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Supermassive Black Holes, Voyager’s Journey & Gravitational Waves Explained | Q&A | Space Nuts:... · Space News Today

• 0:00
  Hello again. Thanks for joining us on
• 0:01
  Space Nuts, where we talk astronomy and
• 0:04
  space and science all at the same time.
• 0:07
  Uh, this is a Q&A episode. My name is
• 0:09
  Andrew Dunley, your host. Great to have
• 0:11
  your company. Coming up, audience
• 0:13
  questions. We're going to answer a
• 0:15
  question from Martin about super massive
• 0:17
  black holes. Uh, Ben has also got a
• 0:20
  question about black holes and
• 0:21
  gravitational waves. Andy, our favorite
• 0:24
  train driver is on about Voyager 1. And
• 0:28
  Jud has some thought experiments for us.
• 0:31
  We'll check it all out on this episode
• 0:33
  of Space Nuts.
• 0:35
  >> 15 seconds. Guidance is internal. 10 9
• 0:40
  Ignition sequence start.
• 0:41
  >> Space nuts.
• 0:42
  >> 5 4 3 2
• 0:45
  >> 1 2 3 4 5 5 4 3 2 1
• 0:47
  >> Space Nuts.
• 0:48
  >> Astronauts report. It feels good.
• 0:52
  And back to unravel, unpack, and solve
• 0:56
  all of that is Professor Fred Watson,
• 0:58
  astronomer at large. Hello, Fred.
• 1:01
  >> Hello, Andrew. Very good to see you.
• 1:03
  >> Good to see you, too. I've still got
• 1:04
  McCroy voice. Um, in fact, I've been so
• 1:07
  unwell, I'm still wearing the same
• 1:09
  clothes as I was last week.
• 1:11
  >> Well, there you go.
• 1:13
  >> Funnily enough, so am I.
• 1:15
  >> Yeah. Well, what a coincidence.
• 1:19
  >> Uh, shall we get down to business?
• 1:22
  Why not?
• 1:22
  >> All right. Something else to do. So,
• 1:24
  yeah.
• 1:24
  >> Now, we've got some text and audio
• 1:26
  questions. We'll go text first today.
• 1:29
  Uh, and forgive my rather um unreliable
• 1:32
  voice as I work my way through this. Hi,
• 1:34
  Fred and Andrew. It's Martin here from
• 1:36
  Hezwall on the Whirl in Murzy side. I
• 1:40
  posted a question before and Fred
• 1:42
  mentioned that he knew Barnston, which
• 1:45
  is just a pleasant walk over the fields
• 1:48
  from here. I have a question about your
• 1:50
  favorite topic, black hole. I thought it
• 1:52
  was going to be golf. Black holes. Uh
• 1:55
  I'm interested specifically in the
• 1:57
  process of their formation and more
• 1:59
  particularly in super massive black
• 2:01
  holes. The mechanism for the creation of
• 2:04
  stellar mass black holes seems to be
• 2:06
  well understood. But I find it hard to
• 2:08
  believe that this can be the same way
• 2:12
  that super massive black holes in the
• 2:13
  early universe were formed. I've read
• 2:15
  that the gravitational instability
• 2:18
  theory posits that black holes can be
• 2:20
  formed directly when a massive cloud of
• 2:23
  matter collapses under its own gravity.
• 2:25
  Why is it not possible that there can be
• 2:28
  two processes at work depending on the
• 2:30
  size? For me, part of the evidence in
• 2:33
  supporting uh in support of invoking
• 2:36
  gravitational instability is the lack of
• 2:38
  evidence for the existence of
• 2:40
  intermediate mass black holes. What are
• 2:43
  the arguments against this theory? As it
• 2:45
  does seem to be that widely, it doesn't
• 2:48
  seem to be that widely accepted. If
• 2:50
  black holes are created in two
• 2:52
  completely different ways, what effect
• 2:54
  would this have on their properties? For
• 2:57
  instance, charge, spin, etc. I really
• 2:59
  enjoy listening to the show. It helps me
• 3:01
  keep up to date with the world of
• 3:03
  science, space, and stuff. That's our
• 3:05
  slogan. Ha. Well done. Well done,
• 3:08
  Martin. That's our slogan. Um, yeah.
• 3:11
  Look, that's a really good question and
• 3:13
  we only talked in the last episode about
• 3:15
  the the the different theories about uh
• 3:18
  how black holes are formed and the
• 3:21
  possible discovery of primordial black
• 3:23
  holes. So uh if you haven't heard that
• 3:24
  episode, wind back because it's worth
• 3:26
  listening to that story. But uh yeah, he
• 3:28
  brings up an interesting point. Uh how
• 3:31
  can it be the same process for a super
• 3:33
  massive black hole versus a um you know
• 3:37
  another one, a smaller one?
