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Stellar Q&A: Rusty Moons, Space Stations & What If Earth Disappeared? | Space Nuts: Astronomy... · Space News Today

• 0:00
  Hi there. Thanks for joining us. This is
• 0:01
  a Q&A edition of Space Nuts. Not only do
• 0:05
  we talk astronomy and space science, we
• 0:07
  pretend to answer questions from our uh
• 0:09
  wonderful audience. We've got a bunch
• 0:11
  today. Uh Bill is asking about small
• 0:14
  bodies in solar systems. I don't think
• 0:17
  that's got anything to do with weight
• 0:19
  loss, but we'll see. Uh Peter is asking
• 0:22
  about leaving something behind that
• 0:23
  could survive the destruction of Earth.
• 0:26
  Wow, that's a what if question. Tiny
• 0:29
  moons and giant planets and issues with
• 0:32
  a giant space station. Those are
• 0:34
  questions we will endeavor to answer
• 0:36
  today on this edition of Space Nuts.
• 0:39
  >> 15 seconds. Guidance is internal. 10 9g
• 0:44
  Ignition sequence start.
• 0:46
  >> Space nuts.
• 0:46
  >> 5 4 3 2 1 2 3 4 5 5 4 3 2 1.
• 0:51
  >> Space nuts.
• 0:53
  >> Astronauts report. It feels good.
• 0:56
  And with us again is Professor Fred
• 0:58
  Watson, astronomer at large. Hello,
• 1:00
  Fred.
• 1:01
  >> Hello, Andrew. Uh, fancy seeing you
• 1:03
  here.
• 1:03
  >> Yes. Unusual. We're both wearing black.
• 1:05
  >> Is it black?
• 1:07
  >> Uh, it is. Yeah.
• 1:11
  >> It's the um this is the the shirt that
• 1:15
  if I have Jordi sitting on my lap, you
• 1:17
  you can't see him at all cuz it's
• 1:19
  exactly the same color as he is. Jet
• 1:22
  black. Uh, that'll make a good Instagram
• 1:24
  photo.
• 1:25
  >> Well, it might do. Yes.
• 1:27
  >> Just two eyes poking out.
• 1:29
  >> Now, um, we got a lot to get through, so
• 1:32
  we'll start straight away with, uh, a
• 1:34
  question that comes from Bill, and he
• 1:38
  asks, "If small bodies in the solar
• 1:40
  system formed by accretion of fine dust
• 1:43
  and gas, why are they not all fluffy,
• 1:47
  low gravity powder puffs? Um,
• 1:51
  we're all dense stony uh or uh were all
• 1:54
  dense stony or metallic objects
• 1:57
  originally part of a larger body that
• 1:58
  could differentiate under uh decent
• 2:01
  gravity levels then were smashed to
• 2:04
  small pieces in collisions. Uh thanks
• 2:07
  for the great podcast uh that comes from
• 2:09
  Bill. Um so yeah, why isn't everything
• 2:12
  puffy?
• 2:14
  >> Um I think it was to start with. Uh well
• 2:17
  so yeah so we you know um people often
• 2:22
  say
• 2:23
  people who should know better often say
• 2:26
  that if you want to know how planet
• 2:28
  formation starts look under your bed
• 2:30
  because the bits of the bits of fluff
• 2:33
  that you tend to find under your bed are
• 2:36
  made of dust sticking together uh
• 2:38
  usually by electrostatic forces which we
• 2:41
  think played a part in in the early
• 2:44
  evolution of planets. uh these things
• 2:47
  stick together, you build up bigger and
• 2:49
  bigger fluff balls. Um and eventually
• 2:54
  the fluff balls because as exactly as um
• 2:58
  as Bill says, they do tend to collide
• 3:00
  with one another. We're now talking
• 3:01
  about a very very densely a very very
• 3:05
  dense dusty environment. We're talking
• 3:07
  about the protolanetary disc that
• 3:10
  surrounded the sun. uh very dusty place
• 3:13
  with lots of um basically lots of
• 3:17
  capacity for uh dust fluff balls to
• 3:20
  build up to have bigger and bigger
• 3:22
  sizes. Eventually these various forces
• 3:27
  uh will cause the dust balls to sort of
• 3:30
  collapse. Probably collisions will
• 3:32
  contribute to that. Um by that I mean
• 3:35
  that they tend to lose their porosity.
• 3:38
  In other words, they become more solid.
• 3:41
  Um, now having said that, there are
• 3:44
  objects in space that we know are very
• 3:47
  porous. Um, well, we've we've found
• 3:50
  powder puff planets, haven't we?
