Alien Signals, Bone Density & Cosmic Disks: #496 - The Great Space Q&A Returns

Space Nuts Episode 496: Life on Other Planets, Centrifugal Forces, and Bone Density in Space
Join Andrew Dunkley and Professor Jonti Horner in this thought-provoking Q&A edition of Space Nuts, where they tackle some of the most intriguing questions from our listeners. From the possibility of detecting life on distant planets to the fascinating dynamics of centrifugal force, and the effects of zero gravity on bone density, this episode is brimming with scientific insights that will spark your curiosity about the universe.
Episode Highlights:
- Detecting Life on Distant Planets: Ron's compelling question leads the discussion on whether scientists in other solar systems could identify life on Earth using current technology, and vice versa. Jonti elaborates on the challenges and potential methods for detecting life beyond our planet.
- Spheres vs. Disks: Dean asks why celestial objects form as spheres while others appear as disks. Jonti explains the physical processes at play, including hydrostatic equilibrium and angular momentum, shedding light on the fascinating shapes of stars, planets, and galaxies.
- Bone Density in Space: Ann's insightful question about calcium loss in astronauts prompts a deep dive into the effects of microgravity on bone health. Jonti shares findings from recent studies and discusses the implications for long-term space missions.
- Centrifugal Force Explained: Aussie Dean's inquiry about the nature of centrifugal force and its measurement leads to a discussion on reference frames and how they relate to our understanding of gravity and motion on Earth.
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Stay curious, keep looking up, and join us next time for more stellar insights and cosmic wonders. Until then, clear skies and happy stargazing.
00:00 - Introduction to the episode and topics
02:15 - Discussion on detecting life on other planets
10:30 - Exploring the shapes of celestial objects
18:00 - Insights into bone density loss in space
26:45 - Understanding centrifugal force and reference frames
30:00 - Closing thoughts and listener engagement
✍️ Episode References
NASA's Studies on Bone Density
https://www.nasa.gov/spaceflight
Hydrostatic Equilibrium in Celestial Bodies
https://en.wikipedia.org/wiki/Hydrostatic_equilibrium
Centrifugal Force and Gravity
https://www.physicsclassroom.com/class/circles/Lesson-2/Centrifugal-Force

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Episode Transcript

Speaker 1 (00:00):
Hi there, Andrew Dunkley here, Thanks for joining us on
a Q and A edition of Space Nuts, and coming up,
we're going to answer a question from Ron. He wants
to know if we could see a planet that sustains life,
would we know it? And vice versa. If there was
an alien race out there and they spotted Earth, would
they know we are here? Good question. Dean is a

(00:22):
bit confused about spheres versus discs. Why does it happen?
Why aren't they all spheres or all discs? And has
a brilliant question love this one about bone density in
space and some of the problems that are associated with
being in zero gravity for long periods of time, and
Dean two, it's not the same. Dean is asking us

(00:44):
about centrifugal force. We'll cover all that in this episode
of Space.

Speaker 2 (00:49):
Nuts fifteen, Channel ten nine.

Speaker 3 (00:55):
Ignition Space Nuts Guy or three spaces hasn't actually bought it?
Neils Good Here he is again.

Speaker 1 (01:07):
Professor John T. Horder, Professor of estrophysics at the University
of Southern Queensland.

Speaker 4 (01:13):
Johnty, Hello, Hey, how are you going?

Speaker 1 (01:15):
I'm all right? A question without notice?

Speaker 4 (01:20):
Yes?

Speaker 1 (01:21):
Did you ever sort of have people review at school?
Like John ty Horner said in the corner eating his
Christmas pie, down came the comet that made Johnty vomit,
and now he only is flies.

Speaker 4 (01:34):
Oh that's brilliant. That would have been far more pleasurable
than marchall skill experience. It's probably not worth getting into
too depressing a thing, but up until I got to
Upper Clamento University, I had a horrendous, horrendous time at
school because I was I grew up in a very
working class area, lost social economic area with hugely high unemployment,
neurly the minor strikes in the eighties, and I was

(01:57):
an only child, so I'm not necessarily blessed with the
best social aptitude particular that age. But I was smart
enough to be very smart, but not smart enough to
realize that there were the right way and the wrong
way to go about that. So I had a horrible,
horrible time for the twelve years at school. In terms
of bully I was catastrophically bullied, but you know, it

(02:18):
mainly who I am today, so I'm not going to
complain too much about it. But yeah, it's a curse
of having aspiration and the curse of being smart in
an area where that wasn't a common thing. You know,
a lot of empathy for the kids who went to
school with because you're talking about an area where many
of them didn't have any family members who were employed
because of what was going on. There was a huge

(02:39):
epidemic of men taking their own lives because of all
the things that were going on. So it was a
pretty rough time, a pretty rough place. But such as
life unfortunately, you know.

Speaker 1 (02:49):
Yeah, yeah, I certainly had my share of bullying at school,
and yeah, not often, wasn't an every day thing. It was,
I suppose, looking back, reasonably rare. But it never sits well,
it's it's a horrible thing.

Speaker 4 (03:08):
At least, he says. Nowadays, there is more being done
to counter and more al wavers of it, because you know,
the impression back when I was at school was he
just needed to manna, which is an awful phrase, and
everybody has to deal with it. It's a formative experience,
and he just couldn't tell us. As long as you
weren't getting naive to something it were, they weren't interested.

Speaker 1 (03:27):
I used to talk to my boys about it and
ask them how they were going, and they always said, no,
we never had any trouble, but then teachers would tell
me otherwise, so they're obviously not keen to talk about it.
But my middle son, who was always very tall through school,
he was he tired above all the other kids. I
think he was the second tallest kid in his year

(03:49):
and in the school in general. And I said to
him one day that you get bullied, and he went no,
because he was big. He was a big kid, and
no one, no one went near him. His height was
actually a good defense mechanism. It's funny how it works out.
But there's a lot about anthropology, I suppose when.