• 3:40
  >> Yeah. So I I mean Martin's um hit on one
• 3:45
  of the key questions at the moment in in
• 3:48
  astrophysics and cosmology. So he's
• 3:50
  right up to date there.
• 3:51
  >> Yeah, he sure is. Um because um this
• 3:54
  idea of uh the super massive black holes
• 3:58
  in the early universe forming directly
• 4:01
  as a as a direct result of a cloud of
• 4:03
  gas collapsing without having to go
• 4:06
  through the mechanisms or of of a
• 4:09
  forming a star and then the stars
• 4:11
  basically exploding uh to form a a black
• 4:14
  hole. That's quite new.
• 4:16
  uh and that might be why as Martin says
• 4:19
  it's not yet sort of considered to be
• 4:22
  mainstream but it is it is very much an
• 4:25
  upand cominging idea and theory that
• 4:28
  answers the criticism that the
• 4:31
  conventional theory has uh and that is
• 4:35
  conventionally uh scientists have
• 4:37
  assumed that super massive black holes
• 4:41
  are created over long periods of time by
• 4:46
  the accretion of material. So um we know
• 4:51
  how a stellar mass black hole is formed
• 4:53
  exactly as Martin mentioned we
• 4:55
  understand that's massive star explodes
• 4:58
  at the end of its life when the fuel
• 5:02
  balance runs out. uh the outer layers
• 5:04
  are shed off and a supernova remnant and
• 5:07
  the center basically the central core
• 5:10
  collapses to be the black hole which is
• 5:12
  a point with zero dimensions a point
• 5:14
  where uh density is infinite. Uh so that
• 5:19
  the conventional method says you start
• 5:20
  off with lots of those in a galaxy and
• 5:24
  they eventually uh accrete to form a
• 5:29
  bigger object uh mixing with stuff
• 5:32
  that's sucked in on the accretion disc
• 5:34
  as well. That might include a few odd
• 5:36
  black holes dropping in. Yeah.
• 5:38
  >> To form eventually a super massive black
• 5:40
  hole. But the problem has been how do
• 5:43
  you manage to do that in less than a
• 5:46
  couple of hundred million years which is
• 5:49
  you know where the earliest super
• 5:51
  massive black holes are after the big
• 5:54
  bang we know about those because we can
• 5:56
  we measure them by looking using the
• 5:59
  James web space telescope it's measured
• 6:02
  I think several objects within maybe 250
• 6:05
  million uh years after the big bang in
• 6:08
  other words we're looking back almost
• 6:10
  13.8 billion years, 13.6 or something
• 6:13
  like that. Um, uh, how did they form so
• 6:17
  quickly if that's the mechanism? And
• 6:19
  that's why this alternative mechanism of
• 6:21
  of direct collapse from a an
• 6:23
  interstellar
• 6:24
  >> from from a not interstellar because
• 6:26
  there were no stars then, but from a
• 6:28
  primordial gas cloud might have
• 6:30
  occurred. And in as I understand it,
• 6:35
  the idea of primordial
• 6:39
  uh black holes postulated, this is what
• 6:41
  we talked about last week uh or the last
• 6:43
  episode postulated by Steven Hawking uh
• 6:48
  envisaged that there would be a very
• 6:51
  very wide range of masses of black holes
• 6:54
  ranging from things less than the mass
• 6:56
  of the sun. um as we reported in the
• 6:58
  last episode, we think we found one of
• 7:00
  those now. Yeah.
• 7:01
  >> Uh to super massive black holes. I think
• 7:05
  that is all within the purview of
• 7:08
  Hawking's theory of primordial black
• 7:10
  holes. And so the question, you know,
• 7:14
  maybe the fact that we're finding these
• 7:17
  super massive black holes
• 7:19
  too early in the universe um might to to
• 7:23
  have been formed by stuff coming
• 7:24
  together. uh might be a support for the
• 7:26
  Hawings theory that maybe some of these
• 7:28
  were actually formed immediately after
• 7:30
  the big bang.
• 7:31
  >> Wow. Wouldn't that be interesting?
• 7:33
  >> Um
• 7:34
  >> there was something about um something
• 7:35
  that um Martin mentioned about
• 7:37
  intermediate.
• 7:38
  >> Yeah. He said for me part of the
• 7:41
  evidence in support of invoking
• 7:43
  gravitational instability is the lack of
• 7:45
  evidence for the existence of
• 7:46
  intermediate mass black holes. Although
• 7:49
  they're the ones we were talking about
• 7:51
  recently that we now have discovered,
• 7:54
  have we not?
• 7:55
  >> Yes. Um but they're still and they still
• 7:58
  seem to be Yes. much rarer than the
• 8:01
  super massive black holes or the stellar
• 8:03
  mass black holes which are which exist
• 8:05
  in profusion. Uh intermediate mass black
• 8:08
  holes have been quite hard to find. Uh
• 8:11
  >> maybe they're just beaten up.