• 3:52
  >> Yes, that's right. Uh, yes, almost
• 3:54
  exactly a good description of them. I'm
• 3:57
  just thinking more nearer to home,
• 3:58
  though. Um uh uh Phobos, the larger moon
• 4:02
  of Mars, is thought to have a
• 4:05
  composition a bit a bit like um God, the
• 4:08
  word's gone. Uh stuff that forms when
• 4:12
  eruptions uh take place under water.
• 4:15
  >> A honeycomb.
• 4:16
  >> Yes. Um but it's got a word. Oh, that's
• 4:19
  ridiculous. When you get to a certain
• 4:20
  age, words just disappear. Um it'll come
• 4:23
  to me in a minute. I know. Uh but yeah,
• 4:26
  the the stuff that floats on on the
• 4:28
  water from an underground eruption.
• 4:31
  Pummus, the very word. That's what I was
• 4:32
  looking for. Thank you. Thank you,
• 4:34
  Andrew. So, pummus is, you know, it's
• 4:37
  porous. It's a it's a a stony structure
• 4:40
  uh that's got a lot of gaps in it. And I
• 4:42
  guess that might well be an intermediate
• 4:45
  structure of many of these objects. As I
• 4:47
  said, Phobos is like that. Uh one of
• 4:50
  Saturn's moons, and I can't remember
• 4:53
  which one it is. It's the one shaped
• 4:54
  like a potato. That'll probably come to
• 4:56
  me in a minute as well. Uh it's also got
• 4:59
  that sort of structure. Um so maybe you
• 5:02
  know when you get things like that
• 5:03
  colliding uh then you and and building
• 5:08
  up in size then you're eventually going
• 5:10
  to get to this situation where gravity
• 5:13
  takes over uh and it pulls um these low
• 5:18
  density materials into something more
• 5:21
  solid. Um
• 5:22
  >> is it a m A malfia. A mouth.
• 5:26
  >> No. Uh, it's one with a better known
• 5:27
  name. It's It's very highly created and
• 5:31
  potato-shaped.
• 5:33
  >> Okay.
• 5:33
  >> Uh, it's uh, yeah, it's one of the most
• 5:36
  created objects in the in the solar
• 5:38
  system. I'm annoyed I can't remember it.
• 5:40
  It's ridiculous.
• 5:42
  >> I was getting too old for this, Andrew.
• 5:44
  >> Oh, no you're not.
• 5:45
  >> No, I know. Maybe I'm not. No. Keeps
• 5:47
  your brain active. Well, except it's
• 5:50
  demonstrating quite clearly uh that the
• 5:52
  memory banks are disappearing. Anyway,
• 5:55
  um it'll come to me as I said in a
• 5:57
  minute. It's not Enceladus, but it's
• 5:58
  something like that. Uh so, uh if you've
• 6:02
  got, you know, gravity taking over, then
• 6:04
  you're likely to get basically solid
• 6:06
  rock emerging from that. Uh as as uh as
• 6:10
  Bill says, dense stony or metallic
• 6:12
  objects, that's basically what they turn
• 6:14
  into. And then they collide. uh uh the
• 6:18
  larger objects are differentiated that
• 6:20
  means the heavy stuff sinks to the
• 6:22
  middle uh exactly as Bill says but they
• 6:24
  collide and that's how you can get stony
• 6:27
  meteorites or metallic meteorites
• 6:30
  because the metal tends to sink mostly
• 6:32
  uh to the middle so I think it's um it
• 6:35
  is a natural process but it's one in a
• 6:38
  way it's counterintuitive to us you know
• 6:40
  how do you get from a dust a fluff ball
• 6:43
  under your bed how do you get from that
• 6:45
  to a to a stone to rock gravity
• 6:48
  >> and yes that's right gravity but over a
• 6:50
  long period of time
• 6:52
  >> uh and probably heat as well you know
• 6:53
  you've got heat processes coming into
• 6:55
  this too
• 6:56
  >> so um uh I think I think uh what um
• 7:03
  Bill's saying is right if the small
• 7:05
  bodies in the solar system formed by
• 7:07
  accretion of fine dust and gas why are
• 7:10
  they not all fluffy lowg gravity powder
• 7:12
  puffs well some of them are and that's
• 7:14
  perhaps you could describe them like uh
• 7:17
  like um Phobos. Perhaps he could
• 7:20
  describe them as unevolved. They haven't
• 7:22
  evolved much. I think it might be
• 7:25
  Hyperion, the one I'm thinking of.
