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.
For more Space Nuts, including our continually updating newsfeed and to listen to all our episodes, visit our website. (https://www.spacenutspodcast.com/about)
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
Become a supporter of this podcast: https://www.spreaker.com/podcast/space-nuts-exploring-the-cosmos--2631155/support (https://www.spreaker.com/podcast/space-nuts-exploring-the-cosmos--2631155/support?utm_source=rss&utm_medium=rss&utm_campaign=rss) .
Episode link: https://play.headliner.app/episode/25623575?utm_source=youtube
00:00:00 --> 00:00:02 hi there Andrew Dunley here thanks for
00:00:02 --> 00:00:05 joining us on a Q&A edition of Space
00:00:05 --> 00:00:07 Nuts and coming up we're going to answer
00:00:07 --> 00:00:10 a question from Ron he wants to know if
00:00:10 --> 00:00:12 we could see a planet that sustains life
00:00:12 --> 00:00:15 would we know it and vice versa if there
00:00:15 --> 00:00:17 was an alien race out there and they
00:00:17 --> 00:00:19 spotted Earth would they know we are
00:00:19 --> 00:00:22 here good question uh Dean is a bit
00:00:22 --> 00:00:26 confused about spheres versus discs why
00:00:26 --> 00:00:28 does it happen why why aren't they all
00:00:28 --> 00:00:31 spheres or all discs uh an has a a
00:00:31 --> 00:00:33 brilliant question love this one about
00:00:33 --> 00:00:36 bone density in space and some of the
00:00:36 --> 00:00:38 problems that are associated with being
00:00:38 --> 00:00:40 in zero gravity for long periods of time
00:00:40 --> 00:00:44 and Dean to it's not the same Dean uh is
00:00:44 --> 00:00:46 asking us about centrifugal force we'll
00:00:46 --> 00:00:49 cover all that in this episode of Space
00:00:49 --> 00:00:54 Nuts 15 seconds guidance is internal 10
00:00:54 --> 00:00:59 n ignition sequence start Space Nuts 5 4
00:00:59 --> 00:01:00 3 2
00:01:00 --> 00:01:04 1 2 3 4 5 5 4 3 2 1 Space Nuts as the
00:01:04 --> 00:01:07 nuts report feels good here he is again
00:01:07 --> 00:01:10 Professor JY hoer professor of
00:01:10 --> 00:01:11 astrophysics at the University of
00:01:11 --> 00:01:15 Southern Queensland JY hello hey how you
00:01:15 --> 00:01:18 going I'm all right um I got a question
00:01:18 --> 00:01:22 without notice yes did you ever sort of
00:01:22 --> 00:01:26 have people rebiew at school like jonty
00:01:26 --> 00:01:27 herner sat in the corner eating his
00:01:27 --> 00:01:31 Christmas pie down came the comet that
00:01:31 --> 00:01:33 made jonty vomit and now he only is
00:01:33 --> 00:01:35 flies oh that's brilliant that would
00:01:35 --> 00:01:37 have been far more pleasurable than
00:01:37 --> 00:01:39 maral skill experience it's probably not
00:01:39 --> 00:01:40 worth getting into too depressing of
00:01:40 --> 00:01:43 thing but up until I got to up until I
00:01:43 --> 00:01:45 went to University I had a horrendous
00:01:45 --> 00:01:47 horrendous time at school because I was
00:01:47 --> 00:01:50 um I grew up in a very workingclass area
00:01:50 --> 00:01:53 um low social economic area with hugely
00:01:53 --> 00:01:54 high unemployment during the minor
00:01:54 --> 00:01:57 strikes in the 80s and I was an only
00:01:57 --> 00:01:59 child so I'm I'm not necessarily blessed
00:01:59 --> 00:02:01 with the best social aptitude particular
00:02:01 --> 00:02:04 at that age but I was smart enough to be
00:02:04 --> 00:02:06 very smart but not smart enough to
00:02:06 --> 00:02:09 realize that there were the right way
00:02:09 --> 00:02:12 and the wrong way to go about that um so
00:02:12 --> 00:02:14 I had a horrible horrible time for the
00:02:14 --> 00:02:16 12 years at school in terms of bully I
00:02:16 --> 00:02:18 was catastrophically bullied but you
00:02:18 --> 00:02:19 know it made me who I am today so I'm
00:02:19 --> 00:02:22 not going to complain too much about it
00:02:22 --> 00:02:25 um but yes a curse of having aspiration
00:02:25 --> 00:02:27 and the curse of being smart in an area
00:02:27 --> 00:02:28 where that wasn't a common thing you
00:02:29 --> 00:02:30 know a lot of empathy the kids I went to
00:02:30 --> 00:02:31 school with because you're talking about
00:02:31 --> 00:02:33 an area where many of them didn't have
00:02:33 --> 00:02:35 any family members who were employed
00:02:35 --> 00:02:37 because of what was going on there was a
00:02:37 --> 00:02:41 huge um epidemic of men taking their own
00:02:41 --> 00:02:43 lives because of all the things that
00:02:43 --> 00:02:45 were going on so it was a pretty rough
00:02:45 --> 00:02:48 time a pretty rough place um but such as
00:02:48 --> 00:02:51 life unfortunately you know yeah
00:02:51 --> 00:02:53 yeah I certainly had my share of
00:02:53 --> 00:02:57 bullying at school and um yeah uh not
00:02:57 --> 00:02:59 not not often wasn't an everyday thing
00:02:59 --> 00:03:03 it was I suppose looking back reasonably
00:03:03 --> 00:03:07 rare but it never sits well it's it's a
00:03:07 --> 00:03:09 horrible thing at least these days
00:03:09 --> 00:03:11 nowadays there is more being done to
00:03:11 --> 00:03:12 counter it and more awareness of it
00:03:12 --> 00:03:14 because you know the impression back
00:03:14 --> 00:03:16 when I was at school was you just needed
00:03:16 --> 00:03:18 to Manor which sful phrase and everybody
00:03:18 --> 00:03:20 has to deal with it it's a formative
00:03:20 --> 00:03:22 experience and teachers couldn't care
00:03:22 --> 00:03:23 less as long as you weren't getting
00:03:23 --> 00:03:26 knife or something it was they weren't
00:03:26 --> 00:03:29 interested I I used to talk to my boys
00:03:29 --> 00:03:30 about it and asked them how they were
00:03:30 --> 00:03:32 going and they always said no we never
00:03:32 --> 00:03:34 had any trouble um but then teachers
00:03:34 --> 00:03:35 would tell me otherwise so they're
00:03:36 --> 00:03:39 obviously not keen to talk about it but
00:03:39 --> 00:03:42 my middle son who was always very tall
00:03:42 --> 00:03:44 through school he he was uh he towered
00:03:44 --> 00:03:47 above all the other kids I think he was
00:03:47 --> 00:03:49 the second tallest kid in his year and
00:03:49 --> 00:03:52 in the school in general and I said to
00:03:52 --> 00:03:54 him one day you get bullied and he went
00:03:54 --> 00:03:57 no because he was big he was a big kid
00:03:57 --> 00:04:00 and no one no one went near him so his
00:04:00 --> 00:04:02 height was actually a good defense
00:04:02 --> 00:04:05 mechanism it's funny how it works out
00:04:05 --> 00:04:06 but that that says a lot about
00:04:06 --> 00:04:08 anthropology I
00:04:08 --> 00:04:10 suppose we're not
00:04:10 --> 00:04:12 talking it's all interesting about the
00:04:12 --> 00:04:15 ages in which kids develop awareness of
00:04:15 --> 00:04:17 self and the edges at which they develop
00:04:17 --> 00:04:20 empathy and kindness and all those kind
00:04:20 --> 00:04:21 of things in a specific sense rather
00:04:21 --> 00:04:23 than a general sense it's really
00:04:23 --> 00:04:26 interesting yeah yeah it is all right
00:04:26 --> 00:04:29 let's uh deal with some questions and
00:04:29 --> 00:04:32 our first first question comes from Ron
00:04:32 --> 00:04:34 he said if scientists in a distant solar
00:04:34 --> 00:04:36 system were searching for exoplanets
00:04:36 --> 00:04:38 using the same technology that we're
00:04:38 --> 00:04:40 using and if they were to observe our
00:04:40 --> 00:04:42 planet would they be able to tell with
00:04:43 --> 00:04:45 any degree of certainty that there was
00:04:45 --> 00:04:48 life here or conversely if we were to
00:04:48 --> 00:04:51 observe an exoplanet that's exactly like
00:04:51 --> 00:04:53 Earth teaming with carbon based life and
00:04:54 --> 00:04:56 perhaps with an advanced civilization
00:04:56 --> 00:04:59 modifying their atmosphere which we
00:04:59 --> 00:05:02 talked about last episode could we tell
00:05:02 --> 00:05:05 that there's life there thanks Ron great
00:05:05 --> 00:05:07 question Ron uh we've had questions like
00:05:07 --> 00:05:10 it before but uh I just love this topic
00:05:10 --> 00:05:13 so yeah we'll do it again uh and um
00:05:13 --> 00:05:15 jonty hasn't had to answer this one
00:05:15 --> 00:05:16 before so I thought um it'd be
00:05:16 --> 00:05:19 interesting to get his take on it it's
00:05:19 --> 00:05:21 well it's a fabulous question and I mean
00:05:21 --> 00:05:22 the sad answer is we're not quite there
00:05:22 --> 00:05:25 yet so if we were looking at the soul
00:05:25 --> 00:05:27 system from around another star
00:05:27 --> 00:05:29 depending on which method we used we'd
00:05:29 --> 00:05:31 be able to find Jupiter and probably
00:05:31 --> 00:05:32 Saturn but we'd have to observe for a
00:05:32 --> 00:05:34 very long time to measure the wobbles
00:05:34 --> 00:05:36 for them so we need to observe the Sun
00:05:36 --> 00:05:38 for a decade or two to pick up Jupiter
00:05:38 --> 00:05:41 and Saturn everything else we wouldn't
00:05:41 --> 00:05:43 be able to find now if we had something
00:05:43 --> 00:05:45 like test the Transat Planet survey
00:05:45 --> 00:05:48 satellite looking at our solar system
00:05:48 --> 00:05:50 there's a very small chance it might
00:05:50 --> 00:05:52 pick up the Earth or Venus but test
00:05:52 --> 00:05:54 typically only looks at stars for 27
00:05:54 --> 00:05:57 days the Earth takes 365 days to go
00:05:57 --> 00:05:59 around and would take only 16 hours to
00:05:59 --> 00:06:00 Transit so so the odds of catching a
00:06:00 --> 00:06:03 Transit are pretty much nil so we're not
00:06:03 --> 00:06:05 there yet we are getting better and as
00:06:05 --> 00:06:07 we talked about in the other episode
00:06:07 --> 00:06:09 we're getting to the point where we can
00:06:09 --> 00:06:11 find planets that are a bit bigger than
00:06:11 --> 00:06:12 the earth but on orbits that are
00:06:12 --> 00:06:15 comparable to the Earth around stars
00:06:15 --> 00:06:17 like the sun we can find planets smaller
00:06:17 --> 00:06:19 than the Earth around dim little red
