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How do you navigate in deep space? · Daniel and Kelly’s Extraordinary Universe

0:08
Speaker 1: Hey, Daniel, do you remember the days before we had smartphones?
0:13
Speaker 1: I try not to think about it too much. Well,
0:15
Speaker 1: you can't live with that, Wikipedia do your fingertips? How
0:19
Speaker 1: else would I seem like an expert on anything? But no,
0:21
Speaker 1: mostly I couldn't live without the direction right. Yeah. Are
0:24
Speaker 1: you the kind of driver that needs to check them
0:26
Speaker 1: out every ten seconds? Oh? Yeah, that is me. I
0:29
Speaker 1: like to know exactly where I am on the surface
0:32
Speaker 1: of the air at all times. At all times, I
0:34
Speaker 1: need constant updates to make sure I've not gone off. Well,
0:37
Speaker 1: what are you gonna do when humans get out into space?
0:40
Speaker 1: Are you gonna get around there? I'm just gonna wait
0:42
Speaker 1: until there are enough cell towers or at least WiFi. Yeah,
0:46
Speaker 1: basic human survival needs in space, air, food, and WiFi. Hi.
1:07
Speaker 1: I'm Jorge. I'm a cartoonist and the creator of PhD comments. Hi.
1:10
Speaker 1: I'm Daniel. I'm a particle physicist, and I plan to
1:14
Speaker 1: be the one million person in space. One million there.
1:20
Speaker 1: You know there are seven billion of those, so you
1:21
Speaker 1: know you let's put it pretty far ahead in line. Yeah. Well,
1:24
Speaker 1: I don't want to be the first person, or the
1:26
Speaker 1: second person or the hundredth person, but I also don't
1:29
Speaker 1: want to be the last person. You don't want to
1:30
Speaker 1: go when it's still kind of new and fresh but
1:32
Speaker 1: not dangerous. I'm not a test pilot kind of a person.
1:35
Speaker 1: A million sounds about right. A million sounds about right,
1:38
Speaker 1: but hey, I'm flexible two million, million and a half.
1:40
Speaker 1: You know I'm not going to elbow my way in
1:42
Speaker 1: that line. Well, welcome to our podcast where you are
1:45
Speaker 1: first in line to hear this. It's called Daniel and
1:48
Speaker 1: Jorge Explain the Universe, a production of I Heart Radio
1:51
Speaker 1: where normally we take you on a mental trip around
1:54
Speaker 1: the cosmos, zooming out from the tiniest little particles that
1:57
Speaker 1: define the basic building blocks of the universe all the
2:00
Speaker 1: way out to the grandest structures that shape the nature
2:04
Speaker 1: of the cosmos itself. Yeah. I just think it was
2:06
Speaker 1: as your guide, as your personal GPS to all of
2:09
Speaker 1: the amazing and wonderful things that are in the universe
2:12
Speaker 1: and also all of the unknown things that are out
2:15
Speaker 1: there for us to discover. Do you think we're a
2:16
Speaker 1: good mental GPS. Sometimes we get lost, We get on
2:19
Speaker 1: a discussion about neutrinos and we end up talking about
2:21
Speaker 1: snack foods. Well, you know, I think detours are part
2:25
Speaker 1: of the fun of a trip. Right. I wish that
2:28
Speaker 1: my navigation like Siri would tell me, like, hey, pull
2:30
Speaker 1: over and get some chips. There's a good snack shop
2:33
Speaker 1: right here. Why not? Yeah, that should be a setting, right,
2:37
Speaker 1: suggests snacks. I like that suggests yeah, AI engineers, get
2:41
Speaker 1: on it. Not in a hurry. Should be maybe an
2:43
Speaker 1: option open to wonderful discovery. That's right. And on this
2:46
Speaker 1: podcast we try to open your mind to all the
2:49
Speaker 1: future wonderful discoveries that science will bring us. And we
2:52
Speaker 1: do that by talking about the cutting edge of science,
2:55
Speaker 1: all the questions that science has not answered, all the
2:58
Speaker 1: things scientists are trying to think ground, and all the
3:00
Speaker 1: technical problems they're trying to solve on their journey to
3:04
Speaker 1: give us the answers. Yeah, because I think sometimes to
3:06
Speaker 1: think about a journey of discovery is the journey itself,
3:10
Speaker 1: you know, and the friends you make along the way. Yeah,
3:15
Speaker 1: you know, not just where you go and what do
3:16
Speaker 1: you find when you get there? For also how do
3:18
Speaker 1: you get there and how do you how do you
3:20
Speaker 1: even know where to go when you're going? Yeah, I
3:22
Speaker 1: think people imagine that it's hard to get to Jupiter
3:26
Speaker 1: or Pluto because it's so far out there. It's just
3:28
Speaker 1: like you gotta throw a rock really far into space,
3:32
Speaker 1: but it's not just really far away. It's like very
3:35
Speaker 1: hard to find. You know. Pluto is a small rock
3:38
Speaker 1: in the vast, vast reaches of space. If you're gonna
3:41
Speaker 1: throw something in that direction, you have to be really precise.
3:44
Speaker 1: You have to really know how to aim it and
3:46
Speaker 1: have to be able to course correct along the way.
3:48
Speaker 1: And that turns out to be not so easy. It's
3:51
Speaker 1: much harder than stopping for snacks. Yeah, you know, they
3:53
Speaker 1: have good snacks and jubiter. You know, it makes a
3:56
Speaker 1: little gassy at the end, but you know it's all
3:59
Speaker 1: totally worth it, right right the Red Storm chips. I
4:02
Speaker 1: love this. Yeah. So today we're gonna be asking a
4:05
Speaker 1: question that I personally have had a lot of curiosity
4:08
Speaker 1: about over the years. I've always wondered about this question,
4:10
Speaker 1: and even more so now recently I've been rewatching all
4:13
Speaker 1: the Star Wars movies and so this is a question
4:16
Speaker 1: that's really present in my mind that I've been asking
4:18
Speaker 1: myself recently, And why is that? Are you imagining how
4:21
Speaker 1: you're going to navigate to your in law's house on
4:24
Speaker 1: the Jovian moons from your vacation place in Saturn or
4:27
Speaker 1: what inspires you to think about this? Well, my wife
4:30
Speaker 1: and I are immigrants, but we're not that that kind
4:31
Speaker 1: of alien. But no, I just kind of wondered, you know, Um,
4:37
Speaker 1: in Star Wars they always get lost or they pop
4:39
Speaker 1: up in all kinds of places, and so how do
4:41
Speaker 1: you know where you are? And how do you know
4:43
Speaker 1: where to go? Or you know, they talk about like
4:45
Speaker 1: a map of the galaxy, what does that even look like?
4:48
Speaker 1: Or how would that even be useful? Yeah, it's it's
4:50
Speaker 1: very rare that they're like, make a wrong turn. They're like,
4:53
Speaker 1: we're we supposed to turn left at that pulsar or right.
4:55
Speaker 1: I don't even really remember. It feels like that's all
4:58
Speaker 1: just sort of been integrated into the electron next they
5:00
Speaker 1: have in front of them. But those are hard problems, right,
5:02
Speaker 1: it's not necessarily trivial to figure out. Yeah, and if
5:05
Speaker 1: you think about it, in popular culture, there's only been
5:07
Speaker 1: like one TV show about getting lost in space. You mean,
5:11
Speaker 1: it was called space and you know at least you
5:15
Speaker 1: know what it's about. Yeah, So today on the program,
5:17
Speaker 1: we'll be asking the question, how do you navigate in
5:24
Speaker 1: space space, and this is a problem that's relevant to
5:29
Speaker 1: future navigation. Like imagine you are flying a spaceship with
5:32
Speaker 1: lots of people on board and trying to get everybody
5:34
Speaker 1: safely to Alpha Centauri. And it's also a question today
5:38
Speaker 1: as NASA and the E s A launched satellites to
5:41
Speaker 1: explore our Solar system. How do they make sure they
5:43
Speaker 1: get to the right spot? How do they course correct
5:46
Speaker 1: if they are off? Who does those calculations? Is that
5:48
Speaker 1: on board the satellite or back here on Earth? Are
5:51
Speaker 1: there people with protractors and pencils scribbling things furiously? How
5:55
Speaker 1: does that actually work? Yeah, because you know, space is
5:57
Speaker 1: pretty big, and it's three dementi all, you know, at
6:00
Speaker 1: least three dimensions at least, yeah that we know of
6:05
Speaker 1: that we think about right now. But it's a multi
6:07
Speaker 1: dimensional and you're out there and you know, there's no
6:11
Speaker 1: mountain to reference, no street signs. How do you get around?