• 8:13
  >> Yeah, I mean you know what Martin says
• 8:16
  is right. um that might point to uh to
• 8:20
  the the idea of gravitational
• 8:22
  instability, in other words, sort of
• 8:24
  primordial type black holes as being the
• 8:27
  formation. Uh that might point to that.
• 8:30
  Um and so I don't think there's an issue
• 8:34
  there. Uh but yes, his final question,
• 8:37
  uh if black holes are created in two
• 8:39
  completely different ways, what effect
• 8:40
  would that have on their properties? For
• 8:43
  example, charge, spin, etc.
• 8:46
  >> Now, in fact, the only properties of a
• 8:48
  black hole that you can observe um are
• 8:51
  the charge and the spin as well as the
• 8:54
  mass. Um and that um that's because of
• 8:57
  something that you and I might have
• 8:59
  mentioned before, Andrew, something
• 9:00
  called the no hair theorem, uh which I'm
• 9:03
  very fond of, uh as you can guess. And
• 9:06
  the no hair theorem basically says that
• 9:08
  there's
• 9:10
  you know there's virtually nothing um of
• 9:14
  the black holes characteristics that you
• 9:16
  can see from the outside. It's like
• 9:18
  suggesting a baldness of the of the
• 9:20
  black hole the event horizon. It doesn't
• 9:22
  give much away. Charge and spin are I
• 9:25
  think I think only the only two apart
• 9:28
  from mass. Now I don't know the answer
• 9:30
  to that. Would there be any difference
• 9:32
  in those properties uh for two different
• 9:34
  methods of black hole formation? And
• 9:36
  it's a really good question. Uh and um
• 9:39
  it's something that I probably should
• 9:40
  have a look at and see if I can find
• 9:42
  out.
• 9:42
  >> Yeah, I I thought I'd look up no hair
• 9:44
  theorem to see what happened. And um I I
• 9:47
  didn't get um an ad for a for a hair
• 9:50
  pill. It actually took me it actually
• 9:52
  took me to the
• 9:53
  >> to the to the no hair theorem
• 9:55
  >> to the no hair theorem about black
• 9:56
  holes. Yeah. So there you go.
• 9:59
  The internet actually worked.
• 10:02
  >> Yes,
• 10:02
  >> nice change. Nice change. And a nice
• 10:04
  question. Uh Martin, thanks for sending
• 10:07
  that to us. Hopefully that helped you
• 10:08
  sort a few things out, but uh yeah, it's
• 10:11
  there's still a lot of theory around
• 10:13
  black holes yet to be proven, but we're
• 10:15
  chipping away at it. We are chipping
• 10:17
  away at it. Not me personally. I leave
• 10:19
  that to other people who are more
• 10:21
  astute. Uh thanks for sending it in. Our
• 10:24
  next question comes from our favorite
• 10:26
  train driver. His name is Andy.
• 10:30
  >> Train driver here. Uh just a question
• 10:31
  for you on Voyager One. Um I know that
• 10:35
  he's currently traveling about 38,000
• 10:36
  mph and it's very low on fuel and the
• 10:40
  fuel is used for the thrusters to point
• 10:42
  it antennas back to Earth. Um and I know
• 10:45
  that space is not empty. There's
• 10:47
  particles and space dust. So, because
• 10:50
  he's got such a long journey before he
• 10:52
  reaches anything significant, would the
• 10:54
  particles in space
• 10:57
  slow it enough to bring it to a halt?
• 11:00
  Cuz as far as I'm aware, it's got about
• 11:02
  40,000 years before it reaches something
• 11:04
  significant. So, is that a long enough
• 11:07
  time, would you say, to maybe not bring
• 11:10
  it to a halt, but to to slow it
• 11:12
  significantly that it really does
• 11:14
  increase that time scale?
• 11:17
  Uh, sorry if that doesn't make much
• 11:19
  sense. Uh, thanks for your podcast,
• 11:21
  guys. Really enjoy it. Speak to you
• 11:23
  soon. Bye.
• 11:24
  >> Thank you, Andy. Hope all is well on
• 11:26
  your daily commute, although you're the
• 11:29
  driver, so you just drag everyone else
• 11:31
  around. But what a great job. Um, right.
• 11:35
  Okay. Voyager 1, 38,000 mph. Uh, is
• 11:38
  there enough material to ultimately stop
• 11:40
  it? Cuz it's going to run into a few
• 11:42
  things here and there, possibly. But I
• 11:44
  would question the spread of the dust
• 11:46
  when you get out into those uh
• 11:48
  interstellar places. The amount of
• 11:51
  material thins out significantly,
• 11:54
  doesn't it?
• 11:55
  >> Yeah, very much so. Um there is still
• 11:58
  you know there are still atoms there um
• 12:01
  or nuclei probably subatomic particles
• 12:04
  um but it's not uh it's not enough to
• 12:10
  significantly slow the spacecraft.
