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Transcript

Space Light, Cosmic Shields & Moon Mysteries · Space Nuts: Astronomy Insights & Cosmic Discoveries

• 0:00
  Andrew Dunkley: Space Nuts is taking a bit of a break at the
• 0:02
  moment, Fred. Uh, and I will be back, uh, in
• 0:05
  the not too distant future with fresh
• 0:06
  episodes. In the meantime, enjoy some of, uh,
• 0:09
  the key episodes that we have presented over
• 0:12
  the years. Major events in
• 0:14
  astronomy and space science. And
• 0:17
  we'll see you real soon.
• 0:19
  Generic: Space Nuts.
• 0:20
  Andrew Dunkley: Hi there. Thanks for joining us on a Q and A
• 0:23
  edition of Space Nuts. I'm Andrew Dunkley,
• 0:25
  your host. Once again. Uh, thanks for joining
• 0:28
  us and, um, good to have your company. On
• 0:31
  this edition, we're, uh, answering some
• 0:32
  questions about light in space. Um, this
• 0:35
  one comes from Lee. He's asked a very
• 0:38
  interesting question. I've never actually
• 0:39
  thought about this particular
• 0:42
  concept, but, uh, it's a question that I
• 0:45
  think is worth answering for sure. That's why
• 0:47
  we included it. Fenton wants to know about,
• 0:50
  um, shielding astronauts in the
• 0:52
  outer reaches of the solar system. And he's
• 0:54
  got an idea on how to do that. Uh,
• 0:57
  Robert wants to, uh, talk about things we
• 0:59
  learned from the moon. And what if our moon
• 1:01
  wasn't the same as the moon is now?
• 1:04
  Would our learnings be different? That's a
• 1:06
  really interesting question. And Duncan wants
• 1:09
  to talk about ice giants. And why are they
• 1:11
  ice giants? Why don't we call them something
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  else? That's all coming up shortly on this
• 1:15
  edition of Space Nuts.
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  Generic: 15 seconds. Guidance is internal.
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  10, 9. Ignition
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  sequence start.
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  Professor Fred Watson: Space Nuts.
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  Generic: 5, 4, 3, 2.
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  Duncan: 1.
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  Generic: 2, 3, 4, 5, 5, 4, 3, 2,
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  1.
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  Professor Fred Watson: Space Nuts astronauts report at Beales.
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  Good.
• 1:34
  Andrew Dunkley: Once again we welcome the one and only Fred
• 1:37
  Watson, astronomer at large. Hello, Fred.
• 1:39
  Professor Fred Watson: Hello, Andrew. How have you been since we
• 1:41
  last spoke?
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  Andrew Dunkley: I haven't moved from this seat in all that
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  time.
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  Professor Fred Watson: Well, it's. I know. It's, uh. I can see
• 1:50
  you're glued to your chair there. Um,
• 1:53
  very much so. Uh, yes.
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  Andrew Dunkley: Uh, shall we get, um, straight into it and
• 1:57
  answer some questions from our audience?
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  Professor Fred Watson: Uh, that's a good idea.
• 2:03
  Andrew Dunkley: Yeah, it is. That's what we're here for.
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  This first one, Fred, comes from Lee. He
• 2:07
  lives in New York City. Uh,
• 2:10
  he's asking how much light is in space.
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  He'll qualify that question. For example, if
• 2:17
  you were to visit Voyager 1, where Voyager 1
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  is today, would you be able to see. See it?
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  Would you see just a silhouette? Would you be
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  able to make out, uh, details and colors, if
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  there are any colors on it? Uh, what about
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  if, uh, you and Voyager were midway between
• 2:34
  the sun and Alpha Centauri? Uh, can we
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  know a reasonably accurate answer,
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  or is it pure speculation? Thanks. Love the
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  show. Lee, from New York. I've never
• 2:45
  thought about that. I mean, we take for
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  granted light on Earth because we're
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  illuminated by the sun. But it's a bit
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  different in other parts of the solar system
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  and the universe in general. So, yeah, if we
• 2:56
  could just go, snap, we're out there next to
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  Voyager 1. Could we actually see it? Is it
• 3:02
  illuminated in any way? Is it being
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  illuminated by something? What would it be
• 3:06
  like?
