[DoctorBeaver (OP)]

The universe is big - there's a lot of it. But the universe is greedy and wants more, so it's getting bigger. But nanny gravity is there, lurking in the background.

Nanny gravity starts to get concerned about how big the universe is getting. She has read government warnings about obesity and decides it's time she did something about it. So, she puts the universe on a diet.

Gradually, the universe starts getting smaller. Smaller it gets. And smaller yet, until it's all squashed up in a tiny point.

OK, I've been a bit silly there, but I have got a serious question. If there is enough gravity in the universe to cause it to eventually collapse, what happens to all the space that has been created? Is it just the matter that will contract into a Big Crunch? Will the universe still actually be there but with only the singularity in the middle? Or will space itself contract too?

[Make it Lady]

...And if space does contract as well what will be left? Will something new be created. This is the stuff that makes my head spin. Thanks for raising it Doc. I guess Stephen Hawkin would like to know too.

[Nobody's Confidant]

Bah, I hate questions like these. So complicated.

[DoctorBeaver (OP)]

Bah, I hate questions like these. So complicated.

That's the general idea. Although this is tame compared to some questions I've asked here.

[Soul Surfer]

A great deal of work has been done to try to prove which of the options between; accelerating expansion, continued expansion at the same rate,  decelerating expansion that never really stops, or decelerating expansion that eventually leads to a big crunch (and possibly a big bounce).  The basic equations allow for all of these possibilities.  Current observations tend to favour the accelerating expansion although there are other theories that still suggest that a slowly decreasing expansion is the most likely but models exist for all possibilities.

What would happen depends at what stage the evolution of the universe has reached when the crunch starts to take effect but it essentially a noisy big bang in reverse like the collapse of a star into a black hole.  but mostly the theories suggest that this collape would take so long that there's nothing much left in the universe except for a few black holes,  stars and planets having burned out cooled and collapsed many zillions of years before it happens.

[DoctorBeaver (OP)]

Ian - that's not my question.

The expansion of the universe is causing space to be created. If that expansion turns into a contraction, what happens to the space that has been created? Are we left with empty space, or does the actual space itself contract too?

If space did indeed contract, does that infer that space is no more than a function of the distribution of matter? Or, after all the matter had contracted to a singularity, would space still exist at the maximum size it had expanded to?

[that mad man]

I suppose a lot of this will depend on whether you believe that the universe is infinite or not.

Is the universe expanding or is the matter in it just moving further apart relative to other matter?


If the universe is infinite and the matter in it is moving further apart then no space is being created as the space is already there. A bit like the space in an atom, there is plenty of it and it can be compressed or expanded depending on conditions.  If this is correct then the gravitational effect on each mass relative to each other, I assume, would become weaker so this expansion would carry on.

Under that scenario if the gravitational effect on mass becomes weaker there would be no big crunch as it would  continue to expand and not contract

TBH I think if the gravity effect does becomes weaker then all matter would break down and we could possibly have another plasma stage.

[DