 00:46:24,759
Speaker 3: spin the wheel the other way?

986
00:46:25,040 --> 00:46:27,600
Speaker 1: Just spin the wheel the other way exactly, And so

987
00:46:27,680 --> 00:46:30,160
Speaker 1: you can apply whatever torque you want to yourself as

988
00:46:30,160 --> 00:46:32,560
Speaker 1: long as you're applying the opposite torque to the wheel,

989
00:46:32,760 --> 00:46:35,200
Speaker 1: and that works in both directions, and so the wheel

990
00:46:35,280 --> 00:46:37,760
Speaker 1: isn't like ever stationary. What you're doing is you're speeding

991
00:46:37,840 --> 00:46:40,520
Speaker 1: the wheel up or slowing the wheel down. And I

992
00:46:40,560 --> 00:46:43,920
Speaker 1: do that with a little electric motor which is solar powered.

993
00:46:44,120 --> 00:46:45,840
Speaker 1: So it is sort of like your Tesla as you

994
00:46:45,840 --> 00:46:46,600
Speaker 1: said earlier.

995
00:46:46,440 --> 00:46:49,480
Speaker 3: Yeah, or like the Prios right, or any car with battery,

996
00:46:49,560 --> 00:46:52,280
Speaker 3: Like when you break, you're putting energy into the battery,

997
00:46:52,800 --> 00:46:54,839
Speaker 3: then when you need to accelerate, you take energy from

998
00:46:54,920 --> 00:46:57,400
Speaker 3: the battery. So basically the same concept.

999
00:46:57,120 --> 00:47:01,080
Speaker 1: Right, basically the same concept exactly. You want to change orientation,

1000
00:47:01,160 --> 00:47:03,040
Speaker 1: you have to change the speed of the wheel to

1001
00:47:03,120 --> 00:47:05,360
Speaker 1: create a torque on the rest of the object. And

1002
00:47:05,400 --> 00:47:07,480
Speaker 1: so this thing spins really really fast, so it can

1003
00:47:07,520 --> 00:47:09,719
Speaker 1: store a lot of ing momentum, but it's still very

1004
00:47:09,840 --> 00:47:13,600
Speaker 1: small and low mass compared to the actual telescope, which

1005
00:47:13,640 --> 00:47:16,839
Speaker 1: means you can't turn the telescope very quickly. But that's good, right,

1006
00:47:16,920 --> 00:47:20,360
Speaker 1: you don't want this thing jerking around. They're not super

1007
00:47:20,440 --> 00:47:23,320
Speaker 1: duper powerful, but you don't ever need to ever change

1008
00:47:23,320 --> 00:47:25,400
Speaker 1: the telescope's direction really really quickly.

1009
00:47:26,000 --> 00:47:28,080
Speaker 3: It sort of feels like you got something for free

1010
00:47:28,200 --> 00:47:29,960
Speaker 3: or something for nothing, you know, do you know what

1011
00:47:30,000 --> 00:47:31,960
Speaker 3: I mean? Like I was pointing one way and then

1012
00:47:32,000 --> 00:47:34,040
Speaker 3: I did something, and now I'm pointing it another way,

1013
00:47:34,080 --> 00:47:36,000
Speaker 3: but I didn't lose really any energy.

1014
00:47:36,120 --> 00:47:39,560
Speaker 1: Yeah, there's two different aspects of this, energy and momentum.

1015
00:47:39,719 --> 00:47:43,279
Speaker 1: So momentum conservation is satisfied because part of you spun

1016
00:47:43,360 --> 00:47:45,360
Speaker 1: one way, the other parts spun the other way, so

1017
00:47:45,400 --> 00:47:48,120
Speaker 1: it adds up to zero. Just like your two astronauts,

1018
00:47:48,120 --> 00:47:50,839
Speaker 1: they could also split apart if they push against each other, right,

1019
00:47:50,840 --> 00:47:53,359
Speaker 1: they could float away in space. One you get back

1020
00:47:53,400 --> 00:47:55,280
Speaker 1: to the spaceship and the other one could be lost

1021
00:47:55,400 --> 00:47:58,319
Speaker 1: to infinity, and that would satisfy conservation and momentum. There'd

1022
00:47:58,320 --> 00:48:00,200
Speaker 1: be no net force on the pair of them, even

1023
00:48:00,239 --> 00:48:03,040
Speaker 1: though there is a force relative between them, so momentum

1024
00:48:03,080 --> 00:48:05,880
Speaker 1: is satisfied. But you're right, we are using energy, so

1025
00:48:05,960 --> 00:48:08,520
Speaker 1: this is not for free. You need to speed up

1026
00:48:08,560 --> 00:48:11,919
Speaker 1: that reaction wheel or slow down that reaction wheel that

1027
00:48:12,160 --> 00:48:14,840
Speaker 1: requires some energy, and so this thing is not for free.

1028
00:48:14,920 --> 00:48:17,759
Speaker 1: It does use some energy, but it doesn't need any propellant.

