Is time a dimension in the universe

Time is dependent on mass and movement, if there is no more mass, no more energy then nothing moves making time irrelevant. You have one big ole nothing which is really hard to imagine for me. This is an imaginary scenario that may have no possibility of existing. Its a theory to some but no one knows for sure. I have my doubts about the end of our visible universe being the end of all. I’m curious about that state of maximum entropy I read about and what that might be like exactly. I have read its pretty cold and dark. Where has all that energy we were told can't be created or destroyed? Is there no memory of it anywhere, not even a consciousness of some sort to realize it?

This is what happens to matter in a closed system but how do we know the universe is a closed system? Do we really know it isn't interacting with some other universe or reality? If the universe we know does succumb to the ravages of entropy then yes, time will end but at some point before that happens may there be a spark of order in the chaos similar to what cause the universe we see to come into existence? Many questions but whatever happens, its so far away we need not to worry too much about it.

The current view (which is likely to not be the final one) is that the universe will face heath death. its expansion is accelerating and we know of no mechanism which could slow the expansion down, let alone stop it or reverse it. This means that eventually, aeons from now, every particle in the universe will be at absolute zero temperature and / or too far away from every other particle as to ever be able to interact, and space will still be expanding at an ever increasing rate. The universe will be dead, the only thing changing will be space itself, which will keep expanding forever, but matter and energy in it will be dead, even electromagnetic radiation will not move fast enough to catch up with the space expansion so it will not be able to reach anywhere where other particles are, it will just move along newly created empty space.

Does "time" make any sense at that far remote epoch? Time is a measure of change rate, if nothing in the matter / energy contents of the universe can change, in principle we can say that time does not exist anymore. But, if space itself keeps expanding, there is still some change, so time might still make sense as simply the rate at which space is expanding? There actually are three competing scientific theories about the end of the universe:

1.) The Big Crunch: The theory says that one day the expansion of the universe will we reversed and space will shrink up to the point it forms a new singularity. Time would end.

2.) The Big Rip: The theory says that expansion accelerates to a point where space itself will be ripped apart. The result would also be a singularity. Time would end.

3.) The Big Chill: The theory says that expansion will accelerate and go on forever. At some point matter is too scattered to actually form new stars by gravity. The result would be a cold universe existing forever. Time would remain. It turns into a deep but probably meaningless philosophical question. So our 3d + time (4D) universe could end in a singularity at a Big Rip/Big Crunch but time could continue in a different dimension. There would also obviously also be physical dimensions, without which the continuation of time would have no meaning whatsoever.

Well, time is relative, that is we all as observers are aware of the passage of time. However we all exist in our own individual time bubble. Atomic clocks have proven that if someone synchronises two identical atomic clocks, then travels round the earth (with one of the atomic clocks ) in a jet plane, then arrives back where they started, the two clocks will be out of sync. That is time dilation. If you travel at approaching light speed then return home, then all the people you know will have aged considerably! So as time is relative to each observer, time is also relative to each universe,(based on the multiverse theory) it is an emergent entity.

The universe doesn't have to be expanding into anything in order to expand. I know that sounds ridiculous, so let me give you a different example that is easier to understand. Imagine that you have a line that goes on forever. On that line, you have a mark every inch. There are an infinite number of inches. Now move each marker so they are separated by two inches. The whole pattern has expanded. It still goes to infinity, but the markers are further apart. The pattern has expanded, but the length is still infinite. Now a new example. Suppose you have a long piece of rubber, going all the way to infinity. (That piece of rubber represents the universe.) The rubber has marks on it every inch. Now stretch the rubber, until the markers are two inches apart. It still goes to infinity -- but it has expanded.

Physicists think of "space" not as emptiness, but similar to a piece of rubber. (But they don't call it rubber; they call it the "vacuum". "Particles", in physics, are just vibrations of the vacuum.) The vacuum can expand, just like the piece of rubber. But because it goes all the way to infinity, it doesn't need more space. A clever way to say it is that "there's lots of room at infinity". (That's clever, but it doesn't really explain anything.) Now here is something new that might confuse you, or might help. In the standard physics theory, the galaxies are all getting farther apart; that is the expansion of the Universe. Yet in the way the theory describes it (I mean in General Relativity Theory) none of the galaxies are actually moving. All that is happening is that the amount of space (vacuum) in between them is increasing.

No, you will not learn this in school, or even in college (unless you have an extraordinary professor). It is usually taught in graduate school, when you are earning a Ph.D. degree. At that point the language you will encounter is this: "In the Big Bang Theory, all galaxies have fixed coordinates. (That means they are not moving.) The 'expansion' is described by the 'metric tensor', which describes the distances between those fixed coordinates. In the Big Bang Theory, it is the metric tensor which is changing; that represents the expansion of the Universe, even though the galaxies aren't moving. The recent discovery of accelerated expansion means that the rate of expansion is increasing."

Maybe you've read about the curvature of space. Put a black hole between two unmoving objects, and the distance between them will suddenly increase -- even though they haven't moved. So "distance" is not as simple as people thought. It was Einstein who came up with the remarkable idea that "space" (that is, vacuum) is flexible; it can curve and stretch. I expect you will find this to be very confusing. That's not a bad sign; it is a good one. When you learn new things that are completely different than you ever imagined, then "confusion" is the first step. Cheers!