Speaker 4 (04:09):
You're talking about it. It's all interesting about the edges
in which kids develop awareness of self and the edges
at which they develop empathy and kindness and all those
kind of things in a specific center rather than the
general sense. It's really interesting.

Speaker 1 (04:24):
Yeah, it is, all right. Let's deal with some questions,
and our first question comes from Ron. He said, if
scientists in a distant solar system were searching for exoplanets
using the same technology that we're using, and if they
were to observe our planet, would they be able to
tell with any degree of certainty that there was life

(04:45):
here or Conversely, if we were to observe an exoplanet
that's exactly like Earth, teeming with carbon based life and
perhaps with an advanced civilization modifying their atmosphere, which we
talked about in the last could we tell that there's
life there? Thanks? Ron, great question, Ron, We've had questions

(05:07):
like it before, but I just love this topic, so yeah,
we'll do it again. And Johnty hasn't had to answer
this one before, so I thought it'd be interesting to
get his take on it.

Speaker 4 (05:19):
Well, it's a fabulous question, and I mean, the sad
answer is we're not quite there yet. So if we
were looking at the Solar System from around another star,
depending on which method we use, we'd be able to
find Jupterum, probably Saturn, but we'd have to observe for
a very long time to measure the wobbles for them.
So we need to observe the Sun for a decade
or two to pick up DUP from Saturn. Everything else

(05:40):
we wouldn't be able to find. Now, if we have
something like tests the Transit eight Planet Service that'llite looking
at our Solar system, there's a very small chance it
might pick up the Earth, our venus but test typically
it starts for twenty seven days. The Earth takes three
hundred and sixty five days to around and would take
over sixteen hours to transit, so the old of catching
a transit a pretty much nil. So we're not there yet.

(06:03):
We are getting better, and as we talked about in
the other episode, we're getting to the point where we
can find planets that are a bit bigger than the Earth,
but on all bits that are comparable to the Earth.
Around stars like the Sun. We can find planets smaller
than the Earth around dim little red dwarf stars using
the transit method, but that's partly because as planets are
so close they're stars, they're going around really quickly. So

(06:26):
the upshot of all that is, if we were orbiting
another star looking back at the Solar System, I think
we could only confidently detect one or two planets. The
Earth would probably be the third planet that would be
discovered as a technology got better, because it's the biggest
of the terrestrial planets. But it would depend a little
bit on your line of sight because the treasural planets

(06:46):
are all slightly tilted to each other, So if you're
going to find them through the transit method, the likelihood
is only one of them will transit and the others won't.
In the radial velossy method, you'd pick out Jupter and Saturn,
but you'd struggle for anything else. Eventually you get there,
but you'd need technology a bit better than ours. So
we're not at the point of finding the planets yet,

(07:06):
never mind finding the life on them. But that's like
the next step in the journey. We've only had thirty
years of the exoplanet ere we're only in the first
few decades have been able to do this at all,
and the progress we've made is ugly astonishing, and I
think within the next decade or two will routinely start
being able to find planets that are Earth sized on
Earth like orbits and to start looking for evidence of

(07:27):
life on them. But that is going to be the
hardest observations we've ever to carry out in terms of
detecting life like us, so it's a slightly different proposition.
So finding any evidence of life is going to be challenging.
So people often talk about biomarkers, which is this concept
that there are certain things you could look for that

(07:49):
will be indicative of life. And we've talked about the
possible detection of phosphene and venus atmosphere before. We've talked
about stuff like the chicken soup experiment the Viking land
did on Mars in the nineteen seventies, where they dug
up some soil and put some soup on it, and
so if it gave off gases, because they can be life,
they use of nutrients. When you're looking at planets arounder

(08:10):
the stars, there is no guarantee that life on those
planets would have followed the same evolitary pathways as life
on Earth. So a lot of the very specific biomarkers
people propose there best on our knowledge of life on
Earth because it's the only planet we know does have life,
and it's the only example of life we've got. One
of the examples here is something called the red edge,

(08:32):
which is when you look at the spectrum of light
from a planet, if the planet has a lot of
plants on board that are using chlorophyll, chlorophyll absorbs incredibly
strongly in the red, so you might see a feature
in the red that is the signature of chlorophyll, and
that will be an indication of plant life. The problem is,
and again I'm not a biologist, so there's probably more

(08:54):
to this than I'm going to say. In my simple
version is that chlorophyll is an incredibly efficient compound for
allowing plants to utilize the light like the light from
our suck. But there are many other compounds that could
do a similar job for stars of different temperatures that
are there for different colors, so they put out the
bulk of their light at slightly different wavelengths, And there's

(09:14):
no guarantee that life on another planet would use chlorophyll,
especially if that star was significantly different to the Sun,
So the specific bymarker of the red edge from chlorophyll
wouldn't work very well. Necessarily, it wouldn't be guaranteed to work,
especially because it's also mimicked by the spectrum of olivine,
which is a very common mineral, has a very similar appearance.

(09:37):
But looking more generally for that kind of absorption feature
in the spectrum that you can't explain any other way
is one of the size people have looked for. So
it's not so much case of looking for a specific thing,
but rather for looking for something that is out of place,
trying to explain it, and finding that the only explanation
left is life. You're looking for something out of balance.