• 7:27
  >> Okay.
• 7:27
  >> Um I think it might be Hyperion.
• 7:29
  >> I'll have a look.
• 7:30
  >> Have a look. See if it's uh shaped like
• 7:33
  a potato and got lots of craters on it.
• 7:35
  >> Yeah. There's got to be a photo of it
• 7:36
  somewhere. Yes, it is.
• 7:38
  >> Yeah. Okay. Good.
• 7:39
  >> It's got It's got that big um
• 7:42
  >> It's got a massive crater in it,
• 7:43
  actually.
• 7:44
  >> Yeah, it does. Yes. Yeah. Yeah. So, um,
• 7:47
  so
• 7:47
  >> you got there in the end, Fred,
• 7:48
  >> in the end. Yeah. It's Yes. It's just
• 7:51
  the processing speed's down a bit. I
• 7:53
  must be offline or something like that.
• 7:55
  Uh,
• 7:55
  >> probably need a reboot.
• 7:57
  >> God, don't say that. I might never come
• 7:59
  back.
• 8:01
  >> Well, that's happened. My car did that
• 8:02
  while we were away.
• 8:04
  >> Came home and came home and to uh to to
• 8:07
  stop falling asleep, we decided we'd go
• 8:08
  and do the groceries straight after
• 8:10
  getting off a long haul flight.
• 8:11
  >> Oh, yes. Yeah.
• 8:12
  And the car wouldn't start.
• 8:15
  >> Yeah, the battery died. So
• 8:17
  >> Oh, the battery died.
• 8:18
  >> Yeah, that's another 315 bucks. Thank
• 8:20
  you very much.
• 8:22
  >> Yes.
• 8:22
  >> Anyway, that's okay.
• 8:23
  >> It happens. It was 4 years. It lasted
• 8:25
  four years.
• 8:26
  >> Oh, that's all right. That's about as
• 8:27
  long as you get from a battery. Yes, it
• 8:29
  >> is indeed. Uh, but thanks, Bill, for the
• 8:31
  question. I think you answered it
• 8:33
  yourself, but um yes. Uh, and although
• 8:35
  if if you're um someone like me um and
• 8:39
  you don't clean under the bed, uh you
• 8:41
  can watch pl you can watch planets
• 8:42
  evolve. That's what's happening.
• 8:46
  >> Yep, you can.
• 8:47
  >> All right. Uh thanks, Bill. Our next
• 8:49
  question
• 8:50
  uh is coming from Peter. Hello, this is
• 8:55
  Peter in Bington Spa
• 8:58
  and I want to know what would it take
• 9:02
  for humans
• 9:04
  to make something that will survive the
• 9:09
  destruction of Earth
• 9:12
  and then potentially be incorporated
• 9:15
  into a new planet when all the bits of
• 9:17
  Earth become a different planet in
• 9:20
  sometime in the future. Is it possible?
• 9:24
  >> Have a good evening.
• 9:26
  >> Thank you, Peter. That's a what if
• 9:28
  question. Uh yeah, I wonder that's
• 9:30
  that's a very it's a longhaul science
• 9:33
  fiction situation. You you you build
• 9:35
  something that will survive the
• 9:37
  destruction of Earth and then somehow
• 9:39
  the planet reconstitutes itself and
• 9:41
  billions of years later there's an
• 9:43
  intelligent race living on the planet
• 9:45
  and they go, "Oh, hello. What's all this
• 9:47
  then?
• 9:49
  >> This is some leftover of humankind."
• 9:51
  Yeah,
• 9:51
  >> whatever they were.
• 9:52
  >> There there was a a TV series that I
• 9:55
  watched many years ago called
• 9:56
  Childhood's End and it was about the
• 10:00
  destruction of Earth and before it
• 10:03
  before it was destroyed uh the humans
• 10:06
  asked the aliens that rescued the
• 10:09
  children basically uh can we can we just
• 10:12
  leave something behind so they know we
• 10:14
  were here. So they left music.
• 10:17
  >> Lovely. I like that. Yes, I like that
• 10:20
  very much.
• 10:20
  >> I just spoiled the whole thing too, by
• 10:22
  the way.
• 10:22
  >> Um I don't think you did really. Uh
• 10:26
  because yes, that's that's a kind of
• 10:28
  concept, isn't it, that you're leaving
• 10:29
  behind. Uh and my mind when I read
• 10:34
  Peter's question or heard Peter's
• 10:35
  question went to
• 10:38
  more concrete things, not necessarily
• 10:41
  made of concrete.