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  Professor Fred Watson: Uh, the answer is yes, you'd see it. Um, and
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  so we're talking really now about the
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  sensitivity of the human eye. Um, because,
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  uh, with a camera, uh, you know,
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  with long exposure settings and things you'd
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  be able to see in great detail
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  but thinking about the human eye. So,
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  um, I used
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  to work, as you know, at Siding Spring
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  Observatory. Uh, I spent
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  many hours, uh, outside at
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  night. There it is a place that is truly
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  dark. There's no interference from street
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  lights. Uh, there are a few blobs of
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  light on the horizon, but nothing that
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  affects the pristine darkness of the night
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  sky. And on a starry night
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  with the sun not in the sky, you can see
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  quite clearly. Um, there's enough
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  light from the stars themselves to let
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  you see where you're going. Uh, let
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  you, you know, walk around and be
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  quite confident that you're not going to fall
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  off the mountain, as I nearly did one night
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  when it was, uh, cloudy. I went out without
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  my torch. I thought, oh, yeah, I'll see by
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  the stars. But fortunately, unfortunately,
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  the cloud had come in, I couldn't see
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  anything and I nearly fell off the mountain.
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  Uh, I didn't in the end. But, um.
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  Andrew Dunkley: It's a long drop free.
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  Professor Fred Watson: Yes, it is. Yes. It's quite a long drop
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  anyway, uh, if you, uh, you know,
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  normally on a starry night, you will see,
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  um, by the light of the stars. Now,
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  where voyager is Voyager 1, I
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  just looked it up. Uh, it is, uh,
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  at a distance from the sun
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  in astronomical units, which is
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  163 astronomical units. That's
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  163 times the number
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  of times the distance between the Earth and
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  the sun. So that's 150 million
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  kilometers. Multiply that by 163
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  and you will get,
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  uh. What do you get? I was looking for it in
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  kilometers, but it's not there. I'll have to
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  do the numbers anyway. It doesn't matter. The
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  bad thing is, um, Its distance is
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  22.55 light hours away.
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  That's how long it takes, uh, the signal to
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  get from Voyager to Earth. It's almost a day.
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  It's almost a light day away. Um,
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  so at that distance from the Sun,
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  160 odd astronomical units,
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  there's still significant light coming from
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  the sun, not to mention Venus,
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  uh, and um, you know, Jupiter and
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  uh, the other planets. Mostly the sun though,
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  you'd, you're being illuminated by the sun,
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  so that's certainly opposite, uh, as
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  compared with just being illuminated by the
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  starry sky, which is what I was just talking
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  about. So you'd see it really clearly. You
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  uh, wouldn't have any problem making it out,
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  assuming your eye was dark adapted.
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  Andrew Dunkley: So, um, it's fairly bright out
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  there.
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  We talked about the sensitivity of the human
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  eye as uh, you referred to
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  how sort of small amount of light can we see
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  as human beings?
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  Professor Fred Watson: Um, I think there were some
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  experiments. Let me think, was
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  it one photon.
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  Andrew Dunkley: Or one pixel like that?
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  Professor Fred Watson: There was. That's right. We might have talked
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  about this. There were experiments done that
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  showed that the human eye is capable of
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  detecting single photons. Uh, it was
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  under special circumstances, but uh,
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  and that is just extraordinary, um,
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  when you think that the human eye can also
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  cope with broad daylight. That's the
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  amazing thing about the human eye. It can,
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  you know, it's quite happy, uh, to see
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  light, uh, one brightness and then
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  a light that's only a millionth of as bright.
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  Um, it's fine. You can deal with that. Ah.
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  And that's a combination of what's called
• 7:03
  retinal bleaching and the iris of
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  your eye opening and closing. It's all those
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  things come together to give you this
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  unbelievably versatile and sensitive
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  tool with which we can look at the uh, our
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  surroundings. Whether it's uh, the rock face
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  I'm looking at now because that's what our
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  backyard consists of, or whether it's uh,
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  you know, the night sky where you're looking
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  at faint objects, uh, in the sky.
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  It's quite amazing.
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  Andrew Dunkley: So even if you went deeper into space, way
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  beyond our solar system, you, you would
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  probably still see objects that you were
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  near.
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  Professor Fred Watson: There'd be enough light from the stars. The
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  Milky Way is bright. Uh, it
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  would, it would. You know, even if, as uh,
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  Lee says, even if you were halfway between
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  sun and Alpha Centauri, you'd still see it
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  because of the ambient light, um,
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  that's coming from, from the stars. Yeah.