(09:58):
So another good example is on Earth, we have oxygen,
we have methane. Now, there's a lot of oxygen in
the atmosphere, but that doesn't necessarily mean life, because there
are chemical processes that can produce oxygen without life being involved.
Similarly with a lot of methane in the atmosphere. And
methane is a natural product of animal life. I my

(10:19):
dog line next to me has been quite happily producing
methae through the podcast because we've fed at some broccoli
I think in a puppy food last night. So methane
is produced by life, but there are also lots of
natural ways it can produce. And you know, there's huge
amounts of methane in the atmospheres of Urinus and Neptune,
for example. So finding oxygen or finding methane doesn't necessarily

(10:41):
mean life. There's a lot of other explanations, but the
oddity with Earth is that we've got oxygen and methen together. Now,
when you put oxygen and methne together, they react with
each other a lot, and they react until all of
one of them is gone. So the methane in this
atmosphere has a really short residence time of only a
century or a few centuries I think four hundred year
before it's all gone. So you look at the Earth

(11:03):
and it's got oxygen and methen together, which means something
has to be producing new methane to replace the methen
that's lost. Now, even that doesn't mean it's life, because
volcanoes perished me fed. So what you then have to
do is say, well, this is interesting. It could be life,
it could be something else. Let's measure the methane over time,
and if it's volcanoes, you'll get the methane falling off

(11:23):
and a random time of volcano ups and there's a
spike of methane and then it falls off again, and
a random time later you get another spike. But when
you look at methane in the Earth's atmosphere, it varies
with the seasons. Volcanoes don't do that, so therefore that's
an indication of life. So it's looking for that oddity
that's out of place. There are a couple of things
that would give away arguably technologically developed life, which doesn't

(11:47):
necessarily mean intelligent life, as we're seeing in the political sphere,
at the minute, but technologically developed life. One of them
is chlorophylor of carbons, So the things that we were
putting up into the atmosphere that devastated the layer. Yeah,
we only know of those being produced by technology if
there is no natural process that seems to produce them.

(12:08):
Another is radio broadcasts. So any intelligent aliens within about
eighty light years of us ninety light years of us
now would see our broadcast. Now. The exact date of
the first broadcast that we sent out that was strong
enough to be detected from around the stars depends w
you talked. It could have been the Berlin Olympics in
nineteen thirty six, I think, or the coronation of Queen

(12:30):
Elizabeth in nineteen fifty two. I think with it it was,
and they usually held has been the first big broadcast
that would have been detectable on an interstellar distance. What
that means is that within a certain distance of the
Earth there is a sphere where if there are intelligent
aliens with radio telescopes, they could be watching neighbors and
we could well get a broadcast back at some point

(12:52):
saying please stop. You know, we're a bit like toddlers
at the minute in a room screaming into the void,
and that sound is good further and further away from
as a time goes on. Now that's the motivation for
things like the Cechrectra threasurial intelligence, which is helping fund
the wonderful radiotails go down to paths through the Breakthrough
Listen project. The challenge there is that we are already

(13:14):
starting to become more quiet, well like the baby becoming
a totaler and moderating itself. And the reason for that
is costs. If you were broadcasting in all directions all
the time, you've got to put a lot of energy
in and most of that energy is wasted, so only
a twin a little bit of that is going to
get to your receivers. It's much more efficient to send
your data, like we're talking at the minute, through the

(13:36):
end the end, through wires or through point to point stuff.
So the silent satellites are a bit like this. They're
broadcasting down Therefore venal little is going back out into space,
and anything connecting to them points at the satellite and
beams directly to it. So it's much more energy efficient.
And there are some arguments that the Earth could well
be radio silent again from the point of view of

(13:57):
aliens listening in within just a few decades, so there'd
only be a short window. And then you've got this
shell of broadcasts moving outwards with a void behind it,
and unless you tune in when that shell's passing past,
you'd never hear us. But in that sense, if we
were looking at the Solar System with our biggish radio telescopes,
we'd probably just about be able to pick up the

(14:18):
unusual radio activity if we were at the right radio
we were at the right distance, but it would still
be challenging for us. I think we do have the
capacity for that, but it would be hard. So in
that sense, if there were aliens around, I don't know.
Approxima centaury B, another of the many many planets that
has been argued has been the most earth like ever discovered,

(14:40):
and made me hungry. If there was a planet there,
if there were aliens on it, and there were broadcasting
alien neighbors, we'd be able to tune it.

Speaker 1 (14:49):
Wouldn't that be interesting? The answer to Ron's question is no,
not yet. We're just not quite there. The time may
well come, but again it's nearly in a hast.

Speaker 4 (14:59):
Exter, isn't it you? Absolutely? I said, you don't know
what a needlest and you've never seen a half start befire?

Speaker 1 (15:05):
Yeah, exactly, Yes, thank you Ron, great question, lovely to
hear from you. Okay, we take Space Nuts and our
next question comes from Dean high Space Nuts.

Speaker 4 (15:23):
I'm Dean from Washington, d C. In the United States.

Speaker 3 (15:26):
I originally started listening to the show and okay, anyways,
I was wondering why under gravity do some things form
as discs and others as spheres. You know, we're stars
and planets are spheres, but some galaxies in our soul
systems a disc. But then also planet can have discs
around them. All very anyways, thanks, keep up your.

Speaker 1 (15:48):
Very thank you Dean. I never would have even thought
of that question, and it's a great question. But yeah,
he's right. You've got spheres and you've got discs, you've
got mixtures of spheres and discs, You've got all sorts
of combinations.

