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

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hi there Andrew Dunley here thanks for


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joining us on a Q&A edition of Space


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Nuts and coming up we're going to answer


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a question from Ron he wants to know if


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we could see a planet that sustains life


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would we know it and vice versa if there


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was an alien race out there and they


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spotted Earth would they know we are


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here good question uh Dean is a bit


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confused about spheres versus discs why


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does it happen why why aren't they all


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spheres or all discs uh an has a a


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brilliant question love this one about


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bone density in space and some of the


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problems that are associated with being


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in zero gravity for long periods of time


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and Dean to it's not the same Dean uh is


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asking us about centrifugal force we'll


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cover all that in this episode of Space


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Nuts 15 seconds guidance is internal 10


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n ignition sequence start Space Nuts 5 4


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3 2


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1 2 3 4 5 5 4 3 2 1 Space Nuts as the


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nuts report feels good here he is again


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Professor JY hoer professor of


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astrophysics at the University of


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Southern Queensland JY hello hey how you


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going I'm all right um I got a question


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without notice yes did you ever sort of


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have people rebiew at school like jonty


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herner sat in the corner eating his


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Christmas pie down came the comet that


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made jonty vomit and now he only is


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flies oh that's brilliant that would


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have been far more pleasurable than


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maral skill experience it's probably not


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worth getting into too depressing of


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thing but up until I got to up until I


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went to University I had a horrendous


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horrendous time at school because I was


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um I grew up in a very workingclass area


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um low social economic area with hugely


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high unemployment during the minor


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strikes in the 80s and I was an only


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child so I'm I'm not necessarily blessed


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with the best social aptitude particular


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at that age but I was smart enough to be


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very smart but not smart enough to


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realize that there were the right way


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and the wrong way to go about that um so


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I had a horrible horrible time for the


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12 years at school in terms of bully I


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was catastrophically bullied but you


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know it made me who I am today so I'm


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not going to complain too much about it


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um but yes a curse of having aspiration


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and the curse of being smart in an area


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where that wasn't a common thing you


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know a lot of empathy the kids I went to


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school with because you're talking about


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an area where many of them didn't have


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any family members who were employed


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because of what was going on there was a


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huge um epidemic of men taking their own


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lives because of all the things that


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were going on so it was a pretty rough


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time a pretty rough place um but such as


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life unfortunately you know yeah


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yeah I certainly had my share of


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bullying at school and um yeah uh not


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not not often wasn't an everyday thing


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it was I suppose looking back reasonably


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rare but it never sits well it's it's a


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horrible thing at least these days


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nowadays there is more being done to


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counter it and more awareness of it


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because you know the impression back


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when I was at school was you just needed


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to Manor which sful phrase and everybody


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has to deal with it it's a formative


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experience and teachers couldn't care


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less as long as you weren't getting


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knife or something it was they weren't


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interested I I used to talk to my boys


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about it and asked them how they were


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going and they always said no we never


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had any trouble um but then teachers


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would tell me otherwise so they're


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obviously not keen to talk about it but


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my middle son who was always very tall


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through school he he was uh he towered


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above all the other kids I think he was


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the second tallest kid in his year and


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in the school in general and I said to


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him one day you get bullied and he went


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no because he was big he was a big kid


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and no one no one went near him so his


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height was actually a good defense


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mechanism it's funny how it works out


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but that that says a lot about


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anthropology I


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suppose we're not


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talking it's all interesting about the


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ages in which kids develop awareness of


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self and the edges at which they develop


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empathy and kindness and all those kind


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of things in a specific sense rather


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than a general sense it's really


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interesting yeah yeah it is all right


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let's uh deal with some questions and


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our first first question comes from Ron


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he said if scientists in a distant solar


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system were searching for exoplanets


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using the same technology that we're


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using and if they were to observe our


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planet would they be able to tell with


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any degree of certainty that there was


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life here or conversely if we were to


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observe an exoplanet that's exactly like


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Earth teaming with carbon based life and


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perhaps with an advanced civilization


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modifying their atmosphere which we


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talked about last episode could we tell


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that there's life there thanks Ron great


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question Ron uh we've had questions like


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it before but uh I just love this topic


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so yeah we'll do it again uh and um


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jonty hasn't had to answer this one


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before so I thought um it'd be


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interesting to get his take on it it's


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well it's a fabulous question and I mean


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the sad answer is we're not quite there


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yet so if we were looking at the soul


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system from around another star


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depending on which method we used we'd


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be able to find Jupiter and probably


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Saturn but we'd have to observe for a


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very long time to measure the wobbles


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for them so we need to observe the Sun


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for a decade or two to pick up Jupiter


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and Saturn everything else we wouldn't


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be able to find now if we had something


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like test the Transat Planet survey


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satellite looking at our solar system


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there's a very small chance it might


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pick up the Earth or Venus but test


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typically only looks at stars for 27


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days the Earth takes 365 days to go


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around and would take only 16 hours to


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Transit so so the odds of catching a


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Transit are pretty much nil so we're not


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there yet we are getting better and as


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we talked about in the other episode


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we're getting to the point where we can


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find planets that are a bit bigger than


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the earth but on orbits that are


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comparable to the Earth around stars


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like the sun we can find planets smaller


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than the Earth around dim little red


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dwarf stars using the transit method but


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that's partly because our planets so


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close their STS they're going around


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really quickly so the upshot of all that


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is if we were orbiting in another star


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looking back at the solar system I think


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we could only confidently detect one or


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two planets the Earth would probably be


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the third planet that will be discovered


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as a technology got better because it's


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the biggest of the terrestrial planets


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but it would depend a little bit on your


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line of sight because the terestrial


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planets are all slightly tilted to each


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other so if you're going to find them


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through the transit method the


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likelihood is only one of them will


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Transit and the others


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one in radial velocity method you'd pick


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out jup and Saturn but you'd struggle


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for anything else


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eventually youd get there but you'd need


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technology a bit better than ours so


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we're not at the point of finding the


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planets yet never mind finding the life


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on them but that's like the next step in


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the journey we've only had 30 years of


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the exoplanet era we're only in the


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first few decades have been able to do


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this at all and the progress we've made


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is utterly astonishing and I think


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within the next decade or two we'll


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routinely start being able to find


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planets that are Earth sized on Earth


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likee orbits and to start looking for


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evidence of Life on them that is going


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to be the hardest observations we've


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ever had to carry out in terms of


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detecting life like us so it's a


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slightly different proposition so


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finding any evidence of life is going to


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be challenging so people often talk


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about


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biomarkers yeah which is this concept


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that there are certain things you could


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look for that would be indicative of


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life and we've talked about the possible


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detection of phosphine in Venus


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atmosphere before we've talked about


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stuff like the chicken soup experiment


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the V wers did on Mars in the 1970s


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where they dug up some soil and put some


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soup on it and so if it gave off gases


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cost their could be life they using


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nutrients when you're looking at planets


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around of the stars there is no


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guarantee that life on those planets


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would have follow the same evolutionary


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Pathways as life on Earth so a lot of


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the very specific biomarkers people


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propose a best and our knowledge of life


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on Earth because it's the only planet we


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know does have life and it's the only


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example of Life we've got one of the


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examples here is something called the


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red Edge which is when you look at the


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spectrum of light from a planet if the


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planet has a lot of plants on board that


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are using chlorophyll chlorophyll


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absorbs incredibly strongly in the red


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so you might see a feature in the red


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that is the signature of chlorophyll and


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that will be an indication of plant life


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the problem is and again I'm not a


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biologist so there's probably more to


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this than I'm going to say in my simple


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version is that chlorophyll is an


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incredibly efficient compound for


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allowing plants to utilize light like


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the light from our up but there are many


00:09:04.880 --> 00:09:06.550
other compounds that could do a similar


00:09:06.560 --> 00:09:09.110
job for stars of different temperatures


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that are therefore different colors so


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they put out the bulk of their light at


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slightly different wavelengths and


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there's no guarantee that life on


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another planet would use chlorophyll


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especially if that star was


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significantly different to the Sun so


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the specific biomarker of the red Edge


00:09:24.760 --> 00:09:27.230
from chlorophyll wouldn't work very well


00:09:27.240 --> 00:09:28.750
necessarily it wouldn't be guaranteed to


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work especially because it's also


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mimicked by the spectrum of Olivine


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which is a very common mineral has a


00:09:35.000 --> 00:09:38.269
very similar appearance but looking more


00:09:38.279 --> 00:09:40.269
generally for that kind of absorption


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feature in the spectrum that you can't


00:09:42.040 --> 00:09:44.350
explain any other way is one of the


00:09:44.360 --> 00:09:46.110
signs people have looked for so it's not


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so much a case of looking for a specific


00:09:48.800 --> 00:09:51.110
thing but rather for looking for


00:09:51.120 --> 00:09:53.470
something that is out of place try to


00:09:53.480 --> 00:09:54.990
explain it and finding that the only


00:09:55.000 --> 00:09:57.230
explanation left is life you're looking


00:09:57.240 --> 00:09:58.590
for something out of balance so another


00:09:58.600 --> 00:10:01.509
good example is on Earth we have oxygen


00:10:01.519 --> 00:10:04.269
we have methane now there's a lot of


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oxygen in the atmosphere but that


00:10:06.240 --> 00:10:07.829
doesn't necessarily mean life because


00:10:07.839 --> 00:10:09.590
there are chemical processes that can


00:10:09.600 --> 00:10:11.630
produce oxygen without life being


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involved similarly with a lot of methane


00:10:14.720 --> 00:10:16.670
in the atmosphere and methane is a


00:10:16.680 --> 00:10:19.509
natural product of animal life I know my


00:10:19.519 --> 00:10:21.190
dog line next is been quite happily


00:10:21.200 --> 00:10:22.990
producing methane through the podcast


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because we fed some um broccoli I think


00:10:25.720 --> 00:10:29.069
in a puppy food last night so methane is


00:10:29.079 --> 00:10:30.509
pretty produced by life but there are


00:10:30.519 --> 00:10:32.470
also lots of natural ways it can be


00:10:32.480 --> 00:10:33.630
produced and you know there's huge


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amounts of methane in the atmospheres of


