fredreload Posted April 24, 2018 Share Posted April 24, 2018 Fission is the opposite of fusion, what do you guys think, could it reverse the sun's energy? Link to comment Share on other sites More sharing options...
Strange Posted April 24, 2018 Share Posted April 24, 2018 Why would you want to "reverse the Sun's energy"? Make it absorb light and heat instead of emitting it? Link to comment Share on other sites More sharing options...
Phi for All Posted April 24, 2018 Share Posted April 24, 2018 1 hour ago, Strange said: Why would you want to "reverse the Sun's energy"? Make it absorb light and heat instead of emitting it? To save it from a long, slow death by killing it instantly. Mercy fission. 1 Link to comment Share on other sites More sharing options...
Strange Posted April 24, 2018 Share Posted April 24, 2018 2 hours ago, fredreload said: Fission is the opposite of fusion, what do you guys think, could it reverse the sun's energy? If you are thinking of the release of energy from fission rather than fusion., there are a couple of important points to bear in mind. Fission only works with large atoms, such as uranium, which are rare. Fusion happens with small atoms, such as hydrogen, which makes up 90%(?) of the universe. Also, fusion releases a lot more energy than fission. More here: http://www.physlink.com/education/askexperts/ae534.cfm Link to comment Share on other sites More sharing options...
Moontanman Posted April 24, 2018 Share Posted April 24, 2018 1 minute ago, Strange said: If you are thinking of the release of energy from fission rather than fusion., there are a couple of important points to bear in mind. Fission only works with large atoms, such as uranium, which are rare. Fusion happens with small atoms, such as hydrogen, which makes up 90%(?) of the universe. Also, fusion releases a lot more energy than fission. More here: http://www.physlink.com/education/askexperts/ae534.cfm Doesn't the presence of heavy elements cause fusion to happen at lower mass? I think i read someplace about the first stars having to be much more massive due to a lack of elements heavier than helium. Carbon is significant if I remember, there is at least one star that has a unusual amount of transuranic elements. https://en.wikipedia.org/wiki/Przybylski's_Star Link to comment Share on other sites More sharing options...
Strange Posted April 24, 2018 Share Posted April 24, 2018 5 minutes ago, Moontanman said: I think i read someplace about the first stars having to be much more massive due to a lack of elements heavier than helium. That is true, but I don't know what the mechanism is. Link to comment Share on other sites More sharing options...
Bender Posted April 24, 2018 Share Posted April 24, 2018 3 hours ago, Strange said: Fusion happens with small atoms, such as hydrogen, which makes up 90%(?) of the universe. About 75% 1 Link to comment Share on other sites More sharing options...
Strange Posted April 24, 2018 Share Posted April 24, 2018 3 minutes ago, Bender said: About 75% Thanks. I knew I could rely on someone here! Link to comment Share on other sites More sharing options...
fredreload Posted April 25, 2018 Author Share Posted April 25, 2018 Hmm, the sun is losing mass, the result radiates away as heat and light. Link to comment Share on other sites More sharing options...
Strange Posted April 25, 2018 Share Posted April 25, 2018 It would be a useful exercise for you to work out how much mass it loses that way. And how many years it would take for it to make any difference Link to comment Share on other sites More sharing options...
Janus Posted April 25, 2018 Share Posted April 25, 2018 21 hours ago, fredreload said: Fission is the opposite of fusion, what do you guys think, could it reverse the sun's energy? If you mean use fission to reverse the Sun's energy loss, then no. You are up against the nuclear binding energy curve. You can get an net output of energy from fusion with elements on the lower end of the periodic table up until you start forming Iron, but it takes an net input of energy to go the other way (making lighter elements from heavier ones), Above Iron, it works the other way, you get a net output of energy going from heavy isotope to lighter isotope, but it takes energy to reverse the process. Again, this stops at Iron (FE 56 to be exact, which is the dead end from both directions). 1 Link to comment Share on other sites More sharing options...
swansont Posted April 25, 2018 Share Posted April 25, 2018 5 hours ago, fredreload said: Hmm, the sun is losing mass, the result radiates away as heat and light. In this case, the light is heat. 16 hours ago, Bender said: About 75% ~75 % by mass, ~90% by number of atoms Link to comment Share on other sites More sharing options...
Bender Posted April 25, 2018 Share Posted April 25, 2018 (edited) 5 hours ago, swansont said: ~75 % by mass, ~90% by number of atoms Right. Never looked at it that way, since 75% is the number usually given. (Of course, neither number takes dark matter/energy into account) Edited April 25, 2018 by Bender Link to comment Share on other sites More sharing options...
swansont Posted April 26, 2018 Share Posted April 26, 2018 15 hours ago, Bender said: Right. Never looked at it that way, since 75% is the number usually given. (Of course, neither number takes dark matter/energy into account) That's why units matter (or context), and there's the implied caveat of "normal" matter Link to comment Share on other sites More sharing options...
Sensei Posted May 2, 2018 Share Posted May 2, 2018 (edited) On 24.04.2018 at 5:08 PM, fredreload said: Fission is the opposite of fusion, what do you guys think, could it reverse the sun's energy? Fusion is releasing energy... and fission also is releasing energy.. Reverse of fusion, is artificial radioactivity in laboratory. Scientists are adding missing energy (aka "binding energy") to split nucleus to its constituents. *) e.g. you had Helium-4 nucleus, and turned it to 4 protons.. Then after millions or billions of years they collapsed in newly born star and started fusion again.. and you have new place to live in couple billions of years from now.. *) Artificial radioactivity has been found by Irène Joliot-Curie (daughter of Marie Curie-Sklodowska) with husband. She with her husband received Nobel prize for describing this reaction: Al-27 + He-4 -> P-30 + n0 Edited May 2, 2018 by Sensei Link to comment Share on other sites More sharing options...
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