1029
00:48:18,400 --> 00:48:18,600
Speaker 3: Right.

1030
00:48:18,880 --> 00:48:22,200
Speaker 1: A rocket uses both energy and propellant, has to have

1031
00:48:22,239 --> 00:48:25,080
Speaker 1: some mask to throw out the side. This doesn't require

1032
00:48:25,120 --> 00:48:27,200
Speaker 1: any propellant, though it does use some energy.

1033
00:48:27,320 --> 00:48:29,160
Speaker 3: Yeah, I guess what I mean is like in the

1034
00:48:29,160 --> 00:48:32,560
Speaker 3: two astronaut example, if you and I are in space

1035
00:48:32,760 --> 00:48:35,680
Speaker 3: and I'm like, Daniel, save yourself. I'm going to push

1036
00:48:35,719 --> 00:48:39,279
Speaker 3: you towards the spaceship to save yourself, and I push you.

1037
00:48:39,280 --> 00:48:42,280
Speaker 3: You're moving towards the spaceship, but I'm not. I'm moving

1038
00:48:42,320 --> 00:48:44,640
Speaker 3: away from the spaceship. But then I'm what if? And

1039
00:48:44,640 --> 00:48:46,560
Speaker 3: then but it certainly it's like I changed my mind.

1040
00:48:46,600 --> 00:48:48,320
Speaker 3: I'm like, wait, wait, wait, no, that was a terrible idea,

1041
00:48:49,120 --> 00:48:51,600
Speaker 3: and I pull on the rope that was attached between

1042
00:48:51,680 --> 00:48:55,279
Speaker 3: us to bring us back together. Technically we would not

1043
00:48:55,680 --> 00:48:57,399
Speaker 3: like our center of masks would not have moved.

1044
00:48:57,440 --> 00:49:00,360
Speaker 1: That's right, right, Our center of mask cannot move without

1045
00:49:00,400 --> 00:49:03,239
Speaker 1: some external force. Right, So even if you don't change

1046
00:49:03,280 --> 00:49:05,759
Speaker 1: your mind and I drift back to the spaceship, you're

1047
00:49:05,840 --> 00:49:08,520
Speaker 1: drifting away from the spaceship. So our center of mass

1048
00:49:08,600 --> 00:49:09,880
Speaker 1: is not changing.

1049
00:49:09,719 --> 00:49:12,840
Speaker 3: Right, right, But then the spinning example with the space telescope,

1050
00:49:12,880 --> 00:49:15,080
Speaker 3: I kind of it sort of feels like you did

1051
00:49:15,080 --> 00:49:17,160
Speaker 3: get away with something, right. It's like you spun the

1052
00:49:17,239 --> 00:49:20,080
Speaker 3: mass one way and then you spin it the other way,

1053
00:49:20,120 --> 00:49:22,880
Speaker 3: and now you're in a different spot. Your total orientation

1054
00:49:23,080 --> 00:49:23,880
Speaker 3: changed direction.

1055
00:49:24,160 --> 00:49:27,200
Speaker 1: Well, part of the spaceship changes direction and another part

1056
00:49:27,320 --> 00:49:30,160
Speaker 1: changes direction in the opposite way, So the total angle

1057
00:49:30,239 --> 00:49:31,759
Speaker 1: momentum hasn't changed, right.

1058
00:49:31,760 --> 00:49:33,960
Speaker 3: But then when you slow down to stop, you spin

1059
00:49:34,040 --> 00:49:36,240
Speaker 3: it the other way, and presumably it's the same amount

1060
00:49:36,280 --> 00:49:38,480
Speaker 3: of momentum that you need to take out or put

1061
00:49:38,560 --> 00:49:40,640
Speaker 3: back in. So you and the wheel are in the

1062
00:49:40,680 --> 00:49:43,120
Speaker 3: same spot you started with, but both of you are

1063
00:49:43,160 --> 00:49:44,160
Speaker 3: pointing in a different direction.

1064
00:49:44,200 --> 00:49:47,000
Speaker 1: Now you're both pointing in a different direction, but the

1065
00:49:47,040 --> 00:49:50,680
Speaker 1: anglermentum hasn't changed. You've expended some energy, but the Anguler

1066
00:49:50,719 --> 00:49:51,640
Speaker 1: minum isn't different.

1067
00:49:51,719 --> 00:49:53,680
Speaker 3: Yeah, right, it sort of feels like you're getting something

1068
00:49:53,719 --> 00:49:54,080
Speaker 3: for free.

1069
00:49:54,360 --> 00:49:56,400
Speaker 1: Well, it's sort of like if the astronauts push against

1070
00:49:56,400 --> 00:49:58,880
Speaker 1: each other and they're further away, it costs some energy

1071
00:49:58,920 --> 00:50:01,880
Speaker 1: to change that configuration. It didn't change the overall momentum.