00:10:35.240 --> 00:10:37.790
Uranus and nein for example so finding


00:10:37.800 --> 00:10:40.670
oxygen or finding methane doesn't


00:10:40.680 --> 00:10:42.110
necessarily mean life there's a lot of


00:10:42.120 --> 00:10:43.750
other explanations but the odity with


00:10:43.760 --> 00:10:45.350
Earth is that we've got oxygen and


00:10:45.360 --> 00:10:47.670
methane together now when you put oxygen


00:10:47.680 --> 00:10:49.190
and methane together they react with


00:10:49.200 --> 00:10:51.949
each other a lot and they react until


00:10:51.959 --> 00:10:54.269
all of one of them is gone so the


00:10:54.279 --> 00:10:56.069
methane in Earth atmosphere has a really


00:10:56.079 --> 00:10:58.310
short residance time of only a century


00:10:58.320 --> 00:11:00.990
or a few centuries I 400 years maybe


00:11:01.000 --> 00:11:03.110
before it's all gone so you look at the


00:11:03.120 --> 00:11:04.670
Earth and it's got oxygen and methane


00:11:04.680 --> 00:11:06.230
together which means something has to be


00:11:06.240 --> 00:11:09.389
producing new methane to re replace the


00:11:09.399 --> 00:11:11.870
methane that's lost now even that


00:11:11.880 --> 00:11:13.829
doesn't mean it's life because volcanoes


00:11:13.839 --> 00:11:16.150
prod methane so what You' then have to


00:11:16.160 --> 00:11:17.629
do is say well this is interesting it


00:11:17.639 --> 00:11:19.110
could be life it could be something else


00:11:19.120 --> 00:11:21.350
let's measure the methane over time and


00:11:21.360 --> 00:11:22.990
if it's volcanoes you'll get the methane


00:11:23.000 --> 00:11:24.629
falling off until a random time a


00:11:24.639 --> 00:11:26.190
volcano ER upts in there's a spike of


00:11:26.200 --> 00:11:28.190
methane and then it falls off again and


00:11:28.200 --> 00:11:30.829
a random time l you get another Spike


00:11:30.839 --> 00:11:32.150
but when you look at methane in the


00:11:32.160 --> 00:11:34.110
earth atmosphere it varies with the


00:11:34.120 --> 00:11:36.750
seasons volcanoes don't do that so


00:11:36.760 --> 00:11:38.829
therefore that's an indication of life


00:11:38.839 --> 00:11:40.350
so it's looking for that Oddity that's


00:11:40.360 --> 00:11:43.110
out of place there are a couple of


00:11:43.120 --> 00:11:45.949
things that would give away arguably


00:11:45.959 --> 00:11:47.629
technologically developed life which


00:11:47.639 --> 00:11:49.110
doesn't necessarily mean intelligent


00:11:49.120 --> 00:11:50.350
life as we're seeing in the political


00:11:50.360 --> 00:11:51.910
sphere at the minute but technologically


00:11:51.920 --> 00:11:53.190
developed


00:11:53.200 --> 00:11:55.870
life one of them is chlorofluorocarbon


00:11:55.880 --> 00:11:57.629
so the things that we were putting up


00:11:57.639 --> 00:11:59.150
into the atmosphere that devastated are


00:11:59.160 --> 00:12:03.030
the the ozone layer yeah we only know of


00:12:03.040 --> 00:12:04.870
those being produced by technology there


00:12:04.880 --> 00:12:06.790
is no natural process that seems to


00:12:06.800 --> 00:12:10.710
produce them another is Radio broadcasts


00:12:10.720 --> 00:12:15.230
so any intelligent aliens within about


00:12:15.240 --> 00:12:17.470
80 light years of us 90 light years of


00:12:17.480 --> 00:12:20.030
us now would see our broadcast now the


00:12:20.040 --> 00:12:21.910
exact date of the first broadcast that


00:12:21.920 --> 00:12:23.430
we sent out that was strong enough be


00:12:23.440 --> 00:12:25.710
detected from around the Stars depends


00:12:25.720 --> 00:12:26.790
who you talked it could have been the


00:12:26.800 --> 00:12:29.710
Berlin Olympics in 1936 I think or the


00:12:29.720 --> 00:12:32.629
coronation of Queen Elizabeth in 1952 I


00:12:32.639 --> 00:12:34.310
think where there it was and they're


00:12:34.320 --> 00:12:35.790
usually held as been the first big


00:12:35.800 --> 00:12:37.069
broadcast that would have been


00:12:37.079 --> 00:12:40.350
detectable on an Interstellar distance


00:12:40.360 --> 00:12:42.189
what that means is that within a certain


00:12:42.199 --> 00:12:45.269
distance of the Earth there is a sphere


00:12:45.279 --> 00:12:46.870
where if there are intelligent aliens


00:12:46.880 --> 00:12:48.990
with radio telescopes they could be


00:12:49.000 --> 00:12:50.990
watching neighbors and we could well get


00:12:51.000 --> 00:12:52.509
a broadcast back at some point saying


00:12:52.519 --> 00:12:55.470
please Su you know we're a bit like


00:12:55.480 --> 00:12:57.189
toddlers at the minute in a room


00:12:57.199 --> 00:12:59.710
screaming into the void and that sound


00:12:59.720 --> 00:13:01.069
is getting further and further away from


00:13:01.079 --> 00:13:03.629
it as time goes on now that's the


00:13:03.639 --> 00:13:05.389
motivation for things like the search


00:13:05.399 --> 00:13:06.350
treal


00:13:06.360 --> 00:13:08.389
intelligence which is helping fund the


00:13:08.399 --> 00:13:10.110
wonderful radio telescope down at parks


00:13:10.120 --> 00:13:12.430
through the Breakthrough listen project


00:13:12.440 --> 00:13:14.189
the challenge there is that we are


00:13:14.199 --> 00:13:17.030
already starting to become more quiet we


00:13:17.040 --> 00:13:18.670
like the baby becoming a toddler and


00:13:18.680 --> 00:13:21.230
moderating itself and the reason for


00:13:21.240 --> 00:13:24.030
that is costs if you were broadcasting


00:13:24.040 --> 00:13:25.670
in all directions all the time you've


00:13:25.680 --> 00:13:27.790
got to put a lot of energy in and most


00:13:27.800 --> 00:13:29.550
of that energy is waste exing a tin a


00:13:29.560 --> 00:13:30.670
little bit of that is going to get to


00:13:30.680 --> 00:13:33.069
your receivers it's much more efficient


00:13:33.079 --> 00:13:35.310
to send your data like we're talking at


00:13:35.320 --> 00:13:38.670
the minute through the ndn through wires


00:13:38.680 --> 00:13:40.509
or through pointto Point stuff so The


00:13:40.519 --> 00:13:42.550
Styling satellites are a bit like this


00:13:42.560 --> 00:13:44.269
they're broadcasting


00:13:44.279 --> 00:13:46.590
down therefore V little is going back


00:13:46.600 --> 00:13:48.670
out into space and anything connecting


00:13:48.680 --> 00:13:50.110
to them points at the satellite and


00:13:50.120 --> 00:13:51.749
beams directly to it so it's much more


00:13:51.759 --> 00:13:53.629
energy efficient and there are some


00:13:53.639 --> 00:13:55.110
arguments that the Earth could well be


00:13:55.120 --> 00:13:57.509
radio silent again from the point of


00:13:57.519 --> 00:13:59.350
view of aliens listening in within just


00:13:59.360 --> 00:14:01.509
a few decades so there'd only be a short


00:14:01.519 --> 00:14:02.949
window and then you've got this shell of


00:14:02.959 --> 00:14:05.269
broadcasts moving outwards leaving a


00:14:05.279 --> 00:14:07.710
void behind it and unless you tune in


00:14:07.720 --> 00:14:09.150
when that Shell's passing pass you'd


00:14:09.160 --> 00:14:12.430
never hear us but in that sense if we


00:14:12.440 --> 00:14:13.949
were looking at the solar system with


00:14:13.959 --> 00:14:16.470
our biggest radio telescopes we'd


00:14:16.480 --> 00:14:18.629
probably just about be able to pick up


00:14:18.639 --> 00:14:20.749
the unusual radio activity if we were at


00:14:20.759 --> 00:14:23.430
the right radio we were at the right


00:14:23.440 --> 00:14:25.230
distance but it would still be


00:14:25.240 --> 00:14:26.670
challenging for us I think we do have


00:14:26.680 --> 00:14:29.269
the capacity for that but it would be


00:14:29.279 --> 00:14:32.230
hard so in that sense if there were


00:14:32.240 --> 00:14:34.590
aliens around I don't know proximus


00:14:34.600 --> 00:14:37.110
centor B another of the many many


00:14:37.120 --> 00:14:38.629
planets that has been argued as been the


00:14:38.639 --> 00:14:40.230
most earthlike ever discovered and made


00:14:40.240 --> 00:14:43.430
me angry if there was a planet there if


00:14:43.440 --> 00:14:44.710
there were aliens on it and they were


00:14:44.720 --> 00:14:46.430
broadcasting alien neighbors we'd be


00:14:46.440 --> 00:14:48.150
able to tune


00:14:48.160 --> 00:14:51.310
it wouldn't that be interesting yes so


00:14:51.320 --> 00:14:53.509
the answer to Ron's question is no not


00:14:53.519 --> 00:14:56.269
yet we're just not quite there uh the


00:14:56.279 --> 00:14:58.670
time May well come but again it's


00:14:58.680 --> 00:15:00.590
needless in a high stack stuff isn't it


00:15:00.600 --> 00:15:03.189
you absolutely I you not know what a


00:15:03.199 --> 00:15:04.550
needle is and you've never seen a hair


00:15:04.560 --> 00:15:06.430
stack before yeah


00:15:06.440 --> 00:15:09.470
exactly yes thank you Ron great question


00:15:09.480 --> 00:15:12.870
lovely to hear from


00:15:12.880 --> 00:15:16.629
you okay we check all four system a


00:15:16.639 --> 00:15:20.110
Space Nuts and our next question comes


00:15:20.120 --> 00:15:24.030
from Dean hi Space Nuts I'm Dean from


00:15:24.040 --> 00:15:26.550
Washington DC in the United States I


00:15:26.560 --> 00:15:28.030
recently started listening to the show


00:15:28.040 --> 00:15:29.629
and can't


00:15:29.639 --> 00:15:31.509
anyways I was wondering why under


00:15:31.519 --> 00:15:34.309
Gravity do some things form as discs and


00:15:34.319 --> 00:15:36.470
others as spheres you know where where


00:15:36.480 --> 00:15:39.670
stars and planets or spheres but some


00:15:39.680 --> 00:15:42.430
galaxies and our solar systems a dis but


00:15:42.440 --> 00:15:44.790
then also planet can have discs around


00:15:44.800 --> 00:15:47.710
them I don't know it's all very anyways


00:15:47.720 --> 00:15:50.230
thanks keep up to paper thank you Dean I


00:15:50.240 --> 00:15:52.230
I never would have even thought of that


00:15:52.240 --> 00:15:54.230
question and it's a great question um


00:15:54.240 --> 00:15:56.870
but yeah he's right U you've got spheres


00:15:56.880 --> 00:15:58.629
and you've got discs you've got mixtures


00:15:58.639 --> 00:16:01.230
of spheres and discs you've got all


00:16:01.240 --> 00:16:05.870
sorts of combinations um why is it so


00:16:05.880 --> 00:16:08.509
it's all down to different physical


00:16:08.519 --> 00:16:10.110
processes going on so it's fabulous


00:16:10.120 --> 00:16:11.670
question and we run across this when


