Latest / Space Nuts: Astronomy Insights & Cosmic Discoveries / Alien Signals, Bone Density & Cosmic Disks: #496 - The Great Space Q&A Returns

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Alien Signals, Bone Density & Cosmic Disks: #496 - The Great Space Q&A Returns · Space Nuts: Astronomy Insights & Cosmic Discoveries

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  Speaker 1: Hi there, Andrew Dunkley here, Thanks for joining us on
• 0:03
  Speaker 1: a Q and A edition of Space Nuts, and coming up,
• 0:07
  Speaker 1: we're going to answer a question from Ron. He wants
• 0:10
  Speaker 1: to know if we could see a planet that sustains life,
• 0:12
  Speaker 1: would we know it? And vice versa. If there was
• 0:15
  Speaker 1: an alien race out there and they spotted Earth, would
• 0:18
  Speaker 1: they know we are here? Good question. Dean is a
• 0:22
  Speaker 1: bit confused about spheres versus discs. Why does it happen?
• 0:27
  Speaker 1: Why aren't they all spheres or all discs? And has
• 0:31
  Speaker 1: a brilliant question love this one about bone density in
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  Speaker 1: space and some of the problems that are associated with
• 0:38
  Speaker 1: being in zero gravity for long periods of time, and
• 0:41
  Speaker 1: Dean two, it's not the same. Dean is asking us
• 0:44
  Speaker 1: about centrifugal force. We'll cover all that in this episode
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  Speaker 1: of Space.
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  Speaker 2: Nuts fifteen, Channel ten nine.
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  Speaker 3: Ignition Space Nuts Guy or three spaces hasn't actually bought it?
• 1:05
  Speaker 3: Neils Good Here he is again.
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  Speaker 1: Professor John T. Horder, Professor of estrophysics at the University
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  Speaker 1: of Southern Queensland.
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  Speaker 4: Johnty, Hello, Hey, how are you going?
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  Speaker 1: I'm all right? A question without notice?
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  Speaker 4: Yes?
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  Speaker 1: Did you ever sort of have people review at school?
• 1:24
  Speaker 1: Like John ty Horner said in the corner eating his
• 1:27
  Speaker 1: Christmas pie, down came the comet that made Johnty vomit,
• 1:32
  Speaker 1: and now he only is flies.
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  Speaker 4: Oh that's brilliant. That would have been far more pleasurable
• 1:37
  Speaker 4: than marchall skill experience. It's probably not worth getting into
• 1:40
  Speaker 4: too depressing a thing, but up until I got to
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  Speaker 4: Upper Clamento University, I had a horrendous, horrendous time at
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  Speaker 4: school because I was I grew up in a very
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  Speaker 4: working class area, lost social economic area with hugely high unemployment,
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  Speaker 4: neurly the minor strikes in the eighties, and I was
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  Speaker 4: an only child, so I'm not necessarily blessed with the
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  Speaker 4: best social aptitude particular that age. But I was smart
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  Speaker 4: enough to be very smart, but not smart enough to
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  Speaker 4: realize that there were the right way and the wrong
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  Speaker 4: way to go about that. So I had a horrible,
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  Speaker 4: horrible time for the twelve years at school. In terms
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  Speaker 4: of bully I was catastrophically bullied, but you know, it
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  Speaker 4: mainly who I am today, so I'm not going to
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  Speaker 4: complain too much about it. But yeah, it's a curse
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  Speaker 4: of having aspiration and the curse of being smart in
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  Speaker 4: an area where that wasn't a common thing. You know,
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  Speaker 4: a lot of empathy for the kids who went to
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  Speaker 4: school with because you're talking about an area where many
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  Speaker 4: of them didn't have any family members who were employed
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  Speaker 4: because of what was going on. There was a huge
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  Speaker 4: epidemic of men taking their own lives because of all
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  Speaker 4: the things that were going on. So it was a
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  Speaker 4: pretty rough time, a pretty rough place. But such as
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  Speaker 4: life unfortunately, you know.
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  Speaker 1: Yeah, yeah, I certainly had my share of bullying at school,
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  Speaker 1: and yeah, not often, wasn't an every day thing. It was,
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  Speaker 1: I suppose, looking back, reasonably rare. But it never sits well,
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  Speaker 1: it's it's a horrible thing.
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  Speaker 4: At least, he says. Nowadays, there is more being done
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  Speaker 4: to counter and more al wavers of it, because you know,
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  Speaker 4: the impression back when I was at school was he
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  Speaker 4: just needed to manna, which is an awful phrase, and
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  Speaker 4: everybody has to deal with it. It's a formative experience,
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  Speaker 4: and he just couldn't tell us. As long as you
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  Speaker 4: weren't getting naive to something it were, they weren't interested.
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  Speaker 1: I used to talk to my boys about it and
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  Speaker 1: ask them how they were going, and they always said, no,
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  Speaker 1: we never had any trouble, but then teachers would tell
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  Speaker 1: me otherwise, so they're obviously not keen to talk about it.
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  Speaker 1: But my middle son, who was always very tall through school,
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  Speaker 1: he was he tired above all the other kids. I
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  Speaker 1: think he was the second tallest kid in his year
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  Speaker 1: and in the school in general. And I said to
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  Speaker 1: him one day that you get bullied, and he went no,
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  Speaker 1: because he was big. He was a big kid, and
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  Speaker 1: no one, no one went near him. His height was
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  Speaker 1: actually a good defense mechanism. It's funny how it works out.
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  Speaker 1: But there's a lot about anthropology, I suppose when.
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  Speaker 4: You're talking about it. It's all interesting about the edges
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  Speaker 4: in which kids develop awareness of self and the edges
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  Speaker 4: at which they develop empathy and kindness and all those
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  Speaker 4: kind of things in a specific center rather than the
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  Speaker 4: general sense. It's really interesting.
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  Speaker 1: Yeah, it is, all right. Let's deal with some questions,
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  Speaker 1: and our first question comes from Ron. He said, if
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  Speaker 1: scientists in a distant solar system were searching for exoplanets
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  Speaker 1: using the same technology that we're using, and if they
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  Speaker 1: were to observe our planet, would they be able to
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  Speaker 1: tell with any degree of certainty that there was life
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  Speaker 1: here or Conversely, if we were to observe an exoplanet
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  Speaker 1: that's exactly like Earth, teeming with carbon based life and
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  Speaker 1: perhaps with an advanced civilization modifying their atmosphere, which we
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  Speaker 1: talked about in the last could we tell that there's
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  Speaker 1: life there? Thanks? Ron, great question, Ron, We've had questions
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  Speaker 1: like it before, but I just love this topic, so yeah,
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  Speaker 1: we'll do it again. And Johnty hasn't had to answer
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  Speaker 1: this one before, so I thought it'd be interesting to
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  Speaker 1: get his take on it.
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  Speaker 4: Well, it's a fabulous question, and I mean, the sad
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  Speaker 4: answer is we're not quite there yet. So if we
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  Speaker 4: were looking at the Solar System from around another star,
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  Speaker 4: depending on which method we use, we'd be able to
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  Speaker 4: find Jupterum, probably Saturn, but we'd have to observe for
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  Speaker 4: a very long time to measure the wobbles for them.
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  Speaker 4: So we need to observe the Sun for a decade
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  Speaker 4: or two to pick up DUP from Saturn. Everything else
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  Speaker 4: we wouldn't be able to find. Now, if we have
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  Speaker 4: something like tests the Transit eight Planet Service that'llite looking
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  Speaker 4: at our Solar system, there's a very small chance it
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  Speaker 4: might pick up the Earth, our venus but test typically
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  Speaker 4: it starts for twenty seven days. The Earth takes three
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  Speaker 4: hundred and sixty five days to around and would take
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  Speaker 4: over sixteen hours to transit, so the old of catching
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  Speaker 4: a transit a pretty much nil. So we're not there yet.
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  Speaker 4: We are getting better, and as we talked about in
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  Speaker 4: the other episode, we're getting to the point where we
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  Speaker 4: can find planets that are a bit bigger than the Earth,
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  Speaker 4: but on all bits that are comparable to the Earth.
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  Speaker 4: Around stars like the Sun. We can find planets smaller
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  Speaker 4: than the Earth around dim little red dwarf stars using
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  Speaker 4: the transit method, but that's partly because as planets are
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  Speaker 4: so close they're stars, they're going around really quickly. So
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  Speaker 4: the upshot of all that is, if we were orbiting
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  Speaker 4: another star looking back at the Solar System, I think
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  Speaker 4: we could only confidently detect one or two planets. The
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  Speaker 4: Earth would probably be the third planet that would be
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  Speaker 4: discovered as a technology got better, because it's the biggest
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  Speaker 4: of the terrestrial planets. But it would depend a little
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  Speaker 4: bit on your line of sight because the treasural planets
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  Speaker 4: are all slightly tilted to each other, So if you're
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  Speaker 4: going to find them through the transit method, the likelihood
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  Speaker 4: is only one of them will transit and the others won't.