Speaker 4 (16:03):
Why is it so it's all down to different physical
presses going on? So it's fabulous question. And we run
across this when we're teaching astro, when we're studying it
quite a lot, and there are things that happen in
slightly different situations. So if you've got material falling inwards
under gravity, it will keep falling inwards until either it's

(16:27):
moving around on an orbit it swings back out. But
let's assume it's falling into an object that is going
to become a solid or gasious subject that therefore has
some way of stopping that material, so it slows down
and becomes part of that object. You then have a
balance between gravity trying to pull you inwards and the
physical strength of the material pushing outwards. If you've got

(16:47):
a solid object, if you've got a gasio subject, the
gas can keep going in, but then you build up
pressure of the pressure holds things up. You might have
energy being released that also holds it up, so that
then pushes outwards in all directions. I'll talk about solid
objects first. This ties into a little bit towards the

(17:08):
definition of a planet. There is a concept called hydrostatic equilibrium,
which is basically the shape that something that has no
strength will finish up in. Once everything's moved around, you
say that it's in hydrostatic equilibrium. It's the lowest kind
of energy state. So if you got outside the Earth's atmosphere,

(17:31):
or rather you go away from the gravity of the Earth,
putting things down, and you can have droplets suspended. A
drop of water that is not moving at all will bispherical.
It's held in by surface tension in that case holds
it together, but it will be a sphere. If you
rotate it, it will gradually become more elongated than a blade,
and it become what we call an ablate spheroid, which

(17:52):
is what the Earth is. The Earth is wider at
the equator than the poles because of the rotation, and
the rotation is essentially applying a slight out force. That
means the net force pulling in is weaker at the
equator of the poles, and so you stretch out of it.
That's kind of how I visualize it. Yep. If you
are smaller than a certain size, your material strength is

(18:14):
strong enough to prevent things moving around and flowing, so
you don't become spherical. You don't get that hydrostatic equilibrium.
So if you look at the moons of the planets,
the smallest one that I think is in hydrostatic equilibrium
is possibly mimas at Saturn, about four hundred kilmeters across.
It might be one of the other Saturnian modes, but

(18:34):
I think it's Mimus because that's about the size where
you've got enough mass that the gravitational pull is strong
enough that that can overcome the physical strength of the
material where the object's forming have cause it to then
move and flow, and you end up then getting nearly
a sphere because that's the lowest energy solution. That's your
hydrostatic equilibrium. If you had it being wider than that,

(18:59):
more like a look like an ice hockey puck maybe,
but the material can flow. You've got more mass pushing
down in the horizontal plane, so things try and squeeze
in here and they'll be pushed out that way until
it bounces out, so you'd end up flowing until you've
got that kind of spherical shape. Yeah, your ice hockey puck,
though small enough that its material shredth winds, so it
stays at elongated shape. So that's kind of the lower

(19:22):
end of when people start talking about the definition of
a planet is it has to be in hydrostaphic equilibrium.
Doesn't mean it's spherical, it just means it's in that
lowest energy thing. So if it's rotating quickly. It can
be a kind of oblate spheroid. You get a similar
thing with stars. So you've got all this gas collapsing
in friction, stopping it just opening and escaping again. So
you've got an object. That object has gravity pulling inwards

(19:46):
and it's got a restoring force pushing outwards. In the
case of a cell like the Sun, that's the radiation
pressure from all the nuclear fusion going on.

Speaker 1 (19:52):
In its cot.

Speaker 4 (19:54):
Now the Sun's rotating, albeit once every thirty odd days,
but it is in something that is close to that
hydrostaphic equilibrium. So if you put a load of mass
on the Sun's equator, that would squish in and the
poles would push out until you got back to that
kind of shape. So that's a physical kind of object.
That's why you get them going to be spheres or

(20:16):
nearly spheres. It's that concept of hygrostatic equilibrium, and it's
due to the balance of the force pulling in woods
and the force pushing outwards, radiation pressure of stars, material strength,
material physics going on. For solid objects, with disks, you
don't have the same things going on. So what you've
got is you've got a rotating cloud of gas and
dust that isn't really strong enough told itself up, but

(20:39):
it's rotating quickly under gravity. Now you've got the conservation
of angular momentum going on, so things near the middle
go quicker than things near the outside, and there is
a tendency for things to clapse down in a disc
above the plane of the equator of the thing they're
orbening around. That is due to the conservation of that
angular momentum, but it's also due to the motion things through.

(21:00):
You've got all sorts of things coming in. The analogy
often is when I'm giving public talks. Here involves fittis
that is different, so it's not a perfect analogy, but
it gives you a kind of idea what's going on
with spinning material, And it's if you've ever seen somebody
who's a show off making pizza bases. They get a
ball of very elastic dough and then they spin it
around very quickly and whirl it over their head, and

(21:21):
it flattens out into a big pancake as a result
of the conservation of the annual momentum there, it flattens
out into the pizza bair shape. And if I tried
it it'd either stick to the ceiling or hit me
on the head. It wouldn't go very well. It's a
slightly similar thing with the distant material around planets and stars.
Now what's happening is you've got material collapsing into the

(21:42):
star under gravity, forming the disc around it because there
is a bit of rotation with that rotation. As you
spin in and you get to a smaller and smaller distance,
you move faster and faster and faster. And that's why
a gas cloud rotating every few million years gives you
star rotating every few days or every few hours. It's
like the ballerina bringing their arms in as they do
a spin. There spin quicker and quicker. But that also

(22:04):
tends to lead to things collapsing into the plane because
that's a bit again like the hydro staff keeper whatever
in example, that's kind of the lowest energy solution. You're
rotating around the given rotation axis, you will collapse into
a disc in that plane. Material that's coming in above
that disc can just carry on orbiting normally, but if
there's more material in the disc, there will be friction

(22:25):
and it will get damped down and help to collapse
down into there. But if the bulk is rotating with
the same rotation access, anything falling in at high handles
will probably just fall in and blockstraight onto the stars.
It's rotating that way, but it's coming in here essentially. Yeah,
I appreciate that description was really useful for the people

(22:46):
who were only listening because I can't see me waving.
My flappy hands are out. But if you're coming in
from near the poles, the little bit of rotation around
isn't helping again, so you coming in directly towards the target.
If you're coming in from the poles and you're going
to hit onto the day, you'll be passing through all
that material and that will damp you down a little bit,
so more inclined things will gradually get damp down. To