6:15
Speaker 1: How do you know where to go? Do you think
6:17
Speaker 1: that third dimension is going to lead to like a
6:18
Speaker 1: lot more marital arguments in the future, Like I told
6:21
Speaker 1: you to turn up at that move man, why did
6:24
Speaker 1: you turn down? This is just like so many more
6:26
Speaker 1: ways to call new dimension to divorces. Probably no, but
6:32
Speaker 1: it is really hard and it's also vital because you're
6:34
Speaker 1: so much further away from your resources. Like these spaceships
6:39
Speaker 1: they leave Earth, they're never getting a refill, like they
6:41
Speaker 1: run out of gas because they got lost. They're just lost.
6:44
Speaker 1: So you have like a very limited window to make
6:47
Speaker 1: the moves you need to make to enter that orbit
6:50
Speaker 1: or to fly by the moon. There's no reduce, like
6:53
Speaker 1: you have a one tank and that's it. So it's
6:55
Speaker 1: absolutely critical that you don't get lost and that you
6:58
Speaker 1: figure out how to get where you need to go. Yeah, So,
7:01
Speaker 1: as usually, we were wondering how many people out there
7:04
Speaker 1: have thought about this question or even have an idea
7:06
Speaker 1: about how to navigate in space. So as usual, Daniel
7:09
Speaker 1: went out there and ask the internet to try to
7:12
Speaker 1: answer this question, how do you navigate in space? That's right,
7:15
Speaker 1: and if you'd like to participate in our virtual person
7:18
Speaker 1: on the street interviews, just shoot us an email two
7:21
Speaker 1: questions at Daniel and Jorge dot com. We would love
7:24
Speaker 1: to put your uninformed speculation on the podcast. And so
7:26
Speaker 1: think about it for a second. If you were out
7:28
Speaker 1: in space in the middle of the galaxy or in
7:31
Speaker 1: between galaxies? How would you know which way to make
7:34
Speaker 1: your way home? Here's what people had to say. Because
7:36
Speaker 1: gravity distill space and time and everything. Maybe you'd have
7:39
Speaker 1: to go. Maybe you'd have to shoot a little bit
7:42
Speaker 1: off it because as you as you go close to
7:46
Speaker 1: and an object, you'd kind of be taken into its
7:50
Speaker 1: gravitational swing. Other than that, I don't know how do
7:53
Speaker 1: you navigate through deep space to just keep a set
7:56
Speaker 1: of stars to your left and hopefully you're going the
7:59
Speaker 1: same direct action. I have no idea. Maybe like by
8:03
Speaker 1: distracting energy from the Sun, or if we're very patient,
8:08
Speaker 1: maybe with solar sales, we could navigate deep space, maybe
8:12
Speaker 1: through a pulse of a star, or like I don't know,
8:16
Speaker 1: pole stars or something. I think the only way you
8:18
Speaker 1: can navigating these spaces the way we do it now
8:20
Speaker 1: by using stars and galaxies, things that are consistent, not
8:24
Speaker 1: necessarily constellations, because that could you know, in three D
8:27
Speaker 1: space they have depth and they have angles that they
8:30
Speaker 1: are relative each other. You know, constellations do. But if
8:34
Speaker 1: you use stuff like pulsars and quasars and you know
8:36
Speaker 1: the Andromeda gag, see those things, we can coordinate ourselves
8:40
Speaker 1: using a couple of those angles, we can coordinate ourselves
8:42
Speaker 1: in deep space. I think navere taking in a deep
8:45
Speaker 1: space or americum woulds to need the bicycles of navigation.
8:51
Speaker 1: You're do either use inertial navigation, sitting time, speed, and
8:55
Speaker 1: directions from someone In a short stuff you will have
8:57
Speaker 1: to pick something like the sun and navigating reference to
9:03
Speaker 1: the sun. Let's see, if you're heading to a prime centuri,
9:06
Speaker 1: we should at least have an inbuilt special I had
9:09
Speaker 1: invisible telescopes, I mean lens and meadows and special lists
9:16
Speaker 1: and optimal path correction systems and some kind of special clocks.
9:23
Speaker 1: Navigating in deep space, I would have to assume is
9:26
Speaker 1: much like seiling the ocean. You look at the stars
9:29
Speaker 1: and see whe're at relative to the stars. After your
9:34
Speaker 1: statement that space is expanding faster than um the speed
9:39
Speaker 1: of light, or faster than light can travel through it,
9:43
Speaker 1: I really have no idea. Now I think you could
9:49
Speaker 1: go anywhere you you go. Yeah, well, hopefully you can
9:53
Speaker 1: do that, but how you do it? My idea would
9:56
Speaker 1: be to mount a big giant telescope on the top
9:59
Speaker 1: of your spacecraft, on the front and the back, so
10:03
Speaker 1: you can see where you're going and where you're where
10:05
Speaker 1: you came from. Maybe a telescope as big as hubble,
10:07
Speaker 1: because your spacecraft is going to have to be that big.
10:10
Speaker 1: After we leave the planet and learn about the like
10:14
Speaker 1: further stars that we don't see on Earth, we can
10:17
Speaker 1: pick three stars, and by keeping track of the distance
10:21
Speaker 1: between us and the stars, we can know our position.
10:25
Speaker 1: And when the stars are too far away, we can
10:29
Speaker 1: always peak three new stars that we found out about
10:35
Speaker 1: along the way in our journey. So there are a
10:37
Speaker 1: lot of ideas there. What do you think of that?
10:39
Speaker 1: Pretty good? Pretty good? I feel like people were sort
10:41
Speaker 1: of thinking about triangulation and using the stars somehow to
10:45
Speaker 1: tell where you are. I feel like that's a pretty
10:47
Speaker 1: common idea in science fiction movies and boots. It's like, oh,
10:50
Speaker 1: you just look at the stars around you, and do
10:53
Speaker 1: you know where you are and you know where to go?
10:55
Speaker 1: Or like if you look at the stars and you
10:56
Speaker 1: don't recognize things, then you're kind of in trouble. I
10:59
Speaker 1: like the I said, let's put a huge telescope on
11:01
Speaker 1: the front and on the back of your spaceship, because
11:04
Speaker 1: I want that anyway, Like, if I'm flying through space,
11:06
Speaker 1: I want a big telescope because I want to see
11:08
Speaker 1: with what stuffed around me. You know, I want to
11:10
Speaker 1: do some sight seeing when I'm out there. But what
11:12
Speaker 1: do you need one in the bag though, just to
11:14
Speaker 1: see the fit is of people that you leave behind. Well,
11:18
Speaker 1: because I mean, I guess you could turn your telescope.