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  Andrew Dunkley: And you'd still see color because that's
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  what. Well, it's dark enough, it might turn
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  into the grays, which happens.
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  Professor Fred Watson: That's right. Yeah. And I think that's
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  likely. I think, I don't Think you would see
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  color? Um, you. You would. Where it is now,
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  there's enough light coming from the sun that
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  you'd see color. But I think, uh, when you
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  got further out, you would start to just see
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  the. You know, as you said, that
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  sort of pale gray appearance. Where you're
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  looking at very low light. Low light levels
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  indeed. Where the color cells aren't
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  receptive.
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  Andrew Dunkley: There you go. Lee, uh, the answer to your
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  question's yes to all of the above,
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  Basically.
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  Duncan: Yeah.
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  Andrew Dunkley: Great question. Excellent question.
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  All right, let's move on. This is from
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  Fenton.
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  Duncan: Yeah. Hello, Fred and Andrew. This is
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  Fenton contacting you from St.
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  Paul, Minnesota, in the U.S.
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  um, I sort of have a different type of
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  astrophysical question for you.
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  And this is on how to
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  shield astronauts from
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  radiation outside of the Van Allen Belt.
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  Um, I was curious if you know of any pending
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  technologies. That would allow this
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  obvious choice would some people would say is
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  lead. But I can think of several reasons why
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  this is not a good idea. How about
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  a miniature Van Allen Belt
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  which could surround a
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  spacecraft? How does that sound? How
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  could this become, uh, reality?
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  Thank you very much. I hope you like the
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  question. Bye now.
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  Andrew Dunkley: Thanks, Fenton. Fenton always has these
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  intriguing thoughts. I've noticed in the
• 9:39
  Times that we've heard from him. Um, maybe we
• 9:41
  should start by explaining what the Van Allen
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  Belt is. For those of us who just can't
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  remember, like me.
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  Professor Fred Watson: Um, it's, uh.
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  So the Van Allen belts are the. Basically
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  the. You know, the magnetic shielding
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  around the Earth, uh, which is,
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  uh. Caused by
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  the magnetism of the Earth. It's caused by,
• 10:05
  uh, the fact that we've got an iron core. And
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  basically, uh, it's in two parts. It's solid
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  and liquid. So it acts like a dynamo. It's
• 10:14
  rotating. And that gives us this, uh.
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  Exactly the protection that, um.
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  Um. Um. Fenton is talking about.
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  Andrew Dunkley: Um.
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  Professor Fred Watson: Yeah, I was gonna refer.
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  I'm a bit annoyed actually, because I've lost
• 10:27
  it. Uh, there is a very
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  nice article on, um.
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  Uh, it's actually on the, um.
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  BBC's website. Uh,
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  their sky at Night website. There's a lovely
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  article on exactly this. Here it is. I found
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  it. I hadn't lost it. How astronauts can hide
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  from radiation on Mars. And it goes into,
• 10:50
  uh. Exactly the problem that,
• 10:53
  uh, Fenton's talking about. How do you
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  present. How do you prevent, um, astronauts
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  basically becoming irradiated.
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  Uh, and over time it's
• 11:04
  basically lethal. Uh, because
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  of the cosmic radiation that's coming down
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  through space. Uh, and
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  the cell damage, uh, in your
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  body. Uh, and it can actually trigger cancer.
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  So, um, the whole study of
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  this is. Sorry,
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  the thrust of this article, BBC sky at
• 11:29
  Night magazine, uh, is to
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  discuss how you might protect astronauts,
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  uh, from the radiation. Uh, and that's not
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  just on Mars, but on route. Uh,
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  okay, uh, the
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  solution that Fenton has suggested
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  is covered in a paragraph. I'm going to read
• 11:48
  it because we quoted where the source is. Uh,
• 11:51
  for example. All right,
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  let me go back a paragraph. One method of
• 11:57
  helping astronauts to avoid the radiation on
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  Mars is active shielding. For
• 12:02
  example, superconducting electromagnets could
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  be used to create a powerful magnetic field
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  to deflect the incoming charged radiation
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  particles away, just as the Earth's field
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  does. That's the Van Allen Belt. The problem
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  is that such solutions can demand a lot of
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  power to run, and the technology is a long
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  way from being fully developed. An easier
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  alternative is passive shielding. Simply
• 12:25
  placing a thick bulk of shielding material
• 12:28
  between the crew habitat and the sky.
