On 11/25/2013 12:56 PM, LizR wrote:
I heard that hydrogen nuclei in the sun fuse after on average 5 billion years of wandering around bumping into each other (I guess that's kind of obvious - the Sun is due to "live" for about 10 billion years, so it must use its fuel at a comparable rate). So the energy production per volume would seem fairly low - one in 5 billion nuclei fuse per year, or one in 150 x 10^15 per second. I guess density is around 10^23 per cubic meter give or take an order of magnitude, so about a million atoms fuse per cubic metre/second. If I read Wikipedia right, each one releases about 7 Mev so a million release about 7 x 10^12 ev or around 10^-6 J/sec, which I believe is one microwatt.


Damn, I've slipped up somewhere, haven't I? Maybe someone with more of a head for maths can do the calculation properly.

I think you've set the density way too low.

Although it's interesting that the rate of energy production in the Sun is not very high, the energy density is pretty awesome. If I did the math right, it's 6.1e6 kWh/m^3. That essentially means the Sun is a really good insulator - to keep the core so hot with such low power.

Brent

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