11:20
Speaker 1: Maybe you're saying you'll need one telescope plus like a
11:23
Speaker 1: mount or something, but hey, more telescopes are better. Well,
11:27
Speaker 1: I feel like that is a sort of a common thing,
11:29
Speaker 1: is to look at the stars around you, and somehow
11:31
Speaker 1: you use that to orient yourself, you know, kind of
11:32
Speaker 1: like we use the North Star for a long time
11:35
Speaker 1: to kind of tell which way was north when you're
11:37
Speaker 1: out in the middle of the ocean. Is that kind
11:39
Speaker 1: of an idea that we can use at all? It
11:41
Speaker 1: is an idea that we can use. And the rest
11:43
Speaker 1: on this notion that if you have an accurate map
11:45
Speaker 1: of the stars, you can compare that to what you're
11:48
Speaker 1: seeing and look for landmarks and try to measure angles
11:51
Speaker 1: between the stars to give you a sense for where
11:54
Speaker 1: you are. For example, if two stars are almost lined
11:57
Speaker 1: up in your vision, then that tells you that you're
12:00
Speaker 1: along a line drawn between those two stars. And if
12:03
Speaker 1: you can find other examples measuring angles between stars, you
12:07
Speaker 1: can give you sort of a point in three D
12:09
Speaker 1: space for where you are at that moment. Well, I
12:12
Speaker 1: guess the problem that I have always should have thought
12:14
Speaker 1: about is like, what if you find yourself on the
12:15
Speaker 1: other side of the galaxy, how would you even recognize
12:18
Speaker 1: any of the stars because the stars are gonna look
12:20
Speaker 1: totally different from the other side of the galaxy. Yeah,
12:23
Speaker 1: if you just look at like teleported to a random
12:25
Speaker 1: place in the universe where you have no reference points,
12:28
Speaker 1: there's literally no way to know where you are because
12:31
Speaker 1: there's no absolute reference there's no like point in space
12:35
Speaker 1: that's defined in zero and you can measure your location
12:38
Speaker 1: relative to that. If you get teleported to an arbitrary
12:41
Speaker 1: point in space, special relativity says it's impossible to know
12:44
Speaker 1: where you are. You can only measure your distance relative
12:48
Speaker 1: to other stuff. So if you have no familiar references,
12:50
Speaker 1: you're totally screwed. Wow, and things are like changing in time. Also,
12:53
Speaker 1: everything's moving, so you're sort of totally lost in You're
12:56
Speaker 1: totally lost. You have. The only way to orient yourself
12:59
Speaker 1: in space is relative to known things. So if you
13:02
Speaker 1: get teleported to some part of space that's totally unfamiliar.
13:06
Speaker 1: Then you literally have no way to find your way
13:08
Speaker 1: back except for randomly exploring until you do find a landmark.
13:12
Speaker 1: And when I try that the next time I get
13:14
Speaker 1: lost and my spouse is complaining, I'm like, it's special relativity.
13:18
Speaker 1: It's it's law of the universe. It's not my fault.
13:20
Speaker 1: Daniel said, this should work. Don't you feel like smartphones
13:24
Speaker 1: must have solved this marital complaint? Right, houses don't have
13:27
Speaker 1: to argue about how to navigating anymore, and they just
13:29
Speaker 1: listened to the phone. That's right. The phone has saved
13:32
Speaker 1: a lot of marriages. Probably maybe, or maybe people are like, no,
13:35
Speaker 1: listen to my phone. Well, my phone says it's faster
13:38
Speaker 1: take the expressway using Google Maps. No way, we aren't
13:43
Speaker 1: using ways. People who argue are going to argue anyway.
13:46
Speaker 1: I guess, So I guess the phones can't fix that. Yeah,
13:50
Speaker 1: And you know, navigators in throughout history have used the stars.
13:53
Speaker 1: Like if you have sailed the oceans, then to figure
13:56
Speaker 1: out where you are in this vast sea where you
13:59
Speaker 1: can see no land marks is just to look up
14:01
Speaker 1: and look for star marks. Right, to look for the
14:04
Speaker 1: positions of stars in the sky that gives you a
14:06
Speaker 1: sense for where you might be. All right, well, let's
14:08
Speaker 1: get into the sort of the nitty gritty of this problem.
14:11
Speaker 1: And because I know you, you've told me that there
14:13
Speaker 1: are sort of several ways in which we can right
14:16
Speaker 1: now sort of calculate where we are in space, you know,
14:18
Speaker 1: barring kind of like a complete map of the entire galaxy. Um,
14:22
Speaker 1: so step us through. What's the what's the sort of
14:24
Speaker 1: the basic way that we get around in space. So
14:26
Speaker 1: the simplest way, in the dumbest way, and the worst
14:29
Speaker 1: way is basically dead reckoning. And that says you know
14:33
Speaker 1: where you started, and you started on Earth, and if
14:36
Speaker 1: you have a record of all the moves you took,
14:38
Speaker 1: you went in this direction at this velocity, you should
14:41
Speaker 1: be able to calculate where you went. Because you know,
14:43
Speaker 1: spacecraft follow the laws of physics, and we know what
14:46
Speaker 1: those laws are. We have a whole model of the
14:49
Speaker 1: Solar System, so we should be able to predict if
14:52
Speaker 1: you leave in this direction at this time, and you
14:55
Speaker 1: fire your rockets here and there, we should be able
14:57
Speaker 1: to predict where you end up. That's kind of like
15:00
Speaker 1: closing your eyes and like knowing where you are right now,
15:03
Speaker 1: closing your eyes and just by like counting your steps
15:06
Speaker 1: and how you think you turn, sort of like making
15:08
Speaker 1: it to your fridge or something like that. It's like
15:10
Speaker 1: following one of those treasure maps, like fifteen paces forward
15:13
Speaker 1: then turn left step four paces, then dig right right.
15:17
Speaker 1: And that's a little terrifying. Like if you remember the
15:19
Speaker 1: days before smartphones where people had to like actually write
15:22
Speaker 1: down directions and there were things like drive for fifteen
15:26
Speaker 1: miles then take a left right, and you had no
15:28
Speaker 1: idea is this the correct left or not? You know, yeah, yeah,
15:32
Speaker 1: and we all know how well that works. In the
15:33
Speaker 1: middle of the night when you have to go to
15:34
Speaker 1: the bathroom in total darkness, you know, you better put
15:39
Speaker 1: your hands in front of you, just in cakes. Yeah,
15:41
Speaker 1: and so sailors used to call this dead reckoning, and
15:44
Speaker 1: you know it's not terrible, like it works. Okay, we
15:47
Speaker 1: have a pretty good model of the solar system, and
15:49
Speaker 1: we have rockets, and we can even measure we don't
15:52
Speaker 1: even have to just guess. And like the effect of thrust,
15:54
Speaker 1: you can measure how much you've accelerated using accelerometers, you
15:59
Speaker 1: can measure your the direction that you ended up in
16:01
Speaker 1: using gyroscopes, So we've tried to be really careful about this,
16:05
Speaker 1: and some spacecraft in the history of you know, American
16:08
Speaker 1: exploration have used dead reckoning. But I guess it's tricky too,
16:11
Speaker 1: because you know, in space you can't count your steps,
16:15
Speaker 1: like there's nothing to hold onto to tell you how
16:17
Speaker 1: far you move. You have to you have to measure
16:20
Speaker 1: your exploration and then integrate DAD to convert to velocity,
16:24
Speaker 1: and then integrate DAT to convert it to distance. So
16:26
Speaker 1: it's like a lot of room there to get error. Yes,
16:29
Speaker 1: and you mentioned a very critical step there, which is integration,
16:33
Speaker 1: and that requires knowing the time. You can't count your steps.
16:36
Speaker 1: What you need is a very accurate clock. And the
16:39
Speaker 1: more accurate your clock, the more you accurately you can
16:42
Speaker 1: calculate how far you've gone. Right, you said I shot
16:45
Speaker 1: off in this direction of the speed, Well did you
16:47
Speaker 1: go for two point seven seconds or two point eight seconds?
16:50
Speaker 1: When you're traveling at ten thousand kilometers per second, that
16:53
Speaker 1: makes a big difference. Yeah, And when distances are so huge, right,
16:57
Speaker 1: and the stakes are so high, like you can't if
17:00
Speaker 1: you miss Jupiter by a few miles, it could be
17:02
Speaker 1: bad us. Yeah, as you're gonna do a Jupiter drive by, right,
17:05
Speaker 1: then you only get one shot at it, literally, and
17:08
Speaker 1: so it's pretty tricky. And the problem here is that
17:11
Speaker 1: errors build up, Like you make a little mistake because
17:13
Speaker 1: you turned a little too far, then you're off, and
17:16
Speaker 1: the next time you can't correct it, and so the
17:18
Speaker 1: errors just build up in the integrate and eventually you
17:21
Speaker 1: can be pretty far from where you thought you right.
17:23
Speaker 1: It literally is like walking around with your eyes closed. Yeah, exactly.
17:27
Speaker 1: So that's the most basic strategy, and you can make
17:30
Speaker 1: that more sophisticated by doing corrections. You can say, well,
17:33
Speaker 1: I'm gonna use dead reckoning. Plus I'm going to look
17:37
Speaker 1: at the stars and I'm gonna try to figure out
17:39
Speaker 1: if I'm off. And this is what like a lot
17:41
Speaker 1: of astronauts did, like Apollo eleven and follow their team.