1072
00:50:02,080 --> 00:50:05,120
Speaker 3: Yeah, But in the astronaut example, they didn't move if

1073
00:50:05,160 --> 00:50:08,080
Speaker 3: they come back together. But in the wheelcase, you do

1074
00:50:08,600 --> 00:50:10,759
Speaker 3: sort of like move. You're not pointing in a different direction.

1075
00:50:10,840 --> 00:50:10,960
Speaker 6: Right.

1076
00:50:10,960 --> 00:50:13,120
Speaker 1: Well, in the astro in a case, imagine we're connected

1077
00:50:13,120 --> 00:50:15,760
Speaker 1: by ropes, you push against me so that I drifted

1078
00:50:15,800 --> 00:50:17,839
Speaker 1: back towards the ship, and you drift away from the ship,

1079
00:50:17,880 --> 00:50:19,560
Speaker 1: and then you change your mind, and so you tug

1080
00:50:19,640 --> 00:50:22,440
Speaker 1: on the rope to stop my motion, which also stops you.

1081
00:50:23,080 --> 00:50:25,680
Speaker 1: Now we're further apart than where we were, but we

1082
00:50:25,800 --> 00:50:28,240
Speaker 1: have no change in our center of mass, no change

1083
00:50:28,239 --> 00:50:30,880
Speaker 1: in our overall momentum. We've lost is you spent some

1084
00:50:31,040 --> 00:50:33,719
Speaker 1: energy pushing me away and then pulling me back. So

1085
00:50:33,760 --> 00:50:36,879
Speaker 1: in the same way, when you're orienting the telescope, you've

1086
00:50:36,960 --> 00:50:40,239
Speaker 1: changed its overall configuration, but there's no change in its

1087
00:50:40,239 --> 00:50:43,480
Speaker 1: overall angular momentum. That you have spent some energy to

1088
00:50:43,560 --> 00:50:46,319
Speaker 1: change the directions of both parts, the telescope and the

1089
00:50:46,400 --> 00:50:47,080
Speaker 1: reaction wheel.

1090
00:50:47,200 --> 00:50:47,480
Speaker 6: Hmm.

1091
00:50:47,960 --> 00:50:50,399
Speaker 3: Interesting, So well, well, I feel Also the other part

1092
00:50:50,520 --> 00:50:53,719
Speaker 3: question I had is isn't spinning a little wheel basically

1093
00:50:53,719 --> 00:50:55,920
Speaker 3: the same as flailing your arms? Like if I was

1094
00:50:55,920 --> 00:50:58,239
Speaker 3: stuck out there in space, could I also just like

1095
00:50:58,360 --> 00:51:01,120
Speaker 3: gonna spin my arm, and that would reorient myself.

1096
00:51:01,400 --> 00:51:04,520
Speaker 1: If you could turn your arm effectively into a reaction wheel,

1097
00:51:04,560 --> 00:51:07,160
Speaker 1: then yes, I don't know if you really could get

1098
00:51:07,160 --> 00:51:10,440
Speaker 1: your arm to spin independently along the same axis, though,

1099
00:51:10,760 --> 00:51:12,920
Speaker 1: I had to think about the biomechanics of it. Actually,

1100
00:51:12,960 --> 00:51:15,280
Speaker 1: you're an expert in that, aren't you. I'm not sure

1101
00:51:15,400 --> 00:51:18,080
Speaker 1: if you really can have it spinned independently, or if

1102
00:51:18,080 --> 00:51:20,279
Speaker 1: when you're moving in it, or if you're moving in

1103
00:51:20,320 --> 00:51:23,440
Speaker 1: a circle, if you're effectively pushing back on your body.

1104
00:51:23,520 --> 00:51:25,799
Speaker 1: But yes, if you, for example, ripped your arm off

1105
00:51:25,840 --> 00:51:29,120
Speaker 1: and attached it via mechanical axle to your body, then

1106
00:51:29,239 --> 00:51:31,080
Speaker 1: by spinning it you could change your direction.

1107
00:51:33,680 --> 00:51:36,040
Speaker 3: That seems a little dramatic, but I think the answer,

1108
00:51:36,440 --> 00:51:38,440
Speaker 3: since you say that I'm the expert, I think the

1109
00:51:38,440 --> 00:51:40,719
Speaker 3: answer is yes, I think you could do that. It's

1110
00:51:40,800 --> 00:51:42,600
Speaker 3: kind of the reason why when you jump off a

1111
00:51:42,640 --> 00:51:45,960
Speaker 3: cliff into the water, for example, or of a diving board,

1112
00:51:46,239 --> 00:51:49,480
Speaker 3: people fail their arms. They sort of like move them

1113
00:51:49,480 --> 00:51:51,840
Speaker 3: like a windmill, and that because they're trying not to

1114
00:51:51,920 --> 00:51:53,160
Speaker 3: fall on their face in the water.

