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Cosmic Q&A: Black Holes, Stellar Densities & the Sun's Sudden Disappearance · Space Nuts: Astronomy Insights & Cosmic Discoveries

• 0:00
  Andrew Dunkley: Hi there. Thanks for joining us on a Q and A
• 0:02
  edition of Space Nuts, our first one for the
• 0:04
  year. My name is Andrew Dunkley, your host.
• 0:07
  And we've got questions from Justin,
• 0:10
  who's got, um, a sent us an audio
• 0:12
  question. Um, he's talking about the space
• 0:16
  that contains the equivalent to 4 million
• 0:18
  stars in comparison to a black, ah, hole, I
• 0:21
  think. Can't remember. I don't write down
• 0:23
  enough when I write down the descriptions of
• 0:25
  questions. Uh, Charles,
• 0:28
  you're right. Fred's saying the same thing.
• 0:31
  Uh, Charles says, um, is asking us
• 0:34
  a question about the retraction of, uh, the
• 0:37
  universe, the shrinking of it. Uh, and,
• 0:40
  uh, Dean is asking, uh, about what might
• 0:43
  happen if the sun instantaneously
• 0:45
  disappeared. What would be the effect on our
• 0:48
  solar system and our planet specifically. And
• 0:51
  Patrick has some thoughts about, uh, both the
• 0:54
  voyages one and two, mainly
• 0:57
  the fact that the data we've put on the
• 0:59
  plaques that have been put on board the
• 1:01
  Voyages is actually telling anyone who
• 1:04
  finds them a lie. That's all coming up
• 1:07
  in this edition of Space Butts. And
• 1:10
  with us once again to decipher all of that
• 1:13
  gibberish that I just mentioned. And it's not
• 1:15
  the questions that are gibberish, it's my
• 1:17
  interpretation of them is Professor Fred
• 1:19
  Watson, astronomer at large. Hello, Fred.
• 1:22
  Professor Fred Watson: Hi, Andrew. Your interpretation was more or
• 1:25
  less the same as what I thought when I saw
• 1:27
  them. So I think we're on the same
• 1:29
  wavelength, which is good.
• 1:30
  Andrew Dunkley: Okay. Okay, well, that's good. Uh, we
• 1:33
  might as well just hit them straight on the
• 1:35
  head.
• 1:35
  And our first question is an audio question.
• 1:38
  And this one comes from Justin.
• 1:40
  Justin: G', day, Andrew and Fred. I'm Justin down in
• 1:43
  Melbourne. Like Fred, I'm an
• 1:45
  expat POM and my astronomical claim to
• 1:48
  fame is that I witnessed the total solar
• 1:51
  eclipse in Cornwall in the UK in
• 1:53
  1999. Two friends and
• 1:56
  I camped nearby and joined the crowds at
• 1:58
  Newquay beach on that day for a
• 2:01
  lifetime bucket list event.
• 2:04
  So I have a mathematical question. I've often
• 2:07
  heard it said that the black hole at the
• 2:09
  center of the Milky Way galaxy Sagittarius A
• 2:12
  is 4 million solar masses.
• 2:15
  So for comparison, what would the
• 2:18
  radius be in light years of a
• 2:20
  sphere centered on the Earth that contains
• 2:23
  the nearest 4 million stars?
• 2:26
  Thanks very much.
• 2:28
  Andrew Dunkley: Thank you, Justin. Cornwall. That's where my
• 2:30
  family originated before
• 2:33
  they, um, they got sent out here. Now, I
• 2:36
  think they came voluntarily. We, we didn't
• 2:39
  come with the convicts. We, we came out
• 2:41
  later. But, um, yeah, Justin, good question.
• 2:43
  Four million stars. Um, what sort of Space
• 2:46
  would that take up in terms of a radius in
• 2:49
  light years? I think was the guts of his
• 2:51
  question.
• 2:52
  Professor Fred Watson: Yes. So, uh, a little bit more
• 2:55
  subtle than that. It's, it's saying if
• 2:58
  you, if you're sitting here on planet Earth,
• 3:01
  um, what sort of,
• 3:04
  you know, in our locality, uh, in the
• 3:08
  um, Western spiral,
• 3:11
  the galaxy, it's the Orion spur, where we
• 3:13
  are, uh, that spiral arm that we sit
• 3:16
  in. Um, what's the, it's so it's really
• 3:19
  a question about the density of stars in our
• 3:21
  region. Uh, and that's something very well
• 3:24
  established because we know the distances of
• 3:26
  lots of stars. Uh, so I'm
• 3:29
  going to put it in much rounder figures. Uh,
• 3:33
  uh, but if you
• 3:37
  look at uh, out to
• 3:40
  a thousand light years, okay, so you've got a
• 3:42
  sphere of radius a thousand light years,
• 3:45
  then that's going to have something like 10
• 3:49
  million stars in it. Whoa. So that's more
• 3:52
  than what uh, what um, Justin's
• 3:54
  talking about. Uh, but the way this
• 3:57
  changes, uh, it changes non linearly.
