Latest / Space Nuts: Astronomy Insights & Cosmic Discoveries / Dark Matter Dilemmas, Betelgeuse's Fate & the Mysteries of Lagrange Points

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Dark Matter Dilemmas, Betelgeuse's Fate & the Mysteries of Lagrange Points · Space Nuts: Astronomy Insights & Cosmic Discoveries

0:00
Speaker 1: Hello again, thank you for joining us on Space Nuts
0:03
Speaker 1: Q and A edition. This is where we answer audience questions,
0:06
Speaker 1: or at least we read them out and pretend we
0:09
Speaker 1: know what.
0:09
Speaker 2: We're talking about.
0:10
Speaker 1: Today we will be answering questions about dark matter versus
0:15
Speaker 1: a black hole. It's a titanic struggle.
0:17
Speaker 2: Who would win.
0:19
Speaker 1: We are also going to discuss the demise of beetlejuice
0:24
Speaker 1: or beetlegeis, depending on how you like to pronounce it.
0:27
Speaker 1: We have a question about lagrange points and the Cordeleski
0:32
Speaker 1: plasma clouds question has.
0:35
Speaker 2: Come up from a YouTuber.
0:37
Speaker 1: We'll deal with all that right now on Space Nuts.
0:40
Speaker 3: Fifteen second Channel ten nine ignition Squench Space Nuts or
0:49
Speaker 3: three two.
0:53
Speaker 4: Space nuts as.
0:54
Speaker 5: And I reported Neils good.
0:57
Speaker 2: He's back again for more.
0:58
Speaker 1: Has done all the research, has all the answers to
1:00
Speaker 1: all the questions, except for those four. It's Johnny Horner,
1:03
Speaker 1: professor of astrophysics at the University of Southern Queensland.
1:07
Speaker 2: Johnny, Hello, I'm good afternoon.
1:09
Speaker 4: How are you doing.
1:10
Speaker 2: I'm all right.
1:10
Speaker 1: How are the renots going at your place?
1:12
Speaker 4: Well, not too bad. I think they've clocked off for
1:14
Speaker 4: lunch at the minute, so we might get away with
1:16
Speaker 4: it on I'm waiting for my other doctor insists I
1:19
Speaker 4: pay attention to her. Are you yes?
1:21
Speaker 2: Dogs do that? Yes, indeed they do.
1:25
Speaker 1: All right, let's answer some questions. Firstly, we've got a
1:29
Speaker 1: question from Howard. He said, first, I should say that
1:33
Speaker 1: I think dark matter is going to end up as
1:36
Speaker 1: a follergiston? Is that the word of our times?
1:41
Speaker 2: Sorry? Flodgist?
1:44
Speaker 1: Could be that of our times, a substance dreamed up
1:46
Speaker 1: to resolve an otherwise unsolvable problem and later discarded as
1:52
Speaker 1: science advances. But even so, here's my question. Since gravity
1:56
Speaker 1: seems to be the only force that interacts with dark matter,
1:59
Speaker 1: what happens when a black hole, the ultimate source of gravity,
2:02
Speaker 1: comes into contact with dark matter? Does it eat it?
2:06
Speaker 1: And if so, what happens? And if not, why not?
2:10
Speaker 2: I do?
2:10
Speaker 1: We've had questions of similar style and ilk before, and
2:16
Speaker 1: I can't remember what Fred said, but I think it
2:19
Speaker 1: said doesn't matter, you know, because dark matter? And yeah,
2:25
Speaker 1: but I'm sure you've done your homework, because I didn't.
2:28
Speaker 1: I never did homework as a kid, so why would
2:31
Speaker 1: I start now?
2:32
Speaker 4: Well, there seems to be evidence that homework is fairly pointless. Such, yes,
2:36
Speaker 4: my Apartner's a primary teacher, and you know, I think
2:38
Speaker 4: if she had her where, kids wouldn't have any homework,
2:41
Speaker 4: and at least until you're fairly well through secondary school,
2:45
Speaker 4: it doesn't seem to serve a purpose other than making
2:48
Speaker 4: some parents feel like their kids are getting properly worked,
2:51
Speaker 4: you know. So, but onto something that I actually have
2:54
Speaker 4: expertise in, rather than being talking about teaching what I
2:57
Speaker 4: clearly done that much, is a real interesting one. It's
3:02
Speaker 4: I get what you mean with the flogist, and I
3:04
Speaker 4: think possibly dark energy, i'd argue, is a bit more
3:07
Speaker 4: of a flogist and thing than that matter at this stage,
3:10
Speaker 4: because it's very clear that there is mass out there
3:14
Speaker 4: that it's having an effect but we can't see. And
3:17
Speaker 4: that's fundamentally what dark matter is. We can add up
3:21
Speaker 4: all of the mass of all of the things that
3:22
Speaker 4: we can see in the forms of dust and gas
3:24
Speaker 4: and stars and all the rest of it, and the
3:27
Speaker 4: gravitational pull within galaxies, particularly as you get further out
3:30
Speaker 4: into galaxies, is more significant than can be explained by
3:34
Speaker 4: the luminous material art and that's where dark matter comes from,
3:39
Speaker 4: and we see its effects even if we don't see
3:41
Speaker 4: it in I guess just the same way as back
3:43
Speaker 4: in the eighteen hundreds, astronomers saw the effects of Uranus
3:48
Speaker 4: of Neptune's gravity perturbing the orbit of Uranus as it
3:52
Speaker 4: went round the Sun, and we detected Neptune indirectly. And
3:55
Speaker 4: then people said, only point you tell it's goope here,
3:57
Speaker 4: because it must be a planet in this part of
3:59
Speaker 4: the sky pulling Urinus around and low, and behold, we
4:02
Speaker 4: found it. And this is fairly fundamental to me as
4:05
Speaker 4: an exoplanet science person, in that the vast majority of
4:09
Speaker 4: planets we found around o the cells we found indirectly.
4:11
Speaker 4: We see a star doing something unexplained, We see it
4:15
Speaker 4: winking or we see it wobbling, and we in further
4:17
Speaker 4: presence of a planet as an explanation for that unexplained behavior.
4:21
Speaker 4: And when you rule out all the other explanations, someone
4:23
Speaker 4: that's left as a planet, and Bob's your uncle. You've
4:26
Speaker 4: added one to the Italian. Like we said in the
4:28
Speaker 4: earlier episode, we've now passed six cells, and so whoopy
4:31
Speaker 4: for us, we're doing really well. So there's a lot
4:33
Speaker 4: of evidence that dark matter is a thing, and what
4:37
Speaker 4: it is nobody really knows. There's been a lot of speculation,
4:40
Speaker 4: but what seems to be the case is that dark
4:42
Speaker 4: matter is something that interacts through gravity but doesn't interact
4:46
Speaker 4: with anything else. It doesn't interact with light. It doesn't
4:48
Speaker 4: impede light because we see dust blots light, so dust
4:52
Speaker 4: is not dark matter. So what happens, Well, if dark
4:56
Speaker 4: matter interacts with gravity in just the same way as
4:59
Speaker 4: normal matter, then it will interact with a black hole
5:02
Speaker 4: in almost the same way as normal matter. And they
5:05
Speaker 4: almost said a little asterisk. I'll come to in a minute.