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  Speaker 4: In the radial velossy method, you'd pick out Jupter and Saturn,
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  Speaker 4: but you'd struggle for anything else. Eventually you get there,
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  Speaker 4: but you'd need technology a bit better than ours. So
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  Speaker 4: we're not at the point of finding the planets yet,
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  Speaker 4: never mind finding the life on them. But that's like
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  Speaker 4: the next step in the journey. We've only had thirty
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  Speaker 4: years of the exoplanet ere we're only in the first
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  Speaker 4: few decades have been able to do this at all,
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  Speaker 4: and the progress we've made is ugly astonishing, and I
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  Speaker 4: think within the next decade or two will routinely start
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  Speaker 4: being able to find planets that are Earth sized on
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  Speaker 4: Earth like orbits and to start looking for evidence of
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  Speaker 4: life on them. But that is going to be the
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  Speaker 4: hardest observations we've ever to carry out in terms of
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  Speaker 4: detecting life like us, so it's a slightly different proposition.
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  Speaker 4: So finding any evidence of life is going to be challenging.
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  Speaker 4: So people often talk about biomarkers, which is this concept
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  Speaker 4: that there are certain things you could look for that
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  Speaker 4: will be indicative of life. And we've talked about the
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  Speaker 4: possible detection of phosphene and venus atmosphere before. We've talked
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  Speaker 4: about stuff like the chicken soup experiment the Viking land
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  Speaker 4: did on Mars in the nineteen seventies, where they dug
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  Speaker 4: up some soil and put some soup on it, and
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  Speaker 4: so if it gave off gases, because they can be life,
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  Speaker 4: they use of nutrients. When you're looking at planets arounder
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  Speaker 4: the stars, there is no guarantee that life on those
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  Speaker 4: planets would have followed the same evolitary pathways as life
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  Speaker 4: on Earth. So a lot of the very specific biomarkers
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  Speaker 4: people propose there best on our knowledge of life on
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  Speaker 4: Earth because it's the only planet we know does have life,
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  Speaker 4: and it's the only example of life we've got. One
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  Speaker 4: of the examples here is something called the red edge,
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  Speaker 4: which is when you look at the spectrum of light
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  Speaker 4: from a planet, if the planet has a lot of
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  Speaker 4: plants on board that are using chlorophyll, chlorophyll absorbs incredibly
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  Speaker 4: strongly in the red, so you might see a feature
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  Speaker 4: in the red that is the signature of chlorophyll, and
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  Speaker 4: that will be an indication of plant life. The problem is,
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  Speaker 4: and again I'm not a biologist, so there's probably more
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  Speaker 4: to this than I'm going to say. In my simple
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  Speaker 4: version is that chlorophyll is an incredibly efficient compound for
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  Speaker 4: allowing plants to utilize the light like the light from
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  Speaker 4: our suck. But there are many other compounds that could
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  Speaker 4: do a similar job for stars of different temperatures that
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  Speaker 4: are there for different colors, so they put out the
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  Speaker 4: bulk of their light at slightly different wavelengths, And there's
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  Speaker 4: no guarantee that life on another planet would use chlorophyll,
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  Speaker 4: especially if that star was significantly different to the Sun,
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  Speaker 4: So the specific bymarker of the red edge from chlorophyll
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  Speaker 4: wouldn't work very well. Necessarily, it wouldn't be guaranteed to work,
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  Speaker 4: especially because it's also mimicked by the spectrum of olivine,
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  Speaker 4: which is a very common mineral, has a very similar appearance.
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  Speaker 4: But looking more generally for that kind of absorption feature
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  Speaker 4: in the spectrum that you can't explain any other way
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  Speaker 4: is one of the size people have looked for. So
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  Speaker 4: it's not so much case of looking for a specific thing,
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  Speaker 4: but rather for looking for something that is out of place,
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  Speaker 4: trying to explain it, and finding that the only explanation
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  Speaker 4: left is life. You're looking for something out of balance.
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  Speaker 4: So another good example is on Earth, we have oxygen,
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  Speaker 4: we have methane. Now, there's a lot of oxygen in
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  Speaker 4: the atmosphere, but that doesn't necessarily mean life, because there
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  Speaker 4: are chemical processes that can produce oxygen without life being involved.
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  Speaker 4: Similarly with a lot of methane in the atmosphere. And
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  Speaker 4: methane is a natural product of animal life. I my
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  Speaker 4: dog line next to me has been quite happily producing
• 10:21
  Speaker 4: methae through the podcast because we've fed at some broccoli
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  Speaker 4: I think in a puppy food last night. So methane
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  Speaker 4: is produced by life, but there are also lots of
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  Speaker 4: natural ways it can produce. And you know, there's huge
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  Speaker 4: amounts of methane in the atmospheres of Urinus and Neptune,
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  Speaker 4: for example. So finding oxygen or finding methane doesn't necessarily
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  Speaker 4: mean life. There's a lot of other explanations, but the
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  Speaker 4: oddity with Earth is that we've got oxygen and methen together. Now,
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  Speaker 4: when you put oxygen and methne together, they react with
• 10:49
  Speaker 4: each other a lot, and they react until all of
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  Speaker 4: one of them is gone. So the methane in this
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  Speaker 4: atmosphere has a really short residence time of only a
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  Speaker 4: century or a few centuries I think four hundred year
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  Speaker 4: before it's all gone. So you look at the Earth
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  Speaker 4: and it's got oxygen and methen together, which means something
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  Speaker 4: has to be producing new methane to replace the methen
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  Speaker 4: that's lost. Now, even that doesn't mean it's life, because
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  Speaker 4: volcanoes perished me fed. So what you then have to
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  Speaker 4: do is say, well, this is interesting. It could be life,
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  Speaker 4: it could be something else. Let's measure the methane over time,
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  Speaker 4: and if it's volcanoes, you'll get the methane falling off
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  Speaker 4: and a random time of volcano ups and there's a
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  Speaker 4: spike of methane and then it falls off again, and
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  Speaker 4: a random time later you get another spike. But when
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  Speaker 4: you look at methane in the Earth's atmosphere, it varies
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  Speaker 4: with the seasons. Volcanoes don't do that, so therefore that's
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  Speaker 4: an indication of life. So it's looking for that oddity
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  Speaker 4: that's out of place. There are a couple of things
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  Speaker 4: that would give away arguably technologically developed life, which doesn't
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  Speaker 4: necessarily mean intelligent life, as we're seeing in the political sphere,
• 11:50
  Speaker 4: at the minute, but technologically developed life. One of them
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  Speaker 4: is chlorophylor of carbons, So the things that we were
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  Speaker 4: putting up into the atmosphere that devastated the layer. Yeah,
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  Speaker 4: we only know of those being produced by technology if
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  Speaker 4: there is no natural process that seems to produce them.
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  Speaker 4: Another is radio broadcasts. So any intelligent aliens within about
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  Speaker 4: eighty light years of us ninety light years of us
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  Speaker 4: now would see our broadcast. Now. The exact date of
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  Speaker 4: the first broadcast that we sent out that was strong
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  Speaker 4: enough to be detected from around the stars depends w
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  Speaker 4: you talked. It could have been the Berlin Olympics in
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  Speaker 4: nineteen thirty six, I think, or the coronation of Queen
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  Speaker 4: Elizabeth in nineteen fifty two. I think with it it was,
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  Speaker 4: and they usually held has been the first big broadcast
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  Speaker 4: that would have been detectable on an interstellar distance. What
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  Speaker 4: that means is that within a certain distance of the
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  Speaker 4: Earth there is a sphere where if there are intelligent
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  Speaker 4: aliens with radio telescopes, they could be watching neighbors and
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  Speaker 4: we could well get a broadcast back at some point
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  Speaker 4: saying please stop. You know, we're a bit like toddlers
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  Speaker 4: at the minute in a room screaming into the void,
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  Speaker 4: and that sound is good further and further away from
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  Speaker 4: as a time goes on. Now that's the motivation for
• 13:04
  Speaker 4: things like the Cechrectra threasurial intelligence, which is helping fund
• 13:08
  Speaker 4: the wonderful radiotails go down to paths through the Breakthrough
• 13:10
  Speaker 4: Listen project. The challenge there is that we are already
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  Speaker 4: starting to become more quiet, well like the baby becoming
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  Speaker 4: a totaler and moderating itself. And the reason for that
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  Speaker 4: is costs. If you were broadcasting in all directions all
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  Speaker 4: the time, you've got to put a lot of energy
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  Speaker 4: in and most of that energy is wasted, so only
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  Speaker 4: a twin a little bit of that is going to
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  Speaker 4: get to your receivers. It's much more efficient to send
• 13:33
  Speaker 4: your data, like we're talking at the minute, through the
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  Speaker 4: end the end, through wires or through point to point stuff.