00:16:11.680 --> 00:16:14.269
we're teaching Astro when we're studying


00:16:14.279 --> 00:16:17.550
it quite a lot and there are things that


00:16:17.560 --> 00:16:19.910
happen in slightly different situations


00:16:19.920 --> 00:16:22.430
so if you've got material falling


00:16:22.440 --> 00:16:24.870
inwards under Gravity it will keep


00:16:24.880 --> 00:16:27.790
falling inwards until either it's moving


00:16:27.800 --> 00:16:29.430
around on an orbit sit swings back out


00:16:29.440 --> 00:16:30.990
but let's assume it's falling into an


00:16:31.000 --> 00:16:33.150
object that is going to become a solid


00:16:33.160 --> 00:16:35.629
or gaseous object that therefore has


00:16:35.639 --> 00:16:37.150
some way of stopping that material so it


00:16:37.160 --> 00:16:39.189
slows down and becomes part of that


00:16:39.199 --> 00:16:41.910
object you then have a balance between


00:16:41.920 --> 00:16:44.110
gravity trying to pull you inwards and


00:16:44.120 --> 00:16:45.910
the physical strength of the material


00:16:45.920 --> 00:16:48.309
pushing outwards if you've got a solid


00:16:48.319 --> 00:16:51.189
object if you've got a gaseous object


00:16:51.199 --> 00:16:52.670
the gas can keep going in but then you


00:16:52.680 --> 00:16:54.230
build up pressure and the pressure holds


00:16:54.240 --> 00:16:57.590
things up you might have energy being


00:16:57.600 --> 00:17:00.550
released that also holds it up so that


00:17:00.560 --> 00:17:02.509
then pushes outwards in all


00:17:02.519 --> 00:17:05.549
directions I'll talk about solid objects


00:17:05.559 --> 00:17:07.909
first this ties into a little bit


00:17:07.919 --> 00:17:09.590
towards the definition of a planet there


00:17:09.600 --> 00:17:12.870
is a concept called hydrostatic


00:17:12.880 --> 00:17:16.390
equilibrium which is basically the shape


00:17:16.400 --> 00:17:19.510
that something that has no strength will


00:17:19.520 --> 00:17:21.590
finish up in once everything's moved


00:17:21.600 --> 00:17:24.510
around you say that it's in hydrostatic


00:17:24.520 --> 00:17:26.870
it's at the lowest kind of energy state


00:17:26.880 --> 00:17:29.950
so if you got outside the


00:17:29.960 --> 00:17:32.470
atmosphere or rather you go away from


00:17:32.480 --> 00:17:34.029
the gravity of the edge po things down


00:17:34.039 --> 00:17:37.070
and you could have droplets suspended a


00:17:37.080 --> 00:17:38.789
drop of water that is not moving at all


00:17:38.799 --> 00:17:40.789
will be spherical it's held in by


00:17:40.799 --> 00:17:43.310
surface tension in that case holds it


00:17:43.320 --> 00:17:45.390
together but it would be a sphere if you


00:17:45.400 --> 00:17:47.750
rotate it it will gradually become more


00:17:47.760 --> 00:17:49.669
elongated in a blate and it become what


00:17:49.679 --> 00:17:52.230
we call an a blate spheroid which is


00:17:52.240 --> 00:17:53.870
what the Earth is the Earth is wider at


00:17:53.880 --> 00:17:55.350
the equator than the poles because of


00:17:55.360 --> 00:17:58.029
the rotation and the rotation is


00:17:58.039 --> 00:18:00.310
essentially a applying a slight outward


00:18:00.320 --> 00:18:03.110
force that means the net force pulling


00:18:03.120 --> 00:18:04.549
in is weaker at the equator than the


00:18:04.559 --> 00:18:06.470
poles and so you stretch out of it


00:18:06.480 --> 00:18:10.470
that's kind of how I visualize it yep if


00:18:10.480 --> 00:18:13.070
you are smaller than a certain size your


00:18:13.080 --> 00:18:15.590
material strength is strong enough to


00:18:15.600 --> 00:18:18.110
prevent things moving around and flowing


00:18:18.120 --> 00:18:20.510
so you don't become spherical you don't


00:18:20.520 --> 00:18:22.830
get that hydrostatic equilibrium so if


00:18:22.840 --> 00:18:24.909
you look at the moons of the


00:18:24.919 --> 00:18:28.230
planets the smallest one that I think is


00:18:28.240 --> 00:18:30.070
in H traffic equilibrium is possibly


00:18:30.080 --> 00:18:33.149
mimus at Saturn about 400 km across it


00:18:33.159 --> 00:18:34.750
might be one of the other Saturns but I


00:18:34.760 --> 00:18:37.270
think it's mimus because that's about


00:18:37.280 --> 00:18:39.270
the size where you've got enough mass


00:18:39.280 --> 00:18:40.909
that the gravitational pull is strong


00:18:40.919 --> 00:18:42.990
enough that that can overcome the


00:18:43.000 --> 00:18:44.430
physical strength of the material when


00:18:44.440 --> 00:18:47.270
the objects forming and cause it to then


00:18:47.280 --> 00:18:49.830
move and flow and you end up then


00:18:49.840 --> 00:18:51.750
getting near asphere because that's the


00:18:51.760 --> 00:18:53.190
lowest Energy Solution that's your


00:18:53.200 --> 00:18:54.789
hydrostatic


00:18:54.799 --> 00:18:58.390
equilibrium if you had it being wider


00:18:58.400 --> 00:19:00.789
than that more like a block like an ice


00:19:00.799 --> 00:19:03.350
hockey puck maybe but the material can


00:19:03.360 --> 00:19:06.149
flow you've got more mass pushing down


00:19:06.159 --> 00:19:07.710
in the horizontal plane so things try


00:19:07.720 --> 00:19:08.909
and squeeze in here and they'll be


00:19:08.919 --> 00:19:11.110
pushed out that way until it bounces out


00:19:11.120 --> 00:19:12.909
so you'd end up flowing until you got


00:19:12.919 --> 00:19:15.510
that kind of spherical shap yeah your


00:19:15.520 --> 00:19:17.110
ice hocky po though small enough that


00:19:17.120 --> 00:19:19.110
its material strength wins so it stays


00:19:19.120 --> 00:19:22.350
at elongated shape so that's kind of the


00:19:22.360 --> 00:19:24.190
lower end of when people start talking


00:19:24.200 --> 00:19:26.310
about the definition of a planet is it


00:19:26.320 --> 00:19:28.190
has to be in hydrostatic equilibrium


00:19:28.200 --> 00:19:30.190
doesn't mean it's spherical it just


00:19:30.200 --> 00:19:31.750
means it's in that lowest energy thing


00:19:31.760 --> 00:19:33.390
so if it's rotating quickly it can be a


00:19:33.400 --> 00:19:36.070
kind of oblet spheroid you get a similar


00:19:36.080 --> 00:19:37.830
thing with stars so you've got all this


00:19:37.840 --> 00:19:40.510
gas collapsing in friction stopping it


00:19:40.520 --> 00:19:42.149
just orbiting and escaping again so


00:19:42.159 --> 00:19:43.350
you've got an


00:19:43.360 --> 00:19:45.990
object that object has gravity pulling


00:19:46.000 --> 00:19:47.830
inwards and it's got a restoring Force


00:19:47.840 --> 00:19:49.430
pushing outwards in the case of a cell


00:19:49.440 --> 00:19:51.190
at the sun that's the radiation pressure


00:19:51.200 --> 00:19:52.710
from all the nuclear fusion going on in


00:19:52.720 --> 00:19:55.669
its CAU now the sun's rotating albe it


00:19:55.679 --> 00:19:59.110
once every 30 odd days but it is in


00:19:59.120 --> 00:20:00.950
something that is close to that hyic


00:20:00.960 --> 00:20:03.070
equilibrium so if you put a load of Mass


00:20:03.080 --> 00:20:05.510
on the sun's equator that would squish


00:20:05.520 --> 00:20:07.029
in and the poles will push out until you


00:20:07.039 --> 00:20:09.750
got back to that kind of shape so that's


00:20:09.760 --> 00:20:12.830
a physical kind of object that's why you


00:20:12.840 --> 00:20:16.430
get them going to be spheres or nearly


00:20:16.440 --> 00:20:18.270
spheres it's that concept of hydrostatic


00:20:18.280 --> 00:20:20.230
equilibrium and it's due to the balance


00:20:20.240 --> 00:20:21.669
of the force pulling inwards and the


00:20:21.679 --> 00:20:23.909
force pushing outwards radiation


00:20:23.919 --> 00:20:25.830
pressure for stars material strength


00:20:25.840 --> 00:20:27.630
material physics going on for solid


00:20:27.640 --> 00:20:31.390
objects with diss you don't have the


00:20:31.400 --> 00:20:33.549
same things going on so what you've got


00:20:33.559 --> 00:20:35.350
is you've got a rotating cloud of gas


00:20:35.360 --> 00:20:36.110
and


00:20:36.120 --> 00:20:38.510
dust that isn't really strong enough to


00:20:38.520 --> 00:20:40.789
hold itself up but it's rotating quickly


00:20:40.799 --> 00:20:41.750
under


00:20:41.760 --> 00:20:43.750
Gravity now you've got the conservation


00:20:43.760 --> 00:20:45.549
of angular momentum going on so things


00:20:45.559 --> 00:20:47.029
near the middle go quicker than things


00:20:47.039 --> 00:20:49.669
near the outside and there is a tendency


00:20:49.679 --> 00:20:52.029
for things to collapse down in a disc


00:20:52.039 --> 00:20:53.750
above the plane of the Equator of the


00:20:53.760 --> 00:20:55.870
thing they're orbiting around that is


00:20:55.880 --> 00:20:57.350
due to the conservation of that angular


00:20:57.360 --> 00:20:59.830
momentum but it's alsoe du to the motion


00:20:59.840 --> 00:21:01.190
of things through you've got all sorts


00:21:01.200 --> 00:21:03.710
of things coming in the analogy I often


00:21:03.720 --> 00:21:05.950
used when I'm giving public talks here


00:21:05.960 --> 00:21:07.950
involves fysic that is different so it's


00:21:07.960 --> 00:21:09.669
not a Perfect Analogy but it gives you


00:21:09.679 --> 00:21:10.789
kind of idea what's going on with


00:21:10.799 --> 00:21:12.950
spinning material and it's if you've


00:21:12.960 --> 00:21:14.549
ever seen somebody who's a showoff


00:21:14.559 --> 00:21:17.470
making pizza bases they get a ball of


00:21:17.480 --> 00:21:19.110
very elastic dough and then they spin it


00:21:19.120 --> 00:21:20.630
around very quickly and WHL it over


00:21:20.640 --> 00:21:22.029
their head and it flattens out into a


00:21:22.039 --> 00:21:23.029
big


00:21:23.039 --> 00:21:25.269
pancake as a result of the conservation


00:21:25.279 --> 00:21:26.789
of the anual momentum there it flattens


00:21:26.799 --> 00:21:28.830
out into the pizza bear shape and if I


00:21:28.840 --> 00:21:30.310
tried it it either stick to the ceiling


00:21:30.320 --> 00:21:31.870
or hit me on the head it wouldn't go


00:21:31.880 --> 00:21:32.630
very


00:21:32.640 --> 00:21:35.950
well it's a slightly similar thing with


00:21:35.960 --> 00:21:37.789
the disc of material around planets and


00:21:37.799 --> 00:21:39.470
stars now what's happening is you you've


00:21:39.480 --> 00:21:42.149
got thing material collapsing into the


00:21:42.159 --> 00:21:44.390
star under Gravity forming the disc


00:21:44.400 --> 00:21:46.110