• 12:31
  Uh, and then they go on to consider different
• 12:34
  materials. Aluminium, AKA
• 12:37
  aluminum, the metal that spacecraft are
• 12:40
  constructed from is actually a pretty bad
• 12:42
  radiation shield. Um, and
• 12:45
  they say when hit by an energetic cosmic
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  ray, its atoms can shatter and fly onwards to
• 12:50
  create even more radiation particles.
• 12:53
  And Martian soil, the regolith, uh, which if
• 12:55
  you're on Mars, you might think about digging
• 12:58
  a hole there. Uh, it's got the same problem,
• 13:00
  but it's actually, uh, you know,
• 13:03
  abundant. Um, and so you
• 13:06
  could use that to dig a pole. If you
• 13:09
  put a 2 to 3 meter layer on top of
• 13:12
  your habitat, uh, then you'll,
• 13:14
  you'll get some protection. But, uh, the
• 13:17
  thing that surprised me, Andrew, uh, is once
• 13:20
  again, it comes from this same article. Uh,
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  hydrogen is the best shielding material
• 13:26
  as it's light atoms. Yeah, it's light
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  atoms. Uh, and by light I mean
• 13:31
  not heavy. Its light atoms don't create as
• 13:34
  much secondary radiation. And so tanks of
• 13:37
  rocket fuel or water, which is
• 13:39
  rich in hydrogen, placed over crew quarters
• 13:42
  could double up as effective radiation
• 13:44
  shields. I've heard that before that, um,
• 13:47
  one way of protecting your spacecraft as it
• 13:49
  flies to Mars is put it in a tank of water.
• 13:53
  Uh, it's the last thing you'd expect to do,
• 13:55
  but water is a good shielding material.
• 13:58
  And they also, uh, point out the
• 14:01
  alternative of hydrogen rich plastics like
• 14:03
  polyethylene could be used to cement
• 14:06
  regolith grains together. This is on Mars.
• 14:08
  And improve their shielding effect. Um,
• 14:11
  so, uh, if you want to read more about this,
• 14:13
  it's an article that originally appeared in
• 14:16
  the August 2022 issue of BBC
• 14:19
  sky at Night magazine. And it covers pretty
• 14:21
  well most of the ideas, uh, that have been,
• 14:23
  that have been suggested for this radiation
• 14:26
  issue. It's one that's got to, you know, it's
• 14:28
  got to find an answer soon because, uh,
• 14:31
  good old Elon and his starship, uh,
• 14:34
  is getting nearer to thinking about going to
• 14:36
  Mars. I don't think it's ever going to
• 14:37
  happen, but, uh, that's something he'll
• 14:40
  definitely be thinking about.
• 14:42
  Andrew Dunkley: Yes, indeed. He's too busy dealing with the
• 14:45
  Australian government at the moment.
• 14:47
  Professor Fred Watson: That's right.
• 14:48
  Andrew Dunkley: Some of the content on Twitter that the
• 14:50
  government wants to get rid of simply because
• 14:53
  of its, um, volatility. But anyway, that's a
• 14:55
  different story. Um, but there's plenty of
• 14:57
  water on Mars, so maybe, maybe creating those
• 15:00
  water barriers is probably the simplest thing
• 15:03
  to do. You've already got the material there.
• 15:05
  Professor Fred Watson: If you've landed in the right spot where
• 15:07
  you've got permafrost or whatever.
• 15:09
  Andrew Dunkley: That's the question. Yes, indeed. Uh, well
• 15:11
  done, Fenton. You actually happened across
• 15:14
  some of, uh, the answers too in, uh, asking
• 15:16
  your question. Uh, this is Space
• 15:19
  Nuts Andrew Dunkley here with Professor Fred
• 15:21
  Watson.
• 15:25
  Generic: Three, two, one.
• 15:28
  Andrew Dunkley: Space Nuts.