17:44
Speaker 1: They flew to the Moon by dead reckoning, but occasionally
17:48
Speaker 1: they would check in and they would look at the
17:50
Speaker 1: stars and try to get a more precise measurement for
17:52
Speaker 1: where they were, and they would use that to correct
17:54
Speaker 1: their flight path. Really, so I guess two questions. One
17:57
Speaker 1: is why didn't they just use the moon as reference
18:00
Speaker 1: because they were flying towards it, and they could tell
18:03
Speaker 1: her they were going away from it or towards it.
18:06
Speaker 1: And the size of it too, wouldn't it tell you
18:08
Speaker 1: said of the distance? But and then my second question was,
18:11
Speaker 1: you know, can you actually use the stars to tell
18:13
Speaker 1: where you are? You can? So, yes, they were pointed
18:16
Speaker 1: at the moon. But that's pretty rough, right, And what
18:18
Speaker 1: you want to do was get to the Moon and
18:20
Speaker 1: then enter into orbit around the Moon. And that was
18:22
Speaker 1: a very precise maneuver. And just like with the spacecraft,
18:26
Speaker 1: they had a limited amount of fuel, so if they
18:28
Speaker 1: burnt their fuel the wrong time, they might not be
18:30
Speaker 1: able to make it home. I said. The fuel is
18:32
Speaker 1: very expensive to lift off the surface of the Earth,
18:34
Speaker 1: and so everything was a very tight budget, so they
18:37
Speaker 1: had to be really precise. There are no exactly you
18:41
Speaker 1: can't just pull a eui in space. That costs a
18:43
Speaker 1: lot of energy to pull ui. Like you missed the
18:45
Speaker 1: snack shop. You missed the snack shop, man, you are
18:48
Speaker 1: not going back. And yes, they did stellar navigation. They
18:51
Speaker 1: looked by I to find stars, and they measured the
18:54
Speaker 1: declination using gyroscopes and they use that to correct their calculations.
18:58
Speaker 1: A huge fraction of the time they actually spent in
19:01
Speaker 1: that module was typing data into that computer. You know,
19:05
Speaker 1: it's a complicated system. And remember the whole program was
19:08
Speaker 1: loaded into the computer before it launched, Like you didn't
19:11
Speaker 1: have guys up there, like you know, tip tapping editing
19:13
Speaker 1: the program being like I think we must change the
19:16
Speaker 1: flight path or something. They had it all built in
19:18
Speaker 1: with the opportunity for small corrections based on looking at
19:22
Speaker 1: those stars. So what do you mean declination like where
19:24
Speaker 1: the constellation was relative to the Earth or something like that. No,
19:27
Speaker 1: relative to them, Right, they had an idea for where
19:30
Speaker 1: they were, and they had an idea for if we
19:32
Speaker 1: are here, the stars should appear at this angle relative
19:35
Speaker 1: to the spaceship, and then they would measure where is
19:38
Speaker 1: the star relative to where the spaceship is pointing because
19:41
Speaker 1: I had careful gyroscopes and and those angles helped them
19:45
Speaker 1: figure out exactly where they are. All right, Well that
19:48
Speaker 1: sounds like, um it worked because they got to the
19:51
Speaker 1: a few times, So I can't argue with that. All right, Well,
19:55
Speaker 1: let's get into some of the other ways that we
19:57
Speaker 1: can navigate in space and whether or not they could
20:01
Speaker 1: help us explore the furthest switches of the Cosmos but first,
20:05
Speaker 1: let's take a quick break, all right, Dina. We're talking
20:19
Speaker 1: about navigating in space. Space, space, space, And I just
20:24
Speaker 1: wonder why there's always an echo when people talk about space,
20:27
Speaker 1: because there's no echoes in space. It's because it's cool, man,
20:31
Speaker 1: It's so cool cool. It makes it sound mysterious. It
20:35
Speaker 1: gives you a sense of literally space, right, echoes give
20:38
Speaker 1: you a sense a big emptiness. But you know that's
20:40
Speaker 1: just the um audio version of the artistic impression, which
20:45
Speaker 1: you know, I'm not a fan. You not a fan
20:46
Speaker 1: of the echoes in space. No, I'm a fan of
20:50
Speaker 1: realistic science fiction. It should give us a cent or
20:52
Speaker 1: what it's actually like to be out there. Though maybe
20:55
Speaker 1: you know, if you're in a kind of little metal box,
20:57
Speaker 1: maybe there are actually a lot of echoes, but inside
21:00
Speaker 1: I see. Well, we're talking about how to navigating space,
21:03
Speaker 1: which is a big question, you know. I feel like,
21:06
Speaker 1: you know, whenever you watch a movie like Star Wars,
21:08
Speaker 1: it's like how are they getting around? How do they
21:09
Speaker 1: know where to go? And so we talked about it
21:11
Speaker 1: one way, which is dead reckoning, Like if you know
21:13
Speaker 1: you're an Earth and you leave Earth, you can sort
21:15
Speaker 1: of track your progress, but then you also have to
21:17
Speaker 1: kind of correct your errors as you go. That's right,
21:19
Speaker 1: and a better way to do that is not just
21:22
Speaker 1: be based on your initial calculation from Earth, but it
21:25
Speaker 1: takes inspiration from how your smartphone gets you to your
21:29
Speaker 1: friend's house, which is that it gets messages from satellites.
21:33
Speaker 1: Here on Earth, we have the GPS system, which is
21:36
Speaker 1: constantly broadcasting messages. That's giving your phone an idea for
21:40
Speaker 1: where it is, and your phone figures out where it
21:43
Speaker 1: is by hearing these messages and knowing how long it
21:45
Speaker 1: took the message to get here from the satellite, and
21:48
Speaker 1: it uses that to figure out where the phone is
21:51
Speaker 1: right and it also uses like a map, like your
21:53
Speaker 1: phone knows where all the satellites should be at any time,
21:56
Speaker 1: so once it gets a signal, it sort of knows
21:58
Speaker 1: where it is, yeah, precisely in knows where the satellites are.
22:01
Speaker 1: And then it gets these messages. And the messages have
22:03
Speaker 1: a little time stamp on them. They say I sent
22:05
Speaker 1: this message at exactly this time, and if you get
22:08
Speaker 1: this message, you know, seventeen milliseconds later, then you know
22:11
Speaker 1: how far the message flew because you knew it flew
22:15
Speaker 1: at the speed of light. And you get enough of
22:17
Speaker 1: these things and you can figure out where you are.
22:19
Speaker 1: And there's an analogous system. There's GPS for deep space.
22:23
Speaker 1: There is there's a space GPS. Yeah, there's a space GPS,
22:26
Speaker 1: and it's called the Deep Space Network and NASA runs
22:30
Speaker 1: it and it basically sends messages out in deep space
22:33
Speaker 1: from three locations on the Earth, and satellites get those messages,
22:37
Speaker 1: send them back and then we can use that to
22:39
Speaker 1: figure out where the satellite is. It's like a reverse
22:43
Speaker 1: Why are you seriously, it's like a reverse GPS. It's
22:45
Speaker 1: like a reverse GPS. Yeah. What happens is you send
22:48
Speaker 1: a message to a satellite and then it comes back
22:51
Speaker 1: and you count, well, how long did it take for
22:53
Speaker 1: the message to go there and come back, And that
22:56
Speaker 1: gives you a sense for the distance. And then when
22:59
Speaker 1: the message comes it's a little bit Doppler shifted based
23:02
Speaker 1: on the speed of the satellite, and that tells you
23:05
Speaker 1: how fast this satellite is moving away from you. So
23:08
Speaker 1: it gives you a measure of the current position and
23:10
Speaker 1: the velocity of the satellite. But I guess that only
23:13
Speaker 1: works for satellites, right, like it doesn't work if from
23:16
Speaker 1: in Jupiter or does it. Well, it works for anybody
23:19
Speaker 1: that can receive these deep space messages and send them back.
