when a any system is stable? ANY system like universe.
Answers
Answer:
Universal is not stable at any event
I’ll give you two candidates: spacetime and the proton.
Spacetime, the ultimate and possibly eternal matrix of the universe, is simply more basic than any particle or force it contains. Tracing back to the earliest nths of a second of the universe, before anything coherent emerged, we find seething energy in a spacetime environment. This primal energy was (and remains) not IN spacetime, but OF spacetime; the Planck-Einstein energy. It’s a circular argument to say that each sprang from the other, but there you have it.
Of the things within the universe that appear to be utterly stable and enduring, there’s no better candidate than a proton. The darn things just do not appear to decay, and folks have been watching them for years.
You may wonder how we can say that a thing might be right near eternal when humans certainly can’t have been watching such stuff for, shoot, even a quarter of eternity.
Well, it goes as follows. There being some bajillion protons in a spoonful of anything, a fraction of that bajillion is likely to hang around for a very long time and another fraction is — statistically — likely to be ready to give up and go poof. So scintillation chambers have been wired up to detect a wink here or plink there, indicating that a proton in some scientific swimming pool has, indeed, fried itself into pieces. And we have seen nothing.
So it appears that once protons were assembled way back at the beginning of things, they just stayed.
Anyhow, those are my candidates for eternal stability, if eternity is a thing. Protons (stuff) and spacetime (where stuff lives).
By the way, “poof” is quite the proper scientific term.