00:06:19 --> 00:06:21 dwarf stars using the transit method but
00:06:21 --> 00:06:23 that's partly because our planets so
00:06:23 --> 00:06:24 close their STS they're going around
00:06:24 --> 00:06:27 really quickly so the upshot of all that
00:06:27 --> 00:06:30 is if we were orbiting in another star
00:06:30 --> 00:06:32 looking back at the solar system I think
00:06:32 --> 00:06:34 we could only confidently detect one or
00:06:34 --> 00:06:37 two planets the Earth would probably be
00:06:37 --> 00:06:38 the third planet that will be discovered
00:06:38 --> 00:06:41 as a technology got better because it's
00:06:41 --> 00:06:43 the biggest of the terrestrial planets
00:06:43 --> 00:06:44 but it would depend a little bit on your
00:06:44 --> 00:06:46 line of sight because the terestrial
00:06:46 --> 00:06:48 planets are all slightly tilted to each
00:06:48 --> 00:06:49 other so if you're going to find them
00:06:49 --> 00:06:51 through the transit method the
00:06:51 --> 00:06:52 likelihood is only one of them will
00:06:52 --> 00:06:54 Transit and the others
00:06:54 --> 00:06:56 one in radial velocity method you'd pick
00:06:56 --> 00:06:58 out jup and Saturn but you'd struggle
00:06:58 --> 00:07:00 for anything else
00:07:00 --> 00:07:02 eventually youd get there but you'd need
00:07:02 --> 00:07:04 technology a bit better than ours so
00:07:04 --> 00:07:06 we're not at the point of finding the
00:07:06 --> 00:07:08 planets yet never mind finding the life
00:07:08 --> 00:07:10 on them but that's like the next step in
00:07:10 --> 00:07:12 the journey we've only had 30 years of
00:07:12 --> 00:07:14 the exoplanet era we're only in the
00:07:14 --> 00:07:16 first few decades have been able to do
00:07:16 --> 00:07:18 this at all and the progress we've made
00:07:18 --> 00:07:19 is utterly astonishing and I think
00:07:19 --> 00:07:21 within the next decade or two we'll
00:07:21 --> 00:07:23 routinely start being able to find
00:07:23 --> 00:07:24 planets that are Earth sized on Earth
00:07:25 --> 00:07:27 likee orbits and to start looking for
00:07:27 --> 00:07:29 evidence of Life on them that is going
00:07:29 --> 00:07:30 to be the hardest observations we've
00:07:30 --> 00:07:34 ever had to carry out in terms of
00:07:34 --> 00:07:37 detecting life like us so it's a
00:07:37 --> 00:07:39 slightly different proposition so
00:07:39 --> 00:07:42 finding any evidence of life is going to
00:07:42 --> 00:07:43 be challenging so people often talk
00:07:44 --> 00:07:45 about
00:07:45 --> 00:07:47 biomarkers yeah which is this concept
00:07:47 --> 00:07:48 that there are certain things you could
00:07:48 --> 00:07:50 look for that would be indicative of
00:07:50 --> 00:07:52 life and we've talked about the possible
00:07:52 --> 00:07:54 detection of phosphine in Venus
00:07:54 --> 00:07:57 atmosphere before we've talked about
00:07:57 --> 00:07:59 stuff like the chicken soup experiment
00:07:59 --> 00:08:01 the V wers did on Mars in the 1970s
00:08:01 --> 00:08:03 where they dug up some soil and put some
00:08:03 --> 00:08:06 soup on it and so if it gave off gases
00:08:06 --> 00:08:07 cost their could be life they using
00:08:08 --> 00:08:09 nutrients when you're looking at planets
00:08:09 --> 00:08:12 around of the stars there is no
00:08:12 --> 00:08:15 guarantee that life on those planets
00:08:15 --> 00:08:16 would have follow the same evolutionary
00:08:16 --> 00:08:19 Pathways as life on Earth so a lot of
00:08:19 --> 00:08:22 the very specific biomarkers people
00:08:22 --> 00:08:24 propose a best and our knowledge of life
00:08:24 --> 00:08:25 on Earth because it's the only planet we
00:08:25 --> 00:08:27 know does have life and it's the only
00:08:27 --> 00:08:29 example of Life we've got one of the
00:08:29 --> 00:08:31 examples here is something called the
00:08:31 --> 00:08:34 red Edge which is when you look at the
00:08:34 --> 00:08:36 spectrum of light from a planet if the
00:08:36 --> 00:08:39 planet has a lot of plants on board that
00:08:39 --> 00:08:41 are using chlorophyll chlorophyll
00:08:41 --> 00:08:43 absorbs incredibly strongly in the red
00:08:43 --> 00:08:45 so you might see a feature in the red
00:08:45 --> 00:08:47 that is the signature of chlorophyll and
00:08:47 --> 00:08:50 that will be an indication of plant life
00:08:50 --> 00:08:52 the problem is and again I'm not a
00:08:52 --> 00:08:54 biologist so there's probably more to
00:08:54 --> 00:08:55 this than I'm going to say in my simple
00:08:55 --> 00:08:58 version is that chlorophyll is an
00:08:58 --> 00:09:00 incredibly efficient compound for
00:09:00 --> 00:09:02 allowing plants to utilize light like
00:09:02 --> 00:09:04 the light from our up but there are many
00:09:04 --> 00:09:06 other compounds that could do a similar
00:09:06 --> 00:09:09 job for stars of different temperatures
00:09:09 --> 00:09:10 that are therefore different colors so
00:09:10 --> 00:09:12 they put out the bulk of their light at
00:09:12 --> 00:09:14 slightly different wavelengths and
00:09:14 --> 00:09:15 there's no guarantee that life on
00:09:15 --> 00:09:17 another planet would use chlorophyll
00:09:17 --> 00:09:19 especially if that star was
00:09:19 --> 00:09:22 significantly different to the Sun so
00:09:22 --> 00:09:24 the specific biomarker of the red Edge
00:09:24 --> 00:09:27 from chlorophyll wouldn't work very well
00:09:27 --> 00:09:28 necessarily it wouldn't be guaranteed to
00:09:28 --> 00:09:31 work especially because it's also
00:09:31 --> 00:09:33 mimicked by the spectrum of Olivine
00:09:33 --> 00:09:34 which is a very common mineral has a
00:09:35 --> 00:09:38 very similar appearance but looking more
00:09:38 --> 00:09:40 generally for that kind of absorption
00:09:40 --> 00:09:42 feature in the spectrum that you can't
00:09:42 --> 00:09:44 explain any other way is one of the
00:09:44 --> 00:09:46 signs people have looked for so it's not
00:09:46 --> 00:09:48 so much a case of looking for a specific
00:09:48 --> 00:09:51 thing but rather for looking for
00:09:51 --> 00:09:53 something that is out of place try to
00:09:53 --> 00:09:54 explain it and finding that the only
00:09:55 --> 00:09:57 explanation left is life you're looking
00:09:57 --> 00:09:58 for something out of balance so another
00:09:58 --> 00:10:01 good example is on Earth we have oxygen
00:10:01 --> 00:10:04 we have methane now there's a lot of
00:10:04 --> 00:10:06 oxygen in the atmosphere but that
00:10:06 --> 00:10:07 doesn't necessarily mean life because
00:10:07 --> 00:10:09 there are chemical processes that can
00:10:09 --> 00:10:11 produce oxygen without life being
00:10:11 --> 00:10:14 involved similarly with a lot of methane
00:10:14 --> 00:10:16 in the atmosphere and methane is a
00:10:16 --> 00:10:19 natural product of animal life I know my
00:10:19 --> 00:10:21 dog line next is been quite happily
00:10:21 --> 00:10:22 producing methane through the podcast
00:10:23 --> 00:10:25 because we fed some um broccoli I think
00:10:25 --> 00:10:29 in a puppy food last night so methane is
00:10:29 --> 00:10:30 pretty produced by life but there are
00:10:30 --> 00:10:32 also lots of natural ways it can be
00:10:32 --> 00:10:33 produced and you know there's huge
00:10:33 --> 00:10:35 amounts of methane in the atmospheres of
00:10:35 --> 00:10:37 Uranus and nein for example so finding
00:10:37 --> 00:10:40 oxygen or finding methane doesn't
00:10:40 --> 00:10:42 necessarily mean life there's a lot of
00:10:42 --> 00:10:43 other explanations but the odity with
00:10:43 --> 00:10:45 Earth is that we've got oxygen and
00:10:45 --> 00:10:47 methane together now when you put oxygen
00:10:47 --> 00:10:49 and methane together they react with
00:10:49 --> 00:10:51 each other a lot and they react until
00:10:51 --> 00:10:54 all of one of them is gone so the
00:10:54 --> 00:10:56 methane in Earth atmosphere has a really
00:10:56 --> 00:10:58 short residance time of only a century
00:10:58 --> 00:11:00 or a few centuries I 400 years maybe
00:11:01 --> 00:11:03 before it's all gone so you look at the
00:11:03 --> 00:11:04 Earth and it's got oxygen and methane
00:11:04 --> 00:11:06 together which means something has to be
00:11:06 --> 00:11:09 producing new methane to re replace the
00:11:09 --> 00:11:11 methane that's lost now even that
00:11:11 --> 00:11:13 doesn't mean it's life because volcanoes
00:11:13 --> 00:11:16 prod methane so what You' then have to
00:11:16 --> 00:11:17 do is say well this is interesting it
00:11:17 --> 00:11:19 could be life it could be something else
00:11:19 --> 00:11:21 let's measure the methane over time and
00:11:21 --> 00:11:22 if it's volcanoes you'll get the methane
00:11:23 --> 00:11:24 falling off until a random time a
00:11:24 --> 00:11:26 volcano ER upts in there's a spike of
00:11:26 --> 00:11:28 methane and then it falls off again and
00:11:28 --> 00:11:30 a random time l you get another Spike
00:11:30 --> 00:11:32 but when you look at methane in the
00:11:32 --> 00:11:34 earth atmosphere it varies with the
00:11:34 --> 00:11:36 seasons volcanoes don't do that so
00:11:36 --> 00:11:38 therefore that's an indication of life
00:11:38 --> 00:11:40 so it's looking for that Oddity that's
00:11:40 --> 00:11:43 out of place there are a couple of
00:11:43 --> 00:11:45 things that would give away arguably
00:11:45 --> 00:11:47 technologically developed life which
00:11:47 --> 00:11:49 doesn't necessarily mean intelligent
00:11:49 --> 00:11:50 life as we're seeing in the political
00:11:50 --> 00:11:51 sphere at the minute but technologically
00:11:51 --> 00:11:53 developed
00:11:53 --> 00:11:55 life one of them is chlorofluorocarbon
00:11:55 --> 00:11:57 so the things that we were putting up
00:11:57 --> 00:11:59 into the atmosphere that devastated are
00:11:59 --> 00:12:03 the the ozone layer yeah we only know of
00:12:03 --> 00:12:04 those being produced by technology there
00:12:04 --> 00:12:06 is no natural process that seems to
00:12:06 --> 00:12:10 produce them another is Radio broadcasts
00:12:10 --> 00:12:15 so any intelligent aliens within about
00:12:15 --> 00:12:17 80 light years of us 90 light years of
