Anyhow infinity is unmeasurable so has no size so cannot expand.

Your notion of infinity is just conceptual rubbish.

Think I mentioned that.

Galaxies are flying apart at faster than the speed of light so it is space that is expanding I believe. — Devans99

I don't see a connection between the premise and conclusion.

Galaxies are flying apart at faster than the speed of light

Ok.

so it is space that is expanding I believe.

What directs to such a conclusion?

As you have pointed out,

infinity is unmeasurable so has no size so cannot expand. — Devans99

This could even imply that if space were infinite, then it is just as possible for galaxies to keep moving apart without the need for space to expand. Anyway, this is just more conjecture on an unknown. I think there's no need to calculate probabilities of unknown factors.

Imo, if by space is meant the limits within the universe, then it is probable that it is expanding since by universe we define some sort of limits. If, on the other hand, by space is meant limits pertaining to reality's capacity to contain 'things', then perhaps infinite is a better tag given reality isn't really limited even by our standards.

On the face of it, nothing can move relatively faster than the speed of light, so if galaxies are expanding faster than the speed of light; that suggests space itsself is expanding.

'The expansion of the universe is the increase of the distance between two distant parts of the universe with time. It is an intrinsic expansion whereby the scale of space itself changes. The universe does not expand "into" anything and does not require space to exist "outside" it. Technically, neither space nor objects in space move. Instead it is the metric governing the size and geometry of spacetime itself that changes in scale. Although light and objects within spacetime cannot travel faster than the speed of light, this limitation does not restrict the metric itself. To an observer it appears that space is expanding and all but the nearest galaxies are receding into the distance'

https://en.wikipedia.org/wiki/Expansion_of_the_universe

So it is the metric that is expanding.

The expansion of the universe — Devans99

They have specified their limits as those of a universe. This means that it automatically has the potential capacity for intrinsic expansion as with most limits (or objects).

So it is the metric that is expanding. — Devans99

Hypothetically, yes.
But, the space-time reference is another hypothetical. So they're claiming that a hypothetical factor (space-time) with a hypothetical value (the metric), is undergoing a hypothetical change (an unproven expansion). I think that is the scientific version of faith.

So you doubt the Big Bang theory? The red shifts of galaxies seem to clearly show expansion starting 13 billion years ago. The Cosmic Microwave Background radiation confirms the Big Bang also?

So you doubt the Big Bang theory? — Devans99

The big bang is a theory but not a certainty. There are other theories, all with different probabilities. Right now, the big bang may be the best fit according to our current scientific endeavours.

The red shifts of galaxies seem to clearly show expansion starting 13 billion years ago. — Devans99

The measurements are only within the near (reachable, by our facilities) perimeter of our cosmic environment. So, therefore, it is natural for there to be greater familiarity and proximity of a causal relation.

The Cosmic Microwave Background radiation confirms the Big Bang also? — Devans99

Just a big bang. They have discovered a lot of those and there's no guarantee that the one they reference as 'the big bang' is the first and only one of its kind. It is possible that with the hypothetical of a multiverse, there is potential for multiple big bangs for each universe.

Just a big bang. They have discovered a lot of those and there's no guarantee that the one they reference as 'the big bang' is the first and only one of its kind. It is possible that with the hypothetical of a multiverse, there is potential for multiple big bangs for each universe. — BrianW

That sort of leads to a pet theory of mine: if big bangs were naturally occurring and time was infinite then there would be (with infinite time) infinite big bangs at each point in space leading to infinite matter density. So either the Big Bang was an unnatural singleton or time has a start.

I must admit I do not get these multiverse theories - at least in the most popular one (Eternal Inflation) you have a thing that generates universes - it must be connected (in space) to each of the generated universes. Therefore it follows that all universes are connected to all universes. In what sense is that a multiverse if they are all connected?

That sort of leads to a pet theory of mine: if big bangs were naturally occurring and time was infinite then there would be (with infinite time) infinite big bangs at each point in space leading to infinite matter density. So either the Big Bang was an unnatural singleton or time has a start. — Devans99

Not necessarily. Even if there was infinite matter density, each part of the universe would only interact in relation to its environment. It does not mean that the potential for the whole universe would act in its absoluteness at every point. Also, there already have been multiple super and mega novas in this supposed universe since that hypothetical big-bang and matter still seems to be relatively well-organised.

Therefore it follows that all universes are connected to all universes. In what sense is that a multiverse if they are all connected? — Devans99

A while back and the same could be said of galaxies. Initially it was difficult to tell whether the stars observed all belonged to our galaxy or not. In time, with better facilities even cosmic space will be better perceived. However, personally, the theory that has fewer limitations tends to most approximate what reality has in store. So, for me, if there's one universe, there's bound to be others. And why not?