• 13:40
  Speaker 4: So the silent satellites are a bit like this. They're
• 13:42
  Speaker 4: broadcasting down Therefore venal little is going back out into space,
• 13:47
  Speaker 4: and anything connecting to them points at the satellite and
• 13:50
  Speaker 4: beams directly to it. So it's much more energy efficient.
• 13:53
  Speaker 4: And there are some arguments that the Earth could well
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  Speaker 4: be radio silent again from the point of view of
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  Speaker 4: aliens listening in within just a few decades, so there'd
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  Speaker 4: only be a short window. And then you've got this
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  Speaker 4: shell of broadcasts moving outwards with a void behind it,
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  Speaker 4: and unless you tune in when that shell's passing past,
• 14:08
  Speaker 4: you'd never hear us. But in that sense, if we
• 14:12
  Speaker 4: were looking at the Solar System with our biggish radio telescopes,
• 14:16
  Speaker 4: we'd probably just about be able to pick up the
• 14:18
  Speaker 4: unusual radio activity if we were at the right radio
• 14:22
  Speaker 4: we were at the right distance, but it would still
• 14:25
  Speaker 4: be challenging for us. I think we do have the
• 14:26
  Speaker 4: capacity for that, but it would be hard. So in
• 14:30
  Speaker 4: that sense, if there were aliens around, I don't know.
• 14:34
  Speaker 4: Approxima centaury B, another of the many many planets that
• 14:37
  Speaker 4: has been argued has been the most earth like ever discovered,
• 14:40
  Speaker 4: and made me hungry. If there was a planet there,
• 14:43
  Speaker 4: if there were aliens on it, and there were broadcasting
• 14:45
  Speaker 4: alien neighbors, we'd be able to tune it.
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  Speaker 1: Wouldn't that be interesting? The answer to Ron's question is no,
• 14:53
  Speaker 1: not yet. We're just not quite there. The time may
• 14:57
  Speaker 1: well come, but again it's nearly in a hast.
• 14:59
  Speaker 4: Exter, isn't it you? Absolutely? I said, you don't know
• 15:03
  Speaker 4: what a needlest and you've never seen a half start befire?
• 15:05
  Speaker 1: Yeah, exactly, Yes, thank you Ron, great question, lovely to
• 15:10
  Speaker 1: hear from you. Okay, we take Space Nuts and our
• 15:18
  Speaker 1: next question comes from Dean high Space Nuts.
• 15:23
  Speaker 4: I'm Dean from Washington, d C. In the United States.
• 15:26
  Speaker 3: I originally started listening to the show and okay, anyways,
• 15:30
  Speaker 3: I was wondering why under gravity do some things form
• 15:33
  Speaker 3: as discs and others as spheres. You know, we're stars
• 15:37
  Speaker 3: and planets are spheres, but some galaxies in our soul
• 15:40
  Speaker 3: systems a disc. But then also planet can have discs
• 15:44
  Speaker 3: around them. All very anyways, thanks, keep up your.
• 15:48
  Speaker 1: Very thank you Dean. I never would have even thought
• 15:51
  Speaker 1: of that question, and it's a great question. But yeah,
• 15:54
  Speaker 1: he's right. You've got spheres and you've got discs, you've
• 15:58
  Speaker 1: got mixtures of spheres and discs, You've got all sorts
• 16:01
  Speaker 1: of combinations.
• 16:03
  Speaker 4: Why is it so it's all down to different physical
• 16:08
  Speaker 4: presses going on? So it's fabulous question. And we run
• 16:10
  Speaker 4: across this when we're teaching astro, when we're studying it
• 16:14
  Speaker 4: quite a lot, and there are things that happen in
• 16:18
  Speaker 4: slightly different situations. So if you've got material falling inwards
• 16:22
  Speaker 4: under gravity, it will keep falling inwards until either it's
• 16:27
  Speaker 4: moving around on an orbit it swings back out. But
• 16:29
  Speaker 4: let's assume it's falling into an object that is going
• 16:31
  Speaker 4: to become a solid or gasious subject that therefore has
• 16:35
  Speaker 4: some way of stopping that material, so it slows down
• 16:37
  Speaker 4: and becomes part of that object. You then have a
• 16:41
  Speaker 4: balance between gravity trying to pull you inwards and the
• 16:44
  Speaker 4: physical strength of the material pushing outwards. If you've got
• 16:47
  Speaker 4: a solid object, if you've got a gasio subject, the
• 16:51
  Speaker 4: gas can keep going in, but then you build up
• 16:53
  Speaker 4: pressure of the pressure holds things up. You might have
• 16:56
  Speaker 4: energy being released that also holds it up, so that
• 17:00
  Speaker 4: then pushes outwards in all directions. I'll talk about solid
• 17:04
  Speaker 4: objects first. This ties into a little bit towards the
• 17:08
  Speaker 4: definition of a planet. There is a concept called hydrostatic equilibrium,
• 17:13
  Speaker 4: which is basically the shape that something that has no
• 17:18
  Speaker 4: strength will finish up in. Once everything's moved around, you
• 17:22
  Speaker 4: say that it's in hydrostatic equilibrium. It's the lowest kind
• 17:25
  Speaker 4: of energy state. So if you got outside the Earth's atmosphere,
• 17:31
  Speaker 4: or rather you go away from the gravity of the Earth,
• 17:33
  Speaker 4: putting things down, and you can have droplets suspended. A
• 17:37
  Speaker 4: drop of water that is not moving at all will bispherical.
• 17:39
  Speaker 4: It's held in by surface tension in that case holds
• 17:43
  Speaker 4: it together, but it will be a sphere. If you
• 17:45
  Speaker 4: rotate it, it will gradually become more elongated than a blade,
• 17:49
  Speaker 4: and it become what we call an ablate spheroid, which
• 17:52
  Speaker 4: is what the Earth is. The Earth is wider at
• 17:53
  Speaker 4: the equator than the poles because of the rotation, and
• 17:56
  Speaker 4: the rotation is essentially applying a slight out force. That
• 18:01
  Speaker 4: means the net force pulling in is weaker at the
• 18:03
  Speaker 4: equator of the poles, and so you stretch out of it.
• 18:06
  Speaker 4: That's kind of how I visualize it. Yep. If you
• 18:10
  Speaker 4: are smaller than a certain size, your material strength is
• 18:14
  Speaker 4: strong enough to prevent things moving around and flowing, so
• 18:18
  Speaker 4: you don't become spherical. You don't get that hydrostatic equilibrium.
• 18:22
  Speaker 4: So if you look at the moons of the planets,
• 18:25
  Speaker 4: the smallest one that I think is in hydrostatic equilibrium
• 18:29
  Speaker 4: is possibly mimas at Saturn, about four hundred kilmeters across.
• 18:33
  Speaker 4: It might be one of the other Saturnian modes, but
• 18:34
  Speaker 4: I think it's Mimus because that's about the size where
• 18:37
  Speaker 4: you've got enough mass that the gravitational pull is strong
• 18:41
  Speaker 4: enough that that can overcome the physical strength of the
• 18:43
  Speaker 4: material where the object's forming have cause it to then
• 18:47
  Speaker 4: move and flow, and you end up then getting nearly
• 18:50
  Speaker 4: a sphere because that's the lowest energy solution. That's your
• 18:53
  Speaker 4: hydrostatic equilibrium. If you had it being wider than that,
• 18:59
  Speaker 4: more like a look like an ice hockey puck maybe,
• 19:02
  Speaker 4: but the material can flow. You've got more mass pushing
• 19:05
  Speaker 4: down in the horizontal plane, so things try and squeeze
• 19:08
  Speaker 4: in here and they'll be pushed out that way until
• 19:10
  Speaker 4: it bounces out, so you'd end up flowing until you've
• 19:12
  Speaker 4: got that kind of spherical shape. Yeah, your ice hockey puck,
• 19:16
  Speaker 4: though small enough that its material shredth winds, so it
• 19:18
  Speaker 4: stays at elongated shape. So that's kind of the lower
• 19:22
  Speaker 4: end of when people start talking about the definition of
• 19:25
  Speaker 4: a planet is it has to be in hydrostaphic equilibrium.
• 19:28
  Speaker 4: Doesn't mean it's spherical, it just means it's in that
• 19:30
  Speaker 4: lowest energy thing. So if it's rotating quickly. It can
• 19:33
  Speaker 4: be a kind of oblate spheroid. You get a similar
• 19:36
  Speaker 4: thing with stars. So you've got all this gas collapsing
• 19:38
  Speaker 4: in friction, stopping it just opening and escaping again. So
• 19:42
  Speaker 4: you've got an object. That object has gravity pulling inwards
• 19:46
  Speaker 4: and it's got a restoring force pushing outwards. In the
• 19:48
  Speaker 4: case of a cell like the Sun, that's the radiation
• 19:50
  Speaker 4: pressure from all the nuclear fusion going on.
