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  1. SubscriberSuzianne
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    03 Jul '19 11:25
    @humy said
    I watched that youtube and it gave me an idea for how we could live long after bright stars like our sun have burned themselves out and we are left with brown dwarfs; rather than use energy from the brown dwarfs which as I understand it would be very problematic, we could develop a more advanced form of fusion power on the surface of our chosen planets that uses not just hydroge ...[text shortened]... as silicon we will need much higher temperatures to make that work making it even harder to develop.
    I'm not even sure we could do silicon. The end result of stellar fusion is naturally iron, atomic weights above that cannot be fused naturally except through nova explosions, and up to iron is only possible because of the intense gravity of a star. Could we create the gravity necessary to fuse silicon on earth? Would it be worth the energy we'd have to put into it? Am I confusing different aspects of physics here?
  2. Subscribersonhouse
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    03 Jul '19 15:41
    @suzianne said
    I'm not even sure we could do silicon. The end result of stellar fusion is naturally iron, atomic weights above that cannot be fused naturally except through nova explosions, and up to iron is only possible because of the intense gravity of a star. Could we create the gravity necessary to fuse silicon on earth? Would it be worth the energy we'd have to put into it? Am I confusing different aspects of physics here?
    It would mean fusion at billions of degrees K V millions it takes for hydrogen and such. We can't even do 100 million degrees for more than a few milliseconds right now. AND we pump in tens of megawatts to do THAT😉
    There was a piece I just read that says dumping in rice size pellets of beryllium into the plasma settles it down so that is one new development and there are private companies pushing fusion so we will see.
    The main point is all this talk about humans doing stuff billions of years from now does not seem to be including the pesky detail it is unlikely we will be around even ten million years from now as a species, we have to go extinct at some point and right now we don't have generation spacecraft sending ten thousand colonists to Alpha Centauri or some such. The way things are going now it is not a sure bet we will even have a space program anywhere on the planet in two hundred years if climate change screws everything up so bad we are into total survival mode and forget spaceships....
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    03 Jul '19 15:58
    @sonhouse said
    It would mean fusion at billions of degrees K V millions it takes for hydrogen and such. We can't even do 100 million degrees for more than a few milliseconds right now. AND we pump in tens of megawatts to do THAT😉
    There was a piece I just read that says dumping in rice size pellets of beryllium into the plasma settles it down so that is one new development and there are p ...[text shortened]... climate change screws everything up so bad we are into total survival mode and forget spaceships....
    Put Bezos and Musk in a room together, give them $150 billion of the Pentagon's money (a mere 3% of the US budget) and they'll figure out how to get a habitable Amazon warehouse-sized spaceship into orbit. 200 people can live in that, grow vegetables, raise some rabbits. We'd learn so much.
  4. Standard memberDeepThought
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    05 Jul '19 20:30
    @suzianne said
    I'm not even sure we could do silicon. The end result of stellar fusion is naturally iron, atomic weights above that cannot be fused naturally except through nova explosions, and up to iron is only possible because of the intense gravity of a star. Could we create the gravity necessary to fuse silicon on earth? Would it be worth the energy we'd have to put into it? Am I confusing different aspects of physics here?
    We can fuse silicon in particle accelerators, I don't know if it's been done but I don't see a difficulty of principle. However, to make the process efficient really one needs a star of around 10+ solar masses...
  5. Subscribersonhouse
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    07 Jul '19 15:11
    @deepthought said
    We can fuse silicon in particle accelerators, I don't know if it's been done but I don't see a difficulty of principle. However, to make the process efficient really one needs a star of around 10+ solar masses...
    Which means such a star has a limited lifespan and will blow up into a supernova or neutron star or black hole and now we know some of the heavy stuff in fact is cooking by the debris orbiting close to a black hole, perhaps not the only way heavy elements are created but that is one scenario that seems to create heavy stuff.
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