(23:07):
add to the disc the discs we get there for
around protest stars, a material that's falling in the rotation
spinning it up. You get a disc around that protest
star that this will be a bit fled, It will
have a bit of height mixes, a lot of dynamics
and stirring and things like that going on. If you
could have a big enough region around it, you probably
end up seeing a disc would eventually flare out and

(23:30):
clickly comes a background, but you'd have almost cleared lobes
above and below the star, and that's kind of what
we see with our small body population in the Solar System.
As you go from the planets and the edge of Kooperbalt,
going further outwards, you gradually come out towards the domain
of the art cloud, and when you're far enough from
the Sun, things get stirred up by passing stars and
get put back into a sphere because their tilts are

(23:51):
all random housed. So you've got a disc near the Sun,
and that's because the Sun's gravity is dominating the angual
momentum dominating. When you're very far from the Sun, you're
only loosely hell to the Sun, so nudge of from
passing stars can change your direction quite significantly. And over
the four billion years since the cell system formed, that
material that was flung out into the out cloud in

(24:12):
a disc because it was flung out from a disc,
has been smeared around, so we now get as very
coliche cloud around the Sun. But when you're close enough
to the Sun for the Sun to dominate, you'd have
voids that are fairly empty above and below the plane
and a disc blowed out. So it's all complex and
it's a couple of different bits of physics interacting essentially.

Speaker 1 (24:32):
Yeah, well, now I'd never wondered about it, and I'm
glad Dane asked the question because it really is interesting science.
Hydrostatic equal equally librial lime.

Speaker 4 (24:49):
It's the really good example of how sice works and
how we do it actually, because that's exactly the scientific process.
You see something, you go why is that? And Saturn's
a great example. You look at sat and then it's
a oblet's fair bit of an elongated blobby thing, but
it's nearly spherical, rarely first order, and yet it's got
a disc of material around it. Why is it? The
discal's all block, you know. And so that's what leads

(25:09):
us down that journey discovery to figure all this stuff out.
So that's just how science works. And it's very fun,
brilliant question.

Speaker 1 (25:16):
Thank you, Dane, lovely to hear from you. This is
Space Nuts with Andrew Duckley and Johnty Horner.

Speaker 4 (25:28):
Space Nuts.

Speaker 1 (25:30):
Our next question, I really love. This one comes from
an in Bellevue, Washington. I have a question about calcium
and astronauts on Earth. Estrogen helps prevent calcium loss from bones.
Do pre menopausal astronauts lose less bone or regain bone

(25:51):
faster than mail or postmenopausal astronauts. Does hormone replacement therapy
help minopausal astronauts regain bone. It's a really great question,
and says thanks for the interesting podcast. Appreciate that, and
thanks for the interesting question. I know this isn't your area,

(26:13):
but I know you've done your homework.

Speaker 4 (26:16):
Yeah, I don't a little bit reading. It's a fascinating question,
and it's a really important question to ask because there's
a lot of investigations into the impact of being in
space that are going on, particularly given that there's a
future where people aspire to travel to Mars and live there,
or have you know, space sessions where people with full
time go colonize the asteroids, things like that. It's not

(26:38):
my area of expertise by any means. I'm not a
biologist or a biomechanists, but it is something people are
starting to do research into. I haven't been able to
find anything about the difference between pre and post menopause,
or about estrogen supplements and things like that. That's a
really interesting question, and it's almost possibly the kind of

(26:59):
thing where you could find someone leading that kind of
research and try and get involved if you want to.
But I did do a bit of digging around. I
found there is a paper that was published. I found
it on pub meed that was published a few years
ago in twenty fourteen and titled Men and Women in
Space Bone Loss and Kidney stone Risk after among the
Oration space Flight, which is a slightly intimidating title, but

(27:24):
they not there that. Finally, at that stage there had
been enough people who identified as male and identified as
female that had spent a long time in space that
you could start doing a quantitative comparison. They had in
their sample thirty three men and nine women who had
spent long the Oursan missions on the space station, and

(27:45):
their bodies had been studied when they got back. Essentially,
so I think that bone mineral density was evaluated before
and after the flight and stuff like that, and they
also looked at blood and urine to look at kidney function.
The missions were fifty days to two hundred and fifteen
days flown in this millennium, so twenty twenty twelve, what

(28:06):
they found was the following alreadly out explicitly. They said
the bondance to response to spaceflight was the same for
men and women in both exercise groups, so no difference
bond dens to response to flight was the same for
men and women, and the typical decrease in bone mineral density,
whole body and regional after flight was not observed for
either sex for people who were using the advanced resistance devices,

(28:29):
so they were able to recover equally well. So the
fundamental comment there have as a final sentence of their
abstract is the responses of men and women to spaceflight
with respect to measures of bone health were not different,
which is really interesting. It doesn't entirely talk about the
importance of the hormones, but I guess the fact that

(28:52):
women who were pre menopause and men experienced their bond
density degradation at the same rate suggests that the elevated
levels of estrogen in the women did not prevent that
bondensity loss. Doesn't say anything about the speed at which
the bond icity was recovered when they were back, so
I can't really comment on that, but it reminded me

(29:14):
more widely of a the risks of space flat but
also the amount that we don't know, and the importance
of getting people with different expertises involved, but also the
importance of doctors and medical researchers studying women as well
as men. And I know from a number of my
female friends that they feel very much that a lot
of medications, a lot of treatments assume that the male

(29:37):
body is the normal one, and studies have not been
carried out to such a great extent on the different
impact of that same medication on the female body. True,
and I've also heard of problems where male doctors have
not been as well educated in female problems as they
should have been in giving fairly rubbish responses. So, you know,
acknowledging those biases and acknowledging that I'm in a very
privileged situation, but we need more research into this. NASA

(30:01):
has on its website a segment here talking about the
degree of impact on bond density. So their segment is
astronauts can lose up to one to two percent of
bond density per month in the hip and the spine.
That compares to zero point five to one percent per
year in postmenopausal women and much older men on Earth. So,