00:12:17 --> 00:12:20 us now would see our broadcast now the
00:12:20 --> 00:12:21 exact date of the first broadcast that
00:12:21 --> 00:12:23 we sent out that was strong enough be
00:12:23 --> 00:12:25 detected from around the Stars depends
00:12:25 --> 00:12:26 who you talked it could have been the
00:12:26 --> 00:12:29 Berlin Olympics in 1936 I think or the
00:12:29 --> 00:12:32 coronation of Queen Elizabeth in 1952 I
00:12:32 --> 00:12:34 think where there it was and they're
00:12:34 --> 00:12:35 usually held as been the first big
00:12:35 --> 00:12:37 broadcast that would have been
00:12:37 --> 00:12:40 detectable on an Interstellar distance
00:12:40 --> 00:12:42 what that means is that within a certain
00:12:42 --> 00:12:45 distance of the Earth there is a sphere
00:12:45 --> 00:12:46 where if there are intelligent aliens
00:12:46 --> 00:12:48 with radio telescopes they could be
00:12:49 --> 00:12:50 watching neighbors and we could well get
00:12:51 --> 00:12:52 a broadcast back at some point saying
00:12:52 --> 00:12:55 please Su you know we're a bit like
00:12:55 --> 00:12:57 toddlers at the minute in a room
00:12:57 --> 00:12:59 screaming into the void and that sound
00:12:59 --> 00:13:01 is getting further and further away from
00:13:01 --> 00:13:03 it as time goes on now that's the
00:13:03 --> 00:13:05 motivation for things like the search
00:13:05 --> 00:13:06 treal
00:13:06 --> 00:13:08 intelligence which is helping fund the
00:13:08 --> 00:13:10 wonderful radio telescope down at parks
00:13:10 --> 00:13:12 through the Breakthrough listen project
00:13:12 --> 00:13:14 the challenge there is that we are
00:13:14 --> 00:13:17 already starting to become more quiet we
00:13:17 --> 00:13:18 like the baby becoming a toddler and
00:13:18 --> 00:13:21 moderating itself and the reason for
00:13:21 --> 00:13:24 that is costs if you were broadcasting
00:13:24 --> 00:13:25 in all directions all the time you've
00:13:25 --> 00:13:27 got to put a lot of energy in and most
00:13:27 --> 00:13:29 of that energy is waste exing a tin a
00:13:29 --> 00:13:30 little bit of that is going to get to
00:13:30 --> 00:13:33 your receivers it's much more efficient
00:13:33 --> 00:13:35 to send your data like we're talking at
00:13:35 --> 00:13:38 the minute through the ndn through wires
00:13:38 --> 00:13:40 or through pointto Point stuff so The
00:13:40 --> 00:13:42 Styling satellites are a bit like this
00:13:42 --> 00:13:44 they're broadcasting
00:13:44 --> 00:13:46 down therefore V little is going back
00:13:46 --> 00:13:48 out into space and anything connecting
00:13:48 --> 00:13:50 to them points at the satellite and
00:13:50 --> 00:13:51 beams directly to it so it's much more
00:13:51 --> 00:13:53 energy efficient and there are some
00:13:53 --> 00:13:55 arguments that the Earth could well be
00:13:55 --> 00:13:57 radio silent again from the point of
00:13:57 --> 00:13:59 view of aliens listening in within just
00:13:59 --> 00:14:01 a few decades so there'd only be a short
00:14:01 --> 00:14:02 window and then you've got this shell of
00:14:02 --> 00:14:05 broadcasts moving outwards leaving a
00:14:05 --> 00:14:07 void behind it and unless you tune in
00:14:07 --> 00:14:09 when that Shell's passing pass you'd
00:14:09 --> 00:14:12 never hear us but in that sense if we
00:14:12 --> 00:14:13 were looking at the solar system with
00:14:13 --> 00:14:16 our biggest radio telescopes we'd
00:14:16 --> 00:14:18 probably just about be able to pick up
00:14:18 --> 00:14:20 the unusual radio activity if we were at
00:14:20 --> 00:14:23 the right radio we were at the right
00:14:23 --> 00:14:25 distance but it would still be
00:14:25 --> 00:14:26 challenging for us I think we do have
00:14:26 --> 00:14:29 the capacity for that but it would be
00:14:29 --> 00:14:32 hard so in that sense if there were
00:14:32 --> 00:14:34 aliens around I don't know proximus
00:14:34 --> 00:14:37 centor B another of the many many
00:14:37 --> 00:14:38 planets that has been argued as been the
00:14:38 --> 00:14:40 most earthlike ever discovered and made
00:14:40 --> 00:14:43 me angry if there was a planet there if
00:14:43 --> 00:14:44 there were aliens on it and they were
00:14:44 --> 00:14:46 broadcasting alien neighbors we'd be
00:14:46 --> 00:14:48 able to tune
00:14:48 --> 00:14:51 it wouldn't that be interesting yes so
00:14:51 --> 00:14:53 the answer to Ron's question is no not
00:14:53 --> 00:14:56 yet we're just not quite there uh the
00:14:56 --> 00:14:58 time May well come but again it's
00:14:58 --> 00:15:00 needless in a high stack stuff isn't it
00:15:00 --> 00:15:03 you absolutely I you not know what a
00:15:03 --> 00:15:04 needle is and you've never seen a hair
00:15:04 --> 00:15:06 stack before yeah
00:15:06 --> 00:15:09 exactly yes thank you Ron great question
00:15:09 --> 00:15:12 lovely to hear from
00:15:12 --> 00:15:16 you okay we check all four system a
00:15:16 --> 00:15:20 Space Nuts and our next question comes
00:15:20 --> 00:15:24 from Dean hi Space Nuts I'm Dean from
00:15:24 --> 00:15:26 Washington DC in the United States I
00:15:26 --> 00:15:28 recently started listening to the show
00:15:28 --> 00:15:29 and can't
00:15:29 --> 00:15:31 anyways I was wondering why under
00:15:31 --> 00:15:34 Gravity do some things form as discs and
00:15:34 --> 00:15:36 others as spheres you know where where
00:15:36 --> 00:15:39 stars and planets or spheres but some
00:15:39 --> 00:15:42 galaxies and our solar systems a dis but
00:15:42 --> 00:15:44 then also planet can have discs around
00:15:44 --> 00:15:47 them I don't know it's all very anyways
00:15:47 --> 00:15:50 thanks keep up to paper thank you Dean I
00:15:50 --> 00:15:52 I never would have even thought of that
00:15:52 --> 00:15:54 question and it's a great question um
00:15:54 --> 00:15:56 but yeah he's right U you've got spheres
00:15:56 --> 00:15:58 and you've got discs you've got mixtures
00:15:58 --> 00:16:01 of spheres and discs you've got all
00:16:01 --> 00:16:05 sorts of combinations um why is it so
00:16:05 --> 00:16:08 it's all down to different physical
00:16:08 --> 00:16:10 processes going on so it's fabulous
00:16:10 --> 00:16:11 question and we run across this when
00:16:11 --> 00:16:14 we're teaching Astro when we're studying
00:16:14 --> 00:16:17 it quite a lot and there are things that
00:16:17 --> 00:16:19 happen in slightly different situations
00:16:19 --> 00:16:22 so if you've got material falling
00:16:22 --> 00:16:24 inwards under Gravity it will keep
00:16:24 --> 00:16:27 falling inwards until either it's moving
00:16:27 --> 00:16:29 around on an orbit sit swings back out
00:16:29 --> 00:16:30 but let's assume it's falling into an
00:16:31 --> 00:16:33 object that is going to become a solid
00:16:33 --> 00:16:35 or gaseous object that therefore has
00:16:35 --> 00:16:37 some way of stopping that material so it
00:16:37 --> 00:16:39 slows down and becomes part of that
00:16:39 --> 00:16:41 object you then have a balance between
00:16:41 --> 00:16:44 gravity trying to pull you inwards and
00:16:44 --> 00:16:45 the physical strength of the material
00:16:45 --> 00:16:48 pushing outwards if you've got a solid
00:16:48 --> 00:16:51 object if you've got a gaseous object
00:16:51 --> 00:16:52 the gas can keep going in but then you
00:16:52 --> 00:16:54 build up pressure and the pressure holds
00:16:54 --> 00:16:57 things up you might have energy being
00:16:57 --> 00:17:00 released that also holds it up so that
00:17:00 --> 00:17:02 then pushes outwards in all
00:17:02 --> 00:17:05 directions I'll talk about solid objects
00:17:05 --> 00:17:07 first this ties into a little bit
00:17:07 --> 00:17:09 towards the definition of a planet there
00:17:09 --> 00:17:12 is a concept called hydrostatic
00:17:12 --> 00:17:16 equilibrium which is basically the shape
00:17:16 --> 00:17:19 that something that has no strength will
00:17:19 --> 00:17:21 finish up in once everything's moved
00:17:21 --> 00:17:24 around you say that it's in hydrostatic
00:17:24 --> 00:17:26 it's at the lowest kind of energy state
00:17:26 --> 00:17:29 so if you got outside the
00:17:29 --> 00:17:32 atmosphere or rather you go away from
00:17:32 --> 00:17:34 the gravity of the edge po things down
00:17:34 --> 00:17:37 and you could have droplets suspended a
00:17:37 --> 00:17:38 drop of water that is not moving at all
00:17:38 --> 00:17:40 will be spherical it's held in by
00:17:40 --> 00:17:43 surface tension in that case holds it
00:17:43 --> 00:17:45 together but it would be a sphere if you
00:17:45 --> 00:17:47 rotate it it will gradually become more
00:17:47 --> 00:17:49 elongated in a blate and it become what
00:17:49 --> 00:17:52 we call an a blate spheroid which is
00:17:52 --> 00:17:53 what the Earth is the Earth is wider at
00:17:53 --> 00:17:55 the equator than the poles because of
00:17:55 --> 00:17:58 the rotation and the rotation is
00:17:58 --> 00:18:00 essentially a applying a slight outward
00:18:00 --> 00:18:03 force that means the net force pulling
00:18:03 --> 00:18:04 in is weaker at the equator than the
00:18:04 --> 00:18:06 poles and so you stretch out of it
00:18:06 --> 00:18:10 that's kind of how I visualize it yep if
00:18:10 --> 00:18:13 you are smaller than a certain size your
00:18:13 --> 00:18:15 material strength is strong enough to
00:18:15 --> 00:18:18 prevent things moving around and flowing
00:18:18 --> 00:18:20 so you don't become spherical you don't
00:18:20 --> 00:18:22 get that hydrostatic equilibrium so if
00:18:22 --> 00:18:24 you look at the moons of the
00:18:24 --> 00:18:28 planets the smallest one that I think is
00:18:28 --> 00:18:30 in H traffic equilibrium is possibly
00:18:30 --> 00:18:33 mimus at Saturn about 400 km across it
00:18:33 --> 00:18:34 might be one of the other Saturns but I
00:18:34 --> 00:18:37 think it's mimus because that's about
00:18:37 --> 00:18:39 the size where you've got enough mass
00:18:39 --> 00:18:40 that the gravitational pull is strong
00:18:40 --> 00:18:42 enough that that can overcome the