• 4:00
  Uh, so I'm guessing, so I'm going to take a
• 4:03
  guess that you know, around 9, 900
• 4:06
  light years or thereabouts, you
• 4:09
  would probably have something like 4 million
• 4:12
  stars, which is the same uh,
• 4:15
  mass as the mass of the supermassive uh,
• 4:18
  black hole at, of the galaxy. So it's
• 4:20
  actually quite a long way, you know, you're
• 4:22
  looking out. Yeah, several hundred light
• 4:24
  years. Uh, uh, in terms of
• 4:27
  radius. Uh, and
• 4:30
  um, it's actually I think you would
• 4:32
  probably be able to find a tool online. I
• 4:35
  haven't found it myself because I haven't
• 4:37
  really looked for it, but I bet you can find
• 4:38
  a tool that gives you the exact answer to
• 4:41
  that. Uh, how many stars are within a radius
• 4:43
  of X number of light years. And if you
• 4:46
  put in a good guess of light years, you'll
• 4:49
  probably get the right number of stars.
• 4:51
  Andrew Dunkley: Do you want me to test it?
• 4:53
  Professor Fred Watson: Yeah, if you can find one.
• 4:54
  Andrew Dunkley: Yeah. I've got an idea. So what's the
• 4:56
  question? How many stars
• 4:59
  in uh, say within
• 5:02
  900 light years?
• 5:04
  Professor Fred Watson: Okay, see what it is. This is a
• 5:06
  guess on my part.
• 5:07
  Andrew Dunkley: Uh, radius of
• 5:10
  900 light years.
• 5:13
  Okay, let's see what happens here.
• 5:17
  Um, I'll just make sure I ask the question
• 5:19
  correctly.
• 5:22
  Ah, nothing. Oh, here we go. Uh, uh,
• 5:26
  ah, it's saying 10 to
• 5:29
  15 million.
• 5:31
  Professor Fred Watson: Yeah. Um, which is different from the
• 5:33
  calculation I saw, which is 10 million in a
• 5:36
  thousand. So drop it down a bit. Can you put
• 5:38
  it down to 500 light years, see what it says
• 5:41
  for that. Okay. This is AI, I assume that
• 5:43
  is doing all this for you on
• 5:46
  Mr. Google.
• 5:47
  Andrew Dunkley: I absolutely love it. Um, two
• 5:50
  to two and a half million stars.
• 5:53
  Professor Fred Watson: Yeah. So it's somewhere between 500
• 5:55
  and 1,000 light years.
• 5:56
  Andrew Dunkley: There you go.
• 5:57
  Professor Fred Watson: So you put in whatever number you like, and
• 5:59
  it will give you the right answer. Uh, Justin
• 6:02
  can have a lot of fun doing that. It's a
• 6:03
  great question, actually.
• 6:04
  Andrew Dunkley: Just working out the averages. So
• 6:07
  750 light years transposes to
• 6:10
  7 to 8 million stars. So.
• 6:12
  Professor Fred Watson: Yeah.
• 6:13
  Andrew Dunkley: Yeah, there you go. You could
• 6:16
  do this all day, really.
• 6:20
  Professor Fred Watson: Um, I don't think we've ever been asked that
• 6:22
  before.
• 6:22
  Andrew Dunkley: No, I don't think so either.
• 6:23
  Professor Fred Watson: Not in that. That way. Um, we have had
• 6:26
  questions about, you know, the density. The
• 6:28
  average density of stars in the solar
• 6:30
  neighborhood, and that's really what this is
• 6:31
  all about.
• 6:32
  Andrew Dunkley: Yeah.
• 6:32
  Professor Fred Watson: Uh, but, uh, yeah, good stuff, Justin.
• 6:35
  Thank you for your question and greetings to
• 6:37
  Melbourne. It's 42 in Melbourne today, I
• 6:39
  think.
• 6:39
  Andrew Dunkley: Yes. Um, we've. We'. I've got 38 here
• 6:42
  today. I went and played golf in that this
• 6:43
  morning, and, uh, I was. What's the word I
• 6:46
  used? One of my friends used to use a lot
• 6:49
  when he was tired. I was jiggered by the end
• 6:51
  of it.
• 6:52
  Professor Fred Watson: That's a good.
• 6:53
  Andrew Dunkley: I don't know where it comes from.
• 6:53
  Professor Fred Watson: My granddad used to use that. Yeah, yeah.
• 6:56
  Justin: Ah.
• 6:56
  Professor Fred Watson: Uh, wheel it in. It's jiggered.
• 6:58
  Andrew Dunkley: Yeah, it was, uh. It was a tough day out, I
• 7:01
  must say. Uh, thanks, Justin.
