Is the universe a closed or open system?

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I know that the universe is open, if it is affected by something outside of it. If there is no outside of it then obviously it is a closed system. I think most people define "universe" in terms that require it to be a "closed system".

I know the answer is probably "closed". The reason I asked is because I want to know whether the law of conservation of energy and similar laws apply in both systems. An open system might have energy added to it or subtracted from it by an external source/sink of energy. If the universe isn't connected to anything else, must I definite the word "universe" TO include everything that could possibly affect anything, Thus, there's no reason laws of thermodynamics wouldn't apply in both closed or open systems?.

In an open system could entropy flow forever and anything that could happen might happen , if this is pseudo science please disregard this comment.

Of course there is also isolated systems but lets leave that out.

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I think the short answer we really don't know but we assume it's closed because we don't have any evidence there exists something outside the universe for it to open onto.

And the laws of thermodynamics do apply in closed and open system. Why would you think they wouldn't?

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Noether's theorem implies that any boundary ( ie. an asymmetry ) in time, linear translation and angular translation, means that conservation laws of mass-energy, linear momentum and angular momentum respectively, are violated at those boundaries.

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Actually it must be cyclic.

If you look at Isotopes, there are a finite number which are "stable"

Therefore if Entropy takes its course, and all the stars are burnt out, and all the possible isotope decays take place, then all we are left with is the stable particles.

The only force left is gravity.

These Isotopes, by definition, are irreducible, so what we are left with is an implosion, which collapses the particles to (presumably) the Planck density.

Where (and I speculate) we get a "big bang" reversal, which generates a new universe.

Chew on that

Occam

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"Is the universe finite or infinite"

since the terms only have meaning and validity in finite systems.

Edited by studiot

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Actually it must be cyclic.

If you look at Isotopes, there are a finite number which are "stable"

Therefore if Entropy takes its course, and all the stars are burnt out, and all the possible isotope decays take place, then all we are left with is the stable particles.

The only force left is gravity.

These Isotopes, by definition, are irreducible, so what we are left with is an implosion, which collapses the particles to (presumably) the Planck density.

Where (and I speculate) we get a "big bang" reversal, which generates a new universe.

Chew on that

Occam

But if the galaxy clusters are moving away from each other at escape velocity or greater, wouldn't they just continue to drift apart?

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Actually it must be cyclic.

If you look at Isotopes, there are a finite number which are "stable"

Therefore if Entropy takes its course, and all the stars are burnt out, and all the possible isotope decays take place, then all we are left with is the stable particles.

The only force left is gravity.

These Isotopes, by definition, are irreducible, so what we are left with is an implosion, which collapses the particles to (presumably) the Planck density.

Where (and I speculate) we get a "big bang" reversal, which generates a new universe.

Chew on that

Occam

That's proof (of a sort) that it hasn't been round forever because all the unstable isotopes would have decayed.

But it doesn't prove that it's cyclic.

We may or may not get a "Big Crunch" but the isotopes don't tell us what will happen.

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Actually it must be cyclic.

If you look at Isotopes, there are a finite number which are "stable"

Therefore if Entropy takes its course, and all the stars are burnt out, and all the possible isotope decays take place, then all we are left with is the stable particles.

The only force left is gravity.

These Isotopes, by definition, are irreducible, so what we are left with is an implosion, which collapses the particles to (presumably) the Planck density.

Where (and I speculate) we get a "big bang" reversal, which generates a new universe.

Chew on that

Occam

How can gravity exist without mass?

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The universe cannot be an open nor a closed system. One can create a closed or an open system within the universe.