5:07
Speaker 4: What that means is that if something gets close enough
5:10
Speaker 4: to a black hole to be within its event horizon,
5:14
Speaker 4: then that means it would have to travel faster than
5:16
Speaker 4: the speed of light to escape from the gravitational pull
5:18
Speaker 4: of the black hole. So it's effectively been nombed. And
5:21
Speaker 4: you've got black holes being the pack man of the
5:23
Speaker 4: universe that just go around gobbling everything up. Once it
5:26
Speaker 4: is gobbled up, it doesn't matter if it's dark matter
5:29
Speaker 4: or normal matter. It's been nombed and it just adds
5:32
Speaker 4: to the mass of the black hole. And I guess
5:34
Speaker 4: the black hole is a bit like the ball, and
5:35
Speaker 4: it's your individuality. Indistinctiveness has been added to our own
5:39
Speaker 4: and the dark matter has been nombed in just the
5:41
Speaker 4: same way it would have been with normal matter. So
5:44
Speaker 4: from that point of view, there is actually no problem.
5:48
Speaker 4: We'd expect dark matter to be eaten and to stay eaten.
5:52
Speaker 4: There are suggestions that the supermassive black holes like the
5:55
Speaker 4: one we've got at the middle of the Milky Way
5:58
Speaker 4: are only able to be formed if that matter exists,
6:02
Speaker 4: and even more normal mass black holes have a restriction
6:08
Speaker 4: on the amount that they can eat. It's almost like
6:11
Speaker 4: the celestial equivalent of a gastric band or something like that.
6:14
Speaker 4: It's something called the Eddington limit. Material falling into a
6:17
Speaker 4: black hole, that is normal matter as it falls in
6:22
Speaker 4: gets accelerated, gets heated up in its light. And if
6:25
Speaker 4: you've got a black hole eating a lot of stuff,
6:28
Speaker 4: there's a lot of material falling and emitting incredible aunts
6:31
Speaker 4: of radiation. They can essentially push away or the matter
6:34
Speaker 4: around the black hole and force it to stop eating,
6:38
Speaker 4: effectively putting a limit on the amount that it can
6:41
Speaker 4: devour at any given time. And you do get things
6:45
Speaker 4: that are eating at what's called super Eddington rates, but
6:49
Speaker 4: that's where something's essentially pushing material in so quickly that
6:53
Speaker 4: it overcomes that effect. So I guess it's a bit
6:56
Speaker 4: like saying you can only drink so much water because
6:58
Speaker 4: you can only swallow so much. But if somebody shoves
7:00
Speaker 4: a fire hose in your mouth, the water's going to
7:02
Speaker 4: go somewhere. That's kind of that situation. But that puts
7:07
Speaker 4: a limit on how much a black hole can eat
7:10
Speaker 4: at a given time. At the pace at which can
7:12
Speaker 4: devour matter, dark matter doesn't interact with like al radiation
7:17
Speaker 4: or anything like that, so the Eddington limit doesn't apply
7:20
Speaker 4: because a black hole shining like a searchlight will not
7:23
Speaker 4: impede the motion of dark matter one little bit. And
7:27
Speaker 4: so there is an idea that actually dark matter is
7:30
Speaker 4: a more effective food for black holes and normal matter
7:34
Speaker 4: because dark matter circumvents the Gasrick band. It circumvents this
7:38
Speaker 4: Eddington limit that prevents a black hole from eating to excess,
7:43
Speaker 4: and that may actually have been a significant part of
7:45
Speaker 4: how the supermassive black holes that we get in the
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Speaker 4: middle of galaxies actually got their start where they got
7:51
Speaker 4: their start aided by dark matter. And so it's a
7:55
Speaker 4: really interesting question because I had not really thought of
7:57
Speaker 4: this until Howard's question. Came through and added a bit
7:59
Speaker 4: of reading around. But it's actually one of these scenarios
8:04
Speaker 4: where dark matter, it seems, is a help to black
8:07
Speaker 4: holes rather than a hindrance, and therefore may help to
8:11
Speaker 4: explain why the universe is and where that we see
8:13
Speaker 4: it today, beyond just explaining the rotation curves of galaxies
8:17
Speaker 4: and things like this, which is why it was hypothesized
8:19
Speaker 4: in the first place.
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Speaker 1: Okay, so you do believe there's interaction between dark matter
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Speaker 1: and black holes.
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Speaker 4: Of course, Yeah, and sorry, of course the sounds to dismissive.
8:30
Speaker 4: The reason that it's in, of course, is that dark
8:33
Speaker 4: matter interacts with gravity. That's fundamentally how we found it
8:37
Speaker 4: in the first place. And therefore, if it falls into
8:41
Speaker 4: a black hole, it behaves like any other kind of
8:43
Speaker 4: matter from the point of view gravity.
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Speaker 2: And so therefore, and I.
8:47
Speaker 4: Mean, there are some suggestions that black holes are a
8:50
Speaker 4: significant component of dark matter.
8:53
Speaker 2: Yes, we can only see them when they're feeding.
8:55
Speaker 4: If they're not eating anything, we have no indication of
8:58
Speaker 4: black holes there other than its effect on the mass
9:00
Speaker 4: around it. You know, light gets bent around it and
9:02
Speaker 4: all the rest of it. Yeah, some component of dark
9:06
Speaker 4: matter may well be primordial black holes. That's one of
9:08
Speaker 4: a suggestion.
9:09
Speaker 1: Yeah, there's still so much to learn. We don't know
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Speaker 1: much at all, although they also I think if I
9:15
Speaker 1: recall correctly say that dark matter clusters in around galaxies
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Speaker 1: and around concentrated points, it's much thinner where the universe
9:28
Speaker 1: is emptier.
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Speaker 2: Is that right?
9:30
Speaker 4: And that kind of makes sense as well, because if
9:31
Speaker 4: dark matter is feeling the effects of gravity like everything else,
9:35
Speaker 4: the same things that would have pulled an excess of
9:37
Speaker 4: visible matter together to farm galaxies would have brought together dark.
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Speaker 2: Matter as well.
9:42
Speaker 4: And there is this discussion that galaxies have dark matter
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Speaker 4: halos around them. So the rotation curves of galaxies are
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Speaker 4: evidence for dark matter within those galaxies, meaning that there
9:52
Speaker 4: is more mass interior to a certain distance from the
9:55
Speaker 4: middle of the galaxy than we can account for by
9:57
Speaker 4: what we see. That means that together rotation happening quicker
10:01
Speaker 4: because it's more master left on, more gravitational pulse or
10:03
Speaker 4: faster rotation. But the massive galaxy clusters, in terms of
10:07
Speaker 4: how the galaxies are interacting with each other and how
10:10
Speaker 4: they're moving within the clusters, the mass within the cluster
10:14
Speaker 4: has to been bigger than the masters that the galaxies
10:17
Speaker 4: seem to have from the visible material, even accounting for
10:20
Speaker 4: the dark matterrhithm causing their rotation speeds to be higher.