• 12:14
  >> Uh
• 12:16
  it's you know you you basically to all
• 12:18
  intents and purposes it's moving through
• 12:20
  a vacuum. Um it's I was thinking
• 12:24
  kilometers/s.
• 12:26
  Current speed is uh 16.920
• 12:30
  kilometers/s relative to the sun.
• 12:33
  >> 61,000 kilometers an hour. 17 km a
• 12:36
  secondish. Uh 38,000 mph. Yep. It's
• 12:40
  going. It's fast.
• 12:41
  >> It is. Uh the the speed I like is in
• 12:44
  units of astronomical units per year. Uh
• 12:47
  and that is 3 3.6
• 12:51
  nearly 3.569. So, uh, three times a year
• 12:55
  it covers the distance from the Earth to
• 12:58
  the Sun here. So,
• 13:00
  >> yeah, that's 150 million kilometers.
• 13:03
  >> Sure is. That's that's amazing, isn't
• 13:04
  it? And it's still going strong.
• 13:08
  >> Yeah. So, and andy's right. I think the
• 13:10
  fuel's low, but the fuel is uh just for
• 13:13
  the thrusters. It's just to keep the
• 13:16
  antenna pointed towards Earth.
• 13:19
  >> So, yeah. and and he said it might come
• 13:22
  across something in about 40 40,000
• 13:25
  years. I I thought when we talked about
• 13:27
  this last that it it could just keep
• 13:30
  going. It might not run into anything.
• 13:33
  Yeah. Simply because it's not aimed at
• 13:35
  anything and space is very empty. Uh
• 13:37
  even though there's a you know 400
• 13:39
  billion stars in the Milky Way or
• 13:41
  whatever, the Milky Way is very very big
• 13:43
  indeed. Uh and um it's look it's uh its
• 13:49
  distance is I think I think the odds are
• 13:52
  that it will keep going forever. It
• 13:54
  might be captured by the gravity of
• 13:55
  another star. I think the um the notion
• 13:59
  of a collision is vanishingly small.
• 14:02
  >> Um I've just um
• 14:05
  statistics just come into my head that I
• 14:07
  used to use a lot uh to to give people
• 14:10
  the idea of just how big the galaxy is.
• 14:13
  uh and I'm sure you and I have discussed
• 14:15
  it too. If you imagine a diagram of our
• 14:18
  galaxy uh that was the size of the earth
• 14:22
  so 12 and a half thousand kilometers in
• 14:25
  diameter that's your map of the galaxy
• 14:28
  uh the size of the earth. The separation
• 14:32
  from the sun to the earth on that scale
• 14:35
  is 2 mm. That tells you that the galaxy
• 14:40
  is very very large compared with the
• 14:42
  size of the solar system.
• 14:46
  That's just mind-boggling stuff really
• 14:48
  easily.
• 14:50
  >> And the other thing I suppose like we
• 14:52
  talk about the or cloud which is this
• 14:55
  thing around our um is it around our
• 14:58
  solar system or around a galaxy? I can't
• 15:00
  remember.
• 15:00
  >> No, it's around the solar system.
• 15:01
  >> Solar system. Yeah.
• 15:03
  >> Yeah. Um, they reckon it's going to take
• 15:05
  300 years for Voyager One to reach that.
• 15:07
  >> That That's right. Um, that's right.
• 15:11
  >> That and
• 15:12
  >> still a long way off,
• 15:13
  >> which means it still hasn't really left
• 15:14
  our solar system in real terms.
• 15:17
  >> I'm not even sure that it will be 300
• 15:19
  years because the cloud is about a light
• 15:22
  year away.
• 15:24
  >> Well, actually, it says here um the
• 15:27
  inner edge in 300 years, but it will
• 15:29
  take 30,000 years to pass through it.
• 15:31
  >> That's more like it. Yeah. Yeah. It's
• 15:33
  more like
• 15:34
  >> So, I should have finished reading the
• 15:35
  sentence, shouldn't I?
• 15:39
  >> There was there was an unpredictable
• 15:40
  full stop in there, though. So,
• 15:42
  >> yeah.
• 15:43
  >> But, um,
• 15:44
  >> yeah,
• 15:44
  >> incredible.
• 15:46
  >> Sorry, I meant to say, um, last time
• 15:48
  Andy came on, I meant to tell him that
• 15:50
  I'm a train driver, too. Uh, but it's
• 15:53
  ends scale. Uh, which he'll know. He'll
• 15:56
  know what that is. Not some people might
• 15:58
  not know. Actually, probably quite a lot
• 16:00
  of our listeners do. But I drive my
• 16:02
  trains in Nscale. I love it.
• 16:04
  >> I should send Andy, if if he sends me
• 16:07
  his email address, um some video of our
• 16:09
  brand new regional trains in New South
• 16:11
  Wales that are being
• 16:12
  >> I'd like to see that.