• 19:52
  Speaker 1: In its cot.
• 19:54
  Speaker 4: Now the Sun's rotating, albeit once every thirty odd days,
• 19:57
  Speaker 4: but it is in something that is close to that
• 20:00
  Speaker 4: hydrostaphic equilibrium. So if you put a load of mass
• 20:03
  Speaker 4: on the Sun's equator, that would squish in and the
• 20:05
  Speaker 4: poles would push out until you got back to that
• 20:07
  Speaker 4: kind of shape. So that's a physical kind of object.
• 20:12
  Speaker 4: That's why you get them going to be spheres or
• 20:16
  Speaker 4: nearly spheres. It's that concept of hygrostatic equilibrium, and it's
• 20:19
  Speaker 4: due to the balance of the force pulling in woods
• 20:21
  Speaker 4: and the force pushing outwards, radiation pressure of stars, material strength,
• 20:25
  Speaker 4: material physics going on. For solid objects, with disks, you
• 20:30
  Speaker 4: don't have the same things going on. So what you've
• 20:33
  Speaker 4: got is you've got a rotating cloud of gas and
• 20:35
  Speaker 4: dust that isn't really strong enough told itself up, but
• 20:39
  Speaker 4: it's rotating quickly under gravity. Now you've got the conservation
• 20:43
  Speaker 4: of angular momentum going on, so things near the middle
• 20:46
  Speaker 4: go quicker than things near the outside, and there is
• 20:49
  Speaker 4: a tendency for things to clapse down in a disc
• 20:52
  Speaker 4: above the plane of the equator of the thing they're
• 20:54
  Speaker 4: orbening around. That is due to the conservation of that
• 20:57
  Speaker 4: angular momentum, but it's also due to the motion things through.
• 21:00
  Speaker 4: You've got all sorts of things coming in. The analogy
• 21:03
  Speaker 4: often is when I'm giving public talks. Here involves fittis
• 21:07
  Speaker 4: that is different, so it's not a perfect analogy, but
• 21:09
  Speaker 4: it gives you a kind of idea what's going on
• 21:10
  Speaker 4: with spinning material, And it's if you've ever seen somebody
• 21:13
  Speaker 4: who's a show off making pizza bases. They get a
• 21:17
  Speaker 4: ball of very elastic dough and then they spin it
• 21:19
  Speaker 4: around very quickly and whirl it over their head, and
• 21:21
  Speaker 4: it flattens out into a big pancake as a result
• 21:24
  Speaker 4: of the conservation of the annual momentum there, it flattens
• 21:26
  Speaker 4: out into the pizza bair shape. And if I tried
• 21:29
  Speaker 4: it it'd either stick to the ceiling or hit me
• 21:30
  Speaker 4: on the head. It wouldn't go very well. It's a
• 21:34
  Speaker 4: slightly similar thing with the distant material around planets and stars.
• 21:38
  Speaker 4: Now what's happening is you've got material collapsing into the
• 21:42
  Speaker 4: star under gravity, forming the disc around it because there
• 21:45
  Speaker 4: is a bit of rotation with that rotation. As you
• 21:48
  Speaker 4: spin in and you get to a smaller and smaller distance,
• 21:50
  Speaker 4: you move faster and faster and faster. And that's why
• 21:53
  Speaker 4: a gas cloud rotating every few million years gives you
• 21:56
  Speaker 4: star rotating every few days or every few hours. It's
• 21:59
  Speaker 4: like the ballerina bringing their arms in as they do
• 22:01
  Speaker 4: a spin. There spin quicker and quicker. But that also
• 22:04
  Speaker 4: tends to lead to things collapsing into the plane because
• 22:07
  Speaker 4: that's a bit again like the hydro staff keeper whatever
• 22:09
  Speaker 4: in example, that's kind of the lowest energy solution. You're
• 22:12
  Speaker 4: rotating around the given rotation axis, you will collapse into
• 22:16
  Speaker 4: a disc in that plane. Material that's coming in above
• 22:19
  Speaker 4: that disc can just carry on orbiting normally, but if
• 22:23
  Speaker 4: there's more material in the disc, there will be friction
• 22:25
  Speaker 4: and it will get damped down and help to collapse
• 22:27
  Speaker 4: down into there. But if the bulk is rotating with
• 22:34
  Speaker 4: the same rotation access, anything falling in at high handles
• 22:37
  Speaker 4: will probably just fall in and blockstraight onto the stars.
• 22:40
  Speaker 4: It's rotating that way, but it's coming in here essentially. Yeah,
• 22:44
  Speaker 4: I appreciate that description was really useful for the people
• 22:46
  Speaker 4: who were only listening because I can't see me waving.
• 22:48
  Speaker 4: My flappy hands are out. But if you're coming in
• 22:51
  Speaker 4: from near the poles, the little bit of rotation around
• 22:54
  Speaker 4: isn't helping again, so you coming in directly towards the target.
• 22:57
  Speaker 4: If you're coming in from the poles and you're going
• 22:59
  Speaker 4: to hit onto the day, you'll be passing through all
• 23:01
  Speaker 4: that material and that will damp you down a little bit,
• 23:04
  Speaker 4: so more inclined things will gradually get damp down. To
• 23:07
  Speaker 4: add to the disc the discs we get there for
• 23:10
  Speaker 4: around protest stars, a material that's falling in the rotation
• 23:13
  Speaker 4: spinning it up. You get a disc around that protest
• 23:16
  Speaker 4: star that this will be a bit fled, It will
• 23:19
  Speaker 4: have a bit of height mixes, a lot of dynamics
• 23:21
  Speaker 4: and stirring and things like that going on. If you
• 23:24
  Speaker 4: could have a big enough region around it, you probably
• 23:27
  Speaker 4: end up seeing a disc would eventually flare out and
• 23:30
  Speaker 4: clickly comes a background, but you'd have almost cleared lobes
• 23:32
  Speaker 4: above and below the star, and that's kind of what
• 23:35
  Speaker 4: we see with our small body population in the Solar System.
• 23:37
  Speaker 4: As you go from the planets and the edge of Kooperbalt,
• 23:41
  Speaker 4: going further outwards, you gradually come out towards the domain
• 23:45
  Speaker 4: of the art cloud, and when you're far enough from
• 23:46
  Speaker 4: the Sun, things get stirred up by passing stars and
• 23:49
  Speaker 4: get put back into a sphere because their tilts are
• 23:51
  Speaker 4: all random housed. So you've got a disc near the Sun,
• 23:54
  Speaker 4: and that's because the Sun's gravity is dominating the angual
• 23:57
  Speaker 4: momentum dominating. When you're very far from the Sun, you're
• 24:01
  Speaker 4: only loosely hell to the Sun, so nudge of from
• 24:03
  Speaker 4: passing stars can change your direction quite significantly. And over
• 24:07
  Speaker 4: the four billion years since the cell system formed, that
• 24:10
  Speaker 4: material that was flung out into the out cloud in
• 24:12
  Speaker 4: a disc because it was flung out from a disc,
• 24:14
  Speaker 4: has been smeared around, so we now get as very
• 24:17
  Speaker 4: coliche cloud around the Sun. But when you're close enough
• 24:20
  Speaker 4: to the Sun for the Sun to dominate, you'd have
• 24:22
  Speaker 4: voids that are fairly empty above and below the plane
• 24:25
  Speaker 4: and a disc blowed out. So it's all complex and
• 24:29
  Speaker 4: it's a couple of different bits of physics interacting essentially.
• 24:32
  Speaker 1: Yeah, well, now I'd never wondered about it, and I'm
• 24:36
  Speaker 1: glad Dane asked the question because it really is interesting science.
• 24:43
  Speaker 1: Hydrostatic equal equally librial lime.
• 24:49
  Speaker 4: It's the really good example of how sice works and
• 24:51
  Speaker 4: how we do it actually, because that's exactly the scientific process.
• 24:54
  Speaker 4: You see something, you go why is that? And Saturn's
• 24:56
  Speaker 4: a great example. You look at sat and then it's
• 24:58
  Speaker 4: a oblet's fair bit of an elongated blobby thing, but
• 25:01
  Speaker 4: it's nearly spherical, rarely first order, and yet it's got
• 25:05
  Speaker 4: a disc of material around it. Why is it? The
• 25:06
  Speaker 4: discal's all block, you know. And so that's what leads
• 25:09
  Speaker 4: us down that journey discovery to figure all this stuff out.
• 25:12
  Speaker 4: So that's just how science works. And it's very fun,
• 25:16
  Speaker 4: brilliant question.
• 25:16
  Speaker 1: Thank you, Dane, lovely to hear from you. This is
• 25:20
  Speaker 1: Space Nuts with Andrew Duckley and Johnty Horner.