• 10:42
  >> I wasn't about to say that. But the but
• 10:46
  in a sense we've already done it,
• 10:48
  Andrew, because there are five um little
• 10:53
  spacecraft which are absolute um uh
• 10:59
  monuments to humanity leaving the solar
• 11:02
  system.
• 11:02
  >> Yeah.
• 11:03
  >> Um way way beyond the orbit of Earth.
• 11:05
  Voyager one is probably beyond the
• 11:10
  Actually, that's not quite true. Uh I
• 11:12
  was going to say beyond the limits of
• 11:14
  the sun when it turns into a red giant
• 11:16
  star. Um it will it Voyager one will
• 11:20
  probably survive um the red giant phase
• 11:25
  of our sun. Uh which will take place in
• 11:28
  a few billion years. Yeah.
• 11:30
  >> Uh three or four billion years. um it'll
• 11:33
  survive that but might not survive the
• 11:36
  formation of a planetary nebula when
• 11:37
  you've got hot gas coming off the uh
• 11:41
  being puffed off the surface of the red
• 11:43
  giant. It might actually melt in that
• 11:45
  because it's because planetary nebula
• 11:47
  get to be light years in diameter. Uh
• 11:50
  our voyer is only well it's nearly a
• 11:52
  light day away. Um, on the other hand,
• 11:55
  we've got 3 or 4 billion years to play
• 11:57
  with because the sun's not going to do
• 11:59
  anything really nasty uh within that
• 12:01
  time. So, yes, Voyager One will be well
• 12:03
  out of the way. Probably will survive
• 12:06
  the eventual um evolution and final
• 12:11
  uh final evolutionary stages of the sun
• 12:13
  when it actually turns into a white
• 12:15
  dwarf star. Uh so yes, uh those
• 12:18
  spacecraft, Voyager 1, Voyager 2,
• 12:20
  Pioneer 10, Pioneer 11, is that right?
• 12:23
  and New Horizons. They're the five that
• 12:26
  are leaving the solar system which will
• 12:28
  probably outlive humanity.
• 12:30
  >> They probably won't they probably won't
• 12:32
  be the last. And they won't be the last.
• 12:34
  No, I think that's right. Uh but um
• 12:39
  I mean the the idea of um of the earth
• 12:43
  being destroyed
• 12:46
  the kinds of things that might destroy
• 12:47
  the earth are first of all that eventual
• 12:50
  evolution of the sun to a red giant star
• 12:53
  that will almost certainly melt the
• 12:54
  earth
• 12:55
  >> because it'll you know that this the
• 12:57
  sun's um surface put it that way will be
• 13:01
  um a quarter of a mile from the earth
• 13:04
  and we might be on the inside of it uh
• 13:06
  it'll be it could even overtake the
• 13:08
  planet Mars. So so it's hard to imagine
• 13:11
  how you'd rebuild the earth from the
• 13:14
  debris that is really just molecules uh
• 13:17
  because it will have been vaporized. U
• 13:19
  so I think you've uh in in addressing
• 13:22
  this question you've really got to think
• 13:23
  about things that are have left the
• 13:26
  earth and that really basically pushes
• 13:29
  your mind to the to spacecraft. There
• 13:31
  are some spacecraft which are in orbit
• 13:34
  around the sun uh which have you know
• 13:37
  spacecraft that have been sent exploring
• 13:40
  the inner solar system. Mostly these
• 13:42
  days we we try and get rid of them. We
• 13:44
  plunge them uh into either Jupiter or
• 13:47
  Saturn. Jupiter in the case of Galileo,
• 13:49
  Saturn in the case of Cassini. uh those
• 13:52
  uh spacecraft were destroyed purposely
• 13:55
  so that they didn't accidentally land on
• 13:57
  one of the moons of Jupiter or Saturn
• 13:59
  and leave microbes behind. Yeah.
• 14:01
  >> Um so so you're really talking about
• 14:03
  something that's left the solar system
• 14:05
  and that leaves those five spacecraft
• 14:08
  I've mentioned and they definitely will
• 14:10
  outlast humankind.
• 14:12
  Okay, there you have it, Peter. Um so
• 14:14
  we've already done it kind of. Uh, I I
• 14:16
  don't think you could probably build
• 14:19
  some kind of monolith or something that
• 14:21
  would survive the red giant phase of the
• 14:25
  sun and and overwhelm Earth. That would
• 14:28
  all get destroyed. Um, unless you did it
• 14:31
  deep down inside, but I I don't even
• 14:33
  know if you could do that. I I think a
• 14:36
  red giant phase would be pretty
• 14:38
  cataclysmic, wouldn't it?