• 7:03
  Our next question comes from Charles. Uh,
• 7:06
  but because I've been using, uh, ChatGPT
• 7:08
  to solve all the riddles of the universe,
• 7:11
  I've lost the question. All right. If
• 7:14
  the universe does cease expanding
• 7:17
  and retracts, does that mean the lifetime of
• 7:19
  the universe goes from, uh, untold
• 7:22
  trillion, beyond trillions of years
• 7:25
  or just a, um, measly few billion?
• 7:28
  This one comes from Charles in Brooklyn. In
• 7:31
  New York. I was in Brooklyn not so long ago.
• 7:33
  Walked across the Brooklyn Bridge. Yeah, in
• 7:36
  about August, it was m.
• 7:38
  Professor Fred Watson: Were you jiggered when you got to the end?
• 7:40
  Andrew Dunkley: I was jiggered before I started because we'd
• 7:42
  been walking all day.
• 7:46
  Professor Fred Watson: Yeah, I can imagine. Um, I think Charles
• 7:49
  is right, actually. Uh, look,
• 7:53
  it may still.
• 7:56
  I mean, the difference is really that
• 7:59
  if we have a universe which
• 8:02
  is dominated by a constant, uh,
• 8:05
  um, dark energy term. In other words,
• 8:08
  something that puts more energy into the
• 8:11
  expansion of space. As the expansion. As
• 8:14
  space gets bigger, uh, that means it will go
• 8:16
  on expanding forever. Um, so. And
• 8:19
  Charles has summarized that by untold
• 8:22
  trillions beyond trillions, which I guess is
• 8:24
  forever. Uh, but if the dark
• 8:27
  energy is reducing, and that's
• 8:30
  certainly being hinted at by the latest
• 8:32
  observations, then um,
• 8:35
  we don't know what's going to happen
• 8:38
  because we don't know how quickly it's
• 8:39
  reducing and whether it may even go negative.
• 8:43
  So that suddenly there's a positive
• 8:45
  attraction of stuff, it's not being repelled
• 8:47
  like it is now, that could bring it down to a
• 8:50
  few billion years. Uh, but if it just
• 8:53
  goes settles back to something where
• 8:56
  it's the normal gravitational content of the
• 8:58
  universe that dominates everything, uh, and
• 9:01
  so in other words all the galaxies are
• 9:02
  pulling each other together, uh, then
• 9:06
  you might be talking about a bit longer. It
• 9:07
  might still be a few trillion years rather
• 9:09
  than a few measly billions. Uh, but,
• 9:12
  ah, interesting question. A nice thought
• 9:14
  experiment there from Charles in Brooklyn.
• 9:16
  Andrew Dunkley: Yes, indeed. And as
• 9:19
  you said, the theory about like
• 9:22
  I think I've said it before, when I was
• 9:24
  growing up, it was always assumed that the
• 9:26
  universe would stop expanding and then start
• 9:29
  sort of folding back in on itself. Uh, the
• 9:32
  Big Crunch or the gnab.
• 9:33
  Professor Fred Watson: Gib, whatever you want to call it.
• 9:35
  Andrew Dunkley: But um, then it was decided
• 9:38
  that uh, it was going to continue expanding
• 9:40
  at an accelerating rate. Now they've decided
• 9:43
  and that could lead to a Big Rip. But now
• 9:45
  it's looking more like the acceleration
• 9:48
  is slowing and now
• 9:51
  all the bets are off and we're back to, back
• 9:53
  to square one or something. I'm not sure.
• 9:57
  Yeah. How do you prove it? Well, I mean
• 10:02
  you can measure that. What's going on?
• 10:05
  Professor Fred Watson: Yeah, and that's the trick. I mean
• 10:08
  if we'd been having this conversation a year
• 10:10
  ago, we'd have been completely sold on
• 10:13
  the Big Rip because there was nothing to
• 10:15
  suggest that the expansion was going to slow
• 10:18
  down. The expansion was known to be
• 10:20
  accelerating. That was discovered in 1998.
• 10:23
  Um, but it's only within the last year with
• 10:25
  um, results from project called desi,
• 10:28
  uh, the Dark Energy
• 10:31
  Survey Instrument I think is the right thing.
• 10:34
  Uh, but that's basically established
• 10:37
  that uh. Established is the wrong word. It
• 10:40
  has suggested that the acceleration
• 10:43
  is slower now than it was
• 10:46
  a couple of billion years ago. Uh, and
• 10:49
  that uh, is leading people
• 10:51
  to the hint that maybe the acceleration will
• 10:54
  eventually not be there. And that's why we
• 10:57
  might get the gnab Gib. But I think we're
• 10:59
  still talking about, I think, really think
• 11:01
  it's trillions of years into the future.