around it because there is a bit of


00:21:46.120 --> 00:21:48.470
rotation with that rotation as you spin


00:21:48.480 --> 00:21:50.149
in and you get to a smaller and smaller


00:21:50.159 --> 00:21:51.990
distance you move faster and faster and


00:21:52.000 --> 00:21:54.269
faster and that's why a gas cloud


00:21:54.279 --> 00:21:55.950
rotating every few million years gives


00:21:55.960 --> 00:21:58.070
you a St rotating every few days or


00:21:58.080 --> 00:22:00.430
every few hours it's like the ballerina


00:22:00.440 --> 00:22:02.029
bringing their arms in a Zid a spin they


00:22:02.039 --> 00:22:04.710
spin quicker and quicker but that also


00:22:04.720 --> 00:22:06.630
tends to lead to things collapsing into


00:22:06.640 --> 00:22:08.310
the plane because that's a bit again


00:22:08.320 --> 00:22:10.590
like the hydrostatic example that's kind


00:22:10.600 --> 00:22:12.630
of the lowest Energy Solution you're


00:22:12.640 --> 00:22:15.430
rotating around a given rotation axis


00:22:15.440 --> 00:22:17.590
you will collapse into a disc in that


00:22:17.600 --> 00:22:19.909
plane material that's coming in above


00:22:19.919 --> 00:22:22.190
that disc can just carry on orbiting


00:22:22.200 --> 00:22:24.230
normally but if there's more material in


00:22:24.240 --> 00:22:25.950
the disc there will be friction and it


00:22:25.960 --> 00:22:27.549
will get damped down and help to


00:22:27.559 --> 00:22:29.350
collapse down into there


00:22:29.360 --> 00:22:32.549
there but if the bulk is


00:22:32.559 --> 00:22:35.470
rotating with a with the same rotation


00:22:35.480 --> 00:22:36.870
axis anything fallowing in at high


00:22:36.880 --> 00:22:38.630
angles will probably just fall in and


00:22:38.640 --> 00:22:40.789
blop straight onto the star it's it's


00:22:40.799 --> 00:22:42.430
rotating that way but it's coming in


00:22:42.440 --> 00:22:44.669
here essentially yeah and I appreciate


00:22:44.679 --> 00:22:46.269
that description was really useful for


00:22:46.279 --> 00:22:47.669
the people who are on listening because


00:22:47.679 --> 00:22:49.510
they can't see me waving my Flappy hands


00:22:49.520 --> 00:22:51.549
around um but if you're coming in from


00:22:51.559 --> 00:22:53.390
near the pearls the little bit of


00:22:53.400 --> 00:22:55.230
rotation around isn't helping against


00:22:55.240 --> 00:22:56.710
you coming in directly towards the


00:22:56.720 --> 00:22:58.950
target if you're coming in from PS and


00:22:58.960 --> 00:23:00.470
you're going to hit onto the disc you'll


00:23:00.480 --> 00:23:02.630
be passing through all that material and


00:23:02.640 --> 00:23:04.630
that will damp you down a little bit so


00:23:04.640 --> 00:23:06.710
more inclined things will gradually get


00:23:06.720 --> 00:23:09.590
dumped down to add to the disc the discs


00:23:09.600 --> 00:23:11.950
we get there for around protoy our


00:23:11.960 --> 00:23:13.549
material that's falling in the rotation


00:23:13.559 --> 00:23:16.029
speeding it up you get a disc around


00:23:16.039 --> 00:23:18.510
that Proto star that this will be a bit


00:23:18.520 --> 00:23:19.830
flared it'll have a bit of height


00:23:19.840 --> 00:23:21.190
because there's a lot of Dynamics and


00:23:21.200 --> 00:23:24.190
stirring and things like that going on


00:23:24.200 --> 00:23:26.390
if you could have a big enough region


00:23:26.400 --> 00:23:27.909
around it you probably end up seeing a


00:23:27.919 --> 00:23:30.310
disc would eventually flare out until it


00:23:30.320 --> 00:23:31.590
becomes a background but you'd have


00:23:31.600 --> 00:23:33.590
almost cleared lobes above and below the


00:23:33.600 --> 00:23:35.669
star and that's kind of what we see with


00:23:35.679 --> 00:23:37.430
our small body population of the solar


00:23:37.440 --> 00:23:40.390
system as you go from the planets and


00:23:40.400 --> 00:23:42.390
the edge with cop Bel going further


00:23:42.400 --> 00:23:44.590
outwards you gradually come out towards


00:23:44.600 --> 00:23:45.990
the domain of the AR cloud and when


00:23:46.000 --> 00:23:47.510
you're far enough from the Sun things


00:23:47.520 --> 00:23:49.870
get stirred up by passing stars and get


00:23:49.880 --> 00:23:51.390
put back into a sphere because their


00:23:51.400 --> 00:23:53.990
tilts are all randomized so you've got a


00:23:54.000 --> 00:23:55.549
disc near the Sun and that's because the


00:23:55.559 --> 00:23:57.549
Sun's gravity is dominating the angular


00:23:57.559 --> 00:23:59.190
momentum's dominating


00:23:59.200 --> 00:24:01.430
when you're very far from the Sun you're


00:24:01.440 --> 00:24:03.470
only loosely held to the Sun so nudes


00:24:03.480 --> 00:24:04.909
from passing Stars can change your


00:24:04.919 --> 00:24:07.110
direction quite significantly and over


00:24:07.120 --> 00:24:08.669
the four billion years since the cell


00:24:08.679 --> 00:24:10.990
system formed that material that was


00:24:11.000 --> 00:24:12.870
flung out into the AR cloud in a disc


00:24:12.880 --> 00:24:14.990
because it was flung out from a disc has


00:24:15.000 --> 00:24:16.710
been smeared around so we now get a


00:24:16.720 --> 00:24:19.710
spherical is cloud around the Sun but


00:24:19.720 --> 00:24:20.990
when you're close enough to the Sun for


00:24:21.000 --> 00:24:23.430
the sun to dominate you'd have voids


00:24:23.440 --> 00:24:24.909
that are fairly empty above and below


00:24:24.919 --> 00:24:28.830
the plane and a disc load out so all


00:24:28.840 --> 00:24:30.590
complex and it's a couple of different


00:24:30.600 --> 00:24:33.029
Ms of physics interacting essentially


00:24:33.039 --> 00:24:35.510
yeah wow now i' I'd never wondered about


00:24:35.520 --> 00:24:37.710
it and I'm glad Dean asked the question


00:24:37.720 --> 00:24:41.350
because uh yeah it it it really is


00:24:41.360 --> 00:24:44.149
interesting science uh hydrostatic


00:24:44.159 --> 00:24:45.789
equili




00:24:48.480 --> 00:24:50.430
equilibrium it's a really good example


00:24:50.440 --> 00:24:51.870
of how science works and how we do it


00:24:51.880 --> 00:24:53.230
actually because that's exactly the


00:24:53.240 --> 00:24:54.950
scientific process you see something you


00:24:54.960 --> 00:24:57.430
go why is that and sat's a great example


00:24:57.440 --> 00:24:59.510
you look at sat and then say oblet


00:24:59.520 --> 00:25:01.350
spheroid it's a bit of an elonga Blobby


00:25:01.360 --> 00:25:03.389
thing but it's nearly spherical really


00:25:03.399 --> 00:25:05.430
first order and yet it's got a disc of


00:25:05.440 --> 00:25:06.990
material around it why isn't the disc


00:25:07.000 --> 00:25:09.470
all block you know and so that's what


00:25:09.480 --> 00:25:11.110
leads us down that Journey Discovery to


00:25:11.120 --> 00:25:13.470
figure all this stuff out so that's just


00:25:13.480 --> 00:25:15.950
how science works and it's very fun


00:25:15.960 --> 00:25:17.750
brilliant question thank you Dane lovely


00:25:17.760 --> 00:25:20.830
to hear from you this is Space Nuts with


00:25:20.840 --> 00:25:25.110
Andrew Dunley and johy


00:25:25.120 --> 00:25:28.870
hona 3 2 1


00:25:28.880 --> 00:25:32.669
Space Nuts uh our next question uh I


00:25:32.679 --> 00:25:35.230
really love this one comes from Anne in


00:25:35.240 --> 00:25:37.350
Belleview Washington I have a question


00:25:37.360 --> 00:25:40.310
about calcium and astronauts on Earth


00:25:40.320 --> 00:25:42.870
estrogen helps prevent calcium loss from


00:25:42.880 --> 00:25:47.350
bones do premenopausal astronauts lose


00:25:47.360 --> 00:25:51.310
less bone or regone uh regain bone


00:25:51.320 --> 00:25:55.190
faster than male or postmenopausal


00:25:55.200 --> 00:25:58.310
astronauts uh do does hormone


00:25:58.320 --> 00:26:00.669
replacement therapy help postmen


00:26:00.679 --> 00:26:03.909
menopausal astronauts regain bone it's a


00:26:03.919 --> 00:26:06.950
really great question uh and says thanks


00:26:06.960 --> 00:26:08.590
for the interesting podcast appreciate


00:26:08.600 --> 00:26:10.389
that an thanks for the interesting


00:26:10.399 --> 00:26:13.909
question um I know this isn't your area


00:26:13.919 --> 00:26:16.230
but I know you've done your homework


00:26:16.240 --> 00:26:17.310
yeah I've done a little bit reading it's


00:26:17.320 --> 00:26:18.990
a fascinating question and me it's a


00:26:19.000 --> 00:26:20.630
really important question to ask because


00:26:20.640 --> 00:26:23.470
there's a lot of Investigations into the


00:26:23.480 --> 00:26:25.230
impact of being in space that are going


00:26:25.240 --> 00:26:27.070
on particularly given that there's a


00:26:27.080 --> 00:26:30.269
future where people aspire to travel to


00:26:30.279 --> 00:26:32.950
Mars and live there or have you know


00:26:32.960 --> 00:26:34.310
space stations where people live


00:26:34.320 --> 00:26:36.070
full-time go colonize the asteroids


00:26:36.080 --> 00:26:38.590
things like that yeah um it's not my


00:26:38.600 --> 00:26:40.789
area of expertise by any means I'm not a


00:26:40.799 --> 00:26:42.590
biologist or a bi


00:26:42.600 --> 00:26:44.710
biomechanist um but it is something


00:26:44.720 --> 00:26:47.510
people are starting to do research into


00:26:47.520 --> 00:26:49.950
um I haven't been able to find anything


00:26:49.960 --> 00:26:51.750
about the difference between pre and


00:26:51.760 --> 00:26:55.110
postmenopause or about um estrogen


00:26:55.120 --> 00:26:56.710
supplements and things like that that's


00:26:56.720 --> 00:26:58.470
a really interesting question and it's


00:26:58.480 --> 00:27:00.549
almost possibly the kind of thing where


00:27:00.559 --> 00:27:02.110
you could find someone leading that kind


00:27:02.120 --> 00:27:03.669
of research and try and get involved if


00:27:03.679 --> 00:27:04.870
you want to but I did do a bit of


00:27:04.880 --> 00:27:07.750
digging around I found there is a paper


00:27:07.760 --> 00:27:11.029
that was published I found it on PubMed


00:27:11.039 --> 00:27:13.230
that was published a few years ago in


00:27:13.240 --> 00:27:16.630
2014 entitled men and women in space bur


00:27:16.640 --> 00:27:18.950
loss and kidney stone risk after long


00:27:18.960 --> 00:27:21.710
deoration space flight um which is a


00:27:21.720 --> 00:27:25.190
slightly intimidating title but they


00:27:25.200 --> 00:27:28.269
note there that finally at that stage