1115
00:51:53,280 --> 00:51:55,959
Speaker 1: Yeah. Well, I'll trust you on whether that's possible. I'd

1116
00:51:55,960 --> 00:51:58,759
Speaker 1: prefer the cleaner physics, but more gory example where you

1117
00:51:58,760 --> 00:52:00,880
Speaker 1: actually pull the arm off. But I trust you that

1118
00:52:00,920 --> 00:52:03,440
Speaker 1: it's possible even without fulling your arm.

1119
00:52:04,080 --> 00:52:06,120
Speaker 3: All right, we're in space. You can rip your arm out,

1120
00:52:06,520 --> 00:52:09,919
Speaker 3: and but in order to look back at the spaceship.

1121
00:52:10,520 --> 00:52:12,120
Speaker 3: Although I'm not sure what you're going to do once

1122
00:52:12,160 --> 00:52:13,799
Speaker 3: you get the spaceship, how are you going to open

1123
00:52:13,800 --> 00:52:17,359
Speaker 3: the door? And I'll do my way and we'll see

1124
00:52:17,400 --> 00:52:17,879
Speaker 3: how that goes?

1125
00:52:17,920 --> 00:52:19,800
Speaker 1: All right, Well, we'll see if the door was designed

1126
00:52:19,800 --> 00:52:21,160
Speaker 1: to be open one handed.

1127
00:52:21,320 --> 00:52:25,680
Speaker 3: Just if your space suit was the signed for arm removal.

1128
00:52:25,760 --> 00:52:27,840
Speaker 1: I'm not saying it's more practical. I'm just saying the

1129
00:52:27,880 --> 00:52:29,320
Speaker 1: physics of it is clearer.

1130
00:52:29,480 --> 00:52:32,200
Speaker 3: I see, I see, And that's more important than your arm.

1131
00:52:32,320 --> 00:52:35,279
Speaker 1: I guess in this scenario, if it's just hypothetical and

1132
00:52:35,320 --> 00:52:37,800
Speaker 1: I want to give the accurate physics answer, then yes,

1133
00:52:38,200 --> 00:52:41,160
Speaker 1: I prefer the more gruesome but clear physics scenario.

1134
00:52:41,440 --> 00:52:43,360
Speaker 3: Right, I think as an engineer, I will try my

1135
00:52:43,520 --> 00:52:47,760
Speaker 3: way first to see if it works, rather than sticking

1136
00:52:47,880 --> 00:52:49,439
Speaker 3: to the physics dogma here.

1137
00:52:51,080 --> 00:52:53,480
Speaker 1: All right, but you can be expending valuable oxygen as

1138
00:52:53,480 --> 00:52:54,280
Speaker 1: you do your experiment.

1139
00:52:54,360 --> 00:52:56,560
Speaker 3: All right, So then is this how the James Webb

1140
00:52:56,640 --> 00:52:59,080
Speaker 3: space does Cup orient itself? Do they have does it

1141
00:52:59,160 --> 00:53:01,799
Speaker 3: have the spinning wheel? Did the Hubble also do this?

1142
00:53:02,000 --> 00:53:05,439
Speaker 1: Yeah, so basically every spacecraft does this. James Webb has

1143
00:53:05,680 --> 00:53:08,399
Speaker 1: six of these reaction wheels that are spinning that help

1144
00:53:08,440 --> 00:53:11,799
Speaker 1: it turn. Hubble has these things. Kepler has these things.

1145
00:53:11,800 --> 00:53:15,080
Speaker 1: And Kepler is a fascinating story because these things failed

1146
00:53:15,160 --> 00:53:18,000
Speaker 1: on Kepler, which made it very, very difficult for Kepler

1147
00:53:18,040 --> 00:53:18,920
Speaker 1: to do its mission.

1148
00:53:19,320 --> 00:53:20,880
Speaker 3: M what happened?

1149
00:53:20,960 --> 00:53:23,319
Speaker 1: So Kepler, launched in two thousand and nine, had four

1150
00:53:23,360 --> 00:53:25,759
Speaker 1: of these reaction wheels. You only nearly need three, but

1151
00:53:25,840 --> 00:53:28,480
Speaker 1: it had a spare just for good measure. And remember,

1152
00:53:28,560 --> 00:53:32,200
Speaker 1: Kepler is a telescope that's looking for planets to eclipse

1153
00:53:32,239 --> 00:53:34,160
Speaker 1: their stars. So you got to watch a star for

1154
00:53:34,239 --> 00:53:37,439
Speaker 1: a while, for a long time to see one ten

1155
00:53:37,560 --> 00:53:41,120
Speaker 1: thousands drop in brightness as a planet goes across the star,

1156
00:53:41,440 --> 00:53:43,400
Speaker 1: so you really got to be focused on it. A

1157
00:53:43,440 --> 00:53:46,239
Speaker 1: few years into its mission, in twenty twelve, one of

1158
00:53:46,280 --> 00:53:49,480
Speaker 1: these things failed and they didn't understand why. But that's okay.