• 11:03
  Andrew Dunkley: It's m like blowing up a balloon though when
• 11:05
  you start it goes out fast, but as it gets
• 11:08
  bigger, uh, the expansion continues, but
• 11:11
  it just, it slows down. It's the same
• 11:13
  thing.
• 11:15
  Professor Fred Watson: Okay.
• 11:19
  Andrew Dunkley: Maybe not. It does remind me, um, we
• 11:22
  got a question in German the other day
• 11:24
  because apparently now what they're doing on
• 11:27
  YouTube Music, the people who listen to us on
• 11:29
  YouTube Music is, uh,
• 11:32
  English speaking. YouTube Music
• 11:35
  podcasts are being translated into other
• 11:38
  languages. So apparently we were
• 11:41
  being heard in German, and a German listener
• 11:43
  on YouTube Music sent us a question in
• 11:46
  German and we had to translate
• 11:49
  it into English so that we knew what he was
• 11:52
  asking. But I don't think it translated very
• 11:54
  well. But it was something about, how do you
• 11:56
  prove the expansion of the universe
• 11:59
  if you haven't found a particle?
• 12:02
  Professor Fred Watson: Well, I wasn't sure whether I did look at
• 12:05
  that question. In fact, I did send an answer
• 12:07
  which I think, um, Huw might have put through
• 12:09
  some language mangling, um,
• 12:12
  system to give the answer in German.
• 12:15
  Uh, mein Deutsch is
• 12:17
  crap. Uh, so, um,
• 12:21
  that's K R A double P. It's
• 12:24
  not, uh,
• 12:28
  uh, so, um, I think. I wasn't sure
• 12:30
  whether it was somebody talking about dark
• 12:33
  energy or dark matter. Yeah, I wasn't sure
• 12:35
  either. But dark matter, yes, we do need to
• 12:38
  know what the particles are. And, um, I hope
• 12:41
  we'll discover them. I. I'm not optimistic.
• 12:43
  M. We're going to find that out during 2026,
• 12:45
  but you never know.
• 12:46
  Andrew Dunkley: Anything's possible. Thanks for your
• 12:49
  question, Charles.
• 12:50
  This is Space Nuts, uh, Q and A edition with
• 12:52
  Andrew Dunkley and Fred Watson.
• 12:56
  Andrew Dunkley: Now, let's take a break from the show to tell
• 12:58
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• 14:25
  Andrew Dunkley: Uh, next up we've got Dean who's got
• 14:28
  a kind of a what if question for. I love
• 14:30
  these, Fred. These are my favourite
• 14:33
  questions. What if this happens?
• 14:34
  Andrew Dunkley: Hi Fred and Andrew, this is Dean in Redcliffe
• 14:37
  in Queensland. Thanks for answering my
• 14:39
  previous questions. Today I'm asking about
• 14:42
  a thought experiment that was once used to
• 14:44
  consider issues around the speed of light. I
• 14:46
  think it may have been Einstein. The scenario
• 14:49
  asks what happens if our uh, sun suddenly
• 14:51
  disappears and would the sudden lack of
• 14:54
  gravity affect the earth instantly or would
• 14:56
  there be a delay if the gravity effect
• 14:59
  travels at a particular speed? Before
• 15:02
  I get to my actual question, I want to ask
• 15:03
  about thought experiments. They seem like a
• 15:06
  useful tool to get started on a problem, but
• 15:08
  I question the value of an experiment where
• 15:11
  the uh, initial proposition is impossible.
• 15:14
  The mass of the sun can't actually just
• 15:16
  disappear. So maybe basing conclusions
• 15:19
  from this is not reliable. What are your
• 15:21
  thoughts? However, if I just focus on the
• 15:24
  idea of the sun disappearing, I'd say that
• 15:26
  gravity is not a force generated by the sun,
• 15:29
  but is a compression of the spacetime around
• 15:31
  it. If the sun disappeared
• 15:34
  instantly, then space time would decompress
• 15:37
  back to a smooth state, except for the
• 15:40
  planets and moons still in the vicinity.
• 15:42
  There would also have to be an unwinding of
• 15:44
  the frame dragging around where the sun was.
• 15:47
  Let me know if I'm wrong, but it seems to me
• 15:50
  that a sudden decompression and unwinding of
• 15:52
  some local space time would be violent but
• 15:54
  uh, would not be instant.
• 15:57
  Imagine the 2D model of this using
• 16:00
  a large rubber sheet with a heavy ball in the
• 16:02
  center representing the sun. If you suddenly
• 16:05
  removed the ball, then the warped sheet would
• 16:08
  snap back into a flat plane quickly,
• 16:11
  but not instantly.
• 16:13
  Spacetime is very stiff. Maybe the Earth
• 16:16
  would start to feel some effect very
• 16:19
  quickly, but there would be a smooth
• 16:21
  transition to the complete lack of
• 16:24
  sun's gravity while the local spacetime is
• 16:26
  settling into a decompressed state.