• 16:13
  >> Yeah. They're being fitted out in um in
• 16:15
  do where I live and they've been doing
• 16:18
  test runs on them. I've actually heard
• 16:20
  it
• 16:21
  >> uh in the we small hours passing by
• 16:23
  because it it's got a completely
• 16:24
  different sound. And I've actually
• 16:26
  reached a point now where I recognize
• 16:27
  the different trains by sound.
• 16:31
  How pathetic is that? But um
• 16:35
  >> much much quieter than the current train
• 16:38
  which is the XPT uh which is well past
• 16:41
  its use by date but never let the New
• 16:44
  South Wales government, you know, build
• 16:46
  a train because they will they will say,
• 16:48
  "Okay, it's got a 20-y year life, so
• 16:50
  we'll replace it in 50." Cuz that's
• 16:52
  what's happening. Um but uh these are
• 16:57
  very slick. These are Spanish trains
• 16:58
  that are being fitted out in do and um
• 17:01
  really really lovely piece of kit as
• 17:04
  Fred would say. So um Andy sent me your
• 17:07
  email address and I will send you a
• 17:09
  video of of our um our new trains that
• 17:12
  it's weird watching them run around with
• 17:13
  nobody in them. It's just no passengers,
• 17:17
  nothing. Just all the lights are on.
• 17:19
  Nobody's home. Nobody's home.
• 17:22
  >> Yeah. If you're on the metro in Sydney,
• 17:24
  there's not even a driver on board
• 17:25
  either. Yeah, I know. I've been on the
• 17:28
  metro a couple of times. It's a slick
• 17:29
  system.
• 17:30
  >> Oh, it's brilliant.
• 17:31
  >> One of my boys lives in a suburb where
• 17:33
  they're just about to complete a metro
• 17:35
  line. So, he's really happy about that
• 17:37
  cuz it'll get him to work, you know,
• 17:39
  three times as fast.
• 17:40
  >> So, he's really he's thrilled cuz he got
• 17:43
  rid of his car. He doesn't use a car in
• 17:45
  Sydney. Doesn't see the need. Got to
• 17:48
  have one out here though in the country.
• 17:50
  Uh, thanks Andy. Lovely to hear from
• 17:52
  you. This is Space Nuts with Andrew
• 17:53
  Dunley and Professor Fred Watson.
• 17:58
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• 19:15
  this deal. Remember, there's a 30-day
• 19:18
  money back guarantee, so it's riskfree
• 19:20
  to try. Stay safe, stay private, and
• 19:24
  browse with confidence. That's
• 19:26
  nordvpn.com/spacenuts.
• 19:31
  >> Roger, you're here also.
• 19:32
  >> Space nuts.
• 19:34
  >> Oh boy. Um, okay. Next question. Uh, I
• 19:39
  don't even know where we're up to. Where
• 19:40
  are we up to? We've spoken to Andy. All
• 19:42
  right. Um, question three. Hi, Space
• 19:44
  Nuts. Ben Harding here from Kent,
• 19:46
  England. Uh, having listened to your
• 19:48
  show for several years now, uh, I know
• 19:51
  everything there is to know about black
• 19:52
  holes. Indeed, I'm ready to start
• 19:54
  building my own any day now. But wait,
• 19:57
  if I build two and they crash together,
• 20:00
  they will create gravitational waves and
• 20:02
  I need to account for the ensuing
• 20:04
  distortion of the fabric of spaceime or
• 20:06
  my cats will be upset.
• 20:09
  So are gravitational waves spherical or
• 20:13
  flat? I'm thinking they must be
• 20:15
  spherical. But then again, if they are
• 20:18
  created by two objects spiraling in
• 20:20
  together, the waves may be flat uh by
• 20:23
  some sort of uh conservation of angular
• 20:26
  momentum rule. Uh I hope you can help me
• 20:29
  with my cats. Um they get a bit scratchy
• 20:32
  when they're upset.
• 20:34
  Thanks for the awesome show, Ben. H
• 20:37
  Thank you, Ben. Um I'm just imagining
• 20:39
  your cats. Uh freaking out over
• 20:43
  gravitational waves. There's a comic
• 20:44
  strip in that I reckon somewhere. My my
• 20:48
  brother would do a a comic on that. I
• 20:50
  reckon he's very artistic as my brother.
• 20:54
  >> Okay. All right. So, gravitational waves
• 20:56
  from the um cataclysmic collision of uh
• 21:00
  two black holes spherical.
• 21:03
  Um, so I think what uh Ben is
• 21:08
  referring to um in his description is
• 21:11
  whether they whether they're they're
• 21:14
  radiated gravitational waves are
• 21:16
  radiated in all directions. Yeah.
• 21:18
  >> What we would call isotropic or just in
• 21:22
  a plane in the plane of the collision.
• 21:24
  >> And um to the best of my understanding
• 21:27
  the answer is that they're isotropic.