1159
00:53:49,600 --> 00:53:51,319
Speaker 1: They were had four, so they had one spare. They

1160
00:53:51,360 --> 00:53:53,640
Speaker 1: were okay with three, and then the next year they lost.

1161
00:53:53,719 --> 00:53:55,880
Speaker 3: Wait, I have a question, like, you need one for

1162
00:53:55,920 --> 00:53:59,359
Speaker 3: every direction, right, up, down, left, and right from the back.

1163
00:54:00,040 --> 00:54:01,040
Speaker 3: Which one is your spare?

1164
00:54:01,160 --> 00:54:01,279
Speaker 1: Like?

1165
00:54:01,560 --> 00:54:03,480
Speaker 3: Can you spur point in all three directions?

1166
00:54:03,640 --> 00:54:05,759
Speaker 1: Yeah, good question. I don't know the answer. I guess

1167
00:54:05,800 --> 00:54:07,359
Speaker 1: the engineers have probably figured that out.

1168
00:54:07,560 --> 00:54:10,840
Speaker 3: Okay, So then Kepler lost one and they activated the spare,

1169
00:54:11,040 --> 00:54:12,120
Speaker 3: and then what happened.

1170
00:54:11,800 --> 00:54:14,560
Speaker 1: And then they lost another one in twenty thirteen, so

1171
00:54:14,600 --> 00:54:18,160
Speaker 1: now they only had two, which limits how the spacecraft

1172
00:54:18,200 --> 00:54:20,799
Speaker 1: can turn right. And this thing has to be able

1173
00:54:20,840 --> 00:54:23,680
Speaker 1: to turn in three D to track an arbitrary star.

1174
00:54:24,000 --> 00:54:26,000
Speaker 1: So people were pretty bummed. They spent a lot of

1175
00:54:26,000 --> 00:54:28,760
Speaker 1: time and money on this spacecraft, and also it costs

1176
00:54:28,800 --> 00:54:31,000
Speaker 1: money to operate. It's not like once you have it

1177
00:54:31,080 --> 00:54:33,800
Speaker 1: up there in space it's free. This's thing costs millions

1178
00:54:33,800 --> 00:54:36,319
Speaker 1: of dollars to operate the deep space network and the

1179
00:54:36,320 --> 00:54:39,279
Speaker 1: people and all electronics and everything. So it's a real

1180
00:54:39,440 --> 00:54:41,880
Speaker 1: question of like you just shut the thing down or

1181
00:54:41,920 --> 00:54:44,640
Speaker 1: do you try to figure out another way to operate

1182
00:54:44,680 --> 00:54:45,440
Speaker 1: this telescope.

1183
00:54:46,160 --> 00:54:49,400
Speaker 3: I wonder I'm guessing the answers no, because otherwise they

1184
00:54:49,400 --> 00:54:50,719
Speaker 3: would have figured that out. But I wonder if you

1185
00:54:50,760 --> 00:54:53,640
Speaker 3: can just use two to orient yourself in any direction

1186
00:54:53,719 --> 00:54:56,799
Speaker 3: in space. You know what I mean, because the orientations

1187
00:54:56,800 --> 00:54:59,840
Speaker 3: in space are these kinds of weird transformations where you

1188
00:54:59,840 --> 00:55:02,479
Speaker 3: can and like if you wanted to point to the right,

1189
00:55:02,600 --> 00:55:04,960
Speaker 3: you could, but you don't have something that turns it

1190
00:55:05,000 --> 00:55:08,040
Speaker 3: to the right. You could maybe point down, turn left,

1191
00:55:08,560 --> 00:55:10,800
Speaker 3: or you know, turn the other way and then switch

1192
00:55:10,880 --> 00:55:13,640
Speaker 3: back and do some weird complicated maneuver to get you

1193
00:55:13,680 --> 00:55:14,279
Speaker 3: to point right.

1194
00:55:14,360 --> 00:55:17,200
Speaker 1: Well, these things are orthogonal from each other, and so

1195
00:55:17,360 --> 00:55:20,719
Speaker 1: having only two basically only lets you map out a

1196
00:55:20,840 --> 00:55:23,600
Speaker 1: plane in a three D space.

1197
00:55:23,480 --> 00:55:26,279
Speaker 3: Like it used one to turn one way, then that

1198
00:55:26,480 --> 00:55:29,520
Speaker 3: reorients the other one, doesn't it, So you essentially kind

1199
00:55:29,560 --> 00:55:30,800
Speaker 3: of can point in any direction.