• 14:39
  >> Yeah. Uh, yes. If your planet's being
• 14:42
  vaporized, your planet's being
• 14:43
  vaporized. includes a whole.
• 14:46
  >> Yeah,
• 14:47
  >> indeed. Thank you, Peter. Great to hear
• 14:49
  from you. Uh, I love what if questions.
• 14:51
  So, um, thanks for serving it up. This
• 14:53
  is Space Nuts with Andrew Dunley and
• 14:56
  Professor Fred Watson.
• 14:59
  >> Let's take a little break from the show
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  Listen, Tanganity base here. The angle
• 17:20
  has landed.
• 17:21
  >> Space nuts.
• 17:23
  >> Our next question, Fred, comes from
• 17:25
  Martin in Hezwall. Hezwall, is that
• 17:27
  right?
• 17:28
  >> Yes. Hezwall. Yeah.
• 17:29
  >> Where's that? I know. I'm going to guess
• 17:30
  it's the UK somewhere.
• 17:32
  >> It is indeed. It's um uh on the Whirl
• 17:35
  Peninsula. So, if you think of
• 17:37
  Liverpool, you've been to Liverpool.
• 17:38
  >> I have.
• 17:39
  >> And done the Beatles experience. Is that
• 17:42
  right? Yes. Yeah. Well, across the river
• 17:44
  Murzy from Liverpool is the Whirl
• 17:46
  Peninsula and Hezwall is one of the uh
• 17:49
  one of the towns on that. Um I've said
• 17:52
  before and in fact we've had listener
• 17:54
  comments about this. I had a girlfriend
• 17:56
  once who lived on the Whirl Peninsula
• 17:59
  and so I used to be a very regular
• 18:00
  visitor there to a village called
• 18:02
  Barnston which was not that far from
• 18:03
  Hezil.
• 18:04
  >> There you are. All right. It's very
• 18:06
  pretty too. It's a pretty village.
• 18:08
  >> H okay. Um just wanted to know where you
• 18:11
  were Martin. So, thank you for that. Uh,
• 18:13
  I hope uh you'll answer this question.
• 18:15
  According to Wikipedia, there are now
• 18:18
  known to be 292 satellites
• 18:22
  uh with confirmed orbits around Saturn.
• 18:24
  Presumably, many of these moons are very
• 18:26
  small. So, is there a minimum size for
• 18:29
  an object to be called a moon? And is
• 18:32
  there a minimum size for an object to
• 18:34
  maintain a stable orbit around a planet?
• 18:38
  uh as all the giant planets have ring
• 18:40
  systems, would the smaller particles
• 18:43
  just be absorbed into the rings?
• 18:45
  Conversely, I suppose that many objects
• 18:48
  could be knocked out of the rings to
• 18:50
  form independent satellites that may
• 18:52
  become permanently separated from the
• 18:53
  rings. Will Saturn get uh to 1,000 moons
• 18:58
  or more? Also, uh can you recommend a
• 19:01
  website which has the latest data about
• 19:03
  uh the solar system as the numbers vary
• 19:06
  from one site to the next? No doubt due
• 19:09
  to how recent the information is. Keep
• 19:11
  up the good work. Thanks, Martin. That's
• 19:14
  a good question because yeah, we we know
• 19:16
  that the ring systems um are full of
• 19:19
  dust and ice, but they've also got
• 19:21
  larger objects that are referred to
• 19:23
  regularly as moons.
• 19:26
  Um, it's interesting. This was one of
• 19:28
  the exact questions that came up in the
• 19:30
  Q&A night, the science in the pub night
• 19:33
  that we had on Lord How Island uh at the
• 19:36
  Dark Sky Festival.
• 19:37
  >> That was that was Martin. He was he was
• 19:39
  there.
• 19:40
  >> Not No, he probably wasn't. Carry on.
• 19:43
  >> Might have been might be. There was a
• 19:44
  Martin there.
• 19:45
  >> Was Did he have a British accent?
• 19:48
  >> Uh, no. He's he's quite Australian, but
• 19:51
  he's not from not from Haswell. But
• 19:53
  yeah. Uh so but no interesting
• 19:56
  coincidence to get the two and I don't
• 19:58
  think at the moment there is a a
• 20:03
  limiting size to differentiate between a
• 20:06
  ring particle
• 20:08
  and a moon. Um so it's it's a it is a
• 20:15
  great question. Um how do you define a
• 20:18
  moon around a planet which is festoned
• 20:21
  with objects orbiting around it
• 20:23
  >> uh in the form of rings. So we think the
• 20:25
  rings of Saturn are the debris of a
• 20:30
  probably a satellite that came within
• 20:33
  the ro limit of the of the planet. The
• 20:37
  ro limit being the point at which uh a
• 20:40
  solid object can't actually survive
• 20:43
  within that distance. In other words,
• 20:45
  that close to the planet. Um, and so it
• 20:49
  broke up into lots of small particles.