00:18:43 --> 00:18:44 physical strength of the material when
00:18:44 --> 00:18:47 the objects forming and cause it to then
00:18:47 --> 00:18:49 move and flow and you end up then
00:18:49 --> 00:18:51 getting near asphere because that's the
00:18:51 --> 00:18:53 lowest Energy Solution that's your
00:18:53 --> 00:18:54 hydrostatic
00:18:54 --> 00:18:58 equilibrium if you had it being wider
00:18:58 --> 00:19:00 than that more like a block like an ice
00:19:00 --> 00:19:03 hockey puck maybe but the material can
00:19:03 --> 00:19:06 flow you've got more mass pushing down
00:19:06 --> 00:19:07 in the horizontal plane so things try
00:19:07 --> 00:19:08 and squeeze in here and they'll be
00:19:08 --> 00:19:11 pushed out that way until it bounces out
00:19:11 --> 00:19:12 so you'd end up flowing until you got
00:19:12 --> 00:19:15 that kind of spherical shap yeah your
00:19:15 --> 00:19:17 ice hocky po though small enough that
00:19:17 --> 00:19:19 its material strength wins so it stays
00:19:19 --> 00:19:22 at elongated shape so that's kind of the
00:19:22 --> 00:19:24 lower end of when people start talking
00:19:24 --> 00:19:26 about the definition of a planet is it
00:19:26 --> 00:19:28 has to be in hydrostatic equilibrium
00:19:28 --> 00:19:30 doesn't mean it's spherical it just
00:19:30 --> 00:19:31 means it's in that lowest energy thing
00:19:31 --> 00:19:33 so if it's rotating quickly it can be a
00:19:33 --> 00:19:36 kind of oblet spheroid you get a similar
00:19:36 --> 00:19:37 thing with stars so you've got all this
00:19:37 --> 00:19:40 gas collapsing in friction stopping it
00:19:40 --> 00:19:42 just orbiting and escaping again so
00:19:42 --> 00:19:43 you've got an
00:19:43 --> 00:19:45 object that object has gravity pulling
00:19:46 --> 00:19:47 inwards and it's got a restoring Force
00:19:47 --> 00:19:49 pushing outwards in the case of a cell
00:19:49 --> 00:19:51 at the sun that's the radiation pressure
00:19:51 --> 00:19:52 from all the nuclear fusion going on in
00:19:52 --> 00:19:55 its CAU now the sun's rotating albe it
00:19:55 --> 00:19:59 once every 30 odd days but it is in
00:19:59 --> 00:20:00 something that is close to that hyic
00:20:00 --> 00:20:03 equilibrium so if you put a load of Mass
00:20:03 --> 00:20:05 on the sun's equator that would squish
00:20:05 --> 00:20:07 in and the poles will push out until you
00:20:07 --> 00:20:09 got back to that kind of shape so that's
00:20:09 --> 00:20:12 a physical kind of object that's why you
00:20:12 --> 00:20:16 get them going to be spheres or nearly
00:20:16 --> 00:20:18 spheres it's that concept of hydrostatic
00:20:18 --> 00:20:20 equilibrium and it's due to the balance
00:20:20 --> 00:20:21 of the force pulling inwards and the
00:20:21 --> 00:20:23 force pushing outwards radiation
00:20:23 --> 00:20:25 pressure for stars material strength
00:20:25 --> 00:20:27 material physics going on for solid
00:20:27 --> 00:20:31 objects with diss you don't have the
00:20:31 --> 00:20:33 same things going on so what you've got
00:20:33 --> 00:20:35 is you've got a rotating cloud of gas
00:20:35 --> 00:20:36 and
00:20:36 --> 00:20:38 dust that isn't really strong enough to
00:20:38 --> 00:20:40 hold itself up but it's rotating quickly
00:20:40 --> 00:20:41 under
00:20:41 --> 00:20:43 Gravity now you've got the conservation
00:20:43 --> 00:20:45 of angular momentum going on so things
00:20:45 --> 00:20:47 near the middle go quicker than things
00:20:47 --> 00:20:49 near the outside and there is a tendency
00:20:49 --> 00:20:52 for things to collapse down in a disc
00:20:52 --> 00:20:53 above the plane of the Equator of the
00:20:53 --> 00:20:55 thing they're orbiting around that is
00:20:55 --> 00:20:57 due to the conservation of that angular
00:20:57 --> 00:20:59 momentum but it's alsoe du to the motion
00:20:59 --> 00:21:01 of things through you've got all sorts
00:21:01 --> 00:21:03 of things coming in the analogy I often
00:21:03 --> 00:21:05 used when I'm giving public talks here
00:21:05 --> 00:21:07 involves fysic that is different so it's
00:21:07 --> 00:21:09 not a Perfect Analogy but it gives you
00:21:09 --> 00:21:10 kind of idea what's going on with
00:21:10 --> 00:21:12 spinning material and it's if you've
00:21:12 --> 00:21:14 ever seen somebody who's a showoff
00:21:14 --> 00:21:17 making pizza bases they get a ball of
00:21:17 --> 00:21:19 very elastic dough and then they spin it
00:21:19 --> 00:21:20 around very quickly and WHL it over
00:21:20 --> 00:21:22 their head and it flattens out into a
00:21:22 --> 00:21:23 big
00:21:23 --> 00:21:25 pancake as a result of the conservation
00:21:25 --> 00:21:26 of the anual momentum there it flattens
00:21:26 --> 00:21:28 out into the pizza bear shape and if I
00:21:28 --> 00:21:30 tried it it either stick to the ceiling
00:21:30 --> 00:21:31 or hit me on the head it wouldn't go
00:21:31 --> 00:21:32 very
00:21:32 --> 00:21:35 well it's a slightly similar thing with
00:21:35 --> 00:21:37 the disc of material around planets and
00:21:37 --> 00:21:39 stars now what's happening is you you've
00:21:39 --> 00:21:42 got thing material collapsing into the
00:21:42 --> 00:21:44 star under Gravity forming the disc
00:21:44 --> 00:21:46 around it because there is a bit of
00:21:46 --> 00:21:48 rotation with that rotation as you spin
00:21:48 --> 00:21:50 in and you get to a smaller and smaller
00:21:50 --> 00:21:51 distance you move faster and faster and
00:21:52 --> 00:21:54 faster and that's why a gas cloud
00:21:54 --> 00:21:55 rotating every few million years gives
00:21:55 --> 00:21:58 you a St rotating every few days or
00:21:58 --> 00:22:00 every few hours it's like the ballerina
00:22:00 --> 00:22:02 bringing their arms in a Zid a spin they
00:22:02 --> 00:22:04 spin quicker and quicker but that also
00:22:04 --> 00:22:06 tends to lead to things collapsing into
00:22:06 --> 00:22:08 the plane because that's a bit again
00:22:08 --> 00:22:10 like the hydrostatic example that's kind
00:22:10 --> 00:22:12 of the lowest Energy Solution you're
00:22:12 --> 00:22:15 rotating around a given rotation axis
00:22:15 --> 00:22:17 you will collapse into a disc in that
00:22:17 --> 00:22:19 plane material that's coming in above
00:22:19 --> 00:22:22 that disc can just carry on orbiting
00:22:22 --> 00:22:24 normally but if there's more material in
00:22:24 --> 00:22:25 the disc there will be friction and it
00:22:25 --> 00:22:27 will get damped down and help to
00:22:27 --> 00:22:29 collapse down into there
00:22:29 --> 00:22:32 there but if the bulk is
00:22:32 --> 00:22:35 rotating with a with the same rotation
00:22:35 --> 00:22:36 axis anything fallowing in at high
00:22:36 --> 00:22:38 angles will probably just fall in and
00:22:38 --> 00:22:40 blop straight onto the star it's it's
00:22:40 --> 00:22:42 rotating that way but it's coming in
00:22:42 --> 00:22:44 here essentially yeah and I appreciate
00:22:44 --> 00:22:46 that description was really useful for
00:22:46 --> 00:22:47 the people who are on listening because
00:22:47 --> 00:22:49 they can't see me waving my Flappy hands
00:22:49 --> 00:22:51 around um but if you're coming in from
00:22:51 --> 00:22:53 near the pearls the little bit of
00:22:53 --> 00:22:55 rotation around isn't helping against
00:22:55 --> 00:22:56 you coming in directly towards the
00:22:56 --> 00:22:58 target if you're coming in from PS and
00:22:58 --> 00:23:00 you're going to hit onto the disc you'll
00:23:00 --> 00:23:02 be passing through all that material and
00:23:02 --> 00:23:04 that will damp you down a little bit so
00:23:04 --> 00:23:06 more inclined things will gradually get
00:23:06 --> 00:23:09 dumped down to add to the disc the discs
00:23:09 --> 00:23:11 we get there for around protoy our
00:23:11 --> 00:23:13 material that's falling in the rotation
00:23:13 --> 00:23:16 speeding it up you get a disc around
00:23:16 --> 00:23:18 that Proto star that this will be a bit
00:23:18 --> 00:23:19 flared it'll have a bit of height
00:23:19 --> 00:23:21 because there's a lot of Dynamics and
00:23:21 --> 00:23:24 stirring and things like that going on
00:23:24 --> 00:23:26 if you could have a big enough region
00:23:26 --> 00:23:27 around it you probably end up seeing a
00:23:27 --> 00:23:30 disc would eventually flare out until it
00:23:30 --> 00:23:31 becomes a background but you'd have
00:23:31 --> 00:23:33 almost cleared lobes above and below the
00:23:33 --> 00:23:35 star and that's kind of what we see with
00:23:35 --> 00:23:37 our small body population of the solar
00:23:37 --> 00:23:40 system as you go from the planets and
00:23:40 --> 00:23:42 the edge with cop Bel going further
00:23:42 --> 00:23:44 outwards you gradually come out towards
00:23:44 --> 00:23:45 the domain of the AR cloud and when
00:23:46 --> 00:23:47 you're far enough from the Sun things
00:23:47 --> 00:23:49 get stirred up by passing stars and get
00:23:49 --> 00:23:51 put back into a sphere because their
00:23:51 --> 00:23:53 tilts are all randomized so you've got a
00:23:54 --> 00:23:55 disc near the Sun and that's because the
00:23:55 --> 00:23:57 Sun's gravity is dominating the angular
00:23:57 --> 00:23:59 momentum's dominating
00:23:59 --> 00:24:01 when you're very far from the Sun you're
00:24:01 --> 00:24:03 only loosely held to the Sun so nudes
00:24:03 --> 00:24:04 from passing Stars can change your
00:24:04 --> 00:24:07 direction quite significantly and over
00:24:07 --> 00:24:08 the four billion years since the cell
00:24:08 --> 00:24:10 system formed that material that was
00:24:11 --> 00:24:12 flung out into the AR cloud in a disc
00:24:12 --> 00:24:14 because it was flung out from a disc has
00:24:15 --> 00:24:16 been smeared around so we now get a
00:24:16 --> 00:24:19 spherical is cloud around the Sun but
00:24:19 --> 00:24:20 when you're close enough to the Sun for
00:24:21 --> 00:24:23 the sun to dominate you'd have voids
00:24:23 --> 00:24:24 that are fairly empty above and below
00:24:24 --> 00:24:28 the plane and a disc load out so all
00:24:28 --> 00:24:30 complex and it's a couple of different
