5 ms·
> Isn’t it possible that there was a period before the Big Bang, and then for some reason the universe became hot everywhere? Well, sure, it's possible. I was
by mr_mitm 3y ago
> Isn’t it possible that there was a period before the Big Bang, and then for some reason the universe became hot everywhere?
Well, sure, it's possible. I was assuming the current cosmological standard model is correct, which might in fact be wrong, or at least incomplete. Actually, I'm certain it's incomplete.
Today we can trace back the universe to when it was a tiny fraction of a second old using standard physics. Everything is well understood. Before that: who knows?
> An apple is a definite size, and can fit only a certain number of atoms.
There were no atoms when the current observable universe was the size of an apple. It was too hot for atoms. It was more like a quark-gluon plasma.
> Therefore all apples would’ve been the same size they were today, just packed more closely together. Hence “the size of an apple” seems to lose all meaning.
Obviously "the size of an apple" is a phrase for laymen. We could say "10cm in diameter" using the standard definitions of the meter and second.
>This contradiction seems to clear itself up if one allows for a “before the big bang”, since there’s no need to say that everything was compressed to a single small volume.
There is no contradiction.
- sillysaurusx 3y agoOkay, but 10cm can only fit a certain number of quarks and gluons, far fewer than today’s observable universe. Or is it true that there were always 10^80 atoms worth of quarks and gluons in the observable universe, and always will be? Galaxies recede faster than light, so atoms are shedded by that process. If anything it seems like there must have been more matter in the early observable universe than today. But “10cm in diameter” seems to imply otherwise.
- mr_mitm 3y ago> Or is it true that there were always 10^80 atoms worth of quarks and gluons in the observable universe, and always will be? Pretty much, yes. (Let's ignore the possibility of proton decay for now.) > Galaxies recede faster than light, so atoms are shedded by that process. If anything it seems like there must have been more matter in the early observable universe than today. But “10cm in diameter” seems to imply otherwise. Not sure what you mean by "shedding atoms", but I'm pretty sure I can say that this is not the case.
- sillysaurusx 3y agoAlright. Thank you.
- ClumsyPilot 3y agowell we loose access to them, so for all intents and purposes observable universe looses atoms. Very anthropo-centric, but not wrong.
- ben_w 3y agoWe've lost access to many which are still visible, thanks to the continuing expansion of the universe; eventually the light from them may be red-shifted to a wavelength larger than the visible universe, making them undetectable in any meaningful sense.
- bowsamic 3y agoPhysics is always anthropocentric: if we can't measure it, we can't say anything about if it exists