1200
00:55:31,040 --> 00:55:32,719
Speaker 1: No, yeah, that's a really good point, and I think

1201
00:55:32,719 --> 00:55:34,680
Speaker 1: that that's essentially what they tried to do. But you

1202
00:55:34,760 --> 00:55:37,239
Speaker 1: still need help in that third direction because you don't

1203
00:55:37,280 --> 00:55:39,239
Speaker 1: want to drift right. You don't want to drift in

1204
00:55:39,280 --> 00:55:42,120
Speaker 1: that third direction. And once you've turned and pointed at

1205
00:55:42,160 --> 00:55:45,360
Speaker 1: the star, now you've used your two reaction wheels along

1206
00:55:45,400 --> 00:55:48,480
Speaker 1: those two planes, which means you're susceptible. You're always susceptible

1207
00:55:48,520 --> 00:55:51,040
Speaker 1: to moving in that third dimension, and so in order

1208
00:55:51,080 --> 00:55:54,200
Speaker 1: to correct you then need to turn twice basically in

1209
00:55:54,280 --> 00:55:56,840
Speaker 1: order to correct which you'd bring you off of the star.

1210
00:55:57,200 --> 00:55:59,520
Speaker 1: So they actually came up with an ingenious way to

1211
00:55:59,560 --> 00:56:01,040
Speaker 1: try to that from happening.

1212
00:56:01,320 --> 00:56:03,480
Speaker 3: Oh, I see what you're saying is that you could

1213
00:56:04,200 --> 00:56:08,200
Speaker 3: point anywhere you want with maybe two a reaction wheels active,

1214
00:56:08,320 --> 00:56:12,040
Speaker 3: but you wouldn't be able to maybe track a star smoothly.

1215
00:56:12,160 --> 00:56:14,520
Speaker 1: Yeah, you might have to take like zigzags, right, and

1216
00:56:14,560 --> 00:56:16,759
Speaker 1: which means you couldn't keep it in your field of view.

1217
00:56:17,560 --> 00:56:18,440
Speaker 3: So then what did they do?

1218
00:56:18,600 --> 00:56:20,680
Speaker 1: So they came up with this really cool scheme to

1219
00:56:20,840 --> 00:56:24,000
Speaker 1: use the sun. Right, the Sun is actually pushing on

1220
00:56:24,040 --> 00:56:26,839
Speaker 1: these things. Remember our conversation earlier about like zapping a

1221
00:56:26,880 --> 00:56:29,880
Speaker 1: solar sail attached to a telescope with lasers from Earth.

1222
00:56:30,040 --> 00:56:32,920
Speaker 1: They basically are doing that, except they're using sunlight instead

1223
00:56:32,920 --> 00:56:35,520
Speaker 1: of lasers from Earth. So as it moves around the Sun,

1224
00:56:35,719 --> 00:56:38,840
Speaker 1: the solar wind and the photons push against the solar

1225
00:56:38,920 --> 00:56:43,120
Speaker 1: panels on Kepler, and so now instead of compensating for that,

1226
00:56:43,160 --> 00:56:45,360
Speaker 1: they're using that to help keep it stable.

1227
00:56:45,760 --> 00:56:47,920
Speaker 3: Interesting using the solar wind.

1228
00:56:48,040 --> 00:56:51,440
Speaker 1: Yeah, they're actually using the photon pressure, right, not just

1229
00:56:51,480 --> 00:56:53,600
Speaker 1: the solar wind, but the actual photon pressure. It's like

1230
00:56:53,640 --> 00:56:56,080
Speaker 1: a solar sail, So the solar panels are in sort

1231
00:56:56,120 --> 00:56:59,600
Speaker 1: of like a hexagon around Kepler and if the pointy

1232
00:56:59,640 --> 00:57:01,840
Speaker 1: part where the solar panels meet, if that thing is

1233
00:57:01,880 --> 00:57:04,799
Speaker 1: oriented right along the direction of the photons, then it

1234
00:57:04,840 --> 00:57:07,799
Speaker 1: sort of stays stable and it's turned a little bit,

1235
00:57:07,840 --> 00:57:10,759
Speaker 1: then it's unstable. So they can use that orientation to

1236
00:57:10,800 --> 00:57:13,719
Speaker 1: help either push on the spacecraft or to keep it.

1237
00:57:13,640 --> 00:57:16,800
Speaker 3: Stable, but would that help it track a start?

1238
00:57:17,000 --> 00:57:19,080
Speaker 1: It really limits what they can do. They can only

1239
00:57:19,120 --> 00:57:21,320
Speaker 1: look at sort of a couple different places in the sky,

1240
00:57:21,560 --> 00:57:24,160
Speaker 1: but for a couple of spots in its orbit around

1241
00:57:24,240 --> 00:57:27,320
Speaker 1: the Sun, they can use the Sun to compensate for

1242
00:57:27,400 --> 00:57:29,920
Speaker 1: the lack of the third reaction wheel and keep it

1243
00:57:29,960 --> 00:57:32,080
Speaker 1: stable and keep it tracked on a planet for a

1244
00:57:32,120 --> 00:57:34,720
Speaker 1: little while. So it's not a complete recovery of its

1245
00:57:34,760 --> 00:57:37,800
Speaker 1: abilities by any means, but it's a partial recovery of

1246
00:57:37,840 --> 00:57:38,960
Speaker 1: the science mission.