10:24
Speaker 4: And that's suggesting that that matter is also in a
10:27
Speaker 4: halo around the galaxy, given that galaxy even more muster
10:30
Speaker 4: even more.
10:32
Speaker 2: Yes, it is so fascinating.
10:35
Speaker 1: And Flogiston was a hypothetical fire like element once thought
10:38
Speaker 1: to be contained within combustible bodies and released during combustion,
10:42
Speaker 1: a theory proposed by Johann Beecher, and it's an outdated
10:47
Speaker 1: theory that was eventually disproved by Antoine Levosier through his
10:53
Speaker 1: experience with oxygen, which demonstrated that burning is a chemical
10:56
Speaker 1: reaction involving the combination of a substance with oxyde, not
11:00
Speaker 1: the release of flogiston. There you are, all right, Howard,
11:05
Speaker 1: Thank you so much for a great question. Let's take
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12:36
Speaker 2: Now back to the show.
12:38
Speaker 1: Three space nuts now. Gary is next. He's a fan
12:45
Speaker 1: from Canada's East Coast. I was only recently on Canada's
12:49
Speaker 1: East Coast, visited Peggy's Cove and Halifax and lovely part
12:54
Speaker 1: of the world. He goes on to say, I enjoy
12:56
Speaker 1: your humor mixed with actual scientific knowledge out of part's
13:00
Speaker 1: probably not anyway. Question, can you tell me if beetlejuice
13:04
Speaker 1: Beetlegeiss explodes six hundred and eighty million light years away,
13:08
Speaker 1: whether we are just seeing something that happened six hundred
13:12
Speaker 1: and eighty million years ago, traveling at the speed of light.
13:17
Speaker 4: It's a really good question. It comes a plot when
13:20
Speaker 4: I'm doing outreach and stuff like that. Beetlejuice is depending
13:24
Speaker 4: on whose measurements you expect, it's not quite six hundred
13:27
Speaker 4: and eighty million light years away. It's somewhere between about
13:29
Speaker 4: five hundred and seven hundred light years away, so it's
13:32
Speaker 4: a bit closer to home than that. But the question
13:36
Speaker 4: still stands. When we see objects in the universe, we
13:39
Speaker 4: see them as they were when the light was emitted
13:43
Speaker 4: from them, and that's even true for the rumor around you.
13:47
Speaker 4: It's just that everything nearby is cell class that you're
13:50
Speaker 4: effectively seeing instantaneously. Light travels at three hundred thousand kilometers
13:54
Speaker 4: a second, so we see the moon, which is about
13:57
Speaker 4: three hundred and eighty four thousand kilometers away, worrying. We
14:00
Speaker 4: just had all the fuss about the supermoon's yet again.
14:03
Speaker 4: So the distance to the Moon does very a little bit,
14:05
Speaker 4: but that means we see the Moon using light that
14:09
Speaker 4: reflected off the surface of the Moon about one and
14:11
Speaker 4: one third seconds ago. It's one and one third light
14:14
Speaker 4: seconds away. We see the Sun with light that left
14:17
Speaker 4: the surface of the photosphere a bit more than eight
14:20
Speaker 4: minutes ago. And so when you see anything, you're seeing
14:24
Speaker 4: light that left a period of time ago. You see
14:27
Speaker 4: everything as it was in the past, rather than as
14:30
Speaker 4: it would be in a perverse now that if you
14:32
Speaker 4: could teleport there instantaneously, it would look different. I mean
14:36
Speaker 4: that brings into question could you teleport at faster than
14:39
Speaker 4: the speed of light? But then the question is kind
14:40
Speaker 4: of teleport anyway, So that's getting getting into the grounds
14:44
Speaker 4: of science fiction. But it brings open a odd philosophical
14:51
Speaker 4: kind of question, which is what do you define as
14:54
Speaker 4: something happening now? Do you define them now as a
14:59
Speaker 4: perceived now where you are, or do you find now
15:02
Speaker 4: as being the time that the event happens, that the
15:06
Speaker 4: light would reach you once it has traveled that business
15:09
Speaker 4: to get to you. And I'm explaining that badly. But
15:12
Speaker 4: this is essentially the fundamental of the question. If Beetlejuice
15:16
Speaker 4: exploded a thousand years ago, on that light reaches as say,
15:21
Speaker 4: three hundred years in the future, So it turns out
15:23
Speaker 4: it was seven hundred light years away. Beetlejuice exploded a
15:27
Speaker 4: thousand years ago, the light travels for seven hundred years,
15:30
Speaker 4: so it all reaches in three hundred years seven. I'm
15:33
Speaker 4: sure my head has got flipped over there somewhere. But
15:36
Speaker 4: on if Beetlejuice exploded a thousand years ago, we saw
15:38
Speaker 4: it three hundred years in the future, then that'd be
15:40
Speaker 4: thirteen hundred light years away. That's I'm going the wrong way.
15:43
Speaker 4: But anyway, we know, if you have exploded in the past,
15:46
Speaker 4: we see it at some point in the future. Did
15:49
Speaker 4: that explosion happen in the past of the future? Well,
15:52
Speaker 4: in Beetlejuice's frame of reference, if you were stood camping
15:55
Speaker 4: near Beetlejuice, you would have seen it in the past.
15:59
Speaker 4: You'd have seen it happen already. But any signal you
16:02
Speaker 4: sent to tell us that it had have happened would
16:04
Speaker 4: only just arrive at the same time that the explosion did,
16:07
Speaker 4: because you'd have to see it first, and then the
16:08
Speaker 4: signal back. So from the point of view of us
16:11
Speaker 4: here on Earth, when does beetlejuice explode? Is it when
16:15
Speaker 4: we see it or when we calculate back how long
16:18
Speaker 4: ago that explosion had to happen for us to see
16:21
Speaker 4: it today. And it's where we get into the philosophy
16:24
Speaker 4: of perception and what it actually means to be now,
16:28
Speaker 4: because everything around us, even the tip of my own nose,
16:31
Speaker 4: is far enough away that I'm seeing it in the past.
16:35
Speaker 4: I mean, I'm seeing it in the past by nane
16:37
Speaker 4: oh seconds, but it's still in the past. And so
16:42
Speaker 4: there's a weird bit of internal philosophy that has to
16:45
Speaker 4: go on there that is driven by the size of
16:47
Speaker 4: the universe. And we came up with this fine with sound.