• 20:53
  Probably the biggest ring sized, sorry,
• 20:56
  the biggest ring particles
• 21:00
  are in the region of 10 m
• 21:04
  because the rings themselves are only
• 21:05
  about 100 m thick.
• 21:07
  >> Yeah, it's it's quite staggering.
• 21:10
  Um, and 250,000 kilometers in diameter.
• 21:14
  So it's yes it's quite a contrast. Um a
• 21:17
  sort of blade of material in space is
• 21:19
  the way I've always described it.
• 21:21
  >> Uh
• 21:23
  but some of the smaller satellites of
• 21:26
  Saturn and some of them are actually
• 21:28
  embedded in the ring system. Uh some of
• 21:32
  them are measured in single single digit
• 21:35
  kilometers. So they're not that much
• 21:38
  more than the biggest ring particles.
• 21:42
  And I'm not sure that there is a
• 21:44
  definition between the two. And in a
• 21:47
  sense, you could say that every solid
• 21:50
  object within Saturn's rings is a
• 21:52
  satellite. And so you're then talking
• 21:54
  about millions or maybe even billions of
• 21:57
  of moons of Saturn. Uh it's a great
• 22:00
  question and one that I don't have an
• 22:02
  answer for and I perhaps ought to have
• 22:05
  checked it out in the wake of the
• 22:06
  question that came uh at the at the
• 22:09
  science in the pub science in the bolo
• 22:11
  on Lord. Island the week before last
• 22:13
  when we when we did the Dark Sky
• 22:15
  Festival there.
• 22:16
  >> Yeah. Yeah. I He also asked about
• 22:22
  Yeah. Well, I just did a quick check and
• 22:24
  uh top of the tree is is NASA uh for
• 22:28
  upto-date solar system information.
• 22:31
  >> Uh yeah. Uh but the other ones that you
• 22:33
  could try uh the skylive.com
• 22:38
  uh apparently is very highly rated um
• 22:41
  says it offers comprehensive information
• 22:43
  about the most interesting celestial
• 22:45
  objects and sets tools designed to
• 22:47
  support the exploration etc.
• 22:49
  uh the planets today
• 22:52
  uh is also there and there's a specific
• 22:55
  uh NASA page that you can look up called
• 22:58
  eyes on the solar system um and it
• 23:01
  provides a 3D solarcape if you like.
• 23:05
  >> So there's a few ideas if you want to um
• 23:09
  chase them up Martin but um there'd be
• 23:11
  plenty more out there. There's um just
• 23:14
  to name a few more, Global Solar Atlas,
• 23:17
  um the Noah homepage, the space weather
• 23:21
  prediction homepage, um and and Planet
• 23:24
  Labs, just to name a few. So, um and and
• 23:27
  they're constantly being updated as as
• 23:29
  far as I'm aware as things change or as
• 23:32
  new things come to light. So, might be
• 23:34
  worth chasing all of those up because
• 23:36
  they do seem to be um highly
• 23:38
  credentialed. Fred.
• 23:40
  >> Yeah, I was going to say I I usually go
• 23:43
  to NASA when I want the latest figures
• 23:45
  on this sort of thing. Um, so you've uh
• 23:50
  you've confirmed that and also given a
• 23:52
  few other options as well, which is
• 23:53
  good.
• 23:53
  >> Yep. Plenty to look at. There's lots of
• 23:55
  great sites out there. Just just don't
• 23:57
  go to the ones that start with um words
• 24:00
  starting with F and E.
• 24:06
  Um I was thought you were going to say
• 24:09
  don't go to ones that start with space
• 24:11
  and I've not seen the
• 24:14
  that's that's good advice too. Yeah.
• 24:17
  Okay. Uh thank you Martin. Our final
• 24:19
  question today comes from Finn.