(30:22):
in other words, the bone loss that you're getting while
you're in microgravity and space is around twice as significant
as that that you experienced post menopause for women or
when you become significantly older for men, and that they
say this rappid bond loss can place crew members at
risk for both fracturing and risk of elions osioporosis as
a result of the space flag. There's another study which

(30:44):
I just stumbled across, looking on this female astronauts impact
of space radiation on menopause. This came out a bit
more recently in Atal twenty twenty two, and it shows
people are starting to think about this. So this is
a study that is looking at the impacts of the
radiation environment that you experience in space on what they
call the avarian reserve, so the number of viable eggs

(31:06):
that a woman has. And so the statement that really
made my head hurt here is that data suggests that
a typical Mars mission may reduce a woman's avarian reserve
by about fifty percent. This would have consequences to a
woman's reproductive capacity and most significantly decreases a time metaval
to her menopaus. So it all reminds me it's slightly

(31:28):
off topic, but This was prompted by this question. I
every year go to the Australian Space Research Conference in Australia,
which is a fabulous meeting and can be quite multidisciplinary.
But a few years ago, I think possibly about twenty thirteen,
twenty fourteen now, we had a invited lecture from a
doctor who said doctor from Tasmania who works in space

(31:49):
mediciner's researcher on the site. And it's the only lecture
I've ever been to at a research conference which started
with a trigger warning and a health warning, and that
was basically, if there's anybody in the audience who's a
bit squeamish, a bit sensitive, he might want to leave.
Now this is going to be a medical talk and
you're all astronomers and spati researchers. And it included some

(32:09):
fairly unsettling pictures that I won't relay in too much detail.
But this doctor was talking about the future aspiration of
humanity to have a permanent presence on other astronomical bodies,
talking particularly about Mars, and what he was speaking to
was that our science fiction view of that is that

(32:31):
you have a population on Mars that is independent, so
they reproduce and repopulate themselves. That's what we think of,
and he said it isn't as simple as that from
a doctor's point of view, from someone who studied pregnancy,
he was talking about the requirement the importance of gravity
to pregnancy is something we never think about because we're

(32:53):
all living on the surface of the Earth at one G.
But he said it's actually the case, and remember and
remembering to ok from more than a decade ago, he
spoke about how important the gravity that you are moving
within is to the development of the fetus and the
way that the cells know what to make and what
shape to make. And he gave the example of how

(33:15):
even a very small change from the standard atmospheric temperature
and pressure and gravity can cause huge problems by talking
about the invasion of the Spanish into South America back
in the sixteen hundreds and the fact that the high
Andes were never conquered permanently because the conquistados couldn't reproduce there.

(33:35):
They were just not able to be viable there, and
the native people there had obviously adjusted over many, many generations.
And he said, that's barely any different to the conditions here.
What he was going on to say was that his
vision is that because of this, this would be so
insurmountable that for a very long time, once we have
a permanent presence on Mars, it would be a retirement

(33:57):
hard It'd be somewhere that people go to after they've
sawed their wild arts on Earth, that they go to
to spend their later years in a more pleasant environment
with lower gravity, less strains on an aging, aching body.
But he didn't see any possibility of people reproducing there
and unless we went down the incredibly dystopian worldview of

(34:20):
having women living in centrifugures for nine months to simulate
one g which I can imagine would not be a
very popular deficion, But it ties into Mars one, which
was this attempt by I think a Dutch guy to
make a lot of money out of sending a mission
to Mars to try and get the first humans on Mars.

(34:43):
And they ran a huge competition process for this with
more than one hundred thousand initial applicants and they whittled
them down and whittled them down. But there was an
Australian involved in this, guy called Josh Richards, who's a
fabulous science communicator and did a lot of work off
the back of this of going at schools and talking
to kids and saying I could be the first person
on Mars ask me anything. Essentially, one of the things

(35:03):
that Josh told me that led to problems and in
the end led to the breakup of his relationship with
his partners who went through this process was that he
was looking at taking a one way trip to Mars,
but also that the people who were the final selected
ones had to agree to be medically stetilized before they
got on the trip to Mars because they were going

(35:26):
from mixed crew. The mixed crew had to make their
own entertainment during the travels he had because his show
was going to be delivered big brother style. That was
probably part of the motivation for people subscribing to be honest.
The lack of understanding of the possibilities and the risk
of pregnancy during spatifight in microgravity or on Mars in
incredibly reduced gravity was such a nobody could see any

(35:50):
possibility of any viability of pregnancy. But it wasn't like
they were going to send people with the medical skills
to deal with traumatic problems like that on the mission.
So you have to agree to either be subtilized, though
you wouldn't go only pick someone else, which sounds really barbaric,
but it's the unfortunate reality we're going to have to
deal with when we start looking at having a permanent

(36:12):
presence off Earth rather than just going and visit it.
Because if we want to have a permanent presence on
the Moon or on Mars, we view that inherently as
humans has been a self replicating presence. We view it
as been a presence that can sustain itself. You know,
So if the population of Earth got wiped out, at
least we've got the people on Mars. But in order
to do that, it's going to need an incredible amount

(36:34):
of medical research to be done and incredible advances in
medical technology that we just don't have yet. And what's
been asking the question here about bond density in space,
about the role of estrogen in replacing the bonds afterwards,
on the impact of people who are passed to premenopausal,
that all comes into it as well, because we can't

(36:54):
just do the research quite frankly, on old, middle aged
white guys. We need to look at the averse, not
just in terms of gender diversity, but as we move forward,
are different groups of people better suited or worse suited
to life in space. We know that people from different
cultures and different countries have slightly different physiological properties. They

(37:17):
will need to be researched on into this, and we'll
need to look at people across the whole spectrum of
humanity to understand it, rather than just basing everything on
the first few people who went to space, who were
pretty much uniformly very athletic, very well trained, white men
of a certain edge. That's just been part of a subset.
So it's a really interesting question. I don't have more
answers than that, but really thank you for asking it.

