Big bang question
Big bang question
I have a question about the big bang. Why didn't all the stupidly densely packed matter fuse into elements heavier than lithium? The temperatures and density would have been much hotter than a super-nova, so surely we should be seeing primordial elements of all masses? What key bit of science don't I understand here.
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Re: Big bang question
It wasn't anything that you'd recognise as matter at that time.
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Re: Big bang question
Big Bang nucleosynthesis produced very few nuclei of elements heavier than lithium due to a bottleneck: the absence of a stable nucleus with 8 or 5 nucleons.bjn wrote: ↑Fri Dec 17, 2021 6:18 pmI have a question about the big bang. Why didn't all the stupidly densely packed matter fuse into elements heavier than lithium? The temperatures and density would have been much hotter than a super-nova, so surely we should be seeing primordial elements of all masses? What key bit of science don't I understand here.
Also bear in mind that any kind of reaction which is favoured, i.e. leads to a lower energy state than the one it started from, needs to be able to get rid of that energy. Let's say you had two particles in a perfectly sealed box and when they react they join together and emit a photon. Well, then the photon bounces around in the box and eventually hits the joined particles and gives them the energy they need to split apart again.This deficit of larger atoms also limited the amounts of lithium-7 produced during BBN. In stars, the bottleneck is passed by triple collisions of helium-4 nuclei, producing carbon (the triple-alpha process). However, this process is very slow and requires much higher densities, taking tens of thousands of years to convert a significant amount of helium to carbon in stars, and therefore it made a negligible contribution in the minutes following the Big Bang.
All that temperature is a bit useless if you don't have anywhere you can dump the entropy.
having that swing is a necessary but not sufficient condition for it meaning a thing
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Re: Big bang question
Thanks!