• 25:28
  Speaker 4: Space Nuts.
• 25:30
  Speaker 1: Our next question, I really love. This one comes from
• 25:34
  Speaker 1: an in Bellevue, Washington. I have a question about calcium
• 25:38
  Speaker 1: and astronauts on Earth. Estrogen helps prevent calcium loss from bones.
• 25:43
  Speaker 1: Do pre menopausal astronauts lose less bone or regain bone
• 25:51
  Speaker 1: faster than mail or postmenopausal astronauts. Does hormone replacement therapy
• 25:59
  Speaker 1: help minopausal astronauts regain bone. It's a really great question,
• 26:05
  Speaker 1: and says thanks for the interesting podcast. Appreciate that, and
• 26:09
  Speaker 1: thanks for the interesting question. I know this isn't your area,
• 26:13
  Speaker 1: but I know you've done your homework.
• 26:16
  Speaker 4: Yeah, I don't a little bit reading. It's a fascinating question,
• 26:18
  Speaker 4: and it's a really important question to ask because there's
• 26:20
  Speaker 4: a lot of investigations into the impact of being in
• 26:24
  Speaker 4: space that are going on, particularly given that there's a
• 26:27
  Speaker 4: future where people aspire to travel to Mars and live there,
• 26:31
  Speaker 4: or have you know, space sessions where people with full
• 26:34
  Speaker 4: time go colonize the asteroids, things like that. It's not
• 26:38
  Speaker 4: my area of expertise by any means. I'm not a
• 26:40
  Speaker 4: biologist or a biomechanists, but it is something people are
• 26:45
  Speaker 4: starting to do research into. I haven't been able to
• 26:49
  Speaker 4: find anything about the difference between pre and post menopause,
• 26:52
  Speaker 4: or about estrogen supplements and things like that. That's a
• 26:56
  Speaker 4: really interesting question, and it's almost possibly the kind of
• 26:59
  Speaker 4: thing where you could find someone leading that kind of
• 27:02
  Speaker 4: research and try and get involved if you want to.
• 27:04
  Speaker 4: But I did do a bit of digging around. I
• 27:05
  Speaker 4: found there is a paper that was published. I found
• 27:09
  Speaker 4: it on pub meed that was published a few years
• 27:12
  Speaker 4: ago in twenty fourteen and titled Men and Women in
• 27:15
  Speaker 4: Space Bone Loss and Kidney stone Risk after among the
• 27:19
  Speaker 4: Oration space Flight, which is a slightly intimidating title, but
• 27:24
  Speaker 4: they not there that. Finally, at that stage there had
• 27:28
  Speaker 4: been enough people who identified as male and identified as
• 27:32
  Speaker 4: female that had spent a long time in space that
• 27:35
  Speaker 4: you could start doing a quantitative comparison. They had in
• 27:38
  Speaker 4: their sample thirty three men and nine women who had
• 27:41
  Speaker 4: spent long the Oursan missions on the space station, and
• 27:45
  Speaker 4: their bodies had been studied when they got back. Essentially,
• 27:49
  Speaker 4: so I think that bone mineral density was evaluated before
• 27:53
  Speaker 4: and after the flight and stuff like that, and they
• 27:55
  Speaker 4: also looked at blood and urine to look at kidney function.
• 27:58
  Speaker 4: The missions were fifty days to two hundred and fifteen
• 28:01
  Speaker 4: days flown in this millennium, so twenty twenty twelve, what
• 28:06
  Speaker 4: they found was the following alreadly out explicitly. They said
• 28:09
  Speaker 4: the bondance to response to spaceflight was the same for
• 28:12
  Speaker 4: men and women in both exercise groups, so no difference
• 28:16
  Speaker 4: bond dens to response to flight was the same for
• 28:18
  Speaker 4: men and women, and the typical decrease in bone mineral density,
• 28:23
  Speaker 4: whole body and regional after flight was not observed for
• 28:26
  Speaker 4: either sex for people who were using the advanced resistance devices,
• 28:29
  Speaker 4: so they were able to recover equally well. So the
• 28:33
  Speaker 4: fundamental comment there have as a final sentence of their
• 28:35
  Speaker 4: abstract is the responses of men and women to spaceflight
• 28:39
  Speaker 4: with respect to measures of bone health were not different,
• 28:43
  Speaker 4: which is really interesting. It doesn't entirely talk about the
• 28:48
  Speaker 4: importance of the hormones, but I guess the fact that
• 28:52
  Speaker 4: women who were pre menopause and men experienced their bond
• 28:57
  Speaker 4: density degradation at the same rate suggests that the elevated
• 29:01
  Speaker 4: levels of estrogen in the women did not prevent that
• 29:04
  Speaker 4: bondensity loss. Doesn't say anything about the speed at which
• 29:07
  Speaker 4: the bond icity was recovered when they were back, so
• 29:10
  Speaker 4: I can't really comment on that, but it reminded me
• 29:14
  Speaker 4: more widely of a the risks of space flat but
• 29:17
  Speaker 4: also the amount that we don't know, and the importance
• 29:19
  Speaker 4: of getting people with different expertises involved, but also the
• 29:23
  Speaker 4: importance of doctors and medical researchers studying women as well
• 29:29
  Speaker 4: as men. And I know from a number of my
• 29:30
  Speaker 4: female friends that they feel very much that a lot
• 29:33
  Speaker 4: of medications, a lot of treatments assume that the male
• 29:37
  Speaker 4: body is the normal one, and studies have not been
• 29:39
  Speaker 4: carried out to such a great extent on the different
• 29:42
  Speaker 4: impact of that same medication on the female body. True,
• 29:46
  Speaker 4: and I've also heard of problems where male doctors have
• 29:48
  Speaker 4: not been as well educated in female problems as they
• 29:51
  Speaker 4: should have been in giving fairly rubbish responses. So, you know,
• 29:54
  Speaker 4: acknowledging those biases and acknowledging that I'm in a very
• 29:57
  Speaker 4: privileged situation, but we need more research into this. NASA
• 30:01
  Speaker 4: has on its website a segment here talking about the
• 30:04
  Speaker 4: degree of impact on bond density. So their segment is
• 30:08
  Speaker 4: astronauts can lose up to one to two percent of
• 30:10
  Speaker 4: bond density per month in the hip and the spine.
• 30:15
  Speaker 4: That compares to zero point five to one percent per
• 30:18
  Speaker 4: year in postmenopausal women and much older men on Earth. So,
• 30:22
  Speaker 4: in other words, the bone loss that you're getting while
• 30:24
  Speaker 4: you're in microgravity and space is around twice as significant
• 30:29
  Speaker 4: as that that you experienced post menopause for women or
• 30:32
  Speaker 4: when you become significantly older for men, and that they
• 30:36
  Speaker 4: say this rappid bond loss can place crew members at
• 30:38
  Speaker 4: risk for both fracturing and risk of elions osioporosis as
• 30:41
  Speaker 4: a result of the space flag. There's another study which
• 30:44
  Speaker 4: I just stumbled across, looking on this female astronauts impact
• 30:48
  Speaker 4: of space radiation on menopause. This came out a bit
• 30:51
  Speaker 4: more recently in Atal twenty twenty two, and it shows
• 30:54
  Speaker 4: people are starting to think about this. So this is
• 30:57
  Speaker 4: a study that is looking at the impacts of the
• 31:00
  Speaker 4: radiation environment that you experience in space on what they
• 31:03
  Speaker 4: call the avarian reserve, so the number of viable eggs
• 31:06
  Speaker 4: that a woman has. And so the statement that really
• 31:09
  Speaker 4: made my head hurt here is that data suggests that
• 31:12
  Speaker 4: a typical Mars mission may reduce a woman's avarian reserve
• 31:15
  Speaker 4: by about fifty percent. This would have consequences to a
• 31:19
  Speaker 4: woman's reproductive capacity and most significantly decreases a time metaval
• 31:23
  Speaker 4: to her menopaus. So it all reminds me it's slightly
• 31:28
  Speaker 4: off topic, but This was prompted by this question. I
• 31:31
  Speaker 4: every year go to the Australian Space Research Conference in Australia,
• 31:34
  Speaker 4: which is a fabulous meeting and can be quite multidisciplinary.
• 31:38
  Speaker 4: But a few years ago, I think possibly about twenty thirteen,
• 31:40
  Speaker 4: twenty fourteen now, we had a invited lecture from a
• 31:46
  Speaker 4: doctor who said doctor from Tasmania who works in space
• 31:49
  Speaker 4: mediciner's researcher on the site. And it's the only lecture
• 31:52
  Speaker 4: I've ever been to at a research conference which started
• 31:55
  Speaker 4: with a trigger warning and a health warning, and that
• 31:58
  Speaker 4: was basically, if there's anybody in the audience who's a
• 32:00
  Speaker 4: bit squeamish, a bit sensitive, he might want to leave.