16:51
Speaker 4: We see a flash of lightning and then we hear
16:53
Speaker 4: a rumble of thunder a certain amount of time later,
16:56
Speaker 4: and we're aware that the two events happened at the
16:58
Speaker 4: same time, but the sound takes a certain amount of
17:01
Speaker 4: time to reach us. So if we imagine that there
17:04
Speaker 4: was some form of instantaneous communication that could happen that
17:07
Speaker 4: happened faster than the speed of light, and we were
17:10
Speaker 4: able to have a real ay near beetlejuice. Tellers, beetlejuice
17:14
Speaker 4: has now gone back, you will see it in seven
17:16
Speaker 4: hundred years time. Then it makes sense to say that
17:19
Speaker 4: beetlejuice ex blooded in the past and we only see
17:21
Speaker 4: it now. But from your perception point of view, you'd
17:25
Speaker 4: see it happening now when you saw it happen now,
17:27
Speaker 4: and that will be all now. And so this is
17:31
Speaker 4: a really fun question because the reality is that it's
17:35
Speaker 4: all to do with frames of reference and where you stand.
17:40
Speaker 4: And yeah, I'm listening to a fairly pulpy science fiction
17:43
Speaker 4: series at the minute called Expeditionary Force that actually talks
17:47
Speaker 4: about how slow light is when you're having combat happening
17:49
Speaker 4: in space. You know, if you're shooting lasers and mazers
17:53
Speaker 4: that people neural lights second away from them. By the
17:55
Speaker 4: time your laser gets there, they'll have moved, so you've
17:58
Speaker 4: got to shoot whether going to be not whether they
18:00
Speaker 4: actually are, but then they know that, so they're dodging.
18:03
Speaker 4: And the further away you are, the longer it takes
18:05
Speaker 4: for the light to reach you. So you've got the
18:07
Speaker 4: bisarre thing of if you can jump through space and
18:10
Speaker 4: you can go through a wormhole and pay someone else.
18:12
Speaker 4: You could fight someone and then jump through space and
18:14
Speaker 4: watch the battle happen and watch yourself fight them.
18:17
Speaker 2: Wow.
18:17
Speaker 4: And this is where all the philosophy starts to mess
18:20
Speaker 4: with your head. But it makes for wonderful science fiction
18:23
Speaker 4: scenarios so long as you build something into your science
18:27
Speaker 4: fiction world that allows you to have faster than light
18:29
Speaker 4: travel so you can get ahead of the images of
18:31
Speaker 4: yourself doing a certain thing.
18:34
Speaker 1: That is really interesting. I love science fiction for that
18:37
Speaker 1: reason because you can just make all this stuff happen
18:39
Speaker 1: that it is not yet achievable as far as we know.
18:43
Speaker 4: There must be is our example. So that when I
18:45
Speaker 4: was young, I remember the Anne McCaffrey novels really well.
18:48
Speaker 4: And you know, she was most famous across for the
18:51
Speaker 4: Dragons series. You know, all the books about people in
18:55
Speaker 4: a world where they live and bond with dragons and
18:56
Speaker 4: they burned thread from the end, it turns out that
18:58
Speaker 4: it's actually a soft sci fi setting rather than a
19:01
Speaker 4: fantasy setting because reasons you find further down the series.
19:04
Speaker 4: But she also had a series of books about the
19:07
Speaker 4: Talents of Earth, which were these people with psychokinetic and
19:10
Speaker 4: telepathic talents who could transport things using the power of
19:14
Speaker 4: the mind from one place to one other, and they
19:16
Speaker 4: could communicate telekinetically. And of course what you do with
19:20
Speaker 4: people like that in Aan McCaffrey's world is not turn
19:22
Speaker 4: them into soldiers and warriors like Marvel or the X
19:24
Speaker 4: Men would do it, but you turn them into the
19:26
Speaker 4: postal service, and the people effectively become the method by
19:29
Speaker 4: which we send people to other stars. And if you're
19:32
Speaker 4: a powerful enough telekinetic, you can pick something up on
19:35
Speaker 4: Earth and send it to Capella and it'll appear there.
19:39
Speaker 4: But then they had really powerful telescopes, and they have
19:41
Speaker 4: had to be really powerful telescopes the first time they
19:43
Speaker 4: tried sending things to another star, and they'll look at
19:46
Speaker 4: that start and psychic person goes wibily wobbly, whibly wobbly,
19:49
Speaker 4: and the thing disappears, and then it appears x to Capella,
19:52
Speaker 4: and that's all well and good until somebody points out
19:55
Speaker 4: the fact that the light was seeing from Capella left
19:58
Speaker 4: it thirty years ago and we've just seen that thing arrive,
20:01
Speaker 4: so they've obviously teleported it back through time. And then
20:05
Speaker 4: you end up with this bizarre world where you've got
20:07
Speaker 4: this web of world's vast distances from each other that
20:11
Speaker 4: are linked by these postal service workers effectively, who can
20:16
Speaker 4: from an instant communication instant transportation. But in order to
20:21
Speaker 4: have it the instant and to maintain the current, now
20:24
Speaker 4: they've had to send things back in time. But that
20:26
Speaker 4: that means if they send them back in time, but
20:28
Speaker 4: they can communicate instantaneously in both directions, could they tell
20:32
Speaker 4: you thirty years ago to not send them.
20:34
Speaker 5: Yeah, it's a similar story in terms of the Dune
20:42
Speaker 5: sci fi series, because same thing.
20:44
Speaker 1: They fold space, so you can go instantly from one
20:49
Speaker 1: planet to Dune. But it's based on what you just said,
20:55
Speaker 1: that's not the case. They'd have to be going back
20:57
Speaker 1: in time as well.
20:58
Speaker 4: Yeah, and the un stuff got that part right. But
21:01
Speaker 4: then you do have that thing of if it can
21:03
Speaker 4: communicate instantaneously both ways, then you're communicating back in time
21:07
Speaker 4: by thirty years. But if they then looked back at Earth,
21:10
Speaker 4: they would see Earth as it was sixty years earlier,
21:13
Speaker 4: except thirty years back in time. Looking back thirty years,
21:17
Speaker 4: it strikes me that with big enough telescopes that would
21:20
Speaker 4: I mean, it's a science fiction world, so we've already
21:22
Speaker 4: broken the laws of physics. But you would make detective
21:26
Speaker 4: work and police work totally redundant, because what you do
21:29
Speaker 4: is you'd say there was a crime last night, Right,
21:31
Speaker 4: we'll teleport someone fourteen hours away so they're looking back
21:35
Speaker 4: twenty eight hours, so they can just look back and
21:37
Speaker 4: see what happened.
21:38
Speaker 1: Yes, yeah, it makes I love I love it.
21:43
Speaker 2: I love these impossible scenarios.
21:47
Speaker 1: But you know, one day they might come up with
21:50
Speaker 1: a way of doing some weird stuff that we can't
21:52
Speaker 1: explain today, and there'll be some logic attached to it.
21:56
Speaker 4: But I'm sure if we were podcasting one hundred and
21:58
Speaker 4: twenty five years ago, people will come so he couldn't
22:00
Speaker 4: have a heavier heavier than their flight, and look how
22:03
Speaker 4: that worked out.