1247
00:57:40,200 --> 00:57:43,520
Speaker 3: Cool. Well, that's a pretty clever technology, I guess, although

1248
00:57:43,520 --> 00:57:45,360
Speaker 3: I feel like they should change the name from reaction

1249
00:57:45,440 --> 00:57:47,440
Speaker 3: wheels to flailing arms.

1250
00:57:48,640 --> 00:57:51,040
Speaker 1: It's a really big bummer that these things went bad.

1251
00:57:51,080 --> 00:57:54,960
Speaker 1: They've been trying to understand what happened, and in twenty seventeen,

1252
00:57:55,000 --> 00:57:57,360
Speaker 1: there's a paper that came out that suggests that it's

1253
00:57:57,480 --> 00:58:01,720
Speaker 1: due to geomagnetic storms from the Basically, the Sun has

1254
00:58:01,760 --> 00:58:04,600
Speaker 1: like some big energetic event. It dumps out a bunch

1255
00:58:04,640 --> 00:58:07,560
Speaker 1: of plasma and a coronal mass ejection, and as this

1256
00:58:07,720 --> 00:58:11,160
Speaker 1: passes through the spacecraft, it interferes with the operation of

1257
00:58:11,200 --> 00:58:12,120
Speaker 1: the reaction wheel.

1258
00:58:12,200 --> 00:58:12,600
Speaker 12: Wow.

1259
00:58:12,840 --> 00:58:16,320
Speaker 3: Yeah, that's pretty cool and also a pretty convenient story

1260
00:58:18,280 --> 00:58:21,640
Speaker 3: to make up for the fact that the era the

1261
00:58:21,680 --> 00:58:24,160
Speaker 3: thing you design did not last as much as you

1262
00:58:24,520 --> 00:58:25,000
Speaker 3: thought it would.

1263
00:58:25,160 --> 00:58:28,560
Speaker 1: Yeah, and these reaction wheels are very specialized technology. This

1264
00:58:28,720 --> 00:58:31,240
Speaker 1: one manufacturer that has been putting these things out it's

1265
00:58:31,240 --> 00:58:34,120
Speaker 1: called Ithaco, and their reaction wheels have failed not just

1266
00:58:34,160 --> 00:58:38,080
Speaker 1: on Kepler, but also on other spacecraft. So James web

1267
00:58:38,120 --> 00:58:41,320
Speaker 1: actually went to a different manufacturer to produce these things.

1268
00:58:41,640 --> 00:58:44,280
Speaker 1: So we're hoping that James Webb's reaction wheels last a

1269
00:58:44,320 --> 00:58:44,840
Speaker 1: lot longer.

1270
00:58:44,880 --> 00:58:47,960
Speaker 3: Interesting, and so that is a pretty clever way to

1271
00:58:48,000 --> 00:58:51,320
Speaker 3: turn yourself in space to have these reaction wheels. And

1272
00:58:51,360 --> 00:58:54,600
Speaker 3: so basically the space tells goes use them, Do other

1273
00:58:54,640 --> 00:58:57,440
Speaker 3: spacecraft use them like the voyage you're used that, or

1274
00:58:57,640 --> 00:59:00,320
Speaker 3: do some of these like the Parker Solar Pro does

1275
00:59:00,320 --> 00:59:00,920
Speaker 3: it use that too.

1276
00:59:01,200 --> 00:59:03,640
Speaker 1: Some other spacecraft do use these kind of things, but

1277
00:59:03,680 --> 00:59:07,040
Speaker 1: remember they're very slow, so they're not great for navigation.

1278
00:59:07,120 --> 00:59:10,680
Speaker 1: They're really just great for like very gentle orientation. Another

1279
00:59:10,760 --> 00:59:13,440
Speaker 1: example is light Sale. Light Sale is one of these

1280
00:59:13,440 --> 00:59:16,360
Speaker 1: things that's testing out the ability to sail on sunlight.

1281
00:59:16,640 --> 00:59:18,880
Speaker 1: There's a huge solar sale that it's using to gather

1282
00:59:19,000 --> 00:59:22,320
Speaker 1: momentum and navigate around the Solar system. But they also

1283
00:59:22,360 --> 00:59:24,440
Speaker 1: want to be able to steer this thing, and so

1284
00:59:24,480 --> 00:59:26,640
Speaker 1: they have a reaction wheel on it to try to

1285
00:59:26,680 --> 00:59:29,160
Speaker 1: turn it sort of towards and away from the Sun

1286
00:59:29,560 --> 00:59:30,960
Speaker 1: to change how it's sailing.

1287
00:59:31,080 --> 00:59:32,400
Speaker 3: So then it only needs one wheel.