• 16:29
  I also expect there would be a compression
• 16:31
  wave that is a uh, gravity wave generated
• 16:34
  from an event like this. What do you think?
• 16:39
  Andrew Dunkley: There's a lot packaged into that. Thank, uh,
• 16:41
  you Dean.
• 16:42
  Uh, so there's a question or two questions
• 16:45
  effectively uh, that he's asking about,
• 16:48
  um, what's the worth of thought
• 16:50
  experiments? Uh, now
• 16:54
  yeah, I did
• 16:57
  a Little bit of research while I was
• 16:58
  listening to him. And to give you an idea of
• 17:01
  thought experiments, um, there have been many
• 17:03
  famous ones over the years. Schrodinger's
• 17:05
  cat, Galileo's, uh, falling
• 17:08
  bodies. Um, there's
• 17:11
  one called the Trolley Problem. I have to
• 17:13
  look into that. Don't know what that one is.
• 17:15
  But, um, yeah, they have been very
• 17:17
  helpful over the years. I do think there is
• 17:20
  worth in thought experiments. It's a
• 17:23
  way of exploring something that we can't
• 17:25
  solve yet because we haven't got the
• 17:26
  technology to solve it. But it
• 17:29
  gives you something to work with and it
• 17:31
  tosses around ideas that may provide
• 17:34
  solutions. It's, um. I think.
• 17:38
  I love the concept. I think it's very
• 17:40
  valuable. It's how we start making
• 17:43
  inquiries with thought experiments.
• 17:46
  If we didn't use our imaginations, then we
• 17:48
  probably wouldn't solve anything.
• 17:50
  Professor Fred Watson: Exactly. Um, a great answer, actually.
• 17:53
  Andrew. Thank you. Um, I'll. I'll just
• 17:56
  go home and. No,
• 17:59
  I entirely agree. Um, the one that came to my
• 18:02
  mind was a thought experiment that, had the
• 18:05
  real experiment been carried out, physics,
• 18:07
  uh, would have ground to a halt very quickly.
• 18:09
  And that's, uh, Einstein's
• 18:12
  musing in 1907
• 18:15
  about what would happen if he jumped off the
• 18:17
  top of the Patents Building in Berne, which
• 18:20
  is where he was working at the time. He was a
• 18:22
  patent administrator. Uh, and so
• 18:25
  he imagined himself jumping off the top of
• 18:26
  the building. Uh, so if he carried that out
• 18:29
  as a real experiment, that could have been
• 18:30
  the end of a lot of really good stuff. Yeah.
• 18:34
  Uh, but what it gave him was the inspiration
• 18:37
  to, um, define what we now call the
• 18:40
  principle of equivalence. The fact that
• 18:42
  acceleration and gravity are, uh,
• 18:45
  to all intents and purposes, the same. Um,
• 18:49
  so. And the fact that you're accelerating
• 18:51
  towards the Earth, uh, cancels out the
• 18:54
  Earth's gravity because the two are exactly
• 18:56
  equal. And that's why
• 18:59
  as you jump off the building, uh, your pipe
• 19:01
  floats out of your mouth. If you've got money
• 19:03
  in your hands or something like that, it just
• 19:05
  floats away. You can actually demonstrate it
• 19:07
  very easily on a trampoline, uh, without
• 19:09
  jumping off buildings. But it was that
• 19:11
  thought experiment that led to the principle
• 19:13
  of equivalence, which told Einstein that
• 19:16
  gravity is actually a geometrical problem
• 19:19
  rather than, you know, something entwined
• 19:22
  in physics. We know it is. We still don't
• 19:24
  really understand the physics of gravity, but
• 19:26
  the geometry works so well. Well, uh,
• 19:29
  in the general, uh, theory of relativity
• 19:32
  that, um, the principle of equivalence has
• 19:34
  been demonstrated to be accurate to within
• 19:37
  one part, uh, in 10 to the 18 or something. I
• 19:39
  can't remember what the latest thing is, uh,
• 19:42
  that it does work very, very well indeed. Uh,
• 19:45
  so yes, thought experiments are great. Um,
• 19:47
  now the thought experiment regarding taking
• 19:49
  the sun out the solar system is very well
• 19:51
  established as to what happens. Uh,
• 19:55
  the Earth feels nothing for the first eight
• 19:57
  minutes, uh, because gravitational energy
• 20:00
  travels at the same speed as light. Uh,
• 20:02
  and once, um, the message
• 20:05
  that there is no gravitating body
• 20:08
  in the center of the solar system reaches the
• 20:11
  Earth eight minutes after the sun has gone,
• 20:13
  um, the Earth just carries on in a straight
• 20:15
  line. Uh, ah,
• 20:18
  so, uh, that's well understood. So,
• 20:22
  um, I think, uh, um,
• 20:25
  Dean's um, thinking uh, about
• 20:28
  the, you know, the, the two dimensional
• 20:30
  idea of the gravity well, uh, which is a
• 20:33
  great way of thinking of the way, uh, mass
• 20:35
  distorts time. Uh, we're used to
• 20:38
  thinking, okay, you've got a rock in the
• 20:41
  middle of a trampoline. It's pulling it down,
• 20:43
  you take the rock away, the trampoline just
• 20:45
  springs back. Uh, but actually, uh, it
• 20:47
  wouldn't. The space time would take, uh,
• 20:50
  time, uh, basically the message that
• 20:53
  it had sprung back would take, would travel
• 20:56
  outwards at the speed of light. Uh, and so
• 20:58
  it's the same, you know, the same thing
• 21:00
  looking at it either as a gravity well or
• 21:03
  as gravitational energy or radiation.