00:24:30 --> 00:24:33 Ms of physics interacting essentially
00:24:33 --> 00:24:35 yeah wow now i' I'd never wondered about
00:24:35 --> 00:24:37 it and I'm glad Dean asked the question
00:24:37 --> 00:24:41 because uh yeah it it it really is
00:24:41 --> 00:24:44 interesting science uh hydrostatic
00:24:44 --> 00:24:45 equili
00:24:48 --> 00:24:50 equilibrium it's a really good example
00:24:50 --> 00:24:51 of how science works and how we do it
00:24:51 --> 00:24:53 actually because that's exactly the
00:24:53 --> 00:24:54 scientific process you see something you
00:24:54 --> 00:24:57 go why is that and sat's a great example
00:24:57 --> 00:24:59 you look at sat and then say oblet
00:24:59 --> 00:25:01 spheroid it's a bit of an elonga Blobby
00:25:01 --> 00:25:03 thing but it's nearly spherical really
00:25:03 --> 00:25:05 first order and yet it's got a disc of
00:25:05 --> 00:25:06 material around it why isn't the disc
00:25:07 --> 00:25:09 all block you know and so that's what
00:25:09 --> 00:25:11 leads us down that Journey Discovery to
00:25:11 --> 00:25:13 figure all this stuff out so that's just
00:25:13 --> 00:25:15 how science works and it's very fun
00:25:15 --> 00:25:17 brilliant question thank you Dane lovely
00:25:17 --> 00:25:20 to hear from you this is Space Nuts with
00:25:20 --> 00:25:25 Andrew Dunley and johy
00:25:25 --> 00:25:28 hona 3 2 1
00:25:28 --> 00:25:32 Space Nuts uh our next question uh I
00:25:32 --> 00:25:35 really love this one comes from Anne in
00:25:35 --> 00:25:37 Belleview Washington I have a question
00:25:37 --> 00:25:40 about calcium and astronauts on Earth
00:25:40 --> 00:25:42 estrogen helps prevent calcium loss from
00:25:42 --> 00:25:47 bones do premenopausal astronauts lose
00:25:47 --> 00:25:51 less bone or regone uh regain bone
00:25:51 --> 00:25:55 faster than male or postmenopausal
00:25:55 --> 00:25:58 astronauts uh do does hormone
00:25:58 --> 00:26:00 replacement therapy help postmen
00:26:00 --> 00:26:03 menopausal astronauts regain bone it's a
00:26:03 --> 00:26:06 really great question uh and says thanks
00:26:06 --> 00:26:08 for the interesting podcast appreciate
00:26:08 --> 00:26:10 that an thanks for the interesting
00:26:10 --> 00:26:13 question um I know this isn't your area
00:26:13 --> 00:26:16 but I know you've done your homework
00:26:16 --> 00:26:17 yeah I've done a little bit reading it's
00:26:17 --> 00:26:18 a fascinating question and me it's a
00:26:19 --> 00:26:20 really important question to ask because
00:26:20 --> 00:26:23 there's a lot of Investigations into the
00:26:23 --> 00:26:25 impact of being in space that are going
00:26:25 --> 00:26:27 on particularly given that there's a
00:26:27 --> 00:26:30 future where people aspire to travel to
00:26:30 --> 00:26:32 Mars and live there or have you know
00:26:32 --> 00:26:34 space stations where people live
00:26:34 --> 00:26:36 full-time go colonize the asteroids
00:26:36 --> 00:26:38 things like that yeah um it's not my
00:26:38 --> 00:26:40 area of expertise by any means I'm not a
00:26:40 --> 00:26:42 biologist or a bi
00:26:42 --> 00:26:44 biomechanist um but it is something
00:26:44 --> 00:26:47 people are starting to do research into
00:26:47 --> 00:26:49 um I haven't been able to find anything
00:26:49 --> 00:26:51 about the difference between pre and
00:26:51 --> 00:26:55 postmenopause or about um estrogen
00:26:55 --> 00:26:56 supplements and things like that that's
00:26:56 --> 00:26:58 a really interesting question and it's
00:26:58 --> 00:27:00 almost possibly the kind of thing where
00:27:00 --> 00:27:02 you could find someone leading that kind
00:27:02 --> 00:27:03 of research and try and get involved if
00:27:03 --> 00:27:04 you want to but I did do a bit of
00:27:04 --> 00:27:07 digging around I found there is a paper
00:27:07 --> 00:27:11 that was published I found it on PubMed
00:27:11 --> 00:27:13 that was published a few years ago in
00:27:13 --> 00:27:16 2014 entitled men and women in space bur
00:27:16 --> 00:27:18 loss and kidney stone risk after long
00:27:18 --> 00:27:21 deoration space flight um which is a
00:27:21 --> 00:27:25 slightly intimidating title but they
00:27:25 --> 00:27:28 note there that finally at that stage
00:27:28 --> 00:27:31 had been enough people who identified as
00:27:31 --> 00:27:33 male and identified as female that had
00:27:33 --> 00:27:35 spent a long time in space that you
00:27:35 --> 00:27:36 could start doing a quantitative
00:27:36 --> 00:27:39 comparison they had in their sample 33
00:27:39 --> 00:27:41 men and nine women who had spent long
00:27:41 --> 00:27:44 duration missions on the space station
00:27:44 --> 00:27:46 and
00:27:46 --> 00:27:48 their bodies had been studied when they
00:27:48 --> 00:27:50 got back essentially so think like bone
00:27:50 --> 00:27:53 mineral density was evaluated before and
00:27:53 --> 00:27:55 after the flight and stuff like that and
00:27:55 --> 00:27:57 they also looked at blood and urine to
00:27:57 --> 00:27:58 look at kidney function
00:27:58 --> 00:28:02 the missions were 50 days to 215 days
00:28:02 --> 00:28:06 flown in this Millennium so 20 to 2012
00:28:06 --> 00:28:08 what they found was the following I'll
00:28:08 --> 00:28:09 read it out explicitly they said the
00:28:09 --> 00:28:11 bond density response to space flight
00:28:11 --> 00:28:13 was the same for men and women in both
00:28:13 --> 00:28:16 exercise groups so no difference um bone
00:28:16 --> 00:28:18 density response to flight was the same
00:28:18 --> 00:28:20 for men and women and the typical
00:28:20 --> 00:28:23 decrease in bone mineral density whole
00:28:23 --> 00:28:25 body and Regional afterlight was not
00:28:25 --> 00:28:27 observed for either sex for people who
00:28:27 --> 00:28:29 were using the Advanced resistance
00:28:29 --> 00:28:30 devices so they were able to recover
00:28:30 --> 00:28:33 equally well um so the fundamental
00:28:33 --> 00:28:35 comment there have a final sentence of
00:28:35 --> 00:28:37 their obstruct is the responses of men
00:28:37 --> 00:28:39 and women to space flight with respect
00:28:39 --> 00:28:42 to measures of born Health were not
00:28:42 --> 00:28:45 different which is really interesting
00:28:45 --> 00:28:48 yeah um it doesn't entirely talk about
00:28:48 --> 00:28:49 the importance of the hormones but I
00:28:49 --> 00:28:53 guess the fact that um women who are
00:28:53 --> 00:28:56 premenopause and Men experienc their
00:28:56 --> 00:28:58 bond density degradation at the same
00:28:58 --> 00:29:01 rate suggests that the elevated levels
00:29:01 --> 00:29:04 of estrogen in the women did not prevent
00:29:04 --> 00:29:06 that Bond density loss doesn't say
00:29:06 --> 00:29:07 anything about the speed at which the
00:29:07 --> 00:29:09 bond enity was recovered when they were
00:29:09 --> 00:29:12 back so I can't really comment on that
00:29:12 --> 00:29:16 but it reminded me more widely of a the
00:29:16 --> 00:29:18 risks of space flat but also the amount
00:29:18 --> 00:29:19 that we don't know and the importance of
00:29:19 --> 00:29:21 getting people with different expertises
00:29:21 --> 00:29:25 involved but also the importance of
00:29:25 --> 00:29:28 doctors and medical researchers studying
00:29:28 --> 00:29:30 women as well as men and I know from a
00:29:30 --> 00:29:31 number of my female friends that they
00:29:31 --> 00:29:35 feel very much that a lot of medications
00:29:35 --> 00:29:37 a lot of treatments assume that the male
00:29:37 --> 00:29:39 body is the normal one and Studies have
00:29:39 --> 00:29:40 not been carried out to such a great
00:29:40 --> 00:29:43 extent on the different impact of that
00:29:43 --> 00:29:46 same medication on the female body true
00:29:46 --> 00:29:47 and I've also heard of problems where
00:29:47 --> 00:29:49 male doctors have not been as well
00:29:49 --> 00:29:51 educated in female problems as they
00:29:51 --> 00:29:52 should have been and giving fairly
00:29:52 --> 00:29:54 rubbish responses so you know
00:29:54 --> 00:29:55 acknowledging those biases and
00:29:55 --> 00:29:56 acknowledging that I'm in a very
00:29:56 --> 00:29:59 privileged situation but we need more
00:29:59 --> 00:30:01 research into this NASA has on its
00:30:01 --> 00:30:03 website a statement here talking about
00:30:03 --> 00:30:07 the degree of impact on bone density so
00:30:07 --> 00:30:09 their statement is astronauts can lose
00:30:09 --> 00:30:11 up to 1 to two% of bone density per
00:30:11 --> 00:30:14 month in the hip and the
00:30:14 --> 00:30:18 spine that compares to 0.5 to 1% per
00:30:18 --> 00:30:20 year in postmenopausal women and much
00:30:20 --> 00:30:23 older men on Earth so in other words the
00:30:23 --> 00:30:24 bone loss that you're getting while
00:30:24 --> 00:30:27 you're in microgravity in space is
00:30:27 --> 00:30:29 around twice as significant as that that
00:30:29 --> 00:30:32 you experien C menopause for women all
00:30:32 --> 00:30:34 when you become significantly older for
00:30:34 --> 00:30:37 men um and that they say this rapid bone
00:30:37 --> 00:30:38 loss comp play crew members at risk for
00:30:38 --> 00:30:40 bone fractur and risk of alance
00:30:40 --> 00:30:42 osteoporosis as a result of the space
00:30:42 --> 00:30:44 flight yeah there's another study which
00:30:44 --> 00:30:46 I just stumbled across looking on this
00:30:46 --> 00:30:48 um female astronauts impact of space
00:30:49 --> 00:30:51 radiation on menopause this came out a
00:30:51 --> 00:30:54 bit more recently in April 2022 and it
00:30:54 --> 00:30:56 shows people are starting to think about
00:30:56 --> 00:30:58 this so this is a a study that is
00:30:58 --> 00:31:00 looking at the impacts of the radiation
00:31:00 --> 00:31:03 environment that you experience in space
00:31:03 --> 00:31:05 on what they call the avarian reserve so
00:31:05 --> 00:31:06 the number of viable eggs that a woman
00:31:06 --> 00:31:09 has and so the statement that really
00:31:09 --> 00:31:11 made my head hurt here is that data
00:31:11 --> 00:31:14 suggests that a typical Mars mission may