(37:40):
There's a lot to think about, and it does make
my head hurt in a very different way to the
cosmology mating my head hurt thing. It's a different part
of my brain that's hurting at the minute.

Speaker 1 (37:48):
Yes, absolutely, I can tell you that when it comes
to studies in the medicines that you referred to, my
wife and I have experienced firsthand the effect of medicines
that have been created and developed for men by default,
not purposely developed for men, just developed for everybody, but

(38:08):
based on the physiological male, I can take an antibiotic
and not feel a thing. My wife can take the
same tablet and she's sick for a day, classic example
of it. So I know exactly what you're talking about.
It needs to be a lot more research into medicines
for women to suit their physiology. Also, and I can

(38:33):
tell you that people on Earth suffer the same problems
as they do in space, particularly people who are undergoing
hormone therapy for cancer treatment. They lose muscle mass and
bone density, and in long term therapy can develop osteoporosis.
And the solution to that is exercise. But it's yeah,

(38:56):
it's a tough battle. I'm all too aware of it myself,
but it's yeah that it's the same problem on Earth
when it comes to treating cancer at the moment with
some kinds of hormone therapy. But thanks to the question,
brilliant question. Loved it, Keep them coming. Our final question
comes from Dan two. Dean two because we had Dean earlier. Sorry,

(39:20):
Dean two, you became Dan two because you had the
second on the list.

Speaker 4 (39:23):
This is ODID, isn't it? Parton OSSI? Dean?

Speaker 1 (39:27):
Yeah, I think so, let's find out.

Speaker 2 (39:29):
Hi, friend Andrew, this is Dean in Redcliffe and Queensland.
Can you explain why there is a fixed amount of
centrifugal force measurable on an object at the Earth's equator,
But it's angular velocity which is the cause of this
apparent force. It can only be measured relative to another
object's frame of reference. What I mean is an eighty
k g person should weigh about three hundred grams less

(39:51):
at the equator than at the poles, and this can
be measured. However, the calculation for centrifugal force uses the
angular velocity of the person going around the Earth's axis,
which is measured using the frequency of the Earth spin.
Whether the Earth's diameter and circumference are fixed. The Earth
spins once in twenty four hours relative to the Sun,

(40:12):
once in twenty four hours forty minutes relative to the Moon,
and once in twenty three hours fifty six minutes relative
to distant starts. Although these frequencies are all fairly close,
they would each give different answers to the calculation. Yet
we can measure centrifuge before so as a fixed amount.
Although objects in all objects in space are moving, I

(40:36):
suspect that space itself does not move, even though it's expanding,
So does space time have a fixed structure that determines
direction without reference to objects within it? Thanks for the podcast.

Speaker 1 (40:49):
Wow, Thanks Dean. We sort of hinted its centrifugal horser earlier,
but this is a kind of this is a different
angle on it.

Speaker 4 (40:57):
Bomb bomb, bom bomb. It's an all question and there's
a couple of different parts to Itsel'll initially talk about
the effect of the Earth's rotation on your weight. I
think that's a good one in terms of the dependens
on a reference frame. There isn't really dependence on a
reference frame for it, because what we measure is what

(41:18):
is actually happening. So the Earth rotates at a certain speed,
and because you're moving at that speed, you've got gravity
pulling you down. But the movement that you've got the rotation,
is carrying you off at right angles to gravity, and
you're kind of falling around as you go around. So
because you're not falling into the Earth, but you're also

(41:39):
not escaping from the Earth bause of your movement. So
so there's a little bit of an outward false balancing
gravity that's the net result of it. So we can
work this through with all the mass, and I sometimes
do this derivation from my students. It's kind of vaguely
elegant to get the orbital period for things, you can
do this kind of mass. What's effectively happening are is

(42:00):
that you have an acceleration going on. You're an accelerating
object and because of your motion as you rotate around
the Earth, you do one full lap in a certain
amount of time. That means it is as though you're
being pulled towards the middle with the acceleration, and that's
the acceleration due to gravity you feel, and the faster
you spin, the lower that pull towards the middle feels like.

(42:23):
This is because you're offset by the centrifugal force, so
you feel, which is a virtual force, feeling like it's
pushing outwards. By comparison, the real number you measure is
based around what the acceleration on your body actually is,
and that's something that's quantifiable and that is down to
you completing exactly one lap of the Earth in the

(42:46):
reference frame of the Earth. So that's the one thing
that was missing from this. We talk about the sun,
we talk about the distance sounds, we talk about the moon,
but in reality you're talking about in the Earth's rest frame.
So you're going around in a circle around the center
of the Earth. That takes you twenty three hours, fifty
six minutes and four seconds. The distance stars are just

(43:07):
a reference point where we can see that for but
it's all relative to the position of the Earth, and
so that's what gives you your three hundred grams less.
The Sun and the Moon are also moving in the
rest frame of the Earth. The Sun does one full
lap around the Earth in one year, the moon does
one full lap in one month. So that's why you've

(43:27):
got those slightly longer times, because you have got to
turn a little bit more than one full revolution before
the Sun is directly overhead or before the moon is
directly overhead. So that isn't a red frame. That's a
moving frame. That's a rotating frame. Essentially, if you measure
it with respect to the sunbeam overhead, the whole of
the Earth's frame has had to rotate around. In that case,

(43:47):
it brings us onto the concepts of rest frames and
how you measure them on what is the universal rest frame.
That's again where it gets really really headachey. Now my knowledge,
it isn't thought in any of the models of space time,
but space time is fixed and distinct from the objects

(44:10):
within it. Rather, any object that is moving at a
fixed speed and not experiencing any acceleration is in a
rest frame. It's at rest locally, it's not accelerating, and
so it can look out at the entire universe from
its perspective, and any accelerations that it sees and any