00:27:28.279 --> 00:27:31.909
had been enough people who identified as


00:27:31.919 --> 00:27:33.669
male and identified as female that had


00:27:33.679 --> 00:27:35.149
spent a long time in space that you


00:27:35.159 --> 00:27:36.950
could start doing a quantitative


00:27:36.960 --> 00:27:39.389
comparison they had in their sample 33


00:27:39.399 --> 00:27:41.669
men and nine women who had spent long


00:27:41.679 --> 00:27:44.830
duration missions on the space station


00:27:44.840 --> 00:27:46.430
and


00:27:46.440 --> 00:27:48.789
their bodies had been studied when they


00:27:48.799 --> 00:27:50.590
got back essentially so think like bone


00:27:50.600 --> 00:27:53.110
mineral density was evaluated before and


00:27:53.120 --> 00:27:55.710
after the flight and stuff like that and


00:27:55.720 --> 00:27:57.269
they also looked at blood and urine to


00:27:57.279 --> 00:27:58.870
look at kidney function


00:27:58.880 --> 00:28:02.630
the missions were 50 days to 215 days


00:28:02.640 --> 00:28:06.590
flown in this Millennium so 20 to 2012


00:28:06.600 --> 00:28:08.310
what they found was the following I'll


00:28:08.320 --> 00:28:09.710
read it out explicitly they said the


00:28:09.720 --> 00:28:11.590
bond density response to space flight


00:28:11.600 --> 00:28:13.590
was the same for men and women in both


00:28:13.600 --> 00:28:16.710
exercise groups so no difference um bone


00:28:16.720 --> 00:28:18.590
density response to flight was the same


00:28:18.600 --> 00:28:20.590
for men and women and the typical


00:28:20.600 --> 00:28:23.389
decrease in bone mineral density whole


00:28:23.399 --> 00:28:25.590
body and Regional afterlight was not


00:28:25.600 --> 00:28:27.430
observed for either sex for people who


00:28:27.440 --> 00:28:29.190
were using the Advanced resistance


00:28:29.200 --> 00:28:30.830
devices so they were able to recover


00:28:30.840 --> 00:28:33.750
equally well um so the fundamental


00:28:33.760 --> 00:28:35.470
comment there have a final sentence of


00:28:35.480 --> 00:28:37.149
their obstruct is the responses of men


00:28:37.159 --> 00:28:39.789
and women to space flight with respect


00:28:39.799 --> 00:28:42.549
to measures of born Health were not


00:28:42.559 --> 00:28:45.029
different which is really interesting


00:28:45.039 --> 00:28:48.470
yeah um it doesn't entirely talk about


00:28:48.480 --> 00:28:49.950
the importance of the hormones but I


00:28:49.960 --> 00:28:53.830
guess the fact that um women who are


00:28:53.840 --> 00:28:56.710
premenopause and Men experienc their


00:28:56.720 --> 00:28:58.509
bond density degradation at the same


00:28:58.519 --> 00:29:01.830
rate suggests that the elevated levels


00:29:01.840 --> 00:29:04.269
of estrogen in the women did not prevent


00:29:04.279 --> 00:29:06.269
that Bond density loss doesn't say


00:29:06.279 --> 00:29:07.669
anything about the speed at which the


00:29:07.679 --> 00:29:09.509
bond enity was recovered when they were


00:29:09.519 --> 00:29:12.630
back so I can't really comment on that


00:29:12.640 --> 00:29:16.110
but it reminded me more widely of a the


00:29:16.120 --> 00:29:18.389
risks of space flat but also the amount


00:29:18.399 --> 00:29:19.830
that we don't know and the importance of


00:29:19.840 --> 00:29:21.789
getting people with different expertises


00:29:21.799 --> 00:29:25.549
involved but also the importance of


00:29:25.559 --> 00:29:28.750
doctors and medical researchers studying


00:29:28.760 --> 00:29:30.430
women as well as men and I know from a


00:29:30.440 --> 00:29:31.870
number of my female friends that they


00:29:31.880 --> 00:29:35.190
feel very much that a lot of medications


00:29:35.200 --> 00:29:37.389
a lot of treatments assume that the male


00:29:37.399 --> 00:29:39.149
body is the normal one and Studies have


00:29:39.159 --> 00:29:40.950
not been carried out to such a great


00:29:40.960 --> 00:29:43.389
extent on the different impact of that


00:29:43.399 --> 00:29:46.070
same medication on the female body true


00:29:46.080 --> 00:29:47.950
and I've also heard of problems where


00:29:47.960 --> 00:29:49.789
male doctors have not been as well


00:29:49.799 --> 00:29:51.430
educated in female problems as they


00:29:51.440 --> 00:29:52.549
should have been and giving fairly


00:29:52.559 --> 00:29:54.269
rubbish responses so you know


00:29:54.279 --> 00:29:55.830
acknowledging those biases and


00:29:55.840 --> 00:29:56.950
acknowledging that I'm in a very


00:29:56.960 --> 00:29:59.070
privileged situation but we need more


00:29:59.080 --> 00:30:01.710
research into this NASA has on its


00:30:01.720 --> 00:30:03.750
website a statement here talking about


00:30:03.760 --> 00:30:07.549
the degree of impact on bone density so


00:30:07.559 --> 00:30:09.470
their statement is astronauts can lose


00:30:09.480 --> 00:30:11.909
up to 1 to two% of bone density per


00:30:11.919 --> 00:30:14.190
month in the hip and the


00:30:14.200 --> 00:30:18.310
spine that compares to 0.5 to 1% per


00:30:18.320 --> 00:30:20.269
year in postmenopausal women and much


00:30:20.279 --> 00:30:23.110
older men on Earth so in other words the


00:30:23.120 --> 00:30:24.549
bone loss that you're getting while


00:30:24.559 --> 00:30:27.470
you're in microgravity in space is


00:30:27.480 --> 00:30:29.909
around twice as significant as that that


00:30:29.919 --> 00:30:32.190
you experien C menopause for women all


00:30:32.200 --> 00:30:34.029
when you become significantly older for


00:30:34.039 --> 00:30:37.029
men um and that they say this rapid bone


00:30:37.039 --> 00:30:38.590
loss comp play crew members at risk for


00:30:38.600 --> 00:30:40.110
bone fractur and risk of alance


00:30:40.120 --> 00:30:42.029
osteoporosis as a result of the space


00:30:42.039 --> 00:30:44.830
flight yeah there's another study which


00:30:44.840 --> 00:30:46.909
I just stumbled across looking on this


00:30:46.919 --> 00:30:48.990
um female astronauts impact of space


00:30:49.000 --> 00:30:51.669
radiation on menopause this came out a


00:30:51.679 --> 00:30:54.389
bit more recently in April 2022 and it


00:30:54.399 --> 00:30:56.110
shows people are starting to think about


00:30:56.120 --> 00:30:58.310
this so this is a a study that is


00:30:58.320 --> 00:31:00.470
looking at the impacts of the radiation


00:31:00.480 --> 00:31:03.149
environment that you experience in space


00:31:03.159 --> 00:31:05.070
on what they call the avarian reserve so


00:31:05.080 --> 00:31:06.629
the number of viable eggs that a woman


00:31:06.639 --> 00:31:09.310
has and so the statement that really


00:31:09.320 --> 00:31:11.110
made my head hurt here is that data


00:31:11.120 --> 00:31:14.269
suggests that a typical Mars mission may


00:31:14.279 --> 00:31:16.110
reduce a woman's avarian Reserve by


00:31:16.120 --> 00:31:18.909
about 50% whoa this would have


00:31:18.919 --> 00:31:20.629
consequences to a woman's reproductive


00:31:20.639 --> 00:31:22.430
capacity and more significantly


00:31:22.440 --> 00:31:24.509
decreases the time interval to her


00:31:24.519 --> 00:31:28.070
menopause so it all reminds me slightly


00:31:28.080 --> 00:31:30.110
off topic but it this was prompted by


00:31:30.120 --> 00:31:32.590
this question I every year go to the


00:31:32.600 --> 00:31:34.110
Australian space research conference


00:31:34.120 --> 00:31:35.750
here in Australia which is a fabulous


00:31:35.760 --> 00:31:37.509
meeting and can be quite


00:31:37.519 --> 00:31:39.470
multidisciplinary but a few years ago I


00:31:39.480 --> 00:31:43.029
think possibly like 2013 2014 now we had


00:31:43.039 --> 00:31:47.230
a invited lecture from a doctor it's a


00:31:47.240 --> 00:31:48.990
doctor from Tasmania who works in space


00:31:49.000 --> 00:31:51.909
medicine as research on the site and


00:31:51.919 --> 00:31:53.750
it's the only lecture I've ever been to


00:31:53.760 --> 00:31:55.870
at a research conference which started


00:31:55.880 --> 00:31:57.149
with a trigger warning and a health


00:31:57.159 --> 00:31:59.509
warning and that was basically if


00:31:59.519 --> 00:32:00.830
there's anybody in the audience who's a


00:32:00.840 --> 00:32:02.350
bit squeamish a bit sensitive he might


00:32:02.360 --> 00:32:03.870
want to leave now this is going to be a


00:32:03.880 --> 00:32:06.149
medical talk and you're all astronomers


00:32:06.159 --> 00:32:09.149
and space researchers yeah and it


00:32:09.159 --> 00:32:12.110
included some fairly unsettling pictures


00:32:12.120 --> 00:32:14.389
that I won't relay in too much detail


00:32:14.399 --> 00:32:17.430
but this doctor was talking about the


00:32:17.440 --> 00:32:20.190
future aspiration of humanity to have a


00:32:20.200 --> 00:32:23.190
permanent presence on other astronomical


00:32:23.200 --> 00:32:25.549
bodies talk in particular about


00:32:25.559 --> 00:32:29.629
Ms and what he was speaking to was that


00:32:29.639 --> 00:32:31.830
our science fiction view of that is that


00:32:31.840 --> 00:32:33.909
you have a population on Mars that is


00:32:33.919 --> 00:32:35.710
independent so they reproduce and


00:32:35.720 --> 00:32:38.110
repopulate themselves that's what we


00:32:38.120 --> 00:32:41.029
think of and he said it isn't as simple


00:32:41.039 --> 00:32:42.950
as that from a doctor's point of view


00:32:42.960 --> 00:32:44.789
from someone who studied pregnancy he


00:32:44.799 --> 00:32:48.430
was talking about the requirement the


00:32:48.440 --> 00:32:50.470
importance of gravity to gravity to


00:32:50.480 --> 00:32:51.870
pregnancy is something we never think


00:32:51.880 --> 00:32:53.870
about because we're all living on the


00:32:53.880 --> 00:32:56.190
surface of the Earth at one G but he


00:32:56.200 --> 00:32:59.470
said it's actually the case and remember


00:32:59.480 --> 00:33:00.789
I'm remembering a talk here from more


00:33:00.799 --> 00:33:03.549
than a decade ago he spoke about how


00:33:03.559 --> 00:33:06.389
important the gravity that you are


00:33:06.399 --> 00:33:09.389
moving within is to the development of


00:33:09.399 --> 00:33:10.870
the fetus and the way that the cells


00:33:10.880 --> 00:33:13.149
know what to make and what shape to make


00:33:13.159 --> 00:33:15.870
and he gave the example of how even a


00:33:15.880 --> 00:33:18.750
very small change from the standard


00:33:18.760 --> 00:33:21.269