00:31:14 --> 00:31:16 reduce a woman's avarian Reserve by
00:31:16 --> 00:31:18 about 50% whoa this would have
00:31:18 --> 00:31:20 consequences to a woman's reproductive
00:31:20 --> 00:31:22 capacity and more significantly
00:31:22 --> 00:31:24 decreases the time interval to her
00:31:24 --> 00:31:28 menopause so it all reminds me slightly
00:31:28 --> 00:31:30 off topic but it this was prompted by
00:31:30 --> 00:31:32 this question I every year go to the
00:31:32 --> 00:31:34 Australian space research conference
00:31:34 --> 00:31:35 here in Australia which is a fabulous
00:31:35 --> 00:31:37 meeting and can be quite
00:31:37 --> 00:31:39 multidisciplinary but a few years ago I
00:31:39 --> 00:31:43 think possibly like 2013 2014 now we had
00:31:43 --> 00:31:47 a invited lecture from a doctor it's a
00:31:47 --> 00:31:48 doctor from Tasmania who works in space
00:31:49 --> 00:31:51 medicine as research on the site and
00:31:51 --> 00:31:53 it's the only lecture I've ever been to
00:31:53 --> 00:31:55 at a research conference which started
00:31:55 --> 00:31:57 with a trigger warning and a health
00:31:57 --> 00:31:59 warning and that was basically if
00:31:59 --> 00:32:00 there's anybody in the audience who's a
00:32:00 --> 00:32:02 bit squeamish a bit sensitive he might
00:32:02 --> 00:32:03 want to leave now this is going to be a
00:32:03 --> 00:32:06 medical talk and you're all astronomers
00:32:06 --> 00:32:09 and space researchers yeah and it
00:32:09 --> 00:32:12 included some fairly unsettling pictures
00:32:12 --> 00:32:14 that I won't relay in too much detail
00:32:14 --> 00:32:17 but this doctor was talking about the
00:32:17 --> 00:32:20 future aspiration of humanity to have a
00:32:20 --> 00:32:23 permanent presence on other astronomical
00:32:23 --> 00:32:25 bodies talk in particular about
00:32:25 --> 00:32:29 Ms and what he was speaking to was that
00:32:29 --> 00:32:31 our science fiction view of that is that
00:32:31 --> 00:32:33 you have a population on Mars that is
00:32:33 --> 00:32:35 independent so they reproduce and
00:32:35 --> 00:32:38 repopulate themselves that's what we
00:32:38 --> 00:32:41 think of and he said it isn't as simple
00:32:41 --> 00:32:42 as that from a doctor's point of view
00:32:42 --> 00:32:44 from someone who studied pregnancy he
00:32:44 --> 00:32:48 was talking about the requirement the
00:32:48 --> 00:32:50 importance of gravity to gravity to
00:32:50 --> 00:32:51 pregnancy is something we never think
00:32:51 --> 00:32:53 about because we're all living on the
00:32:53 --> 00:32:56 surface of the Earth at one G but he
00:32:56 --> 00:32:59 said it's actually the case and remember
00:32:59 --> 00:33:00 I'm remembering a talk here from more
00:33:00 --> 00:33:03 than a decade ago he spoke about how
00:33:03 --> 00:33:06 important the gravity that you are
00:33:06 --> 00:33:09 moving within is to the development of
00:33:09 --> 00:33:10 the fetus and the way that the cells
00:33:10 --> 00:33:13 know what to make and what shape to make
00:33:13 --> 00:33:15 and he gave the example of how even a
00:33:15 --> 00:33:18 very small change from the standard
00:33:18 --> 00:33:21 atmospheric temperature and pressure and
00:33:21 --> 00:33:23 gravity can cause huge Problems by
00:33:24 --> 00:33:25 talking about the invasion of the
00:33:25 --> 00:33:28 Spanish into South America and in the
00:33:28 --> 00:33:30 1600s and the fact that the high Andes
00:33:30 --> 00:33:32 were never conquered permanently because
00:33:32 --> 00:33:35 the Conquistadors couldn't reproduce
00:33:35 --> 00:33:37 there they were just not able to be
00:33:37 --> 00:33:39 viable there and the native people there
00:33:39 --> 00:33:41 had obviously adusted over many many
00:33:41 --> 00:33:43 generations and he said that's barely
00:33:43 --> 00:33:45 any different to the conditions
00:33:45 --> 00:33:48 here what he was going on to say was
00:33:48 --> 00:33:51 that his vision is that because of this
00:33:51 --> 00:33:53 this would be so insurmountable that for
00:33:53 --> 00:33:55 a very long time once we have a
00:33:55 --> 00:33:56 permanent presence on Mars it would be a
00:33:57 --> 00:33:58 retirement heart
00:33:58 --> 00:34:00 it'll be somewhere that people go to
00:34:00 --> 00:34:01 after they've saw their wild arts on
00:34:01 --> 00:34:04 Earth that they go to to spend their
00:34:04 --> 00:34:06 later years in a in a more pleasant
00:34:06 --> 00:34:08 environment with lower gravity less
00:34:08 --> 00:34:12 strands on an on an aging aching body
00:34:12 --> 00:34:14 but he didn't foresee any possibility of
00:34:14 --> 00:34:17 people reproducing that and unless we
00:34:17 --> 00:34:19 went down the incredibly distopian
00:34:19 --> 00:34:22 worldview of having women living in
00:34:22 --> 00:34:24 centrifuges for nine months to simulate
00:34:24 --> 00:34:27 1 G which I I can imagine would not be a
00:34:27 --> 00:34:31 very popular decision but it ties into
00:34:31 --> 00:34:34 Mars one which was this attempt by I
00:34:34 --> 00:34:37 think a Dutch um guy to make a lot of
00:34:37 --> 00:34:40 money out of sending a mission to Mars
00:34:40 --> 00:34:43 to try and get the first humans on Mars
00:34:43 --> 00:34:45 and they run a huge competition process
00:34:45 --> 00:34:47 for this with more than 100 initial
00:34:47 --> 00:34:48 applicants and they whittled them down
00:34:48 --> 00:34:50 and whittel them down but there was an
00:34:50 --> 00:34:52 Australian involved in this guy called
00:34:52 --> 00:34:53 Josh Richards who's a fabulous science
00:34:53 --> 00:34:55 communicator and did a lot of work off
00:34:55 --> 00:34:58 the back of this of going into schs and
00:34:58 --> 00:34:59 talking to kids and saying I could be
00:34:59 --> 00:35:01 the first person on M ask me anything
00:35:01 --> 00:35:04 essentially one of the things that Josh
00:35:04 --> 00:35:06 told me that led to problems and in the
00:35:06 --> 00:35:08 end led to the breakup of his
00:35:08 --> 00:35:09 relationship with his partner as he went
00:35:09 --> 00:35:12 through this process was that a he was
00:35:12 --> 00:35:14 looking at taking a oneway trip to Mars
00:35:14 --> 00:35:17 um but also that the people who were the
00:35:17 --> 00:35:20 final selected ones had to agree to be
00:35:20 --> 00:35:23 medically sterilized before they got on
00:35:23 --> 00:35:26 the trip to Mars because they were going
00:35:26 --> 00:35:28 from mix to crew the mix crew had to
00:35:28 --> 00:35:30 make their own entertainment during the
00:35:30 --> 00:35:32 travels and because his show was going
00:35:32 --> 00:35:34 to be delivered Big Brother style that
00:35:34 --> 00:35:36 was probably part of the motivation for
00:35:36 --> 00:35:37 people subscribing to
00:35:37 --> 00:35:41 beis the lack of understanding of the
00:35:41 --> 00:35:43 possibilities and the risks of pregnancy
00:35:43 --> 00:35:45 during space fight in micro gravity or
00:35:45 --> 00:35:49 on Mars in incredibly reduced gravity
00:35:49 --> 00:35:50 was such that nobody could see any
00:35:50 --> 00:35:52 possibility of any viability of
00:35:52 --> 00:35:54 pregnancy but it wasn't like they were
00:35:54 --> 00:35:56 going to send people with the medical
00:35:56 --> 00:35:58 skills to deal with traumatic problems
00:35:58 --> 00:36:01 like that on the mission so you had to
00:36:01 --> 00:36:02 agree to either be sterilized or you
00:36:02 --> 00:36:04 wouldn't go and the pick someone else
00:36:04 --> 00:36:06 which sounds really
00:36:06 --> 00:36:08 barbaric but it's the unfortunate
00:36:08 --> 00:36:10 reality we're going to have to deal with
00:36:10 --> 00:36:12 when we start looking at having a
00:36:12 --> 00:36:14 permanent presence of Earth rather than
00:36:14 --> 00:36:16 just going and visiting because if we
00:36:16 --> 00:36:18 want to have a perent presence on the
00:36:18 --> 00:36:21 moon or on Mars we view that inherently
00:36:21 --> 00:36:23 as humans has been a self-replicating
00:36:23 --> 00:36:25 presence we view it as been a presence
00:36:25 --> 00:36:27 that can sustain itself you know so if
00:36:27 --> 00:36:29 the population of Earth got wiped out at
00:36:29 --> 00:36:31 least we've got the people on Mars but
00:36:31 --> 00:36:33 in order to do that it's going to need
00:36:33 --> 00:36:35 an incredible amount of medical research
00:36:35 --> 00:36:38 to be done and incredible advances in
00:36:38 --> 00:36:40 medical technology that we just don't
00:36:40 --> 00:36:43 have yet and what's been asked in the
00:36:43 --> 00:36:45 question here about Bond density in
00:36:45 --> 00:36:47 space about the role of estrogen in
00:36:47 --> 00:36:49 replacing the bonds afterwards on the
00:36:49 --> 00:36:51 impact of people who are passed to
00:36:51 --> 00:36:53 premenopausal that all comes into it as
00:36:53 --> 00:36:54 well because we can't just do the
00:36:55 --> 00:36:56 research quite frankly on Old
00:36:56 --> 00:36:58 middle-aged white guys
00:36:58 --> 00:37:00 we need to look at the diversity not
00:37:00 --> 00:37:03 just in terms of gender diversity but as
00:37:03 --> 00:37:05 we move forward our different groups of
00:37:05 --> 00:37:08 people better suited or Worse suited to
00:37:08 --> 00:37:10 life in space we know that people from
00:37:10 --> 00:37:12 different cultures and different
00:37:12 --> 00:37:14 countries have slightly different
00:37:14 --> 00:37:17 physiological properties there will need
00:37:17 --> 00:37:18 to be research done into this and we'll
00:37:18 --> 00:37:20 need to look at people across the whole
00:37:20 --> 00:37:22 spectrum of humanity to understand it
00:37:22 --> 00:37:24 rather than just basing everything on
00:37:24 --> 00:37:26 the first few people went to space who
00:37:26 --> 00:37:29 were pretty much uniformly very athletic
00:37:29 --> 00:37:32 very well Tred white men of a certain
00:37:32 --> 00:37:34 ede that's just one part of his subset
00:37:34 --> 00:37:36 so it's a really interesting question I
00:37:36 --> 00:37:38 don't have more answers to that but