• 32:02
  Speaker 4: Now this is going to be a medical talk and
• 32:05
  Speaker 4: you're all astronomers and spati researchers. And it included some
• 32:09
  Speaker 4: fairly unsettling pictures that I won't relay in too much detail.
• 32:14
  Speaker 4: But this doctor was talking about the future aspiration of
• 32:19
  Speaker 4: humanity to have a permanent presence on other astronomical bodies,
• 32:23
  Speaker 4: talking particularly about Mars, and what he was speaking to
• 32:28
  Speaker 4: was that our science fiction view of that is that
• 32:31
  Speaker 4: you have a population on Mars that is independent, so
• 32:34
  Speaker 4: they reproduce and repopulate themselves. That's what we think of,
• 32:39
  Speaker 4: and he said it isn't as simple as that from
• 32:42
  Speaker 4: a doctor's point of view, from someone who studied pregnancy,
• 32:44
  Speaker 4: he was talking about the requirement the importance of gravity
• 32:50
  Speaker 4: to pregnancy is something we never think about because we're
• 32:53
  Speaker 4: all living on the surface of the Earth at one G.
• 32:55
  Speaker 4: But he said it's actually the case, and remember and
• 32:59
  Speaker 4: remembering to ok from more than a decade ago, he
• 33:02
  Speaker 4: spoke about how important the gravity that you are moving
• 33:06
  Speaker 4: within is to the development of the fetus and the
• 33:10
  Speaker 4: way that the cells know what to make and what
• 33:12
  Speaker 4: shape to make. And he gave the example of how
• 33:15
  Speaker 4: even a very small change from the standard atmospheric temperature
• 33:19
  Speaker 4: and pressure and gravity can cause huge problems by talking
• 33:24
  Speaker 4: about the invasion of the Spanish into South America back
• 33:27
  Speaker 4: in the sixteen hundreds and the fact that the high
• 33:29
  Speaker 4: Andes were never conquered permanently because the conquistados couldn't reproduce there.
• 33:35
  Speaker 4: They were just not able to be viable there, and
• 33:39
  Speaker 4: the native people there had obviously adjusted over many, many generations.
• 33:42
  Speaker 4: And he said, that's barely any different to the conditions here.
• 33:46
  Speaker 4: What he was going on to say was that his
• 33:49
  Speaker 4: vision is that because of this, this would be so
• 33:52
  Speaker 4: insurmountable that for a very long time, once we have
• 33:55
  Speaker 4: a permanent presence on Mars, it would be a retirement
• 33:57
  Speaker 4: hard It'd be somewhere that people go to after they've
• 34:00
  Speaker 4: sawed their wild arts on Earth, that they go to
• 34:03
  Speaker 4: to spend their later years in a more pleasant environment
• 34:07
  Speaker 4: with lower gravity, less strains on an aging, aching body.
• 34:12
  Speaker 4: But he didn't see any possibility of people reproducing there
• 34:16
  Speaker 4: and unless we went down the incredibly dystopian worldview of
• 34:20
  Speaker 4: having women living in centrifugures for nine months to simulate
• 34:24
  Speaker 4: one g which I can imagine would not be a
• 34:27
  Speaker 4: very popular deficion, But it ties into Mars one, which
• 34:32
  Speaker 4: was this attempt by I think a Dutch guy to
• 34:37
  Speaker 4: make a lot of money out of sending a mission
• 34:39
  Speaker 4: to Mars to try and get the first humans on Mars.
• 34:43
  Speaker 4: And they ran a huge competition process for this with
• 34:45
  Speaker 4: more than one hundred thousand initial applicants and they whittled
• 34:48
  Speaker 4: them down and whittled them down. But there was an
• 34:50
  Speaker 4: Australian involved in this, guy called Josh Richards, who's a
• 34:53
  Speaker 4: fabulous science communicator and did a lot of work off
• 34:56
  Speaker 4: the back of this of going at schools and talking
• 34:58
  Speaker 4: to kids and saying I could be the first person
• 35:00
  Speaker 4: on Mars ask me anything. Essentially, one of the things
• 35:03
  Speaker 4: that Josh told me that led to problems and in
• 35:06
  Speaker 4: the end led to the breakup of his relationship with
• 35:08
  Speaker 4: his partners who went through this process was that he
• 35:11
  Speaker 4: was looking at taking a one way trip to Mars,
• 35:14
  Speaker 4: but also that the people who were the final selected
• 35:18
  Speaker 4: ones had to agree to be medically stetilized before they
• 35:23
  Speaker 4: got on the trip to Mars because they were going
• 35:26
  Speaker 4: from mixed crew. The mixed crew had to make their
• 35:28
  Speaker 4: own entertainment during the travels he had because his show
• 35:32
  Speaker 4: was going to be delivered big brother style. That was
• 35:34
  Speaker 4: probably part of the motivation for people subscribing to be honest.
• 35:38
  Speaker 4: The lack of understanding of the possibilities and the risk
• 35:42
  Speaker 4: of pregnancy during spatifight in microgravity or on Mars in
• 35:46
  Speaker 4: incredibly reduced gravity was such a nobody could see any
• 35:50
  Speaker 4: possibility of any viability of pregnancy. But it wasn't like
• 35:54
  Speaker 4: they were going to send people with the medical skills
• 35:57
  Speaker 4: to deal with traumatic problems like that on the mission.
• 36:00
  Speaker 4: So you have to agree to either be subtilized, though
• 36:02
  Speaker 4: you wouldn't go only pick someone else, which sounds really barbaric,
• 36:07
  Speaker 4: but it's the unfortunate reality we're going to have to
• 36:09
  Speaker 4: deal with when we start looking at having a permanent
• 36:12
  Speaker 4: presence off Earth rather than just going and visit it.
• 36:16
  Speaker 4: Because if we want to have a permanent presence on
• 36:18
  Speaker 4: the Moon or on Mars, we view that inherently as
• 36:22
  Speaker 4: humans has been a self replicating presence. We view it
• 36:24
  Speaker 4: as been a presence that can sustain itself. You know,
• 36:27
  Speaker 4: So if the population of Earth got wiped out, at
• 36:29
  Speaker 4: least we've got the people on Mars. But in order
• 36:32
  Speaker 4: to do that, it's going to need an incredible amount
• 36:34
  Speaker 4: of medical research to be done and incredible advances in
• 36:38
  Speaker 4: medical technology that we just don't have yet. And what's
• 36:42
  Speaker 4: been asking the question here about bond density in space,
• 36:46
  Speaker 4: about the role of estrogen in replacing the bonds afterwards,
• 36:49
  Speaker 4: on the impact of people who are passed to premenopausal,
• 36:52
  Speaker 4: that all comes into it as well, because we can't
• 36:54
  Speaker 4: just do the research quite frankly, on old, middle aged
• 36:57
  Speaker 4: white guys. We need to look at the averse, not
• 37:00
  Speaker 4: just in terms of gender diversity, but as we move forward,
• 37:04
  Speaker 4: are different groups of people better suited or worse suited
• 37:08
  Speaker 4: to life in space. We know that people from different
• 37:11
  Speaker 4: cultures and different countries have slightly different physiological properties. They
• 37:17
  Speaker 4: will need to be researched on into this, and we'll
• 37:19
  Speaker 4: need to look at people across the whole spectrum of
• 37:21
  Speaker 4: humanity to understand it, rather than just basing everything on
• 37:24
  Speaker 4: the first few people who went to space, who were
• 37:27
  Speaker 4: pretty much uniformly very athletic, very well trained, white men
• 37:31
  Speaker 4: of a certain edge. That's just been part of a subset.
• 37:34
  Speaker 4: So it's a really interesting question. I don't have more
• 37:37
  Speaker 4: answers than that, but really thank you for asking it.
• 37:40
  Speaker 4: There's a lot to think about, and it does make
• 37:42
  Speaker 4: my head hurt in a very different way to the
• 37:44
  Speaker 4: cosmology mating my head hurt thing. It's a different part
• 37:46
  Speaker 4: of my brain that's hurting at the minute.
• 37:48
  Speaker 1: Yes, absolutely, I can tell you that when it comes
• 37:52
  Speaker 1: to studies in the medicines that you referred to, my
• 37:55
  Speaker 1: wife and I have experienced firsthand the effect of medicines
• 37:59
  Speaker 1: that have been created and developed for men by default,
• 38:05
  Speaker 1: not purposely developed for men, just developed for everybody, but
• 38:08
  Speaker 1: based on the physiological male, I can take an antibiotic
• 38:15
  Speaker 1: and not feel a thing. My wife can take the
• 38:18
  Speaker 1: same tablet and she's sick for a day, classic example
• 38:22
  Speaker 1: of it. So I know exactly what you're talking about.