• 24:22
  >> Hello Andrew and Fred. It's Finn from
• 24:25
  Nan in the Adelaide Hills in South
• 24:28
  Australia. And a happy May the 4th to
• 24:30
  you as well. I was watching a
• 24:32
  40-year-old documentary the other day
• 24:34
  about a space station orbiting a planet
• 24:37
  and this space station um if it was to
• 24:40
  orbit the earth, I would like to know
• 24:42
  how that would affect the orbit of our
• 24:45
  moon and maybe the orbit of the earth
• 24:47
  around the sun. This space station being
• 24:50
  150 km diameter with a mass of about 10
• 24:53
  the 15 ton. Um, I I'd like to know and
• 24:57
  if for whatever reason this space
• 24:59
  station happened to destroy our planet,
• 25:02
  how would the rest of the planets in the
• 25:04
  solar system be affected by that
• 25:06
  destruction?
• 25:08
  One last question um to you both is um
• 25:11
  what was the first animal in space?
• 25:14
  >> It was a dog.
• 25:16
  >> Ah, don't think it was that. It was
• 25:18
  actually the cow cuz it jumped over the
• 25:21
  moon. Thank you,
• 25:23
  >> dear. Oh, dear Finn. That that was
• 25:25
  probably one of the worst dad jokes I've
• 25:27
  ever heard.
• 25:28
  >> So, but you know, most welcome on this
• 25:31
  show.
• 25:35
  >> Gosh.
• 25:35
  >> Yeah, it was good. It wasn't wasn't even
• 25:37
  adequate that one, was it?
• 25:38
  >> No, it wasn't. No, we strive for
• 25:40
  adequacy and we didn't even achieve
• 25:42
  that.
• 25:44
  >> Thank you, Finn. Uh so the substance of
• 25:46
  his question was uh you got you got a a
• 25:49
  space station orbiting earth at 150
• 25:52
  kilometers in diameter or whatever. Uh
• 25:56
  what kind of effect could that have on
• 25:58
  the orbit of the moon? And
• 26:01
  yeah we'll get to the next part of the
• 26:03
  question after that. Could it have would
• 26:05
  that have any that's pretty big.
• 26:08
  It's it's bit well the critical thing
• 26:10
  was the mass which um which Finn Hley
• 26:14
  mentioned as being 10^ the 15 tons I
• 26:18
  think is what he said. Uh which is 10 to
• 26:22
  the 18 kg. Um and
• 26:27
  so the bottom line is that's not enough.
• 26:30
  Uh the earth just yeah nah forget it. So
• 26:34
  the earth's uh 6* 10 24 kilograms. So
• 26:38
  it's um what is it? It's uh six orders
• 26:43
  of magnitude bigger in mass than uh than
• 26:48
  this space station. And so the other so
• 26:51
  it it it you know it's it's certainly
• 26:54
  not going to affect the orbit of the
• 26:56
  earth. It might perturb the orbit of the
• 26:59
  moon a bit. Yeah. Uh, one of the
• 27:02
  considerations will be how far away is
• 27:05
  it from the earth and our last question
• 27:10
  actually pointed to an answer to that
• 27:13
  and that is that it would if it's 150
• 27:15
  kilometers in diameter it has to be a
• 27:18
  long way away or else it's within the ro
• 27:20
  limit
• 27:21
  >> of of the earth and it would just break
• 27:24
  up straight away. So I I'm not going to
• 27:26
  guess how far away it has to be, but
• 27:28
  it'll be a long way off the Earth if
• 27:29
  it's 150 kilometers in diameter. Um so
• 27:33
  that again um basically mitigates any
• 27:36
  effects it might have on the orbital
• 27:39
  dynamics of the Earth. It certainly
• 27:40
  wouldn't affect the Earth's orbit around
• 27:41
  the Sun. Might just tweak the moon's
• 27:45
  orbit around the Earth a bit. Uh
• 27:48
  wouldn't cause the demolition of the
• 27:50
  Earth. the orbits of the other planets
• 27:53
  wouldn't even bother to to take any
• 27:56
  notice of it. Uh they they are too
• 27:59
  stable compared with uh you know with a
• 28:01
  a thing of that mass and that far away
• 28:04
  from the earth. So, it's a it's an
• 28:06
  interesting thought uh and one that I
• 28:10
  think um we can say yes, you could have
• 28:12
  a space station 150 kilometers in
• 28:14
  diameter weighing 10^ the 15 tons uh and
• 28:18
  it probably would not affect the status
• 28:20
  quo terribly badly.
• 28:22
  >> Okay, there you go. Uh, and I just did a
• 28:24
  quick check, but um, you know, there's
• 28:26
  not much information about how far space
• 28:28
  stations have to be away to avoid the ro
• 28:31
  limit, but a solid object such as a as a
• 28:34
  a rocky body with 150 km diameter would
• 28:38
  have to be at least 141,000 kilometers
• 28:41
  away from Earth.