• 21:06
  One day we'll have a quantum theory of
• 21:07
  gravity and we'll be able to talk about
• 21:09
  gravitons, uh, which are, uh, the
• 21:11
  hypothetical particles that carry gravity and
• 21:13
  they move at the speed of light.
• 21:15
  Andrew Dunkley: Of course, we should mention the catastrophe
• 21:17
  that would then follow 8 minutes after the
• 21:19
  sun suddenly disappeared. 4 example.
• 21:22
  Pavlov's dog and Schroding's Schrodinger's
• 21:25
  cat would live together.
• 21:26
  Professor Fred Watson: Yes. So they would.
• 21:30
  Yeah. Oh, deary me. Uh, that's. Yes.
• 21:34
  Andrew Dunkley: Would be a mess. How long would the
• 21:37
  Earth last after that effect?
• 21:39
  Professor Fred Watson: Uh, it would be fine. It would just keep on
• 21:41
  going. Um, you know, assuming there wasn't
• 21:43
  some sort of, um, uh,
• 21:45
  catastrophic event that caused the sun to
• 21:47
  disappear. If you just remove the sun without
• 21:50
  anything, explodes anything, which you can do
• 21:53
  in a thought experiment, the Earth just
• 21:55
  keeps, keeps on going. It will be like
• 21:57
  Voyager 1 and Voyager 2. It will get very,
• 21:59
  very cold. Uh, we as a species will almost
• 22:02
  certainly not survive, uh, because the
• 22:04
  temperatures would plummet to very low levels
• 22:06
  indeed. Um, so yes, uh,
• 22:09
  an interesting scenario.
• 22:11
  Andrew Dunkley: Doesn't sound like much fun.
• 22:13
  Professor Fred Watson: It's not fun.
• 22:13
  Andrew Dunkley: No. No.
• 22:14
  Professor Fred Watson: Anyway, think about it though.
• 22:16
  Andrew Dunkley: We're stuck with um, with the
• 22:19
  sun for Several more billion years.
• 22:22
  Professor Fred Watson: Yes, indeed we are.
• 22:25
  Andrew Dunkley: But, uh, great questions, Dean. I really
• 22:27
  enjoy those kinds of questions. So, uh,
• 22:30
  yeah, thanks for sending it in.
• 22:33
  Let's take a break from the show.
• 22:34
  Andrew Dunkley: To tell you about our, uh, sponsor, uh, anti
• 22:36
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• 24:00
  Andrew Dunkley: 3, 2, 1.
• 24:03
  Andrew Dunkley: Space nuts.
• 24:05
  Andrew Dunkley: Our, uh, final question today comes from
• 24:08
  Patrick. He's a conspiracy theorist. Well,
• 24:10
  he's probably not, but I do like this
• 24:12
  question because I, I didn't know this.
• 24:15
  Uh, the Voyager spacecraft have plaques on
• 24:17
  them. I did know that. And as far as I can
• 24:20
  find out, both show them leaving the solar
• 24:23
  system ecliptic, um, between
• 24:25
  Jupiter and Saturn. That didn't happen.
• 24:29
  And from what I've read, Voyager 1 left after
• 24:32
  a visit to Titan while Voyager, uh, 2
• 24:34
  carried on. Uh, Voyager 1,
• 24:38
  uh, had a chance to visit Pluto. So his the
• 24:41
  questions. Why does the plaque show an early
• 24:44
  departure of Voyager 1? And why does Voyager
• 24:46
  2's path show the same? Um,
• 24:49
  hope you both had a wonderful Christmas and
• 24:52
  um, hello from a wet northern island.
• 24:56
  Patrick. Wet Northern Ireland. It's probably
• 24:59
  still wet, just like we're still dry.
• 25:02
  We've hit the hottest, driest part of the
• 25:04
  year in Australia and, um, it is dry as a
• 25:07
  chip, as we say in this country
• 25:10
  at the moment. Um, yeah,
• 25:12
  okay. I didn't realize that the plaques had
• 25:15
  the supposed path of both
• 25:17
  spacecraft, but they didn't go that way. Did
• 25:20
  they get pulled over by an RBT Perhaps.