00:37:38 --> 00:37:40 really thank you for asking it make
00:37:40 --> 00:37:42 there's a lot to think about and it does
00:37:42 --> 00:37:43 make my head hurt in a very different
00:37:44 --> 00:37:45 way to the cosmology making my head hurt
00:37:45 --> 00:37:46 thing it's a different part of my brain
00:37:47 --> 00:37:48 that's hurting at the minute yes
00:37:48 --> 00:37:51 absolutely I I can tell you that uh you
00:37:51 --> 00:37:53 know when it comes to studies into
00:37:53 --> 00:37:55 medicines that you referred to um my
00:37:55 --> 00:37:58 wife and I have experienced firstand and
00:37:58 --> 00:38:00 the effective medicines that have been
00:38:00 --> 00:38:05 created and developed for men yeah um by
00:38:05 --> 00:38:07 default not purposely developed for men
00:38:07 --> 00:38:09 just developed for everybody but based
00:38:09 --> 00:38:10 on the
00:38:10 --> 00:38:14 physiological uh male um I can take an
00:38:15 --> 00:38:17 antibiotic and not feel a thing my wife
00:38:17 --> 00:38:19 can take the same tablet and she's sick
00:38:19 --> 00:38:23 for a day classic example of it so I I
00:38:23 --> 00:38:24 know exactly what you're talking about
00:38:24 --> 00:38:26 there needs to be a lot more research
00:38:26 --> 00:38:30 into medicines for wom um to suit their
00:38:30 --> 00:38:33 physiology uh also an I can tell you
00:38:33 --> 00:38:36 that um people on Earth suffer the same
00:38:36 --> 00:38:38 problems as they do in space
00:38:38 --> 00:38:40 particularly people who are uh
00:38:40 --> 00:38:42 undergoing hormone therapy for cancer
00:38:42 --> 00:38:46 treatment they lose muscle mass and bone
00:38:46 --> 00:38:49 density and in long-term therapy can
00:38:49 --> 00:38:50 develop
00:38:50 --> 00:38:53 osteoporosis and the solution to that is
00:38:53 --> 00:38:56 exercise but it's um yeah it's it's a
00:38:56 --> 00:38:57 tough battle
00:38:58 --> 00:39:01 um I'm all too aware of it myself but uh
00:39:01 --> 00:39:04 it's yeah that it's the same problem on
00:39:04 --> 00:39:06 earth when it comes to to treating
00:39:06 --> 00:39:08 cancer at the moment with some kinds of
00:39:08 --> 00:39:10 hormone therapy but thanks for the
00:39:10 --> 00:39:12 question brilliant question loved it
00:39:12 --> 00:39:14 keep them coming uh our final question
00:39:14 --> 00:39:18 comes from Dean two Dean two because we
00:39:18 --> 00:39:20 had Dean earlier sorry Dean two you
00:39:20 --> 00:39:21 became Dean two because you're the
00:39:21 --> 00:39:23 second on the
00:39:23 --> 00:39:27 list it pardon aie Dean uh yeah think so
00:39:27 --> 00:39:30 let's find out hi Fred and Andrew this
00:39:30 --> 00:39:32 is Dean in redcliff in Queensland can
00:39:32 --> 00:39:34 you explain why there is a fixed amount
00:39:34 --> 00:39:36 of centrifugal force measurable on an
00:39:36 --> 00:39:39 object at the earth's equator but its
00:39:39 --> 00:39:41 angular velocity which is the cause of
00:39:41 --> 00:39:44 this apparent force can only be measured
00:39:44 --> 00:39:46 relative to another object's frame of
00:39:46 --> 00:39:49 reference what I mean is an 80 kilogram
00:39:49 --> 00:39:51 person should weigh about 300 gram less
00:39:51 --> 00:39:53 at the equator than at the pole and this
00:39:53 --> 00:39:55 can be measured however the calculation
00:39:55 --> 00:39:58 for centrifugal force uses the angular
00:39:58 --> 00:40:00 velocity of the person going around the
00:40:00 --> 00:40:03 earth axis which is measured using the
00:40:03 --> 00:40:06 frequency of the earth spin where the
00:40:06 --> 00:40:07 Earth's diameter and circumference are
00:40:07 --> 00:40:10 fixed the Earth spins once in 24 hours
00:40:11 --> 00:40:14 relative to the sun once in 24 hours 40
00:40:14 --> 00:40:16 minutes relative to the moon and once in
00:40:16 --> 00:40:20 23 hours 56 minutes relative to distant
00:40:20 --> 00:40:22 Stars although these frequencies are all
00:40:22 --> 00:40:25 fairly close they would each give
00:40:25 --> 00:40:27 different answers to the calculation yet
00:40:27 --> 00:40:29 we can measure centrifugal force as a
00:40:29 --> 00:40:34 fixed amount although objects in all
00:40:34 --> 00:40:36 objects in space are moving I suspect
00:40:36 --> 00:40:38 that space itself does not move even
00:40:38 --> 00:40:42 though it's expanding so does space time
00:40:42 --> 00:40:44 have a fixed structure that determines
00:40:44 --> 00:40:46 Direction without reference to objects
00:40:46 --> 00:40:50 within it thanks for the podcast wow
00:40:50 --> 00:40:52 thanks Dane we sort of hinted at
00:40:52 --> 00:40:55 centrifugal force earlier but this is a
00:40:55 --> 00:40:56 kind of this is a different angle on it
00:40:57 --> 00:41:00 B boom boom boom it's an awesome
00:41:00 --> 00:41:01 question there's a couple of different
00:41:01 --> 00:41:04 parts to it so I'll initially talk about
00:41:04 --> 00:41:07 the effect of the earth rotation on your
00:41:07 --> 00:41:09 weight I think that's a good one in
00:41:09 --> 00:41:12 terms of the dependence on reference
00:41:12 --> 00:41:14 frame there isn't really dependence on a
00:41:14 --> 00:41:17 reference frame for it because what we
00:41:17 --> 00:41:20 measure is what is actually happening so
00:41:20 --> 00:41:23 the Earth rotates at a certain speed and
00:41:23 --> 00:41:25 because you're moving at that speed
00:41:25 --> 00:41:28 you've got gravity pulling you down
00:41:28 --> 00:41:30 but the movement that you've got the
00:41:30 --> 00:41:32 rotation is carrying you off at right
00:41:32 --> 00:41:34 angles to gravity and you're kind of
00:41:34 --> 00:41:36 falling around as you go around so
00:41:36 --> 00:41:38 because you're not falling into the
00:41:38 --> 00:41:40 Earth but you're also not escaping from
00:41:40 --> 00:41:42 the earth because of your movement so
00:41:42 --> 00:41:43 there there's a little bit of an outward
00:41:43 --> 00:41:46 false balancing gravity that's the net
00:41:46 --> 00:41:48 result of it so we we can work this
00:41:48 --> 00:41:50 through with all the maths and I
00:41:50 --> 00:41:51 sometimes do this derivation from my
00:41:51 --> 00:41:53 students it's kind of vaguely elegant
00:41:53 --> 00:41:55 and again the orbital period for things
00:41:55 --> 00:41:58 you can do this kind of mats
00:41:58 --> 00:42:00 what's effectively happening though is
00:42:00 --> 00:42:03 that you have an acceleration going on
00:42:03 --> 00:42:06 you're you're an accelerating object and
00:42:06 --> 00:42:07 because of your motion as you rotate
00:42:07 --> 00:42:10 around the earth you do one full app in
00:42:10 --> 00:42:12 a certain amount of time that means it
00:42:12 --> 00:42:14 is as though you're being pulled towards
00:42:14 --> 00:42:15 the Middle with a certain acceleration
00:42:15 --> 00:42:17 and that's the acceleration due to
00:42:17 --> 00:42:20 gravity you feel and the faster you spin
00:42:20 --> 00:42:22 the lower that pull towards the middle
00:42:23 --> 00:42:24 feels like it is because you're offset
00:42:24 --> 00:42:27 by the you know centrifugal force you
00:42:27 --> 00:42:29 feel which is a virtual force feeling
00:42:29 --> 00:42:31 like it's pushing outwards by
00:42:31 --> 00:42:34 comparison the real number you measure
00:42:34 --> 00:42:37 is based around what the acceleration on
00:42:37 --> 00:42:38 your body actually is and that's
00:42:38 --> 00:42:40 something that's
00:42:40 --> 00:42:42 quantifiable and that is down to you
00:42:42 --> 00:42:45 completing exactly one lap of the Earth
00:42:45 --> 00:42:49 in the reference frame of the earth so
00:42:49 --> 00:42:50 that's the one thing that was missing
00:42:50 --> 00:42:52 from this we talk about the sun we talk
00:42:52 --> 00:42:53 about the distant Stars we talk about
00:42:53 --> 00:42:55 the moon but in reality you're talking
00:42:55 --> 00:42:58 about in the Earth rest frame so you're
00:42:58 --> 00:43:00 going around in a circle around the
00:43:00 --> 00:43:03 center of the earth that takes you 23
00:43:03 --> 00:43:06 hours 56 minutes and 4 seconds the
00:43:06 --> 00:43:08 distance stars are just a reference
00:43:08 --> 00:43:09 point where we can see that far but it's
00:43:09 --> 00:43:11 all relative to the position of the
00:43:11 --> 00:43:14 earth and so that's what gives you your
00:43:14 --> 00:43:17 300 grams less the sun and the moon are
00:43:17 --> 00:43:20 also moving in the rest frame of the
00:43:20 --> 00:43:22 Earth the Sun does one full lap around
00:43:23 --> 00:43:25 the Earth in one year the moon does one
00:43:25 --> 00:43:27 full lap in one month so that's why
00:43:27 --> 00:43:29 you've got those slightly longer times
00:43:29 --> 00:43:30 because the Earth's got to turn a little
00:43:30 --> 00:43:32 bit more than one full Revolution before
00:43:32 --> 00:43:34 the sun is directly overhead or before
00:43:34 --> 00:43:36 the Moon is directly over head so that
00:43:36 --> 00:43:38 isn't a rest frame that's a moving frame
00:43:38 --> 00:43:41 that's a rotating frame essentially if
00:43:41 --> 00:43:42 you measure it with respect to the
00:43:42 --> 00:43:44 sunbean over head the whole of the
00:43:44 --> 00:43:46 Earth's frame has had to rotate round in
00:43:46 --> 00:43:48 that case it brings us on to the
00:43:48 --> 00:43:51 concepts of rest frames and how you
00:43:51 --> 00:43:53 measure them and what is the universal
00:43:53 --> 00:43:57 rest frame um that's again where it gets
00:43:57 --> 00:44:00 really really headachy now to my
00:44:00 --> 00:44:02 knowledge it isn't thought in any of the
00:44:02 --> 00:44:08 models of space time but SpaceTime is
00:44:08 --> 00:44:10 fixed and distinct from the objects
00:44:10 --> 00:44:13 within it rather any object that is
00:44:13 --> 00:44:16 moving at a fixed speed and not
00:44:16 --> 00:44:19 experiencing any
00:44:19 --> 00:44:23 acceleration is in a rest frame it's at
00:44:23 --> 00:44:25 rest locally it's not
00:44:25 --> 00:44:27 accelerating and so it can look out at
00:44:27 --> 00:44:31 the entire universe from its perspective