• 28:43
  >> Probably better off being over 200,000
• 28:45
  kilometers away.
• 28:46
  >> Yes, that that's the sort of distance I
• 28:48
  had in mind. Something like that. three
• 28:51
  times as far away as the um
• 28:53
  geostationary satellites are. There you
• 28:55
  are. Now, he had a second question as to
• 28:58
  what would happen to the other planets
• 28:59
  if Earth was destroyed, no longer
• 29:02
  existed. I think we've been down this
• 29:03
  road before and I can't remember the
• 29:05
  answer.
• 29:06
  >> Yeah. So, um the other planets would
• 29:09
  more or less stay in the present orbits
• 29:12
  there. Those orbits would be perturbed
• 29:16
  uh differently from what they are now.
• 29:17
  So perturbations are the the
• 29:19
  gravitational effects of other bodies in
• 29:21
  the solar system. Uh on the when you
• 29:24
  when you look at the way things are in
• 29:26
  orbit, you start off with a two-body
• 29:28
  problem with the sun and your object in
• 29:30
  orbit. But then you modify it by have it
• 29:33
  taking into account the gravitational
• 29:35
  attraction of other bodies and it
• 29:36
  becomes a three-body problem and then
• 29:38
  four body problem and all the rest of
• 29:39
  it.
• 29:40
  >> Yeah.
• 29:40
  >> Uh now it that three-body problem would
• 29:43
  change if the earth wasn't there. um or
• 29:46
  the endbody problem. I suppose it would
• 29:48
  be a solar system with seven planets
• 29:50
  rather than eight.
• 29:51
  >> Uh that would change the dynamics of the
• 29:53
  planets a little bit. Uh but they would
• 29:56
  basically remain in their present orbits
• 29:58
  uh with with just changes to the orbit
• 30:01
  rather than the orbits being destroyed.
• 30:03
  >> So in other words, if Earth disappeared,
• 30:05
  no great loss.
• 30:06
  >> No, not really. I mean, you know,
• 30:09
  Douglas Adams had it in one. Mostly
• 30:11
  harmless.
• 30:11
  >> Mostly harmless. Yes,
• 30:13
  >> that's right. Thanks for the white mice.
• 30:15
  >> Yes, that's right.
• 30:18
  >> I wonder how all the other mice felt
• 30:19
  about that.
• 30:21
  You know, it was it was mus musculus
• 30:23
  racism. That's what it was.
• 30:25
  >> There it is. Yes. Mass racism. Exactly.
• 30:28
  So,
• 30:29
  >> yeah. Uh, thanks Finn. Great question.
• 30:31
  We We always love these whatifs. So, um,
• 30:33
  if you'd like to keep sending in
• 30:35
  questions like that, or if you got
• 30:36
  something deadly serious to discuss with
• 30:39
  us, like, I don't know, exploding
• 30:41
  rockets and whatever else, uh, you can
• 30:44
  send them into us. Uh, just go to
• 30:46
  spaceenuts.io
• 30:47
  or spacenutspodcast.com,
• 30:49
  click on the ask me anything button. You
• 30:53
  won't be asking me, you'll be asking
• 30:54
  him, but uh, I'll read it out. Or you
• 30:57
  can send us an audio question. As long
• 30:59
  as you've got a device with a
• 31:00
  microphone, you're all set. Uh, and
• 31:01
  while you're there, have a look around.
• 31:03
  Uh, that brings us to the end. Fred,
• 31:05
  thank you very much.
• 31:06
  >> Great pleasure, Andrew. Always good to
• 31:08
  chew the fat and I hope we'll do it
• 31:10
  again soon.
• 31:11
  >> We will. That's Professor Fred Watson,
• 31:13
  astronomer at large, part of the team
• 31:14
  here at Space Nuts. And thanks to Hugh
• 31:16
  in the studio, uh, who couldn't be with
• 31:18
  us today. He was seeing his dietician
• 31:20
  after he reached 10 to the 15 tons.
• 31:24
  I'm surprised he survived. And from me,
• 31:26
  Andrew Dunley, thanks for your company.
• 31:28
  We'll be back again soon with another
• 31:30
  episode of Space Nuts. See you then.
• 31:32
  Bye-bye.
• 31:33
  >> Space Nuts.
• 31:34
  >> You've been listening to the Space Nuts
• 31:36
  podcast
• 31:39
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• 31:42
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• 31:44
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• 31:47
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• 31:50
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