• 21:29
  They go off in all directions.
• 21:30
  >> Right? So space shutters uh just because
• 21:34
  of the the gravitational interaction.
• 21:37
  It's not got any pref I don't think I do
• 21:40
  not believe it's got any preferred
• 21:42
  direction because of the you know the
• 21:45
  direction of the collision. I think it's
• 21:46
  um it is the same in all directions. Um
• 21:50
  there's another way of interpreting
• 21:52
  Ben's question though and that is uh how
• 21:56
  the oscillations of gravitational waves
• 21:59
  take place. Um, and they're not they're
• 22:02
  not the same as sound waves where which
• 22:05
  are compression waves where things push
• 22:07
  backwards and forwards. And they're not
• 22:09
  the same as light waves which are
• 22:12
  transverse waves where the electric
• 22:14
  field and magnetic field vary in a in a
• 22:17
  transverse manner. In other words,
• 22:19
  opposite to the direction of propagation
• 22:21
  or right angles to the direction of
• 22:23
  propagation. There's something called
• 22:25
  quadruple waves which is a sort of
• 22:28
  combination of not quite a combination
• 22:30
  of the two but certainly um a slightly
• 22:33
  unusual form of of transverse wave
• 22:36
  quadrupole waves is what they are. Um
• 22:38
  but I don't think that's what he means.
• 22:40
  I think what Ben means is what I
• 22:42
  answered in the first place that uh yes
• 22:44
  they're isotropic rather than limited to
• 22:46
  a particular plane. So, they go out in
• 22:48
  all directions, unlike the gravitational
• 22:50
  wave that um I detected on a plane.
• 22:53
  >> Uh I don't know what that guy was
• 22:55
  eating, but um yeah, I hope I don't have
• 22:57
  to experience that again.
• 23:00
  >> Yeah, I know about those things as well.
• 23:02
  >> Pretty awful stuff. Really?
• 23:04
  >> Yep, they are.
• 23:05
  >> I'm impressed that Ben says he knows
• 23:08
  everything there is to know about black
• 23:09
  holes. Does that mean we've been doing
• 23:11
  our job?
• 23:14
  It means he he knows more than us, which
• 23:16
  is pretty easy to do. Really
• 23:18
  >> possible, too. Yeah.
• 23:19
  >> Yes.
• 23:20
  >> But but we're learning more and more
• 23:21
  about them. Um
• 23:22
  >> we are. That's cuz we listen to our
• 23:24
  listeners.
• 23:24
  >> That's that's exactly right. But uh
• 23:28
  yeah, they've been the topic of I I
• 23:30
  think since we started a decade ago,
• 23:32
  Fred, I um you reminded me earlier, uh
• 23:35
  it's been 10 years we've been doing this
• 23:37
  podcast. That's that's extraordinary. We
• 23:39
  should have had a party, but I think we
• 23:41
  just can't stay up that late anymore.
• 23:43
  But um it it's um it's probably been the
• 23:47
  hottest topic on Space Nuts since day
• 23:50
  one is black holes.
• 23:52
  >> Uh closely followed by dark matter, dark
• 23:54
  energy and um I yeah, I don't know where
• 23:57
  you go from there, but uh it's been of
• 23:59
  >> life in space.
• 23:59
  >> Yes, life. Yes, you are right. That's
• 24:02
  those are the top four topics. So, I
• 24:04
  expect next week our four questions will
• 24:06
  be on black holes, dark matter, dark
• 24:09
  energy, and life elsewhere.
• 24:11
  >> Yeah, there's there's a good chance they
• 24:13
  will.
• 24:14
  >> That will be the standard.
• 24:16
  >> Yep. Very good. Thank you, Ben. Uh,
• 24:18
  lovely to hear from you. Hope all is
• 24:20
  well in Kent. Our final question comes
• 24:24
  from Jud.
• 24:26
  >> Good day, Fred and Andrew. It's Jud from
• 24:29
  Brisbane. Been a big fan of the show for
• 24:31
  a long time. My wife and I were
• 24:34
  listening to a recent episode uh where
• 24:38
  one of the stories was about the uh spun
• 24:40
  out asteroid that's spinning at a
• 24:43
  incredibly fast rate. And you know we
• 24:46
  found Andrew's um thought experiments um
• 24:50
  about how that would affect Earth if we
• 24:53
  were spinning at a similar rate. Um and
• 24:57
  yeah got my head spinning and uh came up
• 25:00
  with lots of other thought experiments.