atmospheric temperature and pressure and


00:33:21.279 --> 00:33:23.990
gravity can cause huge Problems by


00:33:24.000 --> 00:33:25.389
talking about the invasion of the


00:33:25.399 --> 00:33:28.110
Spanish into South America and in the


00:33:28.120 --> 00:33:30.070
1600s and the fact that the high Andes


00:33:30.080 --> 00:33:32.830
were never conquered permanently because


00:33:32.840 --> 00:33:35.269
the Conquistadors couldn't reproduce


00:33:35.279 --> 00:33:37.789
there they were just not able to be


00:33:37.799 --> 00:33:39.909
viable there and the native people there


00:33:39.919 --> 00:33:41.789
had obviously adusted over many many


00:33:41.799 --> 00:33:43.909
generations and he said that's barely


00:33:43.919 --> 00:33:45.830
any different to the conditions


00:33:45.840 --> 00:33:48.750
here what he was going on to say was


00:33:48.760 --> 00:33:51.549
that his vision is that because of this


00:33:51.559 --> 00:33:53.750
this would be so insurmountable that for


00:33:53.760 --> 00:33:55.430
a very long time once we have a


00:33:55.440 --> 00:33:56.990
permanent presence on Mars it would be a


00:33:57.000 --> 00:33:58.310
retirement heart


00:33:58.320 --> 00:34:00.070
it'll be somewhere that people go to


00:34:00.080 --> 00:34:01.710
after they've saw their wild arts on


00:34:01.720 --> 00:34:04.470
Earth that they go to to spend their


00:34:04.480 --> 00:34:06.470
later years in a in a more pleasant


00:34:06.480 --> 00:34:08.710
environment with lower gravity less


00:34:08.720 --> 00:34:12.149
strands on an on an aging aching body


00:34:12.159 --> 00:34:14.230
but he didn't foresee any possibility of


00:34:14.240 --> 00:34:17.950
people reproducing that and unless we


00:34:17.960 --> 00:34:19.589
went down the incredibly distopian


00:34:19.599 --> 00:34:22.109
worldview of having women living in


00:34:22.119 --> 00:34:24.230
centrifuges for nine months to simulate


00:34:24.240 --> 00:34:27.389
1 G which I I can imagine would not be a


00:34:27.399 --> 00:34:31.069
very popular decision but it ties into


00:34:31.079 --> 00:34:34.389
Mars one which was this attempt by I


00:34:34.399 --> 00:34:37.629
think a Dutch um guy to make a lot of


00:34:37.639 --> 00:34:40.589
money out of sending a mission to Mars


00:34:40.599 --> 00:34:43.230
to try and get the first humans on Mars


00:34:43.240 --> 00:34:45.430
and they run a huge competition process


00:34:45.440 --> 00:34:47.349
for this with more than 100,000 initial


00:34:47.359 --> 00:34:48.629
applicants and they whittled them down


00:34:48.639 --> 00:34:50.550
and whittel them down but there was an


00:34:50.560 --> 00:34:52.109
Australian involved in this guy called


00:34:52.119 --> 00:34:53.829
Josh Richards who's a fabulous science


00:34:53.839 --> 00:34:55.950
communicator and did a lot of work off


00:34:55.960 --> 00:34:58.069
the back of this of going into schs and


00:34:58.079 --> 00:34:59.390
talking to kids and saying I could be


00:34:59.400 --> 00:35:01.829
the first person on M ask me anything


00:35:01.839 --> 00:35:04.069
essentially one of the things that Josh


00:35:04.079 --> 00:35:06.870
told me that led to problems and in the


00:35:06.880 --> 00:35:08.069
end led to the breakup of his


00:35:08.079 --> 00:35:09.550
relationship with his partner as he went


00:35:09.560 --> 00:35:12.030
through this process was that a he was


00:35:12.040 --> 00:35:14.710
looking at taking a oneway trip to Mars


00:35:14.720 --> 00:35:17.589
um but also that the people who were the


00:35:17.599 --> 00:35:20.630
final selected ones had to agree to be


00:35:20.640 --> 00:35:23.790
medically sterilized before they got on


00:35:23.800 --> 00:35:26.750
the trip to Mars because they were going


00:35:26.760 --> 00:35:28.550
from mix to crew the mix crew had to


00:35:28.560 --> 00:35:30.109
make their own entertainment during the


00:35:30.119 --> 00:35:32.390
travels and because his show was going


00:35:32.400 --> 00:35:34.550
to be delivered Big Brother style that


00:35:34.560 --> 00:35:36.030
was probably part of the motivation for


00:35:36.040 --> 00:35:37.829
people subscribing to


00:35:37.839 --> 00:35:41.470
beis the lack of understanding of the


00:35:41.480 --> 00:35:43.230
possibilities and the risks of pregnancy


00:35:43.240 --> 00:35:45.710
during space fight in micro gravity or


00:35:45.720 --> 00:35:49.030
on Mars in incredibly reduced gravity


00:35:49.040 --> 00:35:50.790
was such that nobody could see any


00:35:50.800 --> 00:35:52.870
possibility of any viability of


00:35:52.880 --> 00:35:54.829
pregnancy but it wasn't like they were


00:35:54.839 --> 00:35:56.550
going to send people with the medical


00:35:56.560 --> 00:35:58.670
skills to deal with traumatic problems


00:35:58.680 --> 00:36:01.030
like that on the mission so you had to


00:36:01.040 --> 00:36:02.550
agree to either be sterilized or you


00:36:02.560 --> 00:36:04.950
wouldn't go and the pick someone else


00:36:04.960 --> 00:36:06.470
which sounds really


00:36:06.480 --> 00:36:08.589
barbaric but it's the unfortunate


00:36:08.599 --> 00:36:10.069
reality we're going to have to deal with


00:36:10.079 --> 00:36:12.309
when we start looking at having a


00:36:12.319 --> 00:36:14.750
permanent presence of Earth rather than


00:36:14.760 --> 00:36:16.829
just going and visiting because if we


00:36:16.839 --> 00:36:18.309
want to have a perent presence on the


00:36:18.319 --> 00:36:21.790
moon or on Mars we view that inherently


00:36:21.800 --> 00:36:23.510
as humans has been a self-replicating


00:36:23.520 --> 00:36:25.349
presence we view it as been a presence


00:36:25.359 --> 00:36:27.829
that can sustain itself you know so if


00:36:27.839 --> 00:36:29.430
the population of Earth got wiped out at


00:36:29.440 --> 00:36:31.870
least we've got the people on Mars but


00:36:31.880 --> 00:36:33.270
in order to do that it's going to need


00:36:33.280 --> 00:36:35.109
an incredible amount of medical research


00:36:35.119 --> 00:36:38.870
to be done and incredible advances in


00:36:38.880 --> 00:36:40.550
medical technology that we just don't


00:36:40.560 --> 00:36:43.230
have yet and what's been asked in the


00:36:43.240 --> 00:36:45.750
question here about Bond density in


00:36:45.760 --> 00:36:47.790
space about the role of estrogen in


00:36:47.800 --> 00:36:49.390
replacing the bonds afterwards on the


00:36:49.400 --> 00:36:51.430
impact of people who are passed to


00:36:51.440 --> 00:36:53.510
premenopausal that all comes into it as


00:36:53.520 --> 00:36:54.990
well because we can't just do the


00:36:55.000 --> 00:36:56.470
research quite frankly on Old


00:36:56.480 --> 00:36:58.550
middle-aged white guys


00:36:58.560 --> 00:37:00.550
we need to look at the diversity not


00:37:00.560 --> 00:37:03.030
just in terms of gender diversity but as


00:37:03.040 --> 00:37:05.390
we move forward our different groups of


00:37:05.400 --> 00:37:08.349
people better suited or Worse suited to


00:37:08.359 --> 00:37:10.630
life in space we know that people from


00:37:10.640 --> 00:37:12.349
different cultures and different


00:37:12.359 --> 00:37:14.910
countries have slightly different


00:37:14.920 --> 00:37:17.430
physiological properties there will need


00:37:17.440 --> 00:37:18.910
to be research done into this and we'll


00:37:18.920 --> 00:37:20.589
need to look at people across the whole


00:37:20.599 --> 00:37:22.950
spectrum of humanity to understand it


00:37:22.960 --> 00:37:24.829
rather than just basing everything on


00:37:24.839 --> 00:37:26.390
the first few people went to space who


00:37:26.400 --> 00:37:29.829
were pretty much uniformly very athletic


00:37:29.839 --> 00:37:32.309
very well Tred white men of a certain


00:37:32.319 --> 00:37:34.829
ede that's just one part of his subset


00:37:34.839 --> 00:37:36.309
so it's a really interesting question I


00:37:36.319 --> 00:37:38.750
don't have more answers to that but


00:37:38.760 --> 00:37:40.630
really thank you for asking it make


00:37:40.640 --> 00:37:42.109
there's a lot to think about and it does


00:37:42.119 --> 00:37:43.990
make my head hurt in a very different


00:37:44.000 --> 00:37:45.750
way to the cosmology making my head hurt


00:37:45.760 --> 00:37:46.990
thing it's a different part of my brain


00:37:47.000 --> 00:37:48.630
that's hurting at the minute yes


00:37:48.640 --> 00:37:51.430
absolutely I I can tell you that uh you


00:37:51.440 --> 00:37:53.270
know when it comes to studies into


00:37:53.280 --> 00:37:55.790
medicines that you referred to um my


00:37:55.800 --> 00:37:58.510
wife and I have experienced firstand and


00:37:58.520 --> 00:38:00.309
the effective medicines that have been


00:38:00.319 --> 00:38:05.030
created and developed for men yeah um by


00:38:05.040 --> 00:38:07.190
default not purposely developed for men


00:38:07.200 --> 00:38:09.109
just developed for everybody but based


00:38:09.119 --> 00:38:10.710
on the


00:38:10.720 --> 00:38:14.990
physiological uh male um I can take an


00:38:15.000 --> 00:38:17.670
antibiotic and not feel a thing my wife


00:38:17.680 --> 00:38:19.589
can take the same tablet and she's sick


00:38:19.599 --> 00:38:23.589
for a day classic example of it so I I


00:38:23.599 --> 00:38:24.790
know exactly what you're talking about


00:38:24.800 --> 00:38:26.270
there needs to be a lot more research


00:38:26.280 --> 00:38:30.550
into medicines for wom um to suit their


00:38:30.560 --> 00:38:33.750
physiology uh also an I can tell you


00:38:33.760 --> 00:38:36.750
that um people on Earth suffer the same


00:38:36.760 --> 00:38:38.349
problems as they do in space


00:38:38.359 --> 00:38:40.510
particularly people who are uh


00:38:40.520 --> 00:38:42.589
undergoing hormone therapy for cancer


00:38:42.599 --> 00:38:46.349
treatment they lose muscle mass and bone


00:38:46.359 --> 00:38:49.270
density and in long-term therapy can


00:38:49.280 --> 00:38:50.270
develop


00:38:50.280 --> 00:38:53.270
osteoporosis and the solution to that is


00:38:53.280 --> 00:38:56.550
exercise but it's um yeah it's it's a


00:38:56.560 --> 00:38:57.990
tough battle


00:38:58.000 --> 00:39:01.510
um I'm all too aware of it myself but uh


00:39:01.520 --> 00:39:04.270
it's yeah that it's the same problem on


00:39:04.280 --> 00:39:06.150
earth when it comes to to treating


00:39:06.160 --> 00:39:08.190
cancer at the moment with some kinds of


00:39:08.200 --> 00:39:10.390