• 15:29
  Now, Fred, uh, our next question comes from
• 15:32
  Robert. Hi guys. Love your show. Sorry for
• 15:34
  the long question, but feel free to
• 15:36
  paraphrase, uh, or shorten it. Our
• 15:39
  moon is heavily crated and has given
• 15:42
  us a lot of insight into the history of the
• 15:44
  solar system and perhaps how the planets
• 15:46
  formed. But what if we had a moon
• 15:49
  like the icy moon Europa or the
• 15:51
  shrouded in, uh, haze Titan, both of
• 15:54
  which don't show immediate evidence of
• 15:56
  cratering? Would our theory about, uh, how
• 15:59
  the planets developed would, uh, be
• 16:02
  different? What other insights about our
• 16:04
  solar system would be missing or would
• 16:07
  we be missing? And lastly, uh, would we have
• 16:10
  spent, uh, or would we have sent people to
• 16:12
  land on such moons, that is, uh,
• 16:15
  would they be more dangerous for
• 16:18
  astronauts? Cheers.
• 16:19
  Robert in Vienna, Austria. Wow. I don't think
• 16:22
  we've had a question from Vienna before, have
• 16:24
  we? Lovely to hear from you, Robert.
• 16:27
  Professor Fred Watson: I think, I think Robert might have been in
• 16:28
  touch once before.
• 16:29
  Andrew Dunkley: Oh, I might have been too. It's very rare to
• 16:32
  hear from Vienna.
• 16:34
  Professor Fred Watson: Yeah, I was in Vienna at the beginning of
• 16:35
  last year and I think, I think we got
• 16:37
  something around about the same time. And I
• 16:39
  was waxing lyrical about being in Vienna at
• 16:41
  the UN when I was at, uh, the copywritten
• 16:44
  meeting. Anyway, that's another, another
• 16:46
  issue. Uh, what if we had a. Yeah, it's a
• 16:49
  really interesting question. Um,
• 16:52
  what would we not know about
• 16:55
  the solar system. If our moon
• 16:58
  was basically one
• 17:01
  that had been resurfaced in recent years
• 17:03
  or even millennia, because that's what makes
• 17:06
  the surface smooth. That's how we
• 17:09
  recognize, um, the
• 17:11
  fact that the universe. Sorry, that the.
• 17:15
  It's how we recognize the age of a surface is
• 17:17
  by how many craters it's got. The older, the
• 17:20
  older the surface, the more craters it has.
• 17:23
  And so the Moon's southern region, which is
• 17:25
  heavily cratered, as is the backside, tell
• 17:28
  uh, us that, uh, early on in the solar
• 17:31
  system's history, it was a very, um, wild and
• 17:33
  woolly place with things charging about all
• 17:36
  over and causing these craters. Now if we
• 17:38
  had a moon that was like Europa, that had,
• 17:41
  um, you know, icy, uh,
• 17:43
  geysers on it that basically covered up the
• 17:46
  craters, would we have known about that? My
• 17:49
  guess is yes, we would, because we'd
• 17:52
  see other bodies within the solar solar
• 17:54
  system, uh, like, you know, other moons,
• 17:56
  like, um, places like,
• 18:00
  um, Ceres, um, the biggest of the
• 18:02
  asteroids, the dwarf planet that dominates
• 18:04
  the asteroid belt that's heavily cratered.
• 18:07
  Uh, parts of Pluto are heavily cratered.
• 18:10
  Duncan: Um.
• 18:11
  Professor Fred Watson: Uh, Mimas, uh, one of Saturn's
• 18:15
  moons is heavily cratered too. So we'd
• 18:18
  know about it by looking at other objects.
• 18:20
  Even if our own moon was smoothly, uh,
• 18:23
  surfaced, um, it's, it's, uh.
• 18:26
  But the. Robert's last point, uh, on,
• 18:29
  um, this would, uh. We have sent
• 18:31
  people to land on such a moon. I,
• 18:34
  uh, think, um. I don't know. That's a really
• 18:37
  good question. I mean, we have sent people to
• 18:39
  land on our moon as it stands, uh, with an
• 18:42
  ancient surface. In fact, where they landed
• 18:45
  were more recent, uh, than the heavily
• 18:48
  cratered surfaces because they were
• 18:49
  principally in the maria, the basalt plains.
• 18:52
  Yeah, so maybe that
• 18:55
  suggests that we would have landed people on
• 18:58
  Europa as well, uh, because I think we
• 19:00
  probably.
• 19:01
  Andrew Dunkley: Yeah, we probably would because it would have
• 19:03
  a solid surface. There'd be places because it
• 19:06
  would be so close to us, we'd be able to
• 19:08
  examine and find the right landing points.
• 19:12
  Might be a bit more difficult with a moon
• 19:15
  that's shrouded in land gas.