• 25:24
  Professor Fred Watson: Um, I thought you'd have spotted this one
• 25:27
  right at the start, Andrew.
• 25:29
  Andrew Dunkley: Really? Is he
• 25:32
  playing us?
• 25:33
  Professor Fred Watson: Uh, no, he's got his spacecraft mixed up.
• 25:36
  Because it's the two, the two pioneers
• 25:39
  that show the spacecraft leaving the solar
• 25:42
  system between orbits of Jupiter.
• 25:45
  Andrew Dunkley: I never even thought of that.
• 25:47
  Professor Fred Watson: Voyager doesn't actually have a diagram like
• 25:50
  that on it. It's got mostly diagrams how to
• 25:52
  play the Golden Record.
• 25:53
  Andrew Dunkley: That's right.
• 25:54
  Professor Fred Watson: Um, so it's the Pioneer spacecraft. So
• 25:57
  Patrick, you, your, your question's a good
• 26:00
  one, but I think the premise is
• 26:03
  wrong. It's not the Voyager spacecraft that
• 26:05
  had the diagram, it's the pioneers.
• 26:06
  Andrew Dunkley: Well, how about that? Yeah, I'm
• 26:09
  just looking at them now. Okay.
• 26:13
  That's really. And it's got the human
• 26:15
  being on it.
• 26:17
  Professor Fred Watson: I actually really like the Pioneer, uh,
• 26:19
  plaques. I think they're elegant and
• 26:21
  decorative and tell, um, the story.
• 26:24
  Just show aliens just how
• 26:27
  chewy we are and you know.
• 26:28
  Andrew Dunkley: Yeah.
• 26:29
  Professor Fred Watson: How tasty we might be and how.
• 26:31
  Andrew Dunkley: Um, unfortunate that male appendage is.
• 26:34
  It's well below par, but.
• 26:38
  And the other factor is that.
• 26:41
  Professor Fred Watson: Thanks, Andrew.
• 26:42
  Andrew Dunkley: Aliens will look at these two human figures
• 26:44
  and they'll go, she does
• 26:47
  not like him.
• 26:50
  Professor Fred Watson: That's right.
• 26:51
  Andrew Dunkley: The body language is not positive.
• 26:53
  Professor Fred Watson: That's true. There is body language on there
• 26:56
  that really. Yeah, I'm with you on M. That
• 26:58
  actually. It's all about
• 27:01
  body language. Yeah.
• 27:03
  Andrew Dunkley: So now I'm going to have to look up what the
• 27:05
  Voyager plaques look like.
• 27:07
  Professor Fred Watson: Yeah. Ah, ah.
• 27:08
  Andrew Dunkley: See, it's. Yes. The Golden Record with the,
• 27:11
  um, bits and bobs on the stuff on
• 27:14
  it. Yeah, yeah. Okay.
• 27:17
  So, um, right idea. Wrong.
• 27:20
  Wrong spacecraft is basically the answer to
• 27:22
  the question.
• 27:24
  Professor Fred Watson: Uh, I think that's correct.
• 27:27
  Andrew Dunkley: Um, I think we can safely say that Voyager 1
• 27:30
  and Voyager 2 did go where we intended them
• 27:32
  to go. And they're still going.
• 27:35
  Professor Fred Watson: Yeah, indeed they are. Voyager 2, well,
• 27:37
  Pioneer 10 and 11 are as well. Uh, Voyager
• 27:39
  2 was the one that flew by Uranus, uh, and
• 27:42
  Neptune as well as Jupiter and Saturn.
• 27:44
  Fantastic details that came from those two
• 27:47
  spacecraft. Voyager 1, as we've said many
• 27:50
  times before, is the most distant human
• 27:53
  made object and is still on
• 27:56
  its way. It's almost a light day away. We
• 27:58
  should have a little party at Space Nuts when
• 28:00
  it crosses a light day. Um, the light
• 28:03
  day boundary. Yeah.
• 28:04
  Andrew Dunkley: Which, uh, is happening in about 500 years
• 28:07
  from now. No, I'm not sure. It can't be that
• 28:10
  far away.
• 28:10
  Professor Fred Watson: Yeah, it's a few years. Yeah, a couple of
• 28:12
  years. I think it's about 23 light hours at
• 28:14
  the moment. Uh, so it'll be. Yes. Four or
• 28:17
  five years.
• 28:18
  Andrew Dunkley: Yeah. Wow. Yeah, we thought we should do
• 28:20
  something special about that.
• 28:22
  Professor Fred Watson: Yes.