22:04
Speaker 1: Yeah, exactly, all right, Thank you Gary. Hopefully we covered
22:09
Speaker 1: that question for you. This is Space Nets with Andrew
22:12
Speaker 1: Dunkley and John y Jonna. Okay, we take all for
22:19
Speaker 1: space Nuts. Next question, Oh, we're still in Canada. This
22:23
Speaker 1: question comes from Mark.
22:26
Speaker 6: Hi. It's Mark in London and Canada. I'm current listening
22:31
Speaker 6: to all the back episodes, so I'm in March twenty
22:36
Speaker 6: twenty one, so if you answer my question, it might
22:39
Speaker 6: take me a while to hear it. But I was
22:42
Speaker 6: wondering about lagrange points and the way they're describe as
22:46
Speaker 6: a gravitational well, and we can send satellites there to
22:51
Speaker 6: orbit around them.
22:52
Speaker 1: Is there a way to.
22:54
Speaker 6: Define the mass of the lagrange point? Like, obviously there's
22:58
Speaker 6: nothing there, it doesn't atch you have a mass, but
23:01
Speaker 6: we define or we observe things orbiting, and we can
23:06
Speaker 6: define the mass of all those objects. So when you
23:10
Speaker 6: see a satellite or design a satellite to go into
23:13
Speaker 6: orbit around a lagrange point, is there an equivalent mass
23:18
Speaker 6: that it's orbiting. That's obviously created by the whole system
23:23
Speaker 6: of the larger objects, But is that does that mass?
23:28
Speaker 6: Is it definable? Thanks Gat, Thank you Mark.
23:32
Speaker 1: So Mark's actually demonstrating time travel. He's listening to us
23:36
Speaker 1: in the past, but we're hearing him today.
23:39
Speaker 4: I was just thinking of that. So the question is
23:40
Speaker 4: when Mark listens to this answer, is he listening to
23:43
Speaker 4: in twenty twenty five or twenty twenty nine.
23:46
Speaker 1: H's that's a good point, very interesting, and yeah, thanks
23:51
Speaker 1: for the question, Mark. So we're looking at lagrange points.
23:55
Speaker 2: Our next question actually kind of focuses on that as well.
23:59
Speaker 1: Lagrange point points, gravitation wheels, the mess of a lagarage
24:04
Speaker 1: point I think was the gats of his question.
24:06
Speaker 4: And it's a really interesting question. In fact, I've got
24:09
Speaker 4: a pH d student, part time student working with me
24:11
Speaker 4: who asked a very similar question a couple of months ago,
24:14
Speaker 4: because he's going to be working and looking at the
24:16
Speaker 4: Nettune Trojans, which are trapped around the L four and
24:18
Speaker 4: L five O the grand points of Neptune, and they're
24:21
Speaker 4: library around following this kind of kidney shaped path over
24:25
Speaker 4: a period of hundreds of years around this point sixty
24:28
Speaker 4: degrees ahead or behind Neptune.
24:29
Speaker 2: And it so, but.
24:31
Speaker 4: What's going on here is, well, take a little bit
24:35
Speaker 4: of a deeto. When I was a kid, I was
24:36
Speaker 4: a member of the Scouts, and me too. When you
24:39
Speaker 4: were in the Scouts and you went walking around the countryside,
24:41
Speaker 4: you had an Ordermance survey map. And I don't know
24:44
Speaker 4: if that's called the same thing overseas, but that's what
24:46
Speaker 4: it was in the UK. And what this map had
24:49
Speaker 4: was a map of all the roads and all the
24:51
Speaker 4: hills and all the rest of it, but drawn on
24:53
Speaker 4: it were contours, and all points on a given contour
24:56
Speaker 4: were the same height.
24:57
Speaker 2: Above sea level yep.
24:58
Speaker 4: And so you could tell how told the hills will
25:00
Speaker 4: how seep the valleys where all the rest of it.
25:03
Speaker 4: What those maps actually are are maps of gravitational potential.
25:08
Speaker 4: So all objects at the same distance from the center
25:10
Speaker 4: of the Earth have the same gravitational potential, and you
25:12
Speaker 4: join them up with a contour that's exactly the same thing.
25:16
Speaker 4: So if you make a hypothetical simplified solar system where
25:20
Speaker 4: you just have the Earth while the Earth and the
25:22
Speaker 4: Moon's mush into one and the Sun and nothing else,
25:26
Speaker 4: you can make a contour map where you measure where
25:29
Speaker 4: you calculate the gravitational potential every location in the solar system,
25:34
Speaker 4: and then you do the same kind of map. You
25:36
Speaker 4: join the points that have the same gravitational potential by
25:40
Speaker 4: a contour, and you get a contoon map, and that
25:44
Speaker 4: is fundamentally the same as your ordinan survey map. Points
25:47
Speaker 4: that have the same gravitational potential will be metaphorically at
25:51
Speaker 4: the same altitude above sea level, same distance above sea
25:54
Speaker 4: level as a solar system. Now, if you draw a
25:57
Speaker 4: line directly between the Sun and the Earth, the Sun
26:00
Speaker 4: is at the bottom of an enormous blooming hole. You know,
26:04
Speaker 4: the contours are circular around it. The Earth is at
26:07
Speaker 4: the bottom of a smaller hole, and this is where
26:09
Speaker 4: the whole metaphor of weights on a rubber sheet bowing
26:12
Speaker 4: the rubber sheet comes from. So the Earth is at
26:15
Speaker 4: the bottom of its own hole that is smaller than
26:16
Speaker 4: the hole that the Sun makes. And so if you
26:19
Speaker 4: have a line between them, you effectively come up all
26:21
Speaker 4: from the Sun until you reach a certain point, and
26:24
Speaker 4: then you tip over and you sat falling down the earthshole.
26:26
Speaker 4: So you go downhill again. So between the two you've
26:29
Speaker 4: got like a saddle point where at the top of
26:33
Speaker 4: that saddle you're at a flat point where s basically
26:36
Speaker 4: gravitational potential is flat and you could balance, Say you
26:39
Speaker 4: could put a marble there and it would sit there.
26:41
Speaker 4: But if that marble goes slightly off in either direction,
26:43
Speaker 4: it'll roll down the hill.
26:44
Speaker 2: So if you get a.
26:45
Speaker 4: Little bit closer, then you'll fall off and roll towards
26:47
Speaker 4: the Sun. If you get a little bit closer to
26:49
Speaker 4: the Earth, you'll roll off and roll towards the Earth. Now,
26:53
Speaker 4: if you move out from two dimensions between the Earth
26:55
Speaker 4: and some three dimensions, if you roll clockwise or anti
26:59
Speaker 4: clockwise away from that saddle point, you'll actually be trying
27:02
Speaker 4: to roll uphill, so you'll fall back down into it.
27:04
Speaker 4: So you've got this kind of really is like a
27:07
Speaker 4: saddle point, where towards the Sun and towards the Earth
27:10
Speaker 4: you fall downhill, but at right angles to that you
27:12
Speaker 4: try and roll up hill. So you've got this local
27:16
Speaker 4: flat area where if you move a little bit ahead
27:18
Speaker 4: or behind it in your orbit, you'll roll back down.
