What happens to matter if it is left undisturbed for a long time?

Since the question isn't clear enough, here's an experiment: If we put some non-radioactive matter in a box and slow the speed of the universe outside the box by a factor of $\lim\limits_{x\to\infty}x$. What would happen to the matter in the box after a second passes in the universe outside?

I'm guessing nothing.

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    $\begingroup$ What does it mean to "slow the speed of the universe"? $\endgroup$ – D. Halsey Jul 7 '19 at 13:24
  • $\begingroup$ Depends on the matter. An apple would go bad, for example. $\endgroup$ – knzhou Jul 7 '19 at 13:50
  • $\begingroup$ Good question, I'm not sure why you were downvoted $\endgroup$ – Dude156 Jul 7 '19 at 17:52
  • $\begingroup$ @D.Halsey I thought it was clear, but in case it isn't, I mean to hasten the passage of time within the box, such that $t_u = t_b \times \lim_{x \rightarrow \infty} x$ where $t_u$ is time outside the universe, and $t_b$ is time inside the box. $\endgroup$ – Amin Shah Gilani Jul 8 '19 at 0:43
  • $\begingroup$ @knzhou an apple would go bad in an infinitely small sliver of "forever", the formal question asks what would happen if after the apple went bad, and the "living" rot turned into "dead" matter, what would happen even infinitely after that? $\endgroup$ – Amin Shah Gilani Jul 8 '19 at 0:56

"Forever" is a very long time indeed.

Given enough time, even the most unlikely quantum transitions will happen with probability approaching a limit of 1. So, it could be that all your matter will transmute into iron-56. Or it could be that proton decay is a thing, and you won't be left with anything but radiation. Or there could be other physical effects that we short-lived creatures haven't encountered.

I think the short answer is "nobody knows".

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  • $\begingroup$ Could you elaborate on the transmutation into iron-56? $\endgroup$ – Amin Shah Gilani Jul 8 '19 at 0:48

It depends on the kind of matter, its temperature, and its initial configuration. Radioactive matter (e.g., plutonium) will gradually decay, emitting radiation and transmuting to lighter elements. Hot matter will gradually cool, and will usually shrink as it cools. Molecules that are not in their lowest energy state will gradually change into their lowest energy form.

One caveat: The outcome also depends on the kind of box the matter is in. If the box allows radiation to pass through, then what was said above is correct. But if the box reflects all radiation so no energy can leave the box, then the matter inside will not change to its lowest energy form and instead will gradually approach thermodynamic equilibrium.

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  • $\begingroup$ Sorry, I meant non-radioactive matter when I said "normal" matter, but I can see how that may not have been clear enough. Updating the question. That said, all that would happen is that the matter would shrink until the temperature in the system is uniform, and then nothing more? $\endgroup$ – Amin Shah Gilani Jul 7 '19 at 9:49
  • $\begingroup$ In principle, the matter will end up eventually in its lowest-energy configuration. Put two duterium atoms in the box, and eventually they will fuse to form a helium atom, because a helium atom has less energy (i.e., mass-energy) than two hydrogen atoms. However, the rate at which that reaction happens when the temperature is low is VERY slow. Also, please see my edit re the type of box being important. $\endgroup$ – S. McGrew Jul 7 '19 at 13:08

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