1288
00:59:32,480 --> 00:59:34,880
Speaker 1: It only needs one wheel. Yeah, though it's also sort

1289
00:59:34,880 --> 00:59:36,760
Speaker 1: of experimental craft, and so I think they're trying to

1290
00:59:36,800 --> 00:59:39,840
Speaker 1: be simpler and cheaper. Everybody would love to have more

1291
00:59:39,880 --> 00:59:41,960
Speaker 1: of these wheels, and a lot of the spacecraft have

1292
00:59:42,040 --> 00:59:46,200
Speaker 1: a combination of reaction wheels and chemical thrusters. Chemical thrusters

1293
00:59:46,200 --> 00:59:49,160
Speaker 1: are for when you've like saturated your reaction wheel it

1294
00:59:49,200 --> 00:59:51,960
Speaker 1: can't turn anymore because it's already spinning in it's max rpm,

1295
00:59:52,400 --> 00:59:54,640
Speaker 1: or when you need to turn faster than you can

1296
00:59:54,720 --> 00:59:56,680
Speaker 1: with your reaction wheels that you want to use your

1297
00:59:56,720 --> 00:59:59,600
Speaker 1: chemical thrusters very sparingly because you just use up the

1298
00:59:59,640 --> 01:00:03,320
Speaker 1: mass and then eventually you run out cool.

1299
01:00:03,600 --> 01:00:06,880
Speaker 3: Well, overall, a pretty clever solution to move yourself at

1300
01:00:06,920 --> 01:00:08,680
Speaker 3: least in orientation in space.

1301
01:00:08,800 --> 01:00:11,160
Speaker 1: Yeah, it's a very clever idea and what I think

1302
01:00:11,200 --> 01:00:12,800
Speaker 1: we'll be using for a long time in the future.

1303
01:00:12,920 --> 01:00:15,560
Speaker 1: If we can make these things more reliable and if

1304
01:00:15,560 --> 01:00:17,320
Speaker 1: they don't require tearing your arm off.

1305
01:00:17,320 --> 01:00:19,240
Speaker 3: Yes, let's try that solution.

1306
01:00:19,600 --> 01:00:25,800
Speaker 1: Second, So first zapping with lasers, second, tearing your arm

1307
01:00:25,840 --> 01:00:26,120
Speaker 1: off from me.

1308
01:00:29,640 --> 01:00:31,360
Speaker 3: That's right, I'm going to be up up there in

1309
01:00:31,360 --> 01:00:33,800
Speaker 3: space going Yes, you can go ahead and shoot the

1310
01:00:33,840 --> 01:00:36,920
Speaker 3: lasers at Daniel and let me know if that works.

1311
01:00:37,640 --> 01:00:39,760
Speaker 3: And if it does, then you can shoot them in me.

1312
01:00:40,160 --> 01:00:42,160
Speaker 3: But I'm going to be flailing my arms out here

1313
01:00:42,600 --> 01:00:44,000
Speaker 3: and I'll see you back into spaceship.

1314
01:00:44,000 --> 01:00:46,560
Speaker 1: I wonder if that big earth laser for zapping astronauts

1315
01:00:46,720 --> 01:00:49,160
Speaker 1: also has a joystick, and who gets to run that one?

1316
01:00:49,480 --> 01:00:50,720
Speaker 3: Oh man? Yeah?

1317
01:00:51,360 --> 01:00:51,560
Speaker 1: Yeah?

1318
01:00:51,560 --> 01:00:53,440
Speaker 3: And what kind of training that person needs to do,

1319
01:00:53,720 --> 01:00:57,280
Speaker 3: you know, likelay a lot of asteroids maybe, or a

1320
01:00:57,280 --> 01:00:59,880
Speaker 3: lot of halo Perhaps you want someone who can get

1321
01:00:59,920 --> 01:01:00,680
Speaker 3: a good headshot.

1322
01:01:00,800 --> 01:01:03,040
Speaker 1: Yeah, good, first try Fortnite experts.

1323
01:01:03,120 --> 01:01:05,480
Speaker 3: All right, Well, hopefully you did not get lost in

1324
01:01:05,560 --> 01:01:09,440
Speaker 3: this discussion and we navigated your brain to understanding how

1325
01:01:09,480 --> 01:01:12,720
Speaker 3: space telescopes move and orient themselves to look at the

1326
01:01:12,800 --> 01:01:13,960
Speaker 3: universe out there.

1327
01:01:13,840 --> 01:01:15,960
Speaker 1: And this is crucial to our ability to understand what

1328
01:01:16,200 --> 01:01:18,400
Speaker 1: is out there in the universe and to continue to

1329
01:01:18,440 --> 01:01:23,000
Speaker 1: build that physical and conceptual map of how the universe works.

1330
01:01:23,320 --> 01:01:25,400
Speaker 3: Thanks for joining us, See you next time.

1331
01:01:33,400 --> 01:01:36,200
Speaker 1: Thanks for listening, and remember that Daniel and Jorge Explain

1332
01:01:36,280 --> 01:01:40,280
Speaker 1: the Universe is a production of iHeartRadio. For more podcasts

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