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michael_nielsen
A wonderful little fact about the maximum power density inside the sun (spoiler: about the same as inside a compost pile!) ht
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Timothy Gowers 31. sij
Odgovor korisniku/ci @michael_nielsen @nattyover
There must be some nice scaling-law explanation for why I'd be instantly fried if I dived into the sun but not if I dived into a compost heap. If the radius of a spherical compost heap doubles, what happens to the temperature at its surface? (Is that even the right question?)
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michael_nielsen 31. sij
Odgovor korisniku/ci @wtgowers @nattyover
Suppose you have fixed power density, and the sun is of (variable) radius r. The energy flux at the surface - the thing frying you - scales as power density * volume / surface. That's proportional to the radius. The Sun is just a really, really big compost heap!
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1/(1 - 1/(1 - 1/(1 - Dan Piponi))) 31. sij
Odgovor korisniku/ci @michael_nielsen @nattyover
I usually make the comparison with the power density generated by human muscle. I guess it makes me feel like Superman or something.
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michael_nielsen 31. sij
Odgovor korisniku/ci @sigfpe @nattyover
Stronger than a shooting star! (Oops, wrong comparison...)
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David Deutsch 1. velj
Odgovor korisniku/ci @michael_nielsen @nattyover
And a nuclear fusion reactor will have many millions of times that power per unit volume. So much for its being merely an "artificial sun"!
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Pradyumna Singh 31. sij
Odgovor korisniku/ci @michael_nielsen @nattyover
Indeed, and humans typically have > 10^4x W/kg than the sun. With bacteria etc. that number gets even higher! There's a nice talk on cellular energetics by Rob Phillips:
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John Carlos Baez 31. sij
Odgovor korisniku/ci @michael_nielsen @nattyover
I like it when on a cold day I dig into my compost pile and warm steam comes out. Now I'll think about the Sun.
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Vladbot 5013 31. sij
Maybe it's just a large collection of space reptiles.
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Paul F. Dietz 31. sij
Odgovor korisniku/ci @michael_nielsen @nattyover
Now compute the thermal energy of a cubic meter of the Sun's core.
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