• 28:22
  Andrew Dunkley: M. All right. Um, well, that was easily
• 28:25
  solved. Thanks for the question, though. Uh,
• 28:26
  Patrick. It sort of. Yeah, it reminds us
• 28:29
  that, uh, as time goes on, you can sort of
• 28:31
  mix two totally different things
• 28:34
  together and.
• 28:36
  Yeah, it throws. Throws your brain out.
• 28:39
  Um, it reminds me of a story once where,
• 28:42
  um. Oh, gosh, a guy I
• 28:45
  worked with in radio did a special about,
• 28:47
  um, uh, Dean Martin and
• 28:50
  Jerry Lewis getting back together. Remember
• 28:52
  them?
• 28:52
  Professor Fred Watson: Yeah.
• 28:53
  Andrew Dunkley: Yeah, but he thought it was Jerry Lee Lewis,
• 28:57
  so he did this whole special with Jerry Lee
• 28:59
  Lewis music.
• 29:02
  Completely wrong. Yes, but it can
• 29:05
  happen.
• 29:06
  Professor Fred Watson: It can happen. Yeah, I, um.
• 29:09
  Yes, I looked at some research recently where
• 29:11
  they'd got the wrong telescope. Uh,
• 29:14
  yeah, well, it's like getting the.
• 29:15
  Andrew Dunkley: Color of the universe wrong when you make.
• 29:17
  Professor Fred Watson: That's another one. That's correct. Yes.
• 29:19
  Yeah.
• 29:20
  Andrew Dunkley: Oh, there's a list of them. There's a list of
• 29:23
  them. So don't feel bad, Patrick. It happens
• 29:25
  to the best of us. Uh, but thanks for the
• 29:27
  question. Lovely to hear from you. If you've
• 29:29
  got questions for us, please send them in to
• 29:31
  us via our website. Just go to
• 29:33
  spacenutspodcast.com or
• 29:36
  spacenuts IO if you're a lazy
• 29:39
  typist, and click on the AMA
• 29:42
  button up the top, and, uh, you can send us
• 29:44
  text and audio questions that away.
• 29:47
  Uh, we sometimes get them through
• 29:48
  YouTube Music, so if you're a YouTube Music
• 29:50
  listener, please, uh, send them in. Be, um,
• 29:52
  happy to hear from you. Uh, and don't forget
• 29:55
  reviews. We. We really appreciate your
• 29:57
  reviews. The more reviews, the better. I, um,
• 30:00
  mean, it's an astronomy podcast, so,
• 30:03
  you know, um, five stars would be the
• 30:06
  absolute minimum I would expect. That's up
• 30:09
  to you. No influence here. No influence
• 30:12
  here.
• 30:12
  Professor Fred Watson: Four million stars.
• 30:13
  Andrew Dunkley: Four million stars. Yes. Deal.
• 30:16
  Uh, and, um, yeah, if you'd like to do that
• 30:18
  for us, that'd be great. And don't forget to,
• 30:20
  um, check out our website if, uh, you. To,
• 30:23
  uh, support us. Some people do through, um,
• 30:26
  Patreon and Supercast. Uh, there's
• 30:29
  a little button where it says, support our
• 30:32
  podcasts. So click that button, you can find
• 30:34
  out more about it. It's totally voluntary.
• 30:37
  Um, Fred, we are done. Thank you so much for
• 30:39
  answering those questions.
• 30:40
  Professor Fred Watson: Oh, uh, it's a pleasure. It's, um, always
• 30:42
  good to interact with our, uh, four
• 30:44
  listeners. Yes, we've
• 30:47
  only got four at a time.
• 30:50
  Yeah, no, it's good. And thank you very much.
• 30:53
  Uh, again, as always, Andre, for being the
• 30:55
  host of Space Notes.
• 30:56
  Andrew Dunkley: Oh, my great pleasure. It's good fun,
• 30:59
  Professor, Uh, Fred Watson, astronomer at
• 31:00
  large. He'll join us again on the next
• 31:02
  episode. Uh, and Huw in the studio couldn't
• 31:04
  be with us today because he was doing a
• 31:06
  thought experiment, uh, where
• 31:09
  he didn't exist.
• 31:13
  What more can I say? Uh, and from me, Andrew
• 31:16
  Dunkley, thanks for your company. We'll catch
• 31:17
  you on the next episode of Space Nuts. Bye.
• 31:19
  Bye. Space Nuts.
• 31:21
  Andrew Dunkley: You've been listening to the Space Nuts
• 31:23
  podcast, available
• 31:26
  at Apple Podcasts, Spotify,
• 31:28
  iHeartRadio, or your favorite podcast
• 31:31
  player. You can also stream on demand at
• 31:33
  bytes.
• 31:34
  Professor Fred Watson: Com.
• 31:34
  Andrew Dunkley: Um, this has been another quality podcast
• 31:37
  production from Bytes.
• 31:38
  Professor Fred Watson: Com.
• 31:38
  Andrew Dunkley: Um.