(44:34):
emotions that it sees are what's actually happening out there.
If you're in an accelerating rest frame, you are not
in a rest frame by definition, because you're accelerating. So
a person on the surface of the Earth is accelerating
as we go around the Earth, as the Earth rotates,
and as the Earth goes around the Sun, and as
the Earth orbits in the central mass of the Earth,
Moon System, and all the rest of it. So we're

(44:56):
not actually in what I think is often described as
an inertial threat. However, you do a lot of thought
experiments that are near enough. If you were free floating
in space away from any of the stars, you'd probably
consider yourself to be an inertial friend. But even then
you'd have some acceleration from the stars. There isn't really

(45:18):
as far as I know. And this is where we
get onto the cosmology stuff, which is more wooly for me.
And so I'm giving a less accurate and less good
quality answer, and I apologize for that. But there isn't,
to my knowledge, any universe accepted rest threat, because everything
is moving and everything is accelerating and feeling the gravity
of everything else. But the way that our models of

(45:39):
the universe work is that they have this concept of
space time, but it isn't like space time is a
fabric that is physical over which everything moves. It is
itself fixed, even space time is moving and dragged around.
I'm aware that this is an answer that's quickly evolving
from sensible into the incohera, and that's because this is

(46:01):
pushing the limits of what my knowledge is. But it's
also pushing the conceptual limits on which we build the
foundations and stuff. And that's because a lot of the models,
and particularly a lot of the way the models we
use are described, we simplify things to make it clearer
how everything works. You know, So we talk about an

(46:21):
object at rest, you know, people are explaining special relativity
for the first time. We'll talk about an object at
rest and another object moving in a finite speed that
is near the speed of like relative to it, and
that's a great thought experiment. The reality is a lot
of the time that we are so close to being
in that situation that you can ignore the effects of
the little bits at per turbit unless you've got incredibly

(46:43):
good measuring equipment. So from the point of view of
to totally switch analogies, I was watching the cricket the
other night. If you imagine two cricketers and somebody running
in and bowling the cricket ball, but instead of it bouncing,
it just goes straight on. So it's a full toss.
It's a beamer, nasty delivery, booh hiss, yeah, very all
the rest of it. The only thing that is going

(47:04):
on in terms of predicting the trajectory of that ball
is that it has that soleration pulling it down. There's
a little bit of air resistance as well. If the
ball spinning, you get benula effects and things that can
cause it swerve. But that ball is moving, and we
can treat it as though the cricket pitch and all
of the players are in a shared inertial rest frame.
There's nothing else going on. Other than this single gravitational

(47:27):
force pulling down. We don't have to take account of
things like the Coriolis effect, which is another virtual force,
like the centrifugal force that is the result of the
rotation of the Earth and the different rotation speeds at
different latitudes. We can treat that in a local, isolated
case as though it is a much simpler scenario than
it is, because all those are the corrections that so

(47:47):
small that they don't really impact things. What it leads to, though,
is we tend to explain things using those simpler things,
simpler scenarios, and that leads to questions like this, because
it leads to the idea that there is something external
to the Earth and the Sun and towards those observers
that is in itself fixed, and that there is an absolute,

(48:11):
idealized frame of reference. My understanding is that all of
our models do not argue that. When you get into
the nitty grittic it's a will the answer. I appreciate,
it's probably not an ideal answer, Deane. And you know,
if that answer was not satisfactory, if you please ask
Fred when he's back and get a different version. I
do think this is important for anybody who's learning. Actually,

(48:33):
I say this to my atudents. I've got a tutor
in a couple of hours which I'm thinking of this
head space. My explanations are one explanation of how things work,
and they'll work for some people. But we all think
about the universe differently, and there is no shame in
saying that explanation did work for me. Let me find another. Yeah,
it's really important. If my explanation of that, which admittedly

(48:56):
you know was probably not a perfect explanation even for me,
doesn't work for you, there will be other explanations around,
and it's worth asking another person to get a different
perspective of what I said that didn't make sense. There
is no problem with that. I will not be offended
if you ask Fred in two weeks and say, John
Ty fail to explain this, his explanation was rubbish. Tellney
what's really happening, Fred, and then let him go and

(49:17):
see what happens.

Speaker 1 (49:20):
Okay, fair enough, great question, very deep thinking. They're Dean,
and thanks for sending it in. If you'd like to
send us a question, you can do that on our website,
space nuts podcast dot com or space nuts dot io.
Click on the AMA button up the top, and you
can send us text and audio questions and have a
look around while you're there. You're always welcome to our
website or our social media on Facebook or Instagram or

(49:44):
YouTube if you're a YouTube follower. Thanks to your support,
we've got quite a large audience on YouTube these days.

Speaker 4 (49:55):
That's it.

Speaker 1 (49:56):
Oh, we've done. I was looking for another question, Johnny,
Thank you so much.

Speaker 4 (50:00):
That stuff STI pleasure. Obviously didn't talk too much today.
First time for everything.

Speaker 1 (50:05):
You might want to look at the time ticking up
here on my clock. Thanks Joddy. We'll catch you next time.
Johnny Horner, Professor of astrophysics at the University of Southern Queensland.
And thanks to Heu in the studio who couldn't be
with us again today because he was over producing me
sane he'll be out of hospital soon, and from me
Andrew Andrew Dunkley, thanks to your company. See you on

(50:27):
the next episode of Space Nuts. Goodbye space.

Speaker 4 (50:31):
You'll be listening to the Space Nuts.

Speaker 5 (50:33):
Podcast available at Apple Podcasts, Spotify, iHeart Radio, or your
favorite podcast player. You can also stream on demand at
bides dot com.

Speaker 1 (50:44):
This has been another quality podcast production from nights dot
com