27:21
Speaker 4: So you've got a bit of a restoring force there,
27:24
Speaker 4: but if you roll inward or outward.
27:25
Speaker 2: You'll fall off the hill.
27:27
Speaker 4: And that's why that lagrange point is an unstable one.
27:30
Speaker 4: It's like a saddle point. And the three lagrange points
27:34
Speaker 4: that are on the line between the Earth and the Sun,
27:37
Speaker 4: L one, which is between the Earth and the Sun,
27:39
Speaker 4: L two, which is on the far side of the
27:40
Speaker 4: Earth beyond the Earth but on that line, and L three,
27:44
Speaker 4: which is on the far side of the Sun opposite
27:46
Speaker 4: the Earth. Yeah, those points are all these kind of
27:49
Speaker 4: saddle points, so they're a bit more stable than normal
27:52
Speaker 4: space because you can imagine balancing on the flat part
27:54
Speaker 4: of the hill, but if you roll in either direction,
27:57
Speaker 4: you fall away. Now a lot of there are spacecraft
28:01
Speaker 4: sit at the inner or the outer lagrange point L
28:03
Speaker 4: one or L two. The ones at L one sit
28:06
Speaker 4: there because they can observe the Sun and give us
28:07
Speaker 4: prior warning if something's coming our way cell a mass ejection,
28:10
Speaker 4: something like that. The ones at L two sit there
28:13
Speaker 4: to be in a good position to observe space, but
28:16
Speaker 4: have station keeping with the Earth. They move around with
28:18
Speaker 4: the Earth, and that seems like the James Web Space telescope.
28:22
Speaker 4: But because those locations are these kind of saddle points,
28:24
Speaker 4: they're not perfectly stable. Those spacecraft have to have fuel
28:28
Speaker 4: to stay on stations, so if they start to drift downhill,
28:30
Speaker 4: they can push themselves back up and get back to
28:33
Speaker 4: the saddle point. And they actually do this by wabbling
28:35
Speaker 4: and librating around that point and have a little orbit.
28:38
Speaker 4: The other two lagrange points are L four and O five,
28:41
Speaker 4: or sixty degrees ahead and behind the Earth in its
28:44
Speaker 4: orbit around the Sun, and these are like enormous flat plateaus.
28:47
Speaker 4: If you look at a contour map of the gravitational
28:51
Speaker 4: potential of the cell system, you get these big kidney
28:53
Speaker 4: shaped areas that are pretty flat, and that means if
28:56
Speaker 4: you have your ball there, it could just sit there,
29:00
Speaker 4: even if you're quite a long way away from the
29:01
Speaker 4: center point of that lagrange point. You'd sit on one
29:04
Speaker 4: of these contours, and if you start to roll, you'd
29:06
Speaker 4: follow the contoe around, and you'd follow this kind of
29:08
Speaker 4: kidney shipped path, staying trapped around the lagrange point but
29:12
Speaker 4: vibrating around it. And they're like plateaus, so they're much
29:16
Speaker 4: more stable than the kind of saddle points, and that's
29:19
Speaker 4: why those are the points which in the outer Solar
29:22
Speaker 4: System have huge populations. In the orbit of Jupiter, have
29:25
Speaker 4: big populations in the orbit of Neptune. Those are the
29:27
Speaker 4: Juter and Neptune trojans. The other planets can have trojans too,
29:31
Speaker 4: but they tend to be temporary because the Solar System
29:34
Speaker 4: is not simply three objects, it's actually got all the planets.
29:38
Speaker 4: So if you're sadden near the lagrange points of Earth,
29:40
Speaker 4: you're getting gravitational pulls from Venus and Mars nearby, from
29:43
Speaker 4: Jupter and all the other planets as well, and eventually
29:46
Speaker 4: they'll pull you off the stable plateau and you'll fall away,
29:48
Speaker 4: so you'll only live there temporarily. Yea. But for Jupter
29:51
Speaker 4: and Neptune, those planets are so dominant compared to the
29:54
Speaker 4: other things around. They can hold things permanently at the
29:56
Speaker 4: least Lagrange points, and the motion of a objects at
30:00
Speaker 4: the alpha and l five points is that over hundreds
30:03
Speaker 4: of orbits, they we'll gradually librate around that alphour point,
30:06
Speaker 4: so they'll be on average sixty degrees our head or
30:09
Speaker 4: behind the planet, but they'll be moving around that and
30:11
Speaker 4: they'll be orbiting it. So the concept of trying to
30:15
Speaker 4: think about whether you can define a mass at the
30:17
Speaker 4: center of the la Grange point that holds them is
30:20
Speaker 4: not quite the physics that's going on. That librating around
30:24
Speaker 4: that point only works if you're in a frame of
30:27
Speaker 4: reference that is rotating with the orbit of the planet.
30:30
Speaker 4: So you're let's imagine we're looking at the Jupiter trojans.
30:33
Speaker 4: You imagine you somehow suspended above the plane of the
30:36
Speaker 4: Solar System, lying there, watching all the objects in the
30:39
Speaker 4: Solar System, and you're spinning once every twelve years, just
30:42
Speaker 4: as Jupiter orbits are some once every twelve years. So
30:45
Speaker 4: from your point of view, Jupiter and the Sun stain
30:47
Speaker 4: exactly the same place in your field of view. And
30:50
Speaker 4: then over much longer time scales of hundreds of years,
30:53
Speaker 4: these trojans would appay to orbit thet lagrange point. I
30:57
Speaker 4: guess you could if you wanted to try and construct
30:59
Speaker 4: some more to visualize that way. You imagine that there
31:03
Speaker 4: is a virtual mass at the Vela Grange points, and
31:05
Speaker 4: that's what the trogans are orbiting while they'll librate. It
31:08
Speaker 4: would have to be a spread out mass because if
31:12
Speaker 4: it was a point mass, they'd have much more circular orbits,
31:14
Speaker 4: they wouldn't have these kidney shaped things, so the Masso'd
31:16
Speaker 4: have to be spread out. But you could, I guess,
31:19
Speaker 4: visualize it and calculate it, but that would only be
31:22
Speaker 4: valid in the rotating reference frame, which is a bit
31:25
Speaker 4: of a conceit anyway. In the normal scheme of things,
31:29
Speaker 4: where everything's rotating around and you're not spinning above watching it,
31:33
Speaker 4: these objects are moving on orbitstead of very similar period
31:36
Speaker 4: to say Jupiter, but slightly longer, slightly shorter, and as
31:39
Speaker 4: they pull if it's a slightly short orbital period than Jupiter,
31:43
Speaker 4: gradually they'll insure head of Jupe to get further and
31:45
Speaker 4: further ahead. Eventually they drift outwards and they're now further
31:49
Speaker 4: from the Sun, so they're now going around the Sun
31:51
Speaker 4: slower than Jupiter. And they sat fall back towards it
31:54
Speaker 4: until Jupiter's gravity tweaks them and they fall inwards a
31:56
Speaker 4: better than they start moving quicker. So it's actually all
31:59
Speaker 4: down to the traction between Ju to the Sun and
32:01
Speaker 4: the object in that case, rather than a virtual mass
32:05
Speaker 4: off there. So I can see what you're thinking about,
32:07
Speaker 4: and I can see it as being something that is
32:09
Speaker 4: a good model to help you visualize what's going on,
32:13
Speaker 4: But it's not the kind of thing we do calculations of,
32:17
Speaker 4: and I don't think it's a sufficiently advanced mental model
32:20
Speaker 4: that you'd want to get to that level with because
32:22
Speaker 4: it starts taking down a rabbit hole of the physics
32:26
Speaker 4: doesn't actually work that way, and you can put yourself
32:28
Speaker 4: in traps when you do that. But it is a
32:31
Speaker 4: really nice way to visualize initially how it works. It's
32:35
Speaker 4: if you're librating around one of the lagrange points, it
32:38
Speaker 4: is as though there is a force keeping you trug
32:40
Speaker 4: to it. So it's as though there is a mass there,
32:43
Speaker 4: keeping attracting you towards the lagrange point. It's just that
32:46
Speaker 4: that isn't actually a mass there. It's simpler to do
32:49
Speaker 4: with the intraction of all the other objects floating around
32:52
Speaker 4: that create that virtual thing that keeps you locked around
32:55
Speaker 4: that place.