• 25:02
  Um uh first my question is uh what is
• 25:06
  the current speed of the earth's
• 25:09
  rotation? Um
• 25:13
  and yeah does that speed affect the pole
• 25:18
  of gravity that we feel on earth? Um
• 25:23
  like for instance if uh if I weigh 100
• 25:27
  kg at spinning at this rate of speed uh
• 25:31
  if the earth stops spinning tomorrow
• 25:34
  would I weigh significantly more? Just
• 25:39
  wondering about that. And another
• 25:41
  question, um, would I weigh less at the
• 25:46
  equator than I would standing at the
• 25:49
  north or south pole because the equator
• 25:52
  is spinning much more rapidly than the
• 25:55
  Earth is at the poles. So, just uh some
• 25:59
  thoughts to make your head spin and
• 26:02
  maybe give me some answers. Thank you.
• 26:05
  >> Thank you, Jud. Thanks to you and your
• 26:07
  wife for being fans of the show for so
• 26:09
  long. Much appreciated and uh we can
• 26:11
  make this quick. Yes. And we're finished
• 26:13
  for the No. Um there's a lot more to it
• 26:16
  than that, but uh I think he he he
• 26:19
  pretty well nailed a few of the thoughts
• 26:20
  that he's had in terms of what the
• 26:23
  answers are. Uh what is the current
• 26:25
  speed of Earth's rotation? If you listen
• 26:26
  to the Monty Python song from the life
• 26:28
  of Brian, or was it one of the others?
• 26:31
  Um,
• 26:33
  yeah, they they were wrong, weren't
• 26:35
  they, with their assessment of the speed
• 26:37
  of the rotation of the planet. Um,
• 26:42
  I can't remember I I do remember from I
• 26:45
  don't know know what the speed is, but
• 26:46
  I'll get to that in a second. I can't
• 26:48
  remember what the song says, but I do
• 26:50
  remember listening to that song a long
• 26:52
  time ago and thinking, "Yeah, pretty
• 26:54
  well most of the astronomical statistics
• 26:56
  in it are correct." uh or they were when
• 26:58
  it was written back in the day. Um but
• 27:02
  uh Jud is right. Um the speed of
• 27:05
  rotation at the earth on the equator,
• 27:08
  which is where your linear speed is
• 27:10
  maximum, is uh 1,600 kilometers an hour.
• 27:15
  So that's significant. It's about uh
• 27:19
  half a kilometer/s roughly. Uh, and
• 27:22
  that's why you tend to build space
• 27:25
  launch sites at the equator because
• 27:27
  you've got that additional.5
• 27:31
  kilometers/s.
• 27:32
  That's quite significant when you're
• 27:34
  trying to get up to 8 kilometers/s to
• 27:36
  get into into orbit. So, you're kind of
• 27:39
  a 16th of the way there already just by
• 27:41
  putting your launch site on the equator
• 27:43
  and of course launching towards the east
• 27:45
  which is the direction that we're
• 27:46
  rotating in. Um, at middle latitudes it
• 27:50
  reduces. At our latitude here in uh, New
• 27:53
  South Wales, it's about 1,400 kilometers
• 27:56
  per hour. Um, uh, at Jud's latitude in
• 28:00
  Brisbane, it's a little bit less. Not
• 28:02
  that much less, though. Uh, but there's
• 28:05
  So, what's the effect on your weight?
• 28:07
  That's the interesting thing. Yeah.
• 28:10
  >> And, um, there are two two parts to
• 28:14
  this. Um,
• 28:16
  one is kind of what we've just alluded
• 28:19
  to, the fact that you are rotating uh
• 28:23
  1,600 kilometers uh an hour, roughly
• 28:26
  1,000 miles an hour. Um, it basically
• 28:29
  there's a centrifugal force that means
• 28:31
  that you are slightly lighter. Uh, your
• 28:34
  mass doesn't change of course, but your
• 28:36
  weight does because of that centrifugal
• 28:38
  force. But there there is another effect
• 28:42
  that acts with that too. And that's
• 28:45
  because the Earth isn't spherical. It's
• 28:48
  slightly bulging. And in the center,
• 28:50
  it's what we call an abl spheroid.
• 28:53
  >> And at the equator, you're about 20
• 28:58
  kilometers
• 29:00
  further away from the Earth's center of
• 29:02
  gravity than you are at the poles. And
• 29:06
  so that too reduces the gravitational
• 29:10
  pull that you feel. Um so those two
• 29:13
  things together the equatorial bulge of
• 29:15
  the earth and the centrifugal force of
• 29:18
  the earth's rotation come they basically
• 29:21
  combine to give you a figure that's a
• 29:24
  bit less than 1% of your weight changes
• 29:28
  if you're at the equator compared with
• 29:30
  the poles.
• 29:30
  >> That that'd be a lot for some people
• 29:32
  maybe.
• 29:33
  >> Yes. Yeah. that I mean it means that if
• 29:35
  you do weigh 100 kg then at the equator
• 29:38
  then you're only going to be 99 at the
• 29:40
  pole.
• 29:40
  >> Yeah.
• 29:41
  >> No, I've got it the other way around. If
• 29:43
  you're 100 kg at the pole, you're only
• 29:45
  going to be 99 at the equator.