23:22
Speaker 1: So it doesn't give you your position relative to Jupiter. Note,
23:25
Speaker 1: only gives you your position and velocity relative to Earth. Right,
23:29
Speaker 1: But like if you know where Earth is, what this
23:32
Speaker 1: signal help you know where you are in this solar system? No,
23:35
Speaker 1: because you can't actually do the calculation yourself. And that's
23:37
Speaker 1: one problem with this deep space network is that only
23:40
Speaker 1: Earth gets to figure it out. Earth gets your message,
23:43
Speaker 1: and then the second link gives Earth the information about
23:46
Speaker 1: where you are, and then the folks on Earth have
23:48
Speaker 1: to calculate Okay, turns out you were in this position
23:50
Speaker 1: and send it to you. So it's kind of a
23:53
Speaker 1: lot of back and forth. It's not that you can
23:55
Speaker 1: just get this message from the deep space network and
23:57
Speaker 1: figured it out yourself. The way your phone can from
24:00
Speaker 1: s GPS is one directional, right, because it comes with
24:02
Speaker 1: these time stamps. Right, So why why couldn't this work
24:06
Speaker 1: the same way? The reason is the clock. The clock
24:08
Speaker 1: on the satellite is not very good because really accurate
24:11
Speaker 1: clocks are necessary to do these calculations. Is because it's
24:14
Speaker 1: much more important to be super accurate more important than
24:17
Speaker 1: your phone's GPS, and the clocks that are on the
24:19
Speaker 1: satellites are not good enough to do this, so they
24:22
Speaker 1: have to do the calculation back on Earth and then
24:24
Speaker 1: send it to the satellite because on Earth to have
24:26
Speaker 1: these super precise atomic clocks that keep everything in lockstep.
24:31
Speaker 1: Interesting alright, So we we can't rely on the Earth
24:36
Speaker 1: to tell us where we are, like if I'm out
24:38
Speaker 1: in space, or can we can we rely on Earth
24:41
Speaker 1: to tell me where I am. Earth can figure out
24:43
Speaker 1: where you are, how far you are from the Earth,
24:45
Speaker 1: and how fast you're going, but you know, it's kind
24:48
Speaker 1: of limited. Like they can get really precise measurements of
24:51
Speaker 1: where you are up to about one meter, which is
24:54
Speaker 1: really pretty amazing, like you're out you know Jupiter distance,
24:57
Speaker 1: and Earth can measure how far away you are to
25:00
Speaker 1: within one meter based on the balance of the echo,
25:03
Speaker 1: like the signal coming back and going there and back. Yeah,
25:06
Speaker 1: just timing the echo because they have really precise atomic clocks.
25:10
Speaker 1: But what they can't do is figure out like where
25:12
Speaker 1: you are laterally, like your angle because there they don't
25:16
Speaker 1: have an echo measurement, right, and so they're the uncertainties
25:19
Speaker 1: more like four kilometers for every a U the distance
25:23
Speaker 1: between the Earth and the Sun. I see, because you know,
25:28
Speaker 1: if we're out by Jupiter, we don't shine like a star,
25:30
Speaker 1: that's right, right, Like we're not visible to the Earth,
25:33
Speaker 1: So they have no idea where we are. They just
25:35
Speaker 1: know kind of how far we are. They know how
25:36
Speaker 1: far you are, and they figure out where you are
25:38
Speaker 1: laterally basically using dead reckoning and then correcting using these
25:41
Speaker 1: radio measurements. But you know, that's a pretty big uncertainty.
25:45
Speaker 1: If you get out to like the distance of Pluto,
25:47
Speaker 1: then they're uncertainties two hundred kilometers, which is really big
25:52
Speaker 1: if you're trying to enter into the orbit of Pluto. Yeah. Yeah,
25:55
Speaker 1: that sounds like a pretty big error. Viewer off by
25:59
Speaker 1: two meters in your phone GPS, you be in a
26:04
Speaker 1: whole different state. Yeah. And so practically, what these folks
26:06
Speaker 1: do is they use landmarks in the Solar system too
26:09
Speaker 1: correct So if you're getting near Jupiter, it sund I
26:12
Speaker 1: can be like, okay, I see where Jupiter is. It
26:14
Speaker 1: can compare it to where thought Jupiter should be, and
26:17
Speaker 1: you can use that to correct. So you're like you're
26:19
Speaker 1: getting landmarks. You're like, oh, you're driving your friend's house
26:22
Speaker 1: is supposed to be a hill there. Hoops, I must
26:24
Speaker 1: be in the wrong spot passing to McDonald. I know
26:27
Speaker 1: I'm halfway there kind of thing. Yeah, And so cameras
26:30
Speaker 1: on board can give accurate measurements of nearby objects, not
26:33
Speaker 1: very far away, only very nearby. You see a big,
26:36
Speaker 1: well known asteroid, you pass the Moon or a planet,
26:39
Speaker 1: then you can correct You're no longer reliant on the
26:42
Speaker 1: messages from earthly interesting, but the satellite does that calculation
26:45
Speaker 1: or like it has to send the picture bag and
26:47
Speaker 1: then here on Earth were like, oh, it just pass Jupiter.
26:49
Speaker 1: This is where you are. Yeah, that's all done on
26:51
Speaker 1: Earth currently sends the data back and then we can
26:54
Speaker 1: get corrections. And that's one of the problems is that
26:56
Speaker 1: a lot of this stuff relies on calculations done on
26:59
Speaker 1: Earth and then these back and forth communications with the
27:02
Speaker 1: deep space network, which tie up the deep space network.
27:05
Speaker 1: You know, you're only talking to one satellite. All the
27:07
Speaker 1: other ones are waiting, so you can only talk to like,
27:10
Speaker 1: you know, a few of them at a time. And
27:12
Speaker 1: that's pretty serious because like GPS doesn't work that way.
27:15
Speaker 1: GPS just sends out its messages and all the phones
27:18
Speaker 1: in the world just kind of listen. It doesn't have
27:20
Speaker 1: to be bothered by the fact that I'm using it
27:22
Speaker 1: and somebody else is using it at the same time.
27:24
Speaker 1: But deep space network gets tied up every time a
27:26
Speaker 1: satellite needs to figure out its position. So they have
27:30
Speaker 1: a new idea for how to improve this so that
27:32
Speaker 1: it can be more like GPS. Well, how does that work?
27:35
Speaker 1: Just put more clocks in it, or yes, build a
27:38
Speaker 1: really precise clock and put it on the satellite. The
27:41
Speaker 1: most precise clocks we have are atomic clocks. These are
27:44
Speaker 1: clocks that measure little atoms doing very precise wiggles that
27:48
Speaker 1: like vibrated very specific frequency. One of the most precise
27:52
Speaker 1: things in the universe because it just happens over and
27:54
Speaker 1: over and over again exactly the same time step. But
27:58
Speaker 1: these atomic clocks are expensive and they're big, and so
28:02
Speaker 1: the reason that we don't have good clocks on satellites
28:05
Speaker 1: is because nobody's ever miniaturized them. So NASA spent a
28:09
Speaker 1: lot of time building a deep space atomic clock, basically
28:12
Speaker 1: a miniaturized version of atomic clock you can put on
28:16
Speaker 1: the satellite. And is it a lot smaller or yeah,
28:18
Speaker 1: it's a lot smaller, and it's a lot cheaper, and
28:21
Speaker 1: it's about the size of a toaster. Wow. So you
28:23
Speaker 1: wouldn't want to wear this atomic clock. It's not it's
28:27
Speaker 1: not ready for wristwatch use. If you want to be
28:31
Speaker 1: super untime to meetings and podcast recordings, I could wear
28:34
Speaker 1: an atomic clock, but it might be a little inconvenient. No,
28:37
Speaker 1: And these atomic clocks cost you know, enough fifty to
28:39
Speaker 1: a hundred thousand dollars, which amazingly is actually cheaper than
28:42
Speaker 1: some wristwatches you can buy for wearing. I never understood that.
28:46
Speaker 1: But some people spend a ridiculous amount the gold plated iPhones, right, Yeah, Well,
28:50
Speaker 1: I spent a few years in Switzerland where they have
28:52
Speaker 1: these ridiculous watch shops. You can go in and spend
28:55
Speaker 1: two hundred thousand dollars on a fancy watch. But it's
28:58
Speaker 1: like hand built with all these little levers and gears thereby,
29:02
Speaker 1: you know, dwarves underground or something I don't know, And
29:04
Speaker 1: it's not even as accurate as a toaster exactly exactly.