• 38:25
  Speaker 1: It needs to be a lot more research into medicines
• 38:27
  Speaker 1: for women to suit their physiology. Also, and I can
• 38:33
  Speaker 1: tell you that people on Earth suffer the same problems
• 38:37
  Speaker 1: as they do in space, particularly people who are undergoing
• 38:41
  Speaker 1: hormone therapy for cancer treatment. They lose muscle mass and
• 38:46
  Speaker 1: bone density, and in long term therapy can develop osteoporosis.
• 38:51
  Speaker 1: And the solution to that is exercise. But it's yeah,
• 38:56
  Speaker 1: it's a tough battle. I'm all too aware of it myself,
• 39:00
  Speaker 1: but it's yeah that it's the same problem on Earth
• 39:04
  Speaker 1: when it comes to treating cancer at the moment with
• 39:07
  Speaker 1: some kinds of hormone therapy. But thanks to the question,
• 39:10
  Speaker 1: brilliant question. Loved it, Keep them coming. Our final question
• 39:14
  Speaker 1: comes from Dan two. Dean two because we had Dean earlier. Sorry,
• 39:20
  Speaker 1: Dean two, you became Dan two because you had the
• 39:21
  Speaker 1: second on the list.
• 39:23
  Speaker 4: This is ODID, isn't it? Parton OSSI? Dean?
• 39:27
  Speaker 1: Yeah, I think so, let's find out.
• 39:29
  Speaker 2: Hi, friend Andrew, this is Dean in Redcliffe and Queensland.
• 39:32
  Speaker 2: Can you explain why there is a fixed amount of
• 39:34
  Speaker 2: centrifugal force measurable on an object at the Earth's equator,
• 39:38
  Speaker 2: But it's angular velocity which is the cause of this
• 39:41
  Speaker 2: apparent force. It can only be measured relative to another
• 39:45
  Speaker 2: object's frame of reference. What I mean is an eighty
• 39:48
  Speaker 2: k g person should weigh about three hundred grams less
• 39:51
  Speaker 2: at the equator than at the poles, and this can
• 39:53
  Speaker 2: be measured. However, the calculation for centrifugal force uses the
• 39:57
  Speaker 2: angular velocity of the person going around the Earth's axis,
• 40:02
  Speaker 2: which is measured using the frequency of the Earth spin.
• 40:06
  Speaker 2: Whether the Earth's diameter and circumference are fixed. The Earth
• 40:08
  Speaker 2: spins once in twenty four hours relative to the Sun,
• 40:12
  Speaker 2: once in twenty four hours forty minutes relative to the Moon,
• 40:16
  Speaker 2: and once in twenty three hours fifty six minutes relative
• 40:19
  Speaker 2: to distant starts. Although these frequencies are all fairly close,
• 40:24
  Speaker 2: they would each give different answers to the calculation. Yet
• 40:27
  Speaker 2: we can measure centrifuge before so as a fixed amount.
• 40:31
  Speaker 2: Although objects in all objects in space are moving, I
• 40:36
  Speaker 2: suspect that space itself does not move, even though it's expanding,
• 40:40
  Speaker 2: So does space time have a fixed structure that determines
• 40:44
  Speaker 2: direction without reference to objects within it? Thanks for the podcast.
• 40:49
  Speaker 1: Wow, Thanks Dean. We sort of hinted its centrifugal horser earlier,
• 40:54
  Speaker 1: but this is a kind of this is a different
• 40:56
  Speaker 1: angle on it.
• 40:57
  Speaker 4: Bomb bomb, bom bomb. It's an all question and there's
• 41:00
  Speaker 4: a couple of different parts to Itsel'll initially talk about
• 41:04
  Speaker 4: the effect of the Earth's rotation on your weight. I
• 41:07
  Speaker 4: think that's a good one in terms of the dependens
• 41:11
  Speaker 4: on a reference frame. There isn't really dependence on a
• 41:14
  Speaker 4: reference frame for it, because what we measure is what
• 41:18
  Speaker 4: is actually happening. So the Earth rotates at a certain speed,
• 41:23
  Speaker 4: and because you're moving at that speed, you've got gravity
• 41:26
  Speaker 4: pulling you down. But the movement that you've got the rotation,
• 41:31
  Speaker 4: is carrying you off at right angles to gravity, and
• 41:34
  Speaker 4: you're kind of falling around as you go around. So
• 41:36
  Speaker 4: because you're not falling into the Earth, but you're also
• 41:39
  Speaker 4: not escaping from the Earth bause of your movement. So
• 41:42
  Speaker 4: so there's a little bit of an outward false balancing
• 41:44
  Speaker 4: gravity that's the net result of it. So we can
• 41:47
  Speaker 4: work this through with all the mass, and I sometimes
• 41:50
  Speaker 4: do this derivation from my students. It's kind of vaguely
• 41:52
  Speaker 4: elegant to get the orbital period for things, you can
• 41:55
  Speaker 4: do this kind of mass. What's effectively happening are is
• 42:00
  Speaker 4: that you have an acceleration going on. You're an accelerating
• 42:04
  Speaker 4: object and because of your motion as you rotate around
• 42:08
  Speaker 4: the Earth, you do one full lap in a certain
• 42:10
  Speaker 4: amount of time. That means it is as though you're
• 42:13
  Speaker 4: being pulled towards the middle with the acceleration, and that's
• 42:16
  Speaker 4: the acceleration due to gravity you feel, and the faster
• 42:19
  Speaker 4: you spin, the lower that pull towards the middle feels like.
• 42:23
  Speaker 4: This is because you're offset by the centrifugal force, so
• 42:27
  Speaker 4: you feel, which is a virtual force, feeling like it's
• 42:29
  Speaker 4: pushing outwards. By comparison, the real number you measure is
• 42:35
  Speaker 4: based around what the acceleration on your body actually is,
• 42:38
  Speaker 4: and that's something that's quantifiable and that is down to
• 42:42
  Speaker 4: you completing exactly one lap of the Earth in the
• 42:46
  Speaker 4: reference frame of the Earth. So that's the one thing
• 42:50
  Speaker 4: that was missing from this. We talk about the sun,
• 42:52
  Speaker 4: we talk about the distance sounds, we talk about the moon,
• 42:54
  Speaker 4: but in reality you're talking about in the Earth's rest frame.
• 42:58
  Speaker 4: So you're going around in a circle around the center
• 43:00
  Speaker 4: of the Earth. That takes you twenty three hours, fifty
• 43:04
  Speaker 4: six minutes and four seconds. The distance stars are just
• 43:07
  Speaker 4: a reference point where we can see that for but
• 43:09
  Speaker 4: it's all relative to the position of the Earth, and
• 43:12
  Speaker 4: so that's what gives you your three hundred grams less.
• 43:16
  Speaker 4: The Sun and the Moon are also moving in the
• 43:19
  Speaker 4: rest frame of the Earth. The Sun does one full
• 43:22
  Speaker 4: lap around the Earth in one year, the moon does
• 43:25
  Speaker 4: one full lap in one month. So that's why you've
• 43:27
  Speaker 4: got those slightly longer times, because you have got to
• 43:30
  Speaker 4: turn a little bit more than one full revolution before
• 43:32
  Speaker 4: the Sun is directly overhead or before the moon is
• 43:35
  Speaker 4: directly overhead. So that isn't a red frame. That's a
• 43:37
  Speaker 4: moving frame. That's a rotating frame. Essentially, if you measure
• 43:41
  Speaker 4: it with respect to the sunbeam overhead, the whole of
• 43:44
  Speaker 4: the Earth's frame has had to rotate around. In that case,
• 43:47
  Speaker 4: it brings us onto the concepts of rest frames and
• 43:51
  Speaker 4: how you measure them on what is the universal rest frame.
• 43:56
  Speaker 4: That's again where it gets really really headachey. Now my knowledge,
• 44:00
  Speaker 4: it isn't thought in any of the models of space time,
• 44:06
  Speaker 4: but space time is fixed and distinct from the objects
• 44:10
  Speaker 4: within it. Rather, any object that is moving at a
• 44:14
  Speaker 4: fixed speed and not experiencing any acceleration is in a
• 44:21
  Speaker 4: rest frame. It's at rest locally, it's not accelerating, and
• 44:26
  Speaker 4: so it can look out at the entire universe from
• 44:29
  Speaker 4: its perspective, and any accelerations that it sees and any
• 44:34
  Speaker 4: emotions that it sees are what's actually happening out there.