• 29:47
  >> I knew what you meant.
• 29:49
  >> Yeah.
• 29:50
  >> Um yeah, it's fascinating really. And um
• 29:54
  yeah, that was one of his questions. Um
• 29:58
  weight at the equator versus the poles.
• 30:00
  Uh what would happen if Earth stops
• 30:04
  spinning? Like I think we'd all be
• 30:07
  doomed for starters. That would be the
• 30:08
  end.
• 30:10
  >> But um
• 30:11
  >> we'd all be projected eastwards at uh
• 30:13
  1,600 kilometers an hour if you're on
• 30:15
  the equator.
• 30:16
  >> Yeah. Yeah. That'd be that'd be pretty
• 30:19
  messy. Um
• 30:20
  >> but it Yeah. But if the Earth stopped
• 30:23
  spinning, you'd only have that uh
• 30:25
  equatorial bulge component that's
• 30:28
  reducing your weight. the fact that
• 30:29
  you're a little bit further away from
• 30:31
  the center and that's almost negligible
• 30:32
  on its own.
• 30:33
  >> Yeah, fair enough. That was easy. And I
• 30:37
  found that Monty Python song. It was
• 30:39
  from the meaning of life, not from the
• 30:40
  life of Brian.
• 30:42
  >> That's right.
• 30:42
  >> And it's called the Galaxy song. And the
• 30:45
  first verse first verse says, just
• 30:47
  remember that you're standing on a
• 30:48
  planet that's evolving and revolving at
• 30:51
  900 miles an hour.
• 30:54
  >> Um, which is Yeah. All right. So, it's
• 30:57
  it's uh A bit slow.
• 31:00
  >> 100 miles an hour slow. Yeah,
• 31:02
  >> but it rhymes.
• 31:05
  >> That's it. A thousand would have rhymed.
• 31:07
  >> It would have worked.
• 31:08
  >> Yeah.
• 31:09
  >> Oh, well, maybe they needed two words
• 31:11
  rather than No, it would have still been
• 31:13
  two words.
• 31:13
  >> Or or or Andrew, maybe the Earth has
• 31:16
  speeded up since they recorded the song.
• 31:18
  >> That's poss. It's slowing down though,
• 31:20
  isn't it?
• 31:21
  >> Yes.
• 31:22
  Yeah.
• 31:24
  >> Well, eventually their song will be
• 31:26
  right.
• 31:27
  Yes, it will.
• 31:30
  >> That's right.
• 31:31
  >> Oh gosh.
• 31:32
  >> All right. Um, thank you so much, Jud.
• 31:34
  Lovely to hear from you. Hope all is
• 31:36
  well in Brisbane. Uh, sorry about your
• 31:38
  football team. Not. Um, and I think that
• 31:42
  brings us to the end. Uh, if you have
• 31:44
  questions for us, uh, we would love to
• 31:47
  hear from you. Uh, you can go to our
• 31:49
  website, spacenuts.io, io and click on
• 31:51
  the AMA uh link at the top of the page
• 31:55
  uh where you can ask me anything or ask
• 31:57
  me and I'll give it to Fred to figure it
• 31:59
  out. Uh so uh send us text and audio
• 32:02
  questions. Don't forget to tell us who
• 32:03
  you are and where you're from. And a
• 32:05
  little request if you will uh when you
• 32:08
  uh next listen or are listening to us
• 32:10
  right now, please leave a review on
• 32:12
  whatever podcast platform you uh use
• 32:15
  because uh reviews are very handy. Um,
• 32:18
  it sort of moves us up some laddery
• 32:22
  thing, ranking thing, which is very good
• 32:25
  for us apparently. I don't understand
• 32:28
  how this works. It's it's all to do with
• 32:31
  gravity. Uh, and thank you, Fred, uh,
• 32:34
  once again for helping us out today. I
• 32:36
  think you did all the work, actually.
• 32:40
  >> Nice to help, Andrew. Always good to
• 32:42
  talk. And we'll catch up again.
• 32:43
  >> We will, Professor Fred Watson,
• 32:45
  astronomer at large. And thanks to Hugh
• 32:48
  in the studio, although he couldn't be
• 32:51
  with us today, he um had a thought and
• 32:56
  um it was experimental and he's going to
• 32:59
  go and investigate that right now and
• 33:00
  see if it's real.
• 33:02
  I don't know what that means. Uh and
• 33:04
  from me, Andrew Dunley, thanks for your
• 33:05
  company. We'll see you on the next
• 33:07
  episode of Space Nuts. Bye-bye.
• 33:09
  >> Space Nuts. You've been listening to the
• 33:11
  Space Nuts podcast
• 33:14
  >> available at Apple Podcasts, Spotify,
• 33:17
  iHeart Radio, or your favorite podcast
• 33:20
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• 33:22
  bytes.com. This has been another quality
• 33:25
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