32:56
Speaker 1: M hm okay ho'pefully then helped you out, Man.
33:02
Speaker 4: Broad piece MutS.
33:05
Speaker 1: And our next question and our final question kind of
33:09
Speaker 1: relates to this question that Mark raised, And this came
33:13
Speaker 1: from a YouTuber. I don't know their name, but that's okay.
33:17
Speaker 1: Can you do a deep dive on the Cordleski plasma
33:22
Speaker 1: clouds or do we not have much information on these
33:25
Speaker 1: strange things now I look them up. The Cordleski or
33:29
Speaker 1: Cordleuski clouds are two large, tenuous dust clouds located at
33:34
Speaker 1: L four and L five lagrange points of the Earth
33:38
Speaker 1: Moon system. Originally predicted in the nineteen fifties, first spotted
33:41
Speaker 1: in the sixties, their existence was long doubted, but recently
33:45
Speaker 1: confirmed in twenty eighteen by observations using a polarizing filter
33:49
Speaker 1: that detected reflected sunlight from the dust. While they are
33:53
Speaker 1: called dust clouds, summary research suggests they are a complex
33:57
Speaker 1: a complex form of dusty PLASMI ah, yes.
34:01
Speaker 4: So this is a fascinating question. The Koondleshki clouds are transient,
34:07
Speaker 4: and I think that's probably part of why they've been
34:09
Speaker 4: hard to confirm because there are areas where as we
34:14
Speaker 4: just described those lagrange points. If you only have the
34:17
Speaker 4: Earth and the Moon in space and nothing else, then
34:20
Speaker 4: the leading alpha and OL five lagrange points of the
34:22
Speaker 4: Moon could be stable on million year, billionaire time scales.
34:26
Speaker 4: But in actuality in the system where you've got the Sun,
34:29
Speaker 4: you've got all the other planets, and for small objects,
34:33
Speaker 4: the influence of the solar wind and the Sun's radiation
34:36
Speaker 4: becomes significant as well. What that means is that it
34:39
Speaker 4: becomes easier to escape from those lagrange points. By being
34:43
Speaker 4: easier to escape, it also means it's easy to get
34:45
Speaker 4: trapped there in the first place. Of course, if you
34:48
Speaker 4: can get out, you can get it. And so what
34:51
Speaker 4: that means is you can imagine as the Moon and
34:54
Speaker 4: the Earth are all but in the common center of mass,
34:56
Speaker 4: sixty degrees ahead and behind of the Moon are these
34:59
Speaker 4: areas are space in the Moon's orbit that are like
35:02
Speaker 4: little dimples in space where it's easy for stuff to
35:05
Speaker 4: build up and get captured there temporarily before getting cleaned
35:08
Speaker 4: out again. They're not deep enough for things to get
35:11
Speaker 4: hooked there permanently. But what that means is interplanetary dust,
35:16
Speaker 4: bits of the solar wind that aren't moving that quick
35:19
Speaker 4: stuff splutted off the Moon by impact events, can some
35:23
Speaker 4: of that can congregate there and spend a certain amount
35:25
Speaker 4: of time there. Now, the dynamics of it as such
35:27
Speaker 4: as been a lot of modeling done of this that
35:30
Speaker 4: if dust is there for a reasonable amount of time,
35:33
Speaker 4: it will actually get congregated into kind of bar features
35:35
Speaker 4: and streams. I think you'll have to get a bit
35:37
Speaker 4: of structure in it before it gets cleaned out. But
35:40
Speaker 4: fundamentally what's going to be happening is that you've got
35:43
Speaker 4: dust and gas getting temporarily captured there and then getting
35:47
Speaker 4: cleaned out again, and so the amount of material there
35:50
Speaker 4: will depend on what's happening at the time. These were
35:53
Speaker 4: proposed a good long time ago, and they were first
35:55
Speaker 4: kind of reported to be observed in nineteen sixty one
35:58
Speaker 4: by Kordolowski. That's why they take that person's name and
36:04
Speaker 4: got photos observe them with the naked eye. There are
36:07
Speaker 4: about two magnitudes at that time fainter than the Gaganshine,
36:11
Speaker 4: which is dust opposite the Moon in its orbit and
36:15
Speaker 4: is visible as a very faint, fuzzy blob. So they're
36:18
Speaker 4: very hard to pick up very hard spot. And for
36:21
Speaker 4: many years after that other people looked for them and
36:23
Speaker 4: could not see them, and that's where the controversy came
36:25
Speaker 4: about that they're probably not there. The much more recent
36:28
Speaker 4: observations by Hungarian astronomers made use of polar eimitary to
36:32
Speaker 4: actually make these things easier to see, and they were
36:35
Speaker 4: able to see them. Now there is I would have
36:39
Speaker 4: thought some debate over whether these have been there permanently
36:42
Speaker 4: since then, or whether what's happening is that the times
36:44
Speaker 4: have been detected at times when the dust and gas
36:47
Speaker 4: there has been a bit denser than normal, making them
36:49
Speaker 4: easier to see. Yeah, because if this is a time
36:51
Speaker 4: varying population of stuff there, there will be times when
36:54
Speaker 4: you see more, times when you see less. And again,
36:58
Speaker 4: PhD student and again it's just sick her over in
37:00
Speaker 4: the US. She's talking with Aaron Bully possibly looking at
37:05
Speaker 4: and doing some modeling of dust ejection from the Moon
37:09
Speaker 4: and where it would end up, and some of that
37:10
Speaker 4: dust would temporarily end up in the La Grande points,
37:13
Speaker 4: become part of the cordialscia clouds, and then disperse again.