29:08
Speaker 1: I'll take a toaster's eye atomic watch from my wrist
29:11
Speaker 1: any day. But the idea there is if you have
29:14
Speaker 1: this atomic clock on the satellite, then it can get
29:18
Speaker 1: messages from the Deep Space Network that have time stamps
29:20
Speaker 1: on them to say we sent this message at whatever time,
29:24
Speaker 1: and you can just compare that too. It's atomic clock
29:27
Speaker 1: and they say, oh, it took x seconds to get here.
29:29
Speaker 1: I can figure out where I am myself. And that's
29:32
Speaker 1: a big step forward in what they call autonomous satellite navigation,
29:36
Speaker 1: with the satellites are just sort of driving themselves, right then,
29:39
Speaker 1: it's more like the GPS we have on our phones. Yeah, exactly,
29:42
Speaker 1: and you can just be sort of passive. The folks
29:44
Speaker 1: at home don't have to do these calculations themselves and
29:47
Speaker 1: updated to the satellite. So there are fewer links because
29:50
Speaker 1: the Deep space network is kind of sort of overburdened
29:52
Speaker 1: right now. It's got like too many things to do,
29:55
Speaker 1: is I mean time slice between too many projects. So
29:58
Speaker 1: this would really free it up, all right. Well, it
30:00
Speaker 1: sounds like things are looking good for navigating within the
30:02
Speaker 1: Solar System. So we're getting better clocks on these satellites
30:06
Speaker 1: and spacecraft, and we're also we can also use familiar
30:10
Speaker 1: landmarks like Jupiter or other planets or the Sun to
30:13
Speaker 1: sort of orient where we are within the Solar System.
30:16
Speaker 1: That's right, but then it sort of gets trickier one
30:18
Speaker 1: once we get out into space. Right, Yeah, all these
30:21
Speaker 1: things still rely on being able to contact Earth. You're
30:24
Speaker 1: getting these messages from the Deep Space Network, which is
30:27
Speaker 1: on Earth, and if you want to navigate to like
30:29
Speaker 1: Alpha Centauri or halfway across the galaxy, you don't want
30:33
Speaker 1: to be getting messages from Earth. They're gonna be way
30:35
Speaker 1: too faint. You're not gonna be able to pick remain.
30:37
Speaker 1: So you need a broader system. You need a galaxy
30:40
Speaker 1: spanning system. In order to get you out of the
30:43
Speaker 1: Solar System and still make it to McDonald's. We need
30:45
Speaker 1: like a like a capital GPS galactic positioning system. All right, Well,
30:51
Speaker 1: let's get into how you would actually navigate if you
30:53
Speaker 1: wanted to venture out from the Solar System or even
30:56
Speaker 1: go to another galaxy. But first let's take a quick break.
31:10
Speaker 1: All right. There we're talking about how did not get
31:13
Speaker 1: lost in space? Although that's such a fun show, is it?
31:18
Speaker 1: You like that show that, the new one or the
31:19
Speaker 1: old one. I like the old one, but the new
31:21
Speaker 1: one's fun watching with the whole family because you know,
31:23
Speaker 1: it's a bit of a family adventure, some family tension there,
31:26
Speaker 1: you know, you leave somebody behind. If you were frozen
31:29
Speaker 1: underwater on some alien moon, would your family stop and
31:32
Speaker 1: save you or not? Oh? Man, To me, it was
31:34
Speaker 1: almost too much family drama. I'm like, where is the
31:36
Speaker 1: space and they're getting lost in space they're like melting ice. Yeah, exactly.
31:42
Speaker 1: I thought it was good anyway, A lot of fun anyway. So, yeah,
31:45
Speaker 1: it's a problem if you go out into space, especially
31:48
Speaker 1: you can like in another part of the galaxy where
31:50
Speaker 1: the stars are in a totally different arrangement. How do
31:52
Speaker 1: you get around, how do you know where you are,
31:53
Speaker 1: and how do you know where to go? So what
31:56
Speaker 1: can we do then, Daniel? Yeah, well, what you need
31:58
Speaker 1: is some other source of signals. Either have a very
32:00
Speaker 1: accurate galactive map of where all the stars are, but
32:03
Speaker 1: as you say, these things are changing in time and
32:06
Speaker 1: we have only measurements from Earth and those positions are
32:09
Speaker 1: not that accurate. Which you really need is some sort
32:11
Speaker 1: of network of signals from all over the galaxy sending
32:16
Speaker 1: you time stamped messages. I mean, if you could design
32:18
Speaker 1: it yourself, you would have a bunch of sources around
32:21
Speaker 1: the galaxy sending you messages saying time equals one time
32:25
Speaker 1: equals two time equals three, right, and from those like
32:28
Speaker 1: the like the GPS satellites we have just now on Earth,
32:32
Speaker 1: you just have If you could just have GPS satellites
32:34
Speaker 1: all the way through the galaxy super powerful, that would
32:37
Speaker 1: be enough because you could use the nearest satellites to
32:39
Speaker 1: figure out how far you are from each one, and
32:42
Speaker 1: you need three of them to triangulate your position in
32:44
Speaker 1: three D space and then you be golden. But you
32:47
Speaker 1: know that's a trillion dollar program, right, could could you
32:50
Speaker 1: use like galaxies to orienter cell? Like you know, like
32:52
Speaker 1: if I'm in somewhere in the Milky Way, I could
32:55
Speaker 1: tell where the center of the Milky Way was maybe,
32:57
Speaker 1: and I could look for other galaxy ease out there,
33:01
Speaker 1: and so can I use that to orient myself? Yeah,
33:03
Speaker 1: And you can get a rough orientation that way, right,
33:05
Speaker 1: you can tell you know where Andrameda is relative to
33:08
Speaker 1: the Milky Way, So you can spin yourself around and
33:11
Speaker 1: tell where and Drameda is. But it's very rough, I mean,
33:14
Speaker 1: and Drameda is really far away, and so measuring its
33:17
Speaker 1: location precisely is not that helpful. We need much more
33:20
Speaker 1: precision than you can get from just like fixing the
33:23
Speaker 1: positions of other galaxies, like, yeah, that will tell you roughly.
33:26
Speaker 1: But if you want to navigate and you want to
33:28
Speaker 1: save fuel and you want to make it with your
33:30
Speaker 1: thousand frozen human bodies to Alpha Centauri or whatever, then
33:35
Speaker 1: you've got to be more precise than that. You don't
33:36
Speaker 1: want to miss by a few million kilometers, You got it,
33:39
Speaker 1: You do not, And then they start to warm up
33:41
Speaker 1: and there, you know, expecting the land in Alpha Centauri
33:45
Speaker 1: and have breakfast, and you didn't bring any months and
33:48
Speaker 1: so and so you're saying that one idea could could be,
33:50
Speaker 1: like to make these GPS satellites and put them all
33:53
Speaker 1: over the galaxy. But that's really expensive. Yeah, that's ridiculous,
33:56
Speaker 1: Like we didn't even know how to get them there, right,
33:58
Speaker 1: that's the whole problem. You're right, How would the satellites
34:03
Speaker 1: know where to go or where they are? How would
34:06
Speaker 1: we know where they are? We'd have to bootstrap them somehow.
34:09
Speaker 1: If you don't know where the satellites are, then they're
34:11
Speaker 1: not very useful right there, Like here's a signal from
34:14
Speaker 1: someplace we don't know, thank you very much. That's useless.
34:17
Speaker 1: So what you need to do is find some naturally
34:20
Speaker 1: occurring equivalent something in the galaxy that operates similar to
34:25
Speaker 1: GPS that lets you figure out where you are. And
34:27
Speaker 1: it turns out the galaxy provides is it alien satellites? Daniel,
34:32
Speaker 1: are you going for the alien button? I didn't even
34:35
Speaker 1: think about the alien button, but now I am. Now
34:38
Speaker 1: I'm wondering if aliens are using our GPS system to
34:41
Speaker 1: navigate our solar system right to us. Yes, well, if
34:45
Speaker 1: you enter the solar system that already had alien civilization
34:49
Speaker 1: and have GPS signals, then yeah, you could use it
34:51
Speaker 1: without them even noticing, because it's a passive system, right right,
34:55
Speaker 1: then maybe they're using us as a GPS exactly exactly,
35:00
Speaker 1: that's the concerned. But even without aliens, there are naturally occurring,
35:04
Speaker 1: very regular clocks in our galaxy interesting and they are
35:07
Speaker 1: called pulsars. You don't have to build them, they're already there.