• 19:17
  Professor Fred Watson: Yeah, yeah, that's right. And
• 19:20
  especially in places, um, like Titan.
• 19:23
  Uh, I still think
• 19:26
  we'd have done it actually. I think, um, you
• 19:28
  know, the JFK's, uh, promise
• 19:31
  to put astronauts on the moon would have
• 19:33
  still held good even if it had been a very
• 19:35
  different place. If it had been like IO, uh,
• 19:38
  it might have been a different story where,
• 19:40
  you know, you've got the most volcanically
• 19:42
  active body in the entire solar system with
• 19:45
  stuff going off all over the place, I think
• 19:47
  we might have been a bit more reluctant to
• 19:49
  land on eo.
• 19:49
  Andrew Dunkley: Uh, yes, possibly. So, uh,
• 19:52
  it would be interesting to have something
• 19:54
  different. But then if we'd always
• 19:57
  had an ice moon, we probably would have
• 19:59
  caught a question from, uh, Robert asking,
• 20:02
  what if we had a rocky moon now.
• 20:04
  Professor Fred Watson: Would we look, would we have
• 20:07
  a.
• 20:07
  Andrew Dunkley: Different interpretation of the formations of
• 20:10
  the planets if there was a rocky moon next to
• 20:11
  us instead of an ice moon? Yes. Um, in an
• 20:14
  alternative universe, Robert, you would have
• 20:16
  flipped your question. Good to hear from you.
• 20:18
  Hope all is well in Austria.
• 20:21
  Our final question for this episode comes
• 20:23
  from Duncan.
• 20:25
  Duncan: Hello, Duncan here from
• 20:27
  Weymouth in the uk.
• 20:30
  Again, a quick question.
• 20:34
  Just looking was doing some reading and I
• 20:37
  noticed that Uranus and Neptune
• 20:39
  are often referred to as ice
• 20:42
  giants. Now
• 20:45
  given that ice is
• 20:48
  basically just sort of like a rock form of
• 20:50
  water or CO2
• 20:53
  or whatever else, but basically just
• 20:56
  a solid form of it, why are they not just
• 20:59
  called rock giants? Why do we
• 21:02
  make the definition of ice rather than just
• 21:05
  calling them rock? It just seems
• 21:08
  odd because the little planets in the
• 21:11
  inner solar system are referred to as rocky
• 21:13
  planets. So given that they're also
• 21:17
  apparently rocky, why are they not called
• 21:19
  rocky giants? Okay,
• 21:22
  thank you, Bye.
• 21:24
  Andrew Dunkley: Thanks, Duncan. Appreciate your questions as
• 21:27
  always. Uh, yeah, why do we call them ice
• 21:30
  giants? Just for the sake of the exercise?
• 21:32
  Because there's gas giants and ice giants.
• 21:36
  Professor Fred Watson: Yeah, except one is a subset of the other.
• 21:39
  And so all four of the outer
• 21:42
  planets, Jupiter, Saturn, Neptune, sorry,
• 21:44
  Uranus, Neptune, they're all gas giants
• 21:47
  because they have, uh, high mass.
• 21:51
  Uh, um, you know, much more,
• 21:54
  um, in the case of Jupiter certainly, than,
• 21:56
  uh, our own planet. Um,
• 21:59
  the. They've got their giants, they're big,
• 22:02
  they've got high mass, and they don't
• 22:05
  have a visible surface,
• 22:08
  which is why they call gas giants, because
• 22:10
  all we see is a gassy envelope.
• 22:12
  Um, just to go to the last of
• 22:15
  Duncan's questions there, we wouldn't call
• 22:17
  the inner planets rocky giants because
• 22:20
  they're not giants. They're, uh, kind of
• 22:22
  normal planet size. You know, if you, if you
• 22:23
  think of the Earth as being your standard
• 22:25
  planet, then, uh, Mercury,
• 22:28
  Venus and Mars are similar, ah, in size.
• 22:31
  They're, uh, all smaller. Venus is about the
• 22:33
  same size, but Mercury and Mars of course are
• 22:35
  smaller. Uh, so it's only when you
• 22:38
  compare with the size of Earth that you'd
• 22:40
  start talking about giants because they are
• 22:42
  much, much bigger than Earth. And so that's
• 22:45
  the gas giants. So why Are, uh,
• 22:48
  Uranus and Neptune called ice giants
• 22:51
  because they have
• 22:53
  hazes of ice in their atmosphere.