Not necessarily. Even if there was infinite matter density, each part of the universe would only interact in relation to its environment. It does not mean that the potential for the whole universe would act in its absoluteness at every point. Also, there already have been multiple super and mega novas in this supposed universe since that hypothetical big-bang and matter still seems to be relatively well-organised. — BrianW

I'm not sure I follow, can you expand? I do not see how you can avoid infinite matter density with infinite time.

So, for me, if there's one universe, there's bound to be others. And why not? — BrianW

I think we'd have evidence. With infinite time, there should have been born, at each point in the universe, an infinite number of universes. They should all be overlapping each other. That is far from the uniform expansion that astronomy reports. The Big Bang looks like a singleton.

What I'm trying to say is, the working of the universe as we have observed so far seems to be intelligently designed such that there are forces which maintain equilibrium. For example, after the super and mega novas (and even the big bang) there follows a considerable period of 'calming' sorta like regaining equilibrium. Therefore, it may be that even with infinite time and a continued occurrence of big bangs, the equilibrium may still be maintained. Perhaps that's what gravity is for, to ensure recovery to the state of stability for the system (universe) and all its components.

For example, after the super and mega novas (and even the big bang) there follows a considerable period of 'calming' sorta like regaining equilibrium. Therefore, it may be that even with infinite time and a continued occurrence of big bangs, the equilibrium may still be maintained — BrianW

Periods of equilibrium or no, I don't see how the infinite density problem can be avoided.

Since time is infinite in this supposition, it means we have an infinite amount of time prior to this moment. So, how come we have not succumbed to the infinite density problem, and how many more infinities does it take for that to occur?
Also, by principle, whatever has a beginning, must have an end. So, I don't think there's anything like infinite density, else, density would be infinite like time (in this supposition).

We have not succumbed to infinite density because time has a start (see https://thephilosophyforum.com/discussion/5302/an-argument-for-eternalism/p1). That start was likely co-incidental with the Big Bang.

so we're back to the initial argument where possibilities abound and there's nothing, as far as we know, that prevents the possibility of a multiverse or other big bangs.

Like I said, time is finite. We have evidence of only one Big Bang and strong reasons to suspect it is coincidental with the start of time.

If there is a multiverse then the start of time would be co-incidental with the start of the multiverse. The multiverse should also be finite.

I don't know. You haven't proven that infinity can't grow. I remember mentioning to you about how, once upon a time, we couldn't count more than 2. 3 was simply ''many''. Any number greater than 2 was also referred to as ''many''. That however didn't mean the ''many'' couldn't grow/increase right? We could have 4 or 5 or n+1 which is growing as you can see but all are simply called ''many''. I think infinity too can be viewed in this way.

Read this: One, two, many

Like I said, time is finite. — Devans99

That is your opinion. Imo, finite or Infinite is a description of time-relations with subjects/objects. Time itself is neither finite nor infinite, just a relation of transciency of the subjects/objects in question.

We have evidence of only one Big Bang — Devans99

We have evidence of numerous super/mega novas but we suspect the one which supposedly took place about 13 billion years ago was biggest and the birth of our cosmic neighbourhood which we, so far, choose to designate as our universe. We have not yet dismissed the probability or possibility of other big bangs like it.

Yawn

space is flat No rotation as far as we can tell and therefore it is infinite. The universe is not expanding as its already infinite. So what's happening - its expanding locally there is another place way far away from here - unimaginably far where space is compressing. There is an infinite number of areas where as far as you can see is expanding and just as many where space is compressing. If the large scale structure goes on forever and there is a similar less defined larger structure and so on and so on out to infinity then the universe is not expanding - it is locally yet for all we can see it is an insignificant spec.

The knots in the large scale structure appear to be forming an endless cloud of something like quarks - sound familiar. I believe it to be doing the same on ever larger scales Less defined As you pull back.

If this happened then DArk matter is all the stuff that did not fall into the singularities that make up the particles of matter. Dark energy is the result of gravity since it cause space to compress and therefor must expand somewhere else.

A black hole sees time go by fast but the stuff outside sees it take forever. When the knots in the large scale structure form particles and cool as the matter around us did - If you were made out of that and looked back at the creation of the particles that made you - it would look like it happened in a bang yet looking up from here it looks like it will take billions if not trillions of years

This is just the prototypical Devan thread. "Infinity is this", despite him contradicting the actual standard mathematical definition of infinity. "Mathematicians are wrong" despite not actually addressing their arguments with a response beyond "Bad definition" with no subsequent elaboration.

I know for a fact I and many others here have walked him through this a dozen times before. It's never any different, and shocker, this thread follows that trend. Devan, define what current mathematicians mean by Infinity, lay out their argument for why they ended up accepting that definition, and then argue against that. If you cannot meet that basic task, a task I know I've done to you more than half a dozen times, you're not an honest participant in these constant infinity threads you make. You're an ideologue.