3 ms·

Einstein did not determine that the sun was nuclear powered. That was Hans Bethe in 1939 (based on data produced by Bengt Strömgren).

ahazred8ta 6y ago
"In 1920, Arthur Eddington suggested hydrogen-helium fusion could be the primary source of stellar energy. ... laboratory fusion of hydrogen isotopes was accomplished by Mark Oliphant in 1932. ... the theory of the main cycle of nuclear fusion in stars was worked out by Hans Bethe." https://en.wikipedia.org/wiki/Nuclear_fusion https://en.wikipedia.org/wiki/Nuclear_fusion
jaggederest 6y ago
Right, I wasn't saying he did. I was trying to say that, without a theoretical framework to hang that kind of energy generation on, there was no capacity to understand what was going on. E=MC^2 is precisely that kind of theoretical framework. Pretty amazing, to me. Being able to say "It's this far away, this hot, and this large, but why?"
- fsh 6y ago
  E=mc^2 is a consequence from special relativity, not a theoretical framework. It also has very little to do with the understand of nuclear reactions. The reason why nuclear reactions release much more energy than chemical reactions is that the binding energies inside the nucleus are much larger than inside the electron shell. Mass-energy equivalence exists in both cases.
  - pfdietz 6y ago
    Indeed. And in a Newtonian universe, it's possible that something like nuclear fusion could exist that would liberate much more than mc^2. There would be no upper limit on nuclear reaction energies set by the total rest energy of the reactants.
- archgoon 6y ago
  I don't think thats true though. In 1903, Radioactivity had already been proposed as an explanation for the Sun's heat (2 years prior to Annus Mirabilis). The connection between E=mc^2 and nuclear reactions doesn't become clear until you start losing mass (proton + neutron) in the reactions, which doesn't happen for the reactions involved in the Sun (Carbon Nitrogen Oxygen Cycle). The connection was recognized by Lise Meitner and Otto Hahn when they discovered fission, where a mass loss does occur. However, they didn't publish their discovery until January 1939; and Hans Bethe had already been working on the Carbon Nitrogen Oxygen Cycle, and didn't need fission to account for the Sun's processes (neutron + proton mass is conserved in the relevant reactions). He was just working off of observed empirical data to make his conclusions.
  - the8472 6y ago
    > which doesn't happen for the reactions involved in the Sun You might want to rephrase that, after all a mass loss occurs in any reaction, it's just not as significant as a whole nucleon.

ahazred8ta 6y ago

"In 1920, Arthur Eddington suggested hydrogen-helium fusion could be the primary source of stellar energy. ... laboratory fusion of hydrogen isotopes was accomplished by Mark Oliphant in 1932. ... the theory of the main cycle of nuclear fusion in stars was worked out by Hans Bethe." https://en.wikipedia.org/wiki/Nuclear_fusion https://en.wikipedia.org/wiki/Nuclear_fusion

jaggederest 6y ago

Right, I wasn't saying he did. I was trying to say that, without a theoretical framework to hang that kind of energy generation on, there was no capacity to understand what was going on. E=MC^2 is precisely that kind of theoretical framework. Pretty amazing, to me. Being able to say "It's this far away, this hot, and this large, but why?"

fsh 6y ago
E=mc^2 is a consequence from special relativity, not a theoretical framework. It also has very little to do with the understand of nuclear reactions. The reason why nuclear reactions release much more energy than chemical reactions is that the binding energies inside the nucleus are much larger than inside the electron shell. Mass-energy equivalence exists in both cases.
- pfdietz 6y ago
  Indeed. And in a Newtonian universe, it's possible that something like nuclear fusion could exist that would liberate much more than mc^2. There would be no upper limit on nuclear reaction energies set by the total rest energy of the reactants.
archgoon 6y ago
I don't think thats true though. In 1903, Radioactivity had already been proposed as an explanation for the Sun's heat (2 years prior to Annus Mirabilis). The connection between E=mc^2 and nuclear reactions doesn't become clear until you start losing mass (proton + neutron) in the reactions, which doesn't happen for the reactions involved in the Sun (Carbon Nitrogen Oxygen Cycle). The connection was recognized by Lise Meitner and Otto Hahn when they discovered fission, where a mass loss does occur. However, they didn't publish their discovery until January 1939; and Hans Bethe had already been working on the Carbon Nitrogen Oxygen Cycle, and didn't need fission to account for the Sun's processes (neutron + proton mass is conserved in the relevant reactions). He was just working off of observed empirical data to make his conclusions.
- the8472 6y ago
  > which doesn't happen for the reactions involved in the Sun You might want to rephrase that, after all a mass loss occurs in any reaction, it's just not as significant as a whole nucleon.