hormone therapy but thanks for the


00:39:10.400 --> 00:39:12.750
question brilliant question loved it


00:39:12.760 --> 00:39:14.630
keep them coming uh our final question


00:39:14.640 --> 00:39:18.230
comes from Dean two Dean two because we


00:39:18.240 --> 00:39:20.670
had Dean earlier sorry Dean two you


00:39:20.680 --> 00:39:21.950
became Dean two because you're the


00:39:21.960 --> 00:39:23.430
second on the


00:39:23.440 --> 00:39:27.829
list it pardon aie Dean uh yeah think so


00:39:27.839 --> 00:39:30.270
let's find out hi Fred and Andrew this


00:39:30.280 --> 00:39:32.670
is Dean in redcliff in Queensland can


00:39:32.680 --> 00:39:34.550
you explain why there is a fixed amount


00:39:34.560 --> 00:39:36.870
of centrifugal force measurable on an


00:39:36.880 --> 00:39:39.230
object at the earth's equator but its


00:39:39.240 --> 00:39:41.470
angular velocity which is the cause of


00:39:41.480 --> 00:39:44.069
this apparent force can only be measured


00:39:44.079 --> 00:39:46.349
relative to another object's frame of


00:39:46.359 --> 00:39:49.390
reference what I mean is an 80 kilogram


00:39:49.400 --> 00:39:51.430
person should weigh about 300 gram less


00:39:51.440 --> 00:39:53.550
at the equator than at the pole and this


00:39:53.560 --> 00:39:55.950
can be measured however the calculation


00:39:55.960 --> 00:39:58.430
for centrifugal force uses the angular


00:39:58.440 --> 00:40:00.950
velocity of the person going around the


00:40:00.960 --> 00:40:03.910
earth axis which is measured using the


00:40:03.920 --> 00:40:06.390
frequency of the earth spin where the


00:40:06.400 --> 00:40:07.910
Earth's diameter and circumference are


00:40:07.920 --> 00:40:10.990
fixed the Earth spins once in 24 hours


00:40:11.000 --> 00:40:14.030
relative to the sun once in 24 hours 40


00:40:14.040 --> 00:40:16.950
minutes relative to the moon and once in


00:40:16.960 --> 00:40:20.510
23 hours 56 minutes relative to distant


00:40:20.520 --> 00:40:22.950
Stars although these frequencies are all


00:40:22.960 --> 00:40:25.230
fairly close they would each give


00:40:25.240 --> 00:40:27.430
different answers to the calculation yet


00:40:27.440 --> 00:40:29.710
we can measure centrifugal force as a


00:40:29.720 --> 00:40:34.270
fixed amount although objects in all


00:40:34.280 --> 00:40:36.589
objects in space are moving I suspect


00:40:36.599 --> 00:40:38.910
that space itself does not move even


00:40:38.920 --> 00:40:42.390
though it's expanding so does space time


00:40:42.400 --> 00:40:44.030
have a fixed structure that determines


00:40:44.040 --> 00:40:46.670
Direction without reference to objects


00:40:46.680 --> 00:40:50.309
within it thanks for the podcast wow


00:40:50.319 --> 00:40:52.430
thanks Dane we sort of hinted at


00:40:52.440 --> 00:40:55.230
centrifugal force earlier but this is a


00:40:55.240 --> 00:40:56.990
kind of this is a different angle on it


00:40:57.000 --> 00:41:00.190
B boom boom boom it's an awesome


00:41:00.200 --> 00:41:01.750
question there's a couple of different


00:41:01.760 --> 00:41:04.630
parts to it so I'll initially talk about


00:41:04.640 --> 00:41:07.069
the effect of the earth rotation on your


00:41:07.079 --> 00:41:09.270
weight I think that's a good one in


00:41:09.280 --> 00:41:12.109
terms of the dependence on reference


00:41:12.119 --> 00:41:14.550
frame there isn't really dependence on a


00:41:14.560 --> 00:41:17.910
reference frame for it because what we


00:41:17.920 --> 00:41:20.670
measure is what is actually happening so


00:41:20.680 --> 00:41:23.829
the Earth rotates at a certain speed and


00:41:23.839 --> 00:41:25.630
because you're moving at that speed


00:41:25.640 --> 00:41:28.390
you've got gravity pulling you down


00:41:28.400 --> 00:41:30.309
but the movement that you've got the


00:41:30.319 --> 00:41:32.430
rotation is carrying you off at right


00:41:32.440 --> 00:41:34.470
angles to gravity and you're kind of


00:41:34.480 --> 00:41:36.829
falling around as you go around so


00:41:36.839 --> 00:41:38.109
because you're not falling into the


00:41:38.119 --> 00:41:40.349
Earth but you're also not escaping from


00:41:40.359 --> 00:41:42.150
the earth because of your movement so


00:41:42.160 --> 00:41:43.510
there there's a little bit of an outward


00:41:43.520 --> 00:41:46.390
false balancing gravity that's the net


00:41:46.400 --> 00:41:48.030
result of it so we we can work this


00:41:48.040 --> 00:41:50.069
through with all the maths and I


00:41:50.079 --> 00:41:51.430
sometimes do this derivation from my


00:41:51.440 --> 00:41:53.950
students it's kind of vaguely elegant


00:41:53.960 --> 00:41:55.470
and again the orbital period for things


00:41:55.480 --> 00:41:58.430
you can do this kind of mats


00:41:58.440 --> 00:42:00.550
what's effectively happening though is


00:42:00.560 --> 00:42:03.309
that you have an acceleration going on


00:42:03.319 --> 00:42:06.230
you're you're an accelerating object and


00:42:06.240 --> 00:42:07.790
because of your motion as you rotate


00:42:07.800 --> 00:42:10.190
around the earth you do one full app in


00:42:10.200 --> 00:42:12.829
a certain amount of time that means it


00:42:12.839 --> 00:42:14.190
is as though you're being pulled towards


00:42:14.200 --> 00:42:15.950
the Middle with a certain acceleration


00:42:15.960 --> 00:42:17.309
and that's the acceleration due to


00:42:17.319 --> 00:42:20.710
gravity you feel and the faster you spin


00:42:20.720 --> 00:42:22.990
the lower that pull towards the middle


00:42:23.000 --> 00:42:24.589
feels like it is because you're offset


00:42:24.599 --> 00:42:27.349
by the you know centrifugal force you


00:42:27.359 --> 00:42:29.069
feel which is a virtual force feeling


00:42:29.079 --> 00:42:31.750
like it's pushing outwards by


00:42:31.760 --> 00:42:34.950
comparison the real number you measure


00:42:34.960 --> 00:42:37.589
is based around what the acceleration on


00:42:37.599 --> 00:42:38.950
your body actually is and that's


00:42:38.960 --> 00:42:40.190
something that's


00:42:40.200 --> 00:42:42.510
quantifiable and that is down to you


00:42:42.520 --> 00:42:45.910
completing exactly one lap of the Earth


00:42:45.920 --> 00:42:49.309
in the reference frame of the earth so


00:42:49.319 --> 00:42:50.670
that's the one thing that was missing


00:42:50.680 --> 00:42:52.430
from this we talk about the sun we talk


00:42:52.440 --> 00:42:53.910
about the distant Stars we talk about


00:42:53.920 --> 00:42:55.910
the moon but in reality you're talking


00:42:55.920 --> 00:42:58.710
about in the Earth rest frame so you're


00:42:58.720 --> 00:43:00.349
going around in a circle around the


00:43:00.359 --> 00:43:03.510
center of the earth that takes you 23


00:43:03.520 --> 00:43:06.309
hours 56 minutes and 4 seconds the


00:43:06.319 --> 00:43:08.150
distance stars are just a reference


00:43:08.160 --> 00:43:09.750
point where we can see that far but it's


00:43:09.760 --> 00:43:11.349
all relative to the position of the


00:43:11.359 --> 00:43:14.069
earth and so that's what gives you your


00:43:14.079 --> 00:43:17.790
300 grams less the sun and the moon are


00:43:17.800 --> 00:43:20.349
also moving in the rest frame of the


00:43:20.359 --> 00:43:22.990
Earth the Sun does one full lap around


00:43:23.000 --> 00:43:25.270
the Earth in one year the moon does one


00:43:25.280 --> 00:43:27.589
full lap in one month so that's why


00:43:27.599 --> 00:43:29.190
you've got those slightly longer times


00:43:29.200 --> 00:43:30.510
because the Earth's got to turn a little


00:43:30.520 --> 00:43:32.270
bit more than one full Revolution before


00:43:32.280 --> 00:43:34.589
the sun is directly overhead or before


00:43:34.599 --> 00:43:36.349
the Moon is directly over head so that


00:43:36.359 --> 00:43:38.910
isn't a rest frame that's a moving frame


00:43:38.920 --> 00:43:41.109
that's a rotating frame essentially if


00:43:41.119 --> 00:43:42.549
you measure it with respect to the


00:43:42.559 --> 00:43:44.349
sunbean over head the whole of the


00:43:44.359 --> 00:43:46.270
Earth's frame has had to rotate round in


00:43:46.280 --> 00:43:48.910
that case it brings us on to the


00:43:48.920 --> 00:43:51.349
concepts of rest frames and how you


00:43:51.359 --> 00:43:53.950
measure them and what is the universal


00:43:53.960 --> 00:43:57.390
rest frame um that's again where it gets


00:43:57.400 --> 00:44:00.309
really really headachy now to my


00:44:00.319 --> 00:44:02.910
knowledge it isn't thought in any of the


00:44:02.920 --> 00:44:08.270
models of space time but SpaceTime is


00:44:08.280 --> 00:44:10.390
fixed and distinct from the objects


00:44:10.400 --> 00:44:13.790
within it rather any object that is


00:44:13.800 --> 00:44:16.349
moving at a fixed speed and not


00:44:16.359 --> 00:44:19.670
experiencing any


00:44:19.680 --> 00:44:23.309
acceleration is in a rest frame it's at


00:44:23.319 --> 00:44:25.630
rest locally it's not


00:44:25.640 --> 00:44:27.910
accelerating and so it can look out at


00:44:27.920 --> 00:44:31.230
the entire universe from its perspective


00:44:31.240 --> 00:44:33.870
and any accelerations that it sees and


00:44:33.880 --> 00:44:35.790
any motions that it sees of what's


00:44:35.800 --> 00:44:38.069
actually happening out there if you're


00:44:38.079 --> 00:44:39.829
in an accelerating rest frame you are


00:44:39.839 --> 00:44:41.589
not in a rest frame by definition


00:44:41.599 --> 00:44:44.349
because you're accelerating so a person


00:44:44.359 --> 00:44:45.910
on the surface of the Earth is


00:44:45.920 --> 00:44:48.270
accelerating as we go around the earth


00:44:48.280 --> 00:44:50.510
as the Earth rotates and as the earth


00:44:50.520 --> 00:44:52.069
goes around the Sun and as the Earth


00:44:52.079 --> 00:44:53.710
orbits in the center of mass of the


00:44:53.720 --> 00:44:56.270
Earth Moon system and all the rest of it


00:44:56.280 --> 00:44:58.870
so we're not at actually in what I think


00:44:58.880 --> 00:45:01.670
is often described as an inertial


00:45:01.680 --> 00:45:04.670
threat however you you do a lot of


00:45:04.680 --> 00:45:07.030
thought experiments that are near enough


00:45:07.040 --> 00:45:09.470
if you were free floating in space away


00:45:09.480 --> 00:45:11.470
from any of the Stars you'd probably


00:45:11.480 --> 00:45:12.829
consider yourself to be an inertial


00:45:12.839 --> 00:45:14.190
