If Nuclear Fusion Defuses and Fuses then why is the sun running out of hydrogen?

Question

If nuclear fusion fuses hydrogen atoms together to make helium atoms and vise versa then why are stars running out of hydrogen if hydrogen is always made again by nuclear de-fusion which would probably mean helium turning back into 2 hydrogen atoms? This is a wierd phenomena. How is it running out when it is made again and again? Is nuclear fusion made more than nuclear de-fusion?

Answer 1

The sun does not turn helium back into hydrogen in any significant quantity. The reaction is pretty much all going the other way, since that is energetically favored (ie, you release energy by fusing hydrogen into helium and it takes energy to do the reverse).

In the early universe, when the temperature was huge compared to this fusion energy, you had fusion and this "de-fusion" as you call it happening in equal measures, so you had H and He in equilibrium. But that was way, way, way hotter than the core of the sun. Eventually, the universe cooled down enough that this reaction stopped. This locked in the ratio of Helium to Hydrogen that we observe in the universe today (only slightly changed via the subsequent work of stars like the sun). We can use basic statistical thermodynamics to calculate what this ratio would have been (and low and behold, it's correct). This is one of the main pieces of evidence we have for the standard model of cosmology (aka, the big bang).

Oh, and as for the sun running out of hydrogen, don't worry, it's got many billions of years' worth left before the hydrogen wanes and the sun has to move on to fusing the helium into carbon.

Answer 2

Diffusion is a net flow of particles due to random motion from a region of high density to low density.

Diffusion is not a process where He splits apart into hydrogen atoms.

Answer 3

ordinary this is extraordinarily obtrusive: you're saying "solar’s preliminary furnish of hydrogen will final: a million.a million×10^10 years" "image voltaic gadget Age = 4.5 billion years previous" So: 10 billion years - 4.5 billion years = 5.5 Billion years/

Answer 4

Please cite a reference (preferably --not-- the National Enquirer or something equivalent) that discusses 'nuclear de-fusion'. I have never heard the term.

Doug