35:11
Speaker 1: They are already there. We talked on the podcast before
35:13
Speaker 1: about what happens when really massive stars collapse that they
35:17
Speaker 1: blow up, there's a supernova, and then if there's enough
35:20
Speaker 1: stuff in the center of it, in the core, but
35:22
Speaker 1: not enough to make a black hole, they can form
35:24
Speaker 1: this thing called a neutron star, which is a ridiculously
35:28
Speaker 1: dense ball of matter. It's called like the mass of
35:31
Speaker 1: the Sun, but it's the size of a city. Right,
35:34
Speaker 1: It's it's like almost a black hole. It's almost a
35:37
Speaker 1: black hole. Yeah, if your star was like eighty two
35:40
Speaker 1: thirty masses of the Sun, then you're probably going to
35:43
Speaker 1: turn into a neutron star. If it was heavier than
35:45
Speaker 1: you probably get into a black hole. But some of
35:47
Speaker 1: these neutron stars are amazing because they have a magnetic
35:51
Speaker 1: field which is really intense, and the magnetic field means
35:55
Speaker 1: that there's a huge column of radiation that's spewed out
35:59
Speaker 1: from the north magnetic field and the south magnetic field.
36:01
Speaker 1: So they're like shining a really bright light of radiation
36:05
Speaker 1: in two directions in space. Right, Because the stars themselves
36:08
Speaker 1: don't shine that much, but like the chaos they cause
36:11
Speaker 1: around them with the magnetic field and all the stuff
36:14
Speaker 1: around them, then that is what glows and points in
36:17
Speaker 1: a particular direction. Exactly. There's no fusion happening inside a
36:20
Speaker 1: neutron star, but there's still an intense amount of other
36:23
Speaker 1: radiation produced, and the magnetic field funnels it into these
36:26
Speaker 1: type beams. And then if the magnetic north pole is
36:30
Speaker 1: not aligned with the spinning of the star, right, it's
36:33
Speaker 1: not perfectly aligned like on Earth. Then what you get
36:36
Speaker 1: is this neutron star that's sweeping around. It's rotating, but
36:40
Speaker 1: the direction in which its signal is beaming keeps scanning
36:44
Speaker 1: through the galg like a galactic lighthouse, you know, like
36:48
Speaker 1: a spotlight that just miss just like that, yeah, Or
36:52
Speaker 1: like just like on the top of a police car,
36:54
Speaker 1: you have this rotating red light and it never turns
36:57
Speaker 1: on or off, but it looks to you like it's flashing.
37:00
Speaker 1: So from Earth, if you look at a pulsar, it
37:02
Speaker 1: goes on off, on off, on off, on off very regularly,
37:07
Speaker 1: just like a lighthouse would or a police light, and
37:09
Speaker 1: it's not actually turning on off, it's just sort of
37:11
Speaker 1: sweeping past you. Right. So if we can use these
37:14
Speaker 1: to kind of tell where we are, like as as
37:17
Speaker 1: literally like lighthouses in space, sort of like lighthouses in space,
37:21
Speaker 1: And the reason is that they're incredibly accurate. They have
37:24
Speaker 1: about as much regularity as an atomic clock. Really, like
37:28
Speaker 1: these little particles in very special conditions and cold climates
37:32
Speaker 1: and special laboratories are very regular. But these enormous, massive
37:36
Speaker 1: spinning hunks of neutrons are also regular, and so they're
37:40
Speaker 1: basically like a very powerful galactic clock that's constantly descending
37:45
Speaker 1: out a pulse like tick tick tick. Suddenly that makes
37:50
Speaker 1: a nice guy a little more stressful. It's full of
37:53
Speaker 1: ticking clocks. But it's it's like crazy periods to right,
37:57
Speaker 1: it's not like tick tack tick. Take. It's like every
37:59
Speaker 1: twenty millis like and they're shining. There's a big variety
38:02
Speaker 1: of them, from radio pulsars down to X ray pulsars.
38:05
Speaker 1: It depends, as you say, on their period. And these
38:08
Speaker 1: ones that are very fast and like twenty milliseconds, these
38:11
Speaker 1: are the best ones to use for timing. And it's
38:14
Speaker 1: hard to imagine, like an enormous, super dense star boiled
38:18
Speaker 1: down into a tiny object that spins every twenty milliseconds. Right,
38:22
Speaker 1: It's like, hey, thousands and thousands of times a second,
38:25
Speaker 1: this huge thing is spinning. It's it's an incredible amount
38:28
Speaker 1: of energy. It's mind blowing. So we can use these
38:31
Speaker 1: because we know from Earth where they are, and so
38:34
Speaker 1: if you're out there in space, you could maybe find
38:37
Speaker 1: them by looking out, and then you can tell kind
38:40
Speaker 1: of where you are because you could recognize them. Buy
38:42
Speaker 1: what their period. Each one has its own fingerprint because
38:45
Speaker 1: of its period, and you already know where they are,
38:48
Speaker 1: so you find them, you identified and you're like, okay,
38:50
Speaker 1: this is pulsar x J seventeen or whatever. And then
38:53
Speaker 1: you listen to the pulses, you know, tick tick tick,
38:57
Speaker 1: and based on the pulses that you hear, you can
39:00
Speaker 1: tell where in the wave form you are. Now, the
39:03
Speaker 1: problem is they don't send messages like the GPS satellites.
39:06
Speaker 1: The GPS satellite say okay, it's time equals seven, it's
39:09
Speaker 1: time equals eight, and then when it gets to you,
39:11
Speaker 1: you can compare against your own clock they have. You
39:13
Speaker 1: have like synchronized clocks on each side, so you can
39:16
Speaker 1: measure how long it takes the signal to get there.
39:19
Speaker 1: That's from the GPS. Pulsars aren't as convenient. They don't
39:22
Speaker 1: have a clock built in that labels each pulse separately,
39:26
Speaker 1: so it's harder to tell exactly how long it took
39:29
Speaker 1: the pulse to get there. Right, But why do you
39:30
Speaker 1: need to know that? Couldn't you just kind of look
39:32
Speaker 1: where they are and you know the angle to you,
39:35
Speaker 1: and then use like three or four of them to
39:37
Speaker 1: kind of triangulate where you are. What you really want
39:39
Speaker 1: to know is your distance to an individual pulsar, because
39:42
Speaker 1: that defines your position on the surface of a sphere
39:45
Speaker 1: that surrounds that pulsar. And you do it for another pulsar,
39:48
Speaker 1: and then your distance is defined by where those spheres intersect,
39:52
Speaker 1: and we do it for three pulsars. Then you can
39:54
Speaker 1: figure out where your distance is exactly in three D space.
39:57
Speaker 1: You're right there. You can tell roughly where you are
39:58
Speaker 1: by the angles, but that's not precise enough. Which you
40:01
Speaker 1: really want to know is the distance to these things? Really?
40:03
Speaker 1: Why is the angle not precise enough? Because these things
40:06
Speaker 1: are really really far away, right, and so a pretty
40:09
Speaker 1: big change in the location of the pulse are relative
40:11
Speaker 1: to you corresponds to a really small change in the angle.