37:16
Speaker 4: So the evidences that they're there, the evidences that they're transient.
37:20
Speaker 4: The idea that there could be plasma there as well
37:22
Speaker 4: is just better around the same physics of it being
37:24
Speaker 4: an area which is like a little dimple where things
37:28
Speaker 4: can build up and be held there for a little while.
37:30
Speaker 4: And we're aware that when you've got a perfectly smooth floor,
37:33
Speaker 4: the dust stays spread evenly, but if you've got any
37:35
Speaker 4: little dimples and stuff like that, dust can build up
37:37
Speaker 4: there until the gust of wind blows it out. It's
37:39
Speaker 4: effectively what's going on there. So they're really interesting. It's
37:43
Speaker 4: quite likely that all the other objects in the Solar
37:47
Speaker 4: System would have things like this as well, So Mars's
37:49
Speaker 4: Moon's Phobos and Demos. They're much less massive than our moon,
37:52
Speaker 4: so the lagrange points won't be much tinier, but you
37:55
Speaker 4: might get similar things there. We know that among the
37:58
Speaker 4: boons of Second we've got a couple of co orbitals satellites,
38:00
Speaker 4: including a couple of satellites that actually have Trojan companions.
38:04
Speaker 4: It's not just Jupter and Neptune that have permanent trojans.
38:07
Speaker 4: It's not just Earth and Mars, Saturn and Euros that
38:10
Speaker 4: have temporary trojans. There are actually Trojan satellites in the
38:14
Speaker 4: Saturnian system. And this is just one aspect of this now.
38:18
Speaker 4: You know, you could imagine that in a very very
38:21
Speaker 4: different world we could have had the moon and then
38:22
Speaker 4: we could have had a couple of small satellites, one
38:24
Speaker 4: leading it, one trailing. It's a bit and it's quite
38:27
Speaker 4: possible that after the moon forming impact there may well
38:30
Speaker 4: have been temporary kind of agglomerations of matter there on
38:34
Speaker 4: a much more substantial level as the Moon was forming.
38:36
Speaker 4: You can even have you know, small objects been accumulating
38:40
Speaker 4: their forming there and then escaping and all the.
38:42
Speaker 2: Rest of it.
38:43
Speaker 4: But hopefully that covers stuff. It is a really fascinating topic.
38:47
Speaker 2: You know.
38:48
Speaker 4: The kind of imagery people have done to figure this
38:50
Speaker 4: out back then was really challenging. You're talking about using
38:53
Speaker 4: a very fast, wide angled lens and doing menthy exposures
38:57
Speaker 4: to try and get a little bit of contrast between
38:59
Speaker 4: the rightness of the sky where the clouds are and
39:02
Speaker 4: the brightness of the sky.
39:03
Speaker 2: Where they aren't.
39:04
Speaker 4: The more recent work by the Hungarian team in twenty
39:06
Speaker 4: eighteen did some very very clever stuff where then it
39:09
Speaker 4: only imaged the clouds at the L five point when
39:13
Speaker 4: they were there, and did the polarimetry, but they also
39:15
Speaker 4: imaged the same part of the sky when the L
39:18
Speaker 4: five point wasn't there. They also imaged it when there
39:22
Speaker 4: were some high clouds like Cyrus there, when aircraft contrails
39:25
Speaker 4: were passing through that area of the sky and things
39:28
Speaker 4: like that, in order to have comparisons from other objects
39:30
Speaker 4: that had in the past been suggested as giving false
39:33
Speaker 4: positives here, and they were able to confirm that actually, no,
39:36
Speaker 4: it was the presence of the L five point and
39:38
Speaker 4: the dust there was what they got because it looked
39:40
Speaker 4: sufficiently different to the other things that it was robust,
39:44
Speaker 4: which is very very cool, And it's a good example
39:46
Speaker 4: of when you're trying to find something that's incredibly hard
39:49
Speaker 4: to see and hard to study, then you need to
39:53
Speaker 4: do some really very impressive and very innovative observations to.
39:56
Speaker 2: Make that work.
39:57
Speaker 4: And you know, people have done some lovely modeling of
39:59
Speaker 4: orbital connects to see how long things would reside there,
40:02
Speaker 4: and there've even been proposals of sending spacecraft there to
40:05
Speaker 4: check it out. But that's about where we sit with
40:08
Speaker 4: them at the minute, and it is a fascinating subject.
40:10
Speaker 4: We'll learn more in the years to come. Doubtless. When
40:15
Speaker 4: Jessica's PhD is finished and she gets to go on
40:17
Speaker 4: and do this further research, we'll learn a little bit
40:19
Speaker 4: more about dust that is kicked off the surface of
40:21
Speaker 4: the moon and where it goes and how that contributes.
40:25
Speaker 4: But like everything, you know, there's more to learn than
40:27
Speaker 4: we already have done, and we're still at the start
40:29
Speaker 4: of this journey realistically.
40:30
Speaker 1: Yeah, yeah, absolutely, Yeah, great question and great to get
40:34
Speaker 1: a question from our YouTube audience, which is ever growing.
40:37
Speaker 2: So thank you for.
40:38
Speaker 1: That, and we are done. Thanks for answering all those questions, Johnny.
40:43
Speaker 2: That's a pleasure.
40:44
Speaker 4: It's good to get some kind of brand teasers and
40:46
Speaker 4: stuff that makes your head hurt a little bit.
40:48
Speaker 1: That does, doesn't it.
40:49
Speaker 7: Yeah, Yeah, I think we're Fred and I and now
40:54
Speaker 7: yourself are constantly amazed by the depth of the inquisitiveness
40:59
Speaker 7: of it audience.
41:00
Speaker 6: Yeah.
41:00
Speaker 2: I think that's a good way of just growing it.
41:02
Speaker 1: But all right, if you have questions for us, and
41:05
Speaker 1: we could sure use some audio questions, we are thin
41:08
Speaker 1: on the ground, jump on our website and send them in.
41:12
Speaker 1: It's space Nuts podcast dot com or space Nuts dot Io.
41:15
Speaker 1: Click on the AMA link at the top and you
41:17
Speaker 1: can send text and audio questions to us that way
41:20
Speaker 1: if you so desire, and don't forget to tell us
41:23
Speaker 1: who you are or where you're from, or both. Thanks Johnny,
41:27
Speaker 1: we'll catch you real soon.
41:29
Speaker 2: Thanks for having me, Always a pleasure.
41:31
Speaker 1: John ty Horner, Professor of Astrophysics at the University of
41:34
Speaker 1: Southern Queensland here in the studio, couldn't be with us
41:38
Speaker 1: again today. You got himself stuck another Grange point and
41:41
Speaker 1: from me Andrew Dunkley, Thanks for your company. See you
41:44
Speaker 1: on the next episode of Space Nuts. Bye bye, You'll
41:48
Speaker 1: be to the Space.
41:49
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Speaker 4: favorite podcast player.
41:58
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41:59
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42:01
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