00:44:31 --> 00:44:33 and any accelerations that it sees and
00:44:33 --> 00:44:35 any motions that it sees of what's
00:44:35 --> 00:44:38 actually happening out there if you're
00:44:38 --> 00:44:39 in an accelerating rest frame you are
00:44:39 --> 00:44:41 not in a rest frame by definition
00:44:41 --> 00:44:44 because you're accelerating so a person
00:44:44 --> 00:44:45 on the surface of the Earth is
00:44:45 --> 00:44:48 accelerating as we go around the earth
00:44:48 --> 00:44:50 as the Earth rotates and as the earth
00:44:50 --> 00:44:52 goes around the Sun and as the Earth
00:44:52 --> 00:44:53 orbits in the center of mass of the
00:44:53 --> 00:44:56 Earth Moon system and all the rest of it
00:44:56 --> 00:44:58 so we're not at actually in what I think
00:44:58 --> 00:45:01 is often described as an inertial
00:45:01 --> 00:45:04 threat however you you do a lot of
00:45:04 --> 00:45:07 thought experiments that are near enough
00:45:07 --> 00:45:09 if you were free floating in space away
00:45:09 --> 00:45:11 from any of the Stars you'd probably
00:45:11 --> 00:45:12 consider yourself to be an inertial
00:45:12 --> 00:45:14 friend but even then you'd have some
00:45:14 --> 00:45:15 acceleration from the
00:45:15 --> 00:45:19 STS there isn't really as far as I know
00:45:19 --> 00:45:20 and this is where we get onto the
00:45:20 --> 00:45:23 cosmology stuff which is more woolly for
00:45:23 --> 00:45:25 me and so I'm giving a less accurate and
00:45:25 --> 00:45:27 less good quality answer apologize for
00:45:27 --> 00:45:30 that but there isn't to my knowledge any
00:45:30 --> 00:45:33 universally accepted rest threat because
00:45:33 --> 00:45:34 everything is moving and everything is
00:45:34 --> 00:45:36 accelerating and feeling the gravity of
00:45:36 --> 00:45:39 everything else but the way that our
00:45:39 --> 00:45:42 models of the universe work is that they
00:45:42 --> 00:45:44 have this concept of SpaceTime but it
00:45:44 --> 00:45:46 isn't like space time is a fra fabric
00:45:47 --> 00:45:48 that is physical over which everything
00:45:48 --> 00:45:51 moves and is itself fixed even space
00:45:51 --> 00:45:54 time is moving and dragged around I'm
00:45:54 --> 00:45:57 aware that this is an answer that
00:45:57 --> 00:45:59 quickly devolving from sensible into the
00:45:59 --> 00:46:01 incoherent and that's because this is
00:46:01 --> 00:46:02 pushing the the limits of what my
00:46:02 --> 00:46:05 knowledge is but it's also pushing the
00:46:05 --> 00:46:07 conceptual limits on which we build the
00:46:07 --> 00:46:09 foundations of stuff and that's because
00:46:09 --> 00:46:11 a lot of the models and particular a lot
00:46:11 --> 00:46:13 of the way the models we use are
00:46:13 --> 00:46:16 described we simplify things to make it
00:46:16 --> 00:46:18 clearer how everything
00:46:18 --> 00:46:21 works you know so we talk about an
00:46:21 --> 00:46:22 object at rest you know people are
00:46:22 --> 00:46:24 explaining special relativity for the
00:46:24 --> 00:46:26 first time will talk about an object at
00:46:26 --> 00:46:28 rest than another object moving at a
00:46:28 --> 00:46:30 fine XX that is near the speed of like
00:46:30 --> 00:46:32 relative to it and that's a great
00:46:32 --> 00:46:35 thought experiment the reality is a lot
00:46:35 --> 00:46:37 of the time that we are so close to
00:46:37 --> 00:46:39 being in that situation that you can
00:46:39 --> 00:46:41 ignore the effects of the little bits at
00:46:41 --> 00:46:43 turb it unless you've got incredibly
00:46:43 --> 00:46:45 good measuring equipment so from the
00:46:45 --> 00:46:47 point of view of to totally switch
00:46:47 --> 00:46:49 analogies I was watching the cricket the
00:46:49 --> 00:46:51 other night if you imagine two
00:46:51 --> 00:46:53 cricketers and somebody running in and
00:46:53 --> 00:46:55 bowling the cricket ball but instead of
00:46:55 --> 00:46:57 it bouncing it just goes straight on so
00:46:57 --> 00:46:59 it's a full toss it's a beamer um nasty
00:46:59 --> 00:47:02 delivery boo his y all the rest of it
00:47:02 --> 00:47:05 the only thing that is going on in terms
00:47:05 --> 00:47:06 of predicting the trajectory of that
00:47:06 --> 00:47:09 ball is that it has that acceleration
00:47:09 --> 00:47:10 pulling it down there's a little bit of
00:47:10 --> 00:47:13 air resistance as well if the ball's
00:47:13 --> 00:47:15 spinning you get boli effects and things
00:47:15 --> 00:47:17 that can cause it swerve but that ball
00:47:17 --> 00:47:20 is moving and we can treat it as the
00:47:20 --> 00:47:22 cricet pitch and all of the players are
00:47:22 --> 00:47:24 in a shared initial rest frame there's
00:47:24 --> 00:47:26 nothing else going on other than this
00:47:26 --> 00:47:27 single gravity ational Force pulling
00:47:27 --> 00:47:30 down we don't have to take account of
00:47:30 --> 00:47:33 things like the coris effect which is
00:47:33 --> 00:47:34 another virtual force like the
00:47:34 --> 00:47:36 centrifugal force that is a result of
00:47:36 --> 00:47:37 the rotation of the earth and the
00:47:38 --> 00:47:39 different rotation of speeds at
00:47:39 --> 00:47:41 different latitudes we can treat that in
00:47:41 --> 00:47:44 local isolated case as though it is a
00:47:44 --> 00:47:46 much simpler scenario than it is because
00:47:46 --> 00:47:48 all those other Corrections are so small
00:47:49 --> 00:47:51 that they don't really impact things
00:47:51 --> 00:47:53 what it leads to though is we tend to
00:47:53 --> 00:47:54 explain things using those simpler
00:47:54 --> 00:47:58 things simpler scenarios
00:47:58 --> 00:48:00 and that leads to questions like this
00:48:00 --> 00:48:02 because it leads to the idea that there
00:48:02 --> 00:48:05 is something external to the Earth and
00:48:05 --> 00:48:08 the Sun and to us us as observers that
00:48:08 --> 00:48:10 is in itself fixed and there that there
00:48:10 --> 00:48:13 is an absolute idealized frame of
00:48:13 --> 00:48:15 reference my understanding is that all
00:48:15 --> 00:48:18 of our models do not argue that when you
00:48:18 --> 00:48:20 get into the nitty
00:48:20 --> 00:48:23 gritt it's a willly answer I appreciate
00:48:23 --> 00:48:25 is probably not an ideal answer Dean and
00:48:25 --> 00:48:26 you know if that answer was not
00:48:26 --> 00:48:28 satisfactory for you please ask Fred
00:48:28 --> 00:48:30 when he's back and get a different
00:48:30 --> 00:48:32 version I do think this is important for
00:48:32 --> 00:48:34 anybody who's learning actually I say
00:48:34 --> 00:48:35 this to my I've got a tutorial in a
00:48:35 --> 00:48:37 couple of hours which why I'm thinking
00:48:37 --> 00:48:40 in this head space my explanations are
00:48:40 --> 00:48:42 one explanation of how things work and
00:48:42 --> 00:48:44 they'll work for some people but we all
00:48:44 --> 00:48:46 think about the universe differently and
00:48:46 --> 00:48:47 there is no shame in saying that
00:48:47 --> 00:48:49 explanation didn't work for me let me
00:48:49 --> 00:48:52 find another yeah it's really important
00:48:52 --> 00:48:54 if my explanation of that which
00:48:54 --> 00:48:57 admittedly you know was probably not a
00:48:57 --> 00:48:59 perfect explanation even for me um
00:48:59 --> 00:49:01 doesn't work for you there will be other
00:49:01 --> 00:49:03 explanations around it's worth asking
00:49:03 --> 00:49:05 another person to get a different
00:49:05 --> 00:49:06 perspective if what I said there didn't
00:49:06 --> 00:49:09 make sense and there is no problem with
00:49:09 --> 00:49:10 that I will not be offended if you ask
00:49:10 --> 00:49:12 Fred in two weeks and say jonty fail to
00:49:13 --> 00:49:14 explain this his explanation was rubbish
00:49:14 --> 00:49:16 tell me what's really happening Fred and
00:49:16 --> 00:49:20 then let him go and see what
00:49:20 --> 00:49:22 happens okay fair enough um great
00:49:22 --> 00:49:25 question very deep thinking there Dean
00:49:25 --> 00:49:27 and thanks for sending it in if you'd
00:49:27 --> 00:49:28 like to send us a question you can do
00:49:28 --> 00:49:30 that on our website SPAC nuts
00:49:30 --> 00:49:33 podcast.com or SPAC nuts.i click on the
00:49:33 --> 00:49:35 AMA button up the top and you can send
00:49:35 --> 00:49:37 us text and audio questions and have a
00:49:37 --> 00:49:39 look around while you're there you're
00:49:39 --> 00:49:40 always welcome to our website or our
00:49:40 --> 00:49:44 social media on Facebook or Instagram or
00:49:44 --> 00:49:47 YouTube if you're a YouTube uh follower
00:49:47 --> 00:49:49 um thanks for your support we got uh
00:49:49 --> 00:49:51 quite a quite a large audience on
00:49:51 --> 00:49:54 YouTube these days
00:49:54 --> 00:49:57 um that's it are we're done was looking
00:49:57 --> 00:49:58 for another question johy thank you so
00:49:58 --> 00:50:00 much that's an absolute pleasure
00:50:00 --> 00:50:02 obviously didn't talk too much today
00:50:02 --> 00:50:04 first time for
00:50:04 --> 00:50:06 everything you might want to look at the
00:50:06 --> 00:50:10 time ticking up here on my on my clock
00:50:10 --> 00:50:11 uh thanks Johnny we'll catch you next
00:50:11 --> 00:50:14 time Johnny Horner professor of Astro
00:50:14 --> 00:50:15 physics at the University of Southern
00:50:15 --> 00:50:17 Queensland and thanks to he in the
00:50:17 --> 00:50:19 studio who couldn't be with us again
00:50:19 --> 00:50:20 today because he was over producing
00:50:21 --> 00:50:23 methane yeah he'll be out of hospital
00:50:23 --> 00:50:25 soon and from me Andrew Andrew Dunley
00:50:25 --> 00:50:27 thanks for your company see you on the
00:50:27 --> 00:50:31 next episode of Space Nuts goodbye nuts
00:50:31 --> 00:50:34 you been listening to the Space Nuts
00:50:34 --> 00:50:37 podcast available at Apple podcasts
00:50:37 --> 00:50:40 Spotify iHeart radio or your favorite
00:50:40 --> 00:50:42 podcast player you can also stream on
00:50:42 --> 00:50:45 demand at bites.com this has been
00:50:45 --> 00:50:47 another quality podcast production from
00:50:47 --> 00:50:50 b.com