40:14
Speaker 1: So what you really want to know is the radial distance,
40:17
Speaker 1: not just the angle. Oh, I see, it works if
40:19
Speaker 1: you're moving a huge distances, but like you couldn't tell
40:22
Speaker 1: you like by the meter where you are, yeah, or
40:24
Speaker 1: if you're really close to something, like if you're really
40:26
Speaker 1: close to Jupiter, then it's angle relative to you has
40:29
Speaker 1: a lot of powerful information about your location. But if
40:32
Speaker 1: Jupiter is really far away, then that information loses value
40:36
Speaker 1: and all these pulsars are pretty far away. But there's
40:38
Speaker 1: actually a really cool trick to overcoming this problem of
40:42
Speaker 1: pulsars not being like GPS statelines just using because great,
40:47
Speaker 1: because I don't have the time stamp. They just have
40:49
Speaker 1: a pulse. Yeah, so all you know is where you
40:51
Speaker 1: are on the pulse. And so say these pulses are like,
40:55
Speaker 1: you know, a kilometer long, for example, So if you
40:58
Speaker 1: listen to a specific pulse, are that you could tell
41:01
Speaker 1: where you are within that one kilometer long pulse. You're like, oh,
41:05
Speaker 1: I'm at the top of it, or I'm at the
41:06
Speaker 1: bottom of it, or I mean the quiet part of
41:08
Speaker 1: it or the loud part of it. That doesn't actually
41:10
Speaker 1: tell you how far you are from the pulse are.
41:12
Speaker 1: What you know is how far you are through one
41:15
Speaker 1: pulse length, but you don't know how many more pulse
41:19
Speaker 1: lengths there are between you and the pulse are. If
41:22
Speaker 1: you know you're halfway through its pulse, then you could
41:24
Speaker 1: be half a pulse length away from the original pulsar,
41:28
Speaker 1: or you could be one and a half pulse lengths away,
41:31
Speaker 1: or three hundred forty two and a half pulse lengths away.
41:35
Speaker 1: There's an infinite number of possibilities. So instead of locating
41:39
Speaker 1: you onto a single sphere when you know the distance,
41:42
Speaker 1: it's actually given you an infinite number of spheres, each
41:46
Speaker 1: one one pulse length away, because all of those are
41:49
Speaker 1: consistent with what you're seeing. That's not as good as GPS,
41:53
Speaker 1: but you know it can still work because you can
41:55
Speaker 1: do the same thing for another pulsar and get another
41:58
Speaker 1: set of spheres, and then find a third pulsar and
42:02
Speaker 1: get a third set of spheres, And where those spheares
42:05
Speaker 1: intersect is the number of places that you could be
42:08
Speaker 1: places that are consistent with the signals you're seeing. Now
42:11
Speaker 1: that's not just one place, it's not a unique solution.
42:14
Speaker 1: There's still a few ambiguities. There's more than one possible
42:18
Speaker 1: location that's consistent with those signals, and then you have
42:21
Speaker 1: to figure out which one is yours based on where
42:23
Speaker 1: you thought you were recently, and you know other clues.
42:27
Speaker 1: I see, you're sort of converting the time stamp of
42:29
Speaker 1: these pulses to like using the speed of light to
42:32
Speaker 1: kind of tell where you are in terms of space. Yeah, exactly,
42:36
Speaker 1: and you don't know exactly how far your way you
42:39
Speaker 1: are from the pulsar, you know, like, I'm a certain
42:41
Speaker 1: number of beats of this pulsar's pulse away plus a
42:46
Speaker 1: little bit, you know, only that extra little bit. And
42:48
Speaker 1: so there's lots of different solutions, lots of different possibilities
42:52
Speaker 1: for how far you might be away from one pulsar.
42:55
Speaker 1: But if you have two or three or four, then
42:57
Speaker 1: you can narrow it down. You can say I'm a
42:59
Speaker 1: certain from this one, a certain distance from that one.
43:01
Speaker 1: It's a harder problem because these pulsars aren't nicely time stamped,
43:06
Speaker 1: but people have figured it out, and if you do
43:08
Speaker 1: all the mathematics, you can figure out where you are
43:11
Speaker 1: in the Solar system to within five kilometers. Wow, that's
43:14
Speaker 1: pretty good. That's pretty good. That's better than the two
43:17
Speaker 1: from before. Yeah, exactly, it's pretty good. And it works
43:20
Speaker 1: all the way across the galaxy, not just within our
43:23
Speaker 1: Solar system, so you can be far from even if
43:26
Speaker 1: Earth in blodes the nuclear war, you can still figure
43:29
Speaker 1: out where you are from these pulsars. Are the pulsars
43:32
Speaker 1: distributed all over the galaxy or are we only looking
43:36
Speaker 1: at the ones around us. They're distributed across the galaxy.
43:38
Speaker 1: People have done a study and they found like fifty
43:40
Speaker 1: or sixty good X ray pulsars that are distributed well
43:44
Speaker 1: enough across the galaxy that you could use them as
43:46
Speaker 1: reference points. And they've actually tried this. They've done it.
43:50
Speaker 1: They've built a little one and they fluid on the
43:53
Speaker 1: International Space Station and they tried it and it worked. Wow.
43:56
Speaker 1: Pretty cool, all right, So it sounds like we do
43:58
Speaker 1: have a GPS for the Alexy. We have a galactic
44:01
Speaker 1: Pulse source system. You should also call it GPS. It's
44:04
Speaker 1: pretty awesome. It's pretty awesome. I love this idea of like,
44:08
Speaker 1: you know, astronomers don't get to build what they want.
44:10
Speaker 1: They just get to look out there and find stuff
44:13
Speaker 1: and use it to be clever to extract the information
44:16
Speaker 1: they need. And here's another great example of just like
44:18
Speaker 1: making do with what you have. Right, it's almost like
44:21
Speaker 1: a nature and the universe made these lighthouses and put
44:24
Speaker 1: them all over the galaxy just for us to kind
44:27
Speaker 1: of used to get around. Yeah, probably not just for us,
44:30
Speaker 1: but it would be a cool science fiction universe where
44:32
Speaker 1: we actually visit one of these pulsars and discover, oh,
44:34
Speaker 1: they're artificial. Maybe they're part of some billion global positions. Oh,
44:38
Speaker 1: it is a lighthouse. It didn't occur naturally, that would
44:42
Speaker 1: be pretty awesome. That would be worth some echoes in space.
44:45
Speaker 1: Space space space space space cool cool cool. All right, Well,
44:51
Speaker 1: I feel a lot better now about Star Wars and
44:53
Speaker 1: about other science fiction movies and books. It sounds like
44:58
Speaker 1: in the future we could be using these pulsars to
45:01
Speaker 1: kind of know where we are in the galaxy and
45:02
Speaker 1: to kind of build a map of the entire place. Yeah,
45:05
Speaker 1: and as we venture out further and further beyond our
45:08
Speaker 1: solar system and try to explore other solar systems, this
45:11
Speaker 1: will be a critical way to know where we are
45:13
Speaker 1: and hopefully how to come home. Yeah, And so future
45:16
Speaker 1: space explorers flying around with their partners and spouses can
45:21
Speaker 1: not argue about where they are getting lost, which would
45:24
Speaker 1: probably make for a messy divorce out in space. Well,
45:26
Speaker 1: they'll probably still argue, like, let's not use that pulsar.
45:29
Speaker 1: That one's not reliable. Everybody's using that pulsar. You sound
45:34
Speaker 1: like you, You sound like your father. All right. Well,
45:37
Speaker 1: I hope that was interesting and gives you a little
45:40
Speaker 1: bit more of a sense that we kind of know
45:42
Speaker 1: where we are in the universe and the galaxy, and
45:45
Speaker 1: that it would be a little bit hard to get
45:46
Speaker 1: lost in space. That's right. And this idea of pulsars
45:49
Speaker 1: took decades to figure out to narrow down to make
45:52
Speaker 1: it work, and it only gives us five kilometer uncertainty.
45:55
Speaker 1: Probably somebody out there will have an even better idea
45:58
Speaker 1: for how to narrow down our edition. So have that
46:01
Speaker 1: idea today so that it's ready for us to use
46:03
Speaker 1: in twenty or thirty years. That's right. You don't want
46:05
Speaker 1: to miss those snacks, you know. If you miss that
46:07
Speaker 1: snack by five kilometers, that's that's not good eating. If
46:11
Speaker 1: you learn nothing else today. Remember there are no U
46:13
Speaker 1: turns in space or echoes, but there probably are snacks,
46:18
Speaker 1: all right. Thanks for joining us, See you next time.
46:28
Speaker 1: Thanks for listening, and remember that Daniel and Jorge Explain
46:31
Speaker 1: the Universe is a production of I Heart Radio. For
46:34
Speaker 1: more podcast for my Heart Radio, visit the I Heart
46:37
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46:41
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