• 22:57
  So. And that's the trick. It's not
• 23:00
  a solid surface. It's not rock.
• 23:03
  It's a haze. It's kind of like, uh, a dust
• 23:06
  of ice which permeates their atmosphere.
• 23:08
  And it's water ice, in fact, uh,
• 23:11
  mostly. Uh, so that's why they
• 23:14
  called ice giants, because unlike Saturn and
• 23:17
  Jupiter, which don't have these hazes,
• 23:20
  uh,
• 23:23
  the two outer planets, Uranus and
• 23:25
  Neptune, do they have ice hazes in their
• 23:28
  atmosphere. Hence the name.
• 23:30
  Andrew Dunkley: Okay. Yeah. And of course, the last episode
• 23:33
  we learned there wasn't much water in
• 23:35
  Jupiter's atmosphere.
• 23:36
  Professor Fred Watson: That's right.
• 23:38
  Andrew Dunkley: In the two outer gas giants. Yeah,
• 23:41
  it sounds like there is. Is that why they're
• 23:43
  a different color?
• 23:44
  Professor Fred Watson: Yes, yes, I think that's right. Um,
• 23:48
  and also their atmospheric constituents are,
• 23:50
  uh, different. They don't have the same belt
• 23:53
  structure that Saturn and Jupiter do. It may
• 23:56
  be that that's because any belts that exist
• 23:58
  are, uh, much lower in the atmosphere, and so
• 24:00
  you don't see them. Um, yeah, I
• 24:03
  mean, uh, there's a strong body of,
• 24:07
  uh, advocacy within the space
• 24:10
  fraternity to get
• 24:14
  more spacecraft out to Uranus and
• 24:16
  Neptune because they're the two planets about
• 24:19
  which we know least. Um, and, uh, will
• 24:22
  be good to know more.
• 24:24
  Duncan: Yeah.
• 24:25
  Andrew Dunkley: Well, if you sit down in snow for long
• 24:27
  enough, Uranus turns into a nice giant.
• 24:32
  I couldn't help it.
• 24:33
  Professor Fred Watson: Sorry. Uh, yeah,
• 24:36
  which is why we call it Uranus in politics.
• 24:39
  I know, I know.
• 24:41
  Andrew Dunkley: Yeah. But it's just a joke.
• 24:43
  Duncan: Got to tell.
• 24:43
  Professor Fred Watson: It's just.
• 24:44
  Andrew Dunkley: You have to.
• 24:46
  Professor Fred Watson: Yes, I. I blame Johannes Boda, who is
• 24:49
  the person who chose the name. He's fine in
• 24:52
  German. There's nothing wrong with
• 24:55
  German ruins. All the jokes
• 24:57
  there.
• 24:59
  Andrew Dunkley: All right, so, yes, uh, they're ice giants
• 25:01
  for a very good reason, Duncan. Because
• 25:03
  they've got ice in them in, uh, the
• 25:05
  atmosphere. But, uh, technically speaking,
• 25:07
  they are, in fact, gas giants. But, yes,
• 25:10
  you differentiate them because of their
• 25:12
  substantially different atmospheres. There
• 25:14
  you are.
• 25:15
  Professor Fred Watson: Thanks, Duncan.
• 25:15
  Andrew Dunkley: Great to hear from you. Great to, uh, hear
• 25:17
  from everybody. Thanks for sending in your
• 25:18
  questions. Don't forget, you can send in
• 25:20
  questions via our website, spacenuts
• 25:22
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• 25:25
  and all you have to do is click on the
• 25:26
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• 25:29
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• 25:31
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• 25:33
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• 25:39
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  button below. Which, yes, it's down
• 25:52
  there somewhere. I don't know one of those
• 25:55
  places. Fred, as always, thank you so much.
• 25:58
  Professor Fred Watson: Pleasure, Andrew. See you soon.
• 26:00
  Andrew Dunkley: Okay. Fred Watson, astronomer at large. We'll
• 26:03
  catch him on the next episode of Space Nuts.
• 26:04
  We might catch Huw then as well because, um,
• 26:09
  not here today. Didn't even call in sick. I
• 26:11
  need a note. And from me, Andrew Dunkley.
• 26:14
  Thanks very much for your company. We'll see
• 26:16
  you again soon on the next episode of Space
• 26:18
  Nuts. Bye. Bye.
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