• 44:37
  Speaker 4: If you're in an accelerating rest frame, you are not
• 44:40
  Speaker 4: in a rest frame by definition, because you're accelerating. So
• 44:43
  Speaker 4: a person on the surface of the Earth is accelerating
• 44:46
  Speaker 4: as we go around the Earth, as the Earth rotates,
• 44:49
  Speaker 4: and as the Earth goes around the Sun, and as
• 44:51
  Speaker 4: the Earth orbits in the central mass of the Earth,
• 44:53
  Speaker 4: Moon System, and all the rest of it. So we're
• 44:56
  Speaker 4: not actually in what I think is often described as
• 44:59
  Speaker 4: an inertial threat. However, you do a lot of thought
• 45:05
  Speaker 4: experiments that are near enough. If you were free floating
• 45:08
  Speaker 4: in space away from any of the stars, you'd probably
• 45:11
  Speaker 4: consider yourself to be an inertial friend. But even then
• 45:13
  Speaker 4: you'd have some acceleration from the stars. There isn't really
• 45:18
  Speaker 4: as far as I know. And this is where we
• 45:19
  Speaker 4: get onto the cosmology stuff, which is more wooly for me.
• 45:23
  Speaker 4: And so I'm giving a less accurate and less good
• 45:26
  Speaker 4: quality answer, and I apologize for that. But there isn't,
• 45:29
  Speaker 4: to my knowledge, any universe accepted rest threat, because everything
• 45:33
  Speaker 4: is moving and everything is accelerating and feeling the gravity
• 45:36
  Speaker 4: of everything else. But the way that our models of
• 45:39
  Speaker 4: the universe work is that they have this concept of
• 45:43
  Speaker 4: space time, but it isn't like space time is a
• 45:46
  Speaker 4: fabric that is physical over which everything moves. It is
• 45:49
  Speaker 4: itself fixed, even space time is moving and dragged around.
• 45:54
  Speaker 4: I'm aware that this is an answer that's quickly evolving
• 45:58
  Speaker 4: from sensible into the incohera, and that's because this is
• 46:01
  Speaker 4: pushing the limits of what my knowledge is. But it's
• 46:03
  Speaker 4: also pushing the conceptual limits on which we build the
• 46:07
  Speaker 4: foundations and stuff. And that's because a lot of the models,
• 46:10
  Speaker 4: and particularly a lot of the way the models we
• 46:12
  Speaker 4: use are described, we simplify things to make it clearer
• 46:17
  Speaker 4: how everything works. You know, So we talk about an
• 46:21
  Speaker 4: object at rest, you know, people are explaining special relativity
• 46:24
  Speaker 4: for the first time. We'll talk about an object at
• 46:26
  Speaker 4: rest and another object moving in a finite speed that
• 46:29
  Speaker 4: is near the speed of like relative to it, and
• 46:31
  Speaker 4: that's a great thought experiment. The reality is a lot
• 46:35
  Speaker 4: of the time that we are so close to being
• 46:37
  Speaker 4: in that situation that you can ignore the effects of
• 46:40
  Speaker 4: the little bits at per turbit unless you've got incredibly
• 46:43
  Speaker 4: good measuring equipment. So from the point of view of
• 46:46
  Speaker 4: to totally switch analogies, I was watching the cricket the
• 46:49
  Speaker 4: other night. If you imagine two cricketers and somebody running
• 46:52
  Speaker 4: in and bowling the cricket ball, but instead of it bouncing,
• 46:56
  Speaker 4: it just goes straight on. So it's a full toss.
• 46:58
  Speaker 4: It's a beamer, nasty delivery, booh hiss, yeah, very all
• 47:01
  Speaker 4: the rest of it. The only thing that is going
• 47:04
  Speaker 4: on in terms of predicting the trajectory of that ball
• 47:08
  Speaker 4: is that it has that soleration pulling it down. There's
• 47:10
  Speaker 4: a little bit of air resistance as well. If the
• 47:13
  Speaker 4: ball spinning, you get benula effects and things that can
• 47:15
  Speaker 4: cause it swerve. But that ball is moving, and we
• 47:18
  Speaker 4: can treat it as though the cricket pitch and all
• 47:21
  Speaker 4: of the players are in a shared inertial rest frame.
• 47:24
  Speaker 4: There's nothing else going on. Other than this single gravitational
• 47:27
  Speaker 4: force pulling down. We don't have to take account of
• 47:30
  Speaker 4: things like the Coriolis effect, which is another virtual force,
• 47:34
  Speaker 4: like the centrifugal force that is the result of the
• 47:36
  Speaker 4: rotation of the Earth and the different rotation speeds at
• 47:39
  Speaker 4: different latitudes. We can treat that in a local, isolated
• 47:42
  Speaker 4: case as though it is a much simpler scenario than
• 47:45
  Speaker 4: it is, because all those are the corrections that so
• 47:47
  Speaker 4: small that they don't really impact things. What it leads to, though,
• 47:52
  Speaker 4: is we tend to explain things using those simpler things,
• 47:55
  Speaker 4: simpler scenarios, and that leads to questions like this, because
• 48:00
  Speaker 4: it leads to the idea that there is something external
• 48:04
  Speaker 4: to the Earth and the Sun and towards those observers
• 48:07
  Speaker 4: that is in itself fixed, and that there is an absolute,
• 48:11
  Speaker 4: idealized frame of reference. My understanding is that all of
• 48:16
  Speaker 4: our models do not argue that. When you get into
• 48:18
  Speaker 4: the nitty grittic it's a will the answer. I appreciate,
• 48:23
  Speaker 4: it's probably not an ideal answer, Deane. And you know,
• 48:25
  Speaker 4: if that answer was not satisfactory, if you please ask
• 48:28
  Speaker 4: Fred when he's back and get a different version. I
• 48:31
  Speaker 4: do think this is important for anybody who's learning. Actually,
• 48:33
  Speaker 4: I say this to my atudents. I've got a tutor
• 48:35
  Speaker 4: in a couple of hours which I'm thinking of this
• 48:37
  Speaker 4: head space. My explanations are one explanation of how things work,
• 48:42
  Speaker 4: and they'll work for some people. But we all think
• 48:44
  Speaker 4: about the universe differently, and there is no shame in
• 48:47
  Speaker 4: saying that explanation did work for me. Let me find another. Yeah,
• 48:51
  Speaker 4: it's really important. If my explanation of that, which admittedly
• 48:56
  Speaker 4: you know was probably not a perfect explanation even for me,
• 48:59
  Speaker 4: doesn't work for you, there will be other explanations around,
• 49:02
  Speaker 4: and it's worth asking another person to get a different
• 49:05
  Speaker 4: perspective of what I said that didn't make sense. There
• 49:08
  Speaker 4: is no problem with that. I will not be offended
• 49:10
  Speaker 4: if you ask Fred in two weeks and say, John
• 49:12
  Speaker 4: Ty fail to explain this, his explanation was rubbish. Tellney
• 49:15
  Speaker 4: what's really happening, Fred, and then let him go and
• 49:17
  Speaker 4: see what happens.
• 49:20
  Speaker 1: Okay, fair enough, great question, very deep thinking. They're Dean,
• 49:25
  Speaker 1: and thanks for sending it in. If you'd like to
• 49:27
  Speaker 1: send us a question, you can do that on our website,
• 49:29
  Speaker 1: space nuts podcast dot com or space nuts dot io.
• 49:32
  Speaker 1: Click on the AMA button up the top, and you
• 49:35
  Speaker 1: can send us text and audio questions and have a
• 49:37
  Speaker 1: look around while you're there. You're always welcome to our
• 49:40
  Speaker 1: website or our social media on Facebook or Instagram or
• 49:44
  Speaker 1: YouTube if you're a YouTube follower. Thanks to your support,
• 49:48
  Speaker 1: we've got quite a large audience on YouTube these days.
• 49:55
  Speaker 4: That's it.
• 49:56
  Speaker 1: Oh, we've done. I was looking for another question, Johnny,
• 49:58
  Speaker 1: Thank you so much.
• 50:00
  Speaker 4: That stuff STI pleasure. Obviously didn't talk too much today.
• 50:02
  Speaker 4: First time for everything.
• 50:05
  Speaker 1: You might want to look at the time ticking up
• 50:07
  Speaker 1: here on my clock. Thanks Joddy. We'll catch you next time.
• 50:12
  Speaker 1: Johnny Horner, Professor of astrophysics at the University of Southern Queensland.
• 50:16
  Speaker 1: And thanks to Heu in the studio who couldn't be
• 50:18
  Speaker 1: with us again today because he was over producing me
• 50:21
  Speaker 1: sane he'll be out of hospital soon, and from me
• 50:24
  Speaker 1: Andrew Andrew Dunkley, thanks to your company. See you on
• 50:27
  Speaker 1: the next episode of Space Nuts. Goodbye space.
• 50:31
  Speaker 4: You'll be listening to the Space Nuts.
• 50:33
  Speaker 5: Podcast available at Apple Podcasts, Spotify, iHeart Radio, or your
• 50:40
  Speaker 5: favorite podcast player. You can also stream on demand at
• 50:43
  Speaker 5: bides dot com.
• 50:44
  Speaker 1: This has been another quality podcast production from nights dot
• 50:48
  Speaker 1: com