friend but even then you'd have some


00:45:14.200 --> 00:45:15.790
acceleration from the


00:45:15.800 --> 00:45:19.230
STS there isn't really as far as I know


00:45:19.240 --> 00:45:20.349
and this is where we get onto the


00:45:20.359 --> 00:45:23.109
cosmology stuff which is more woolly for


00:45:23.119 --> 00:45:25.870
me and so I'm giving a less accurate and


00:45:25.880 --> 00:45:27.750
less good quality answer apologize for


00:45:27.760 --> 00:45:30.430
that but there isn't to my knowledge any


00:45:30.440 --> 00:45:33.190
universally accepted rest threat because


00:45:33.200 --> 00:45:34.790
everything is moving and everything is


00:45:34.800 --> 00:45:36.430
accelerating and feeling the gravity of


00:45:36.440 --> 00:45:39.069
everything else but the way that our


00:45:39.079 --> 00:45:42.950
models of the universe work is that they


00:45:42.960 --> 00:45:44.670
have this concept of SpaceTime but it


00:45:44.680 --> 00:45:46.990
isn't like space time is a fra fabric


00:45:47.000 --> 00:45:48.710
that is physical over which everything


00:45:48.720 --> 00:45:51.910
moves and is itself fixed even space


00:45:51.920 --> 00:45:54.549
time is moving and dragged around I'm


00:45:54.559 --> 00:45:57.190
aware that this is an answer that


00:45:57.200 --> 00:45:59.349
quickly devolving from sensible into the


00:45:59.359 --> 00:46:01.030
incoherent and that's because this is


00:46:01.040 --> 00:46:02.510
pushing the the limits of what my


00:46:02.520 --> 00:46:05.549
knowledge is but it's also pushing the


00:46:05.559 --> 00:46:07.510
conceptual limits on which we build the


00:46:07.520 --> 00:46:09.910
foundations of stuff and that's because


00:46:09.920 --> 00:46:11.630
a lot of the models and particular a lot


00:46:11.640 --> 00:46:13.390
of the way the models we use are


00:46:13.400 --> 00:46:16.870
described we simplify things to make it


00:46:16.880 --> 00:46:18.829
clearer how everything


00:46:18.839 --> 00:46:21.270
works you know so we talk about an


00:46:21.280 --> 00:46:22.829
object at rest you know people are


00:46:22.839 --> 00:46:24.630
explaining special relativity for the


00:46:24.640 --> 00:46:26.670
first time will talk about an object at


00:46:26.680 --> 00:46:28.430
rest than another object moving at a


00:46:28.440 --> 00:46:30.470
fine XX that is near the speed of like


00:46:30.480 --> 00:46:32.430
relative to it and that's a great


00:46:32.440 --> 00:46:35.109
thought experiment the reality is a lot


00:46:35.119 --> 00:46:37.510
of the time that we are so close to


00:46:37.520 --> 00:46:39.069
being in that situation that you can


00:46:39.079 --> 00:46:41.470
ignore the effects of the little bits at


00:46:41.480 --> 00:46:43.750
turb it unless you've got incredibly


00:46:43.760 --> 00:46:45.910
good measuring equipment so from the


00:46:45.920 --> 00:46:47.870
point of view of to totally switch


00:46:47.880 --> 00:46:49.829
analogies I was watching the cricket the


00:46:49.839 --> 00:46:51.589
other night if you imagine two


00:46:51.599 --> 00:46:53.109
cricketers and somebody running in and


00:46:53.119 --> 00:46:55.790
bowling the cricket ball but instead of


00:46:55.800 --> 00:46:57.349
it bouncing it just goes straight on so


00:46:57.359 --> 00:46:59.589
it's a full toss it's a beamer um nasty


00:46:59.599 --> 00:47:02.910
delivery boo his y all the rest of it


00:47:02.920 --> 00:47:05.150
the only thing that is going on in terms


00:47:05.160 --> 00:47:06.950
of predicting the trajectory of that


00:47:06.960 --> 00:47:09.270
ball is that it has that acceleration


00:47:09.280 --> 00:47:10.829
pulling it down there's a little bit of


00:47:10.839 --> 00:47:13.430
air resistance as well if the ball's


00:47:13.440 --> 00:47:15.150
spinning you get boli effects and things


00:47:15.160 --> 00:47:17.750
that can cause it swerve but that ball


00:47:17.760 --> 00:47:20.109
is moving and we can treat it as the


00:47:20.119 --> 00:47:22.150
cricet pitch and all of the players are


00:47:22.160 --> 00:47:24.829
in a shared initial rest frame there's


00:47:24.839 --> 00:47:26.230
nothing else going on other than this


00:47:26.240 --> 00:47:27.870
single gravity ational Force pulling


00:47:27.880 --> 00:47:30.190
down we don't have to take account of


00:47:30.200 --> 00:47:33.030
things like the coris effect which is


00:47:33.040 --> 00:47:34.270
another virtual force like the


00:47:34.280 --> 00:47:36.510
centrifugal force that is a result of


00:47:36.520 --> 00:47:37.990
the rotation of the earth and the


00:47:38.000 --> 00:47:39.230
different rotation of speeds at


00:47:39.240 --> 00:47:41.710
different latitudes we can treat that in


00:47:41.720 --> 00:47:44.549
local isolated case as though it is a


00:47:44.559 --> 00:47:46.430
much simpler scenario than it is because


00:47:46.440 --> 00:47:48.990
all those other Corrections are so small


00:47:49.000 --> 00:47:51.349
that they don't really impact things


00:47:51.359 --> 00:47:53.069
what it leads to though is we tend to


00:47:53.079 --> 00:47:54.870
explain things using those simpler


00:47:54.880 --> 00:47:58.150
things simpler scenarios


00:47:58.160 --> 00:48:00.309
and that leads to questions like this


00:48:00.319 --> 00:48:02.790
because it leads to the idea that there


00:48:02.800 --> 00:48:05.190
is something external to the Earth and


00:48:05.200 --> 00:48:08.270
the Sun and to us us as observers that


00:48:08.280 --> 00:48:10.950
is in itself fixed and there that there


00:48:10.960 --> 00:48:13.390
is an absolute idealized frame of


00:48:13.400 --> 00:48:15.790
reference my understanding is that all


00:48:15.800 --> 00:48:18.430
of our models do not argue that when you


00:48:18.440 --> 00:48:20.270
get into the nitty


00:48:20.280 --> 00:48:23.069
gritt it's a willly answer I appreciate


00:48:23.079 --> 00:48:25.430
is probably not an ideal answer Dean and


00:48:25.440 --> 00:48:26.829
you know if that answer was not


00:48:26.839 --> 00:48:28.790
satisfactory for you please ask Fred


00:48:28.800 --> 00:48:30.670
when he's back and get a different


00:48:30.680 --> 00:48:32.790
version I do think this is important for


00:48:32.800 --> 00:48:34.190
anybody who's learning actually I say


00:48:34.200 --> 00:48:35.950
this to my I've got a tutorial in a


00:48:35.960 --> 00:48:37.150
couple of hours which why I'm thinking


00:48:37.160 --> 00:48:40.309
in this head space my explanations are


00:48:40.319 --> 00:48:42.549
one explanation of how things work and


00:48:42.559 --> 00:48:44.630
they'll work for some people but we all


00:48:44.640 --> 00:48:46.109
think about the universe differently and


00:48:46.119 --> 00:48:47.510
there is no shame in saying that


00:48:47.520 --> 00:48:49.630
explanation didn't work for me let me


00:48:49.640 --> 00:48:52.549
find another yeah it's really important


00:48:52.559 --> 00:48:54.910
if my explanation of that which


00:48:54.920 --> 00:48:57.150
admittedly you know was probably not a


00:48:57.160 --> 00:48:59.630
perfect explanation even for me um


00:48:59.640 --> 00:49:01.829
doesn't work for you there will be other


00:49:01.839 --> 00:49:03.910
explanations around it's worth asking


00:49:03.920 --> 00:49:05.349
another person to get a different


00:49:05.359 --> 00:49:06.870
perspective if what I said there didn't


00:49:06.880 --> 00:49:09.190
make sense and there is no problem with


00:49:09.200 --> 00:49:10.630
that I will not be offended if you ask


00:49:10.640 --> 00:49:12.990
Fred in two weeks and say jonty fail to


00:49:13.000 --> 00:49:14.789
explain this his explanation was rubbish


00:49:14.799 --> 00:49:16.950
tell me what's really happening Fred and


00:49:16.960 --> 00:49:20.030
then let him go and see what


00:49:20.040 --> 00:49:22.549
happens okay fair enough um great


00:49:22.559 --> 00:49:25.109
question very deep thinking there Dean


00:49:25.119 --> 00:49:27.190
and thanks for sending it in if you'd


00:49:27.200 --> 00:49:28.950
like to send us a question you can do


00:49:28.960 --> 00:49:30.549
that on our website SPAC nuts


00:49:30.559 --> 00:49:33.309
podcast.com or SPAC nuts.i click on the


00:49:33.319 --> 00:49:35.549
AMA button up the top and you can send


00:49:35.559 --> 00:49:37.670
us text and audio questions and have a


00:49:37.680 --> 00:49:39.150
look around while you're there you're


00:49:39.160 --> 00:49:40.870
always welcome to our website or our


00:49:40.880 --> 00:49:44.349
social media on Facebook or Instagram or


00:49:44.359 --> 00:49:47.430
YouTube if you're a YouTube uh follower


00:49:47.440 --> 00:49:49.309
um thanks for your support we got uh


00:49:49.319 --> 00:49:51.510
quite a quite a large audience on


00:49:51.520 --> 00:49:54.630
YouTube these days


00:49:54.640 --> 00:49:57.109
um that's it are we're done was looking


00:49:57.119 --> 00:49:58.910
for another question johy thank you so


00:49:58.920 --> 00:50:00.750
much that's an absolute pleasure


00:50:00.760 --> 00:50:02.750
obviously didn't talk too much today


00:50:02.760 --> 00:50:04.789
first time for


00:50:04.799 --> 00:50:06.789
everything you might want to look at the


00:50:06.799 --> 00:50:10.230
time ticking up here on my on my clock


00:50:10.240 --> 00:50:11.670
uh thanks Johnny we'll catch you next


00:50:11.680 --> 00:50:14.230
time Johnny Horner professor of Astro


00:50:14.240 --> 00:50:15.630
physics at the University of Southern


00:50:15.640 --> 00:50:17.510
Queensland and thanks to he in the


00:50:17.520 --> 00:50:19.190
studio who couldn't be with us again


00:50:19.200 --> 00:50:20.990
today because he was over producing


00:50:21.000 --> 00:50:23.150
methane yeah he'll be out of hospital


00:50:23.160 --> 00:50:25.950
soon and from me Andrew Andrew Dunley


00:50:25.960 --> 00:50:27.549
thanks for your company see you on the


00:50:27.559 --> 00:50:31.069
next episode of Space Nuts goodbye nuts


00:50:31.079 --> 00:50:34.430
you been listening to the Space Nuts


00:50:34.440 --> 00:50:37.510
podcast available at Apple podcasts


00:50:37.520 --> 00:50:40.510
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00:50:40.520 --> 00:50:42.789
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00:50:42.799 --> 00:50:45.510
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00:50:45.520 --> 00:50:47.910
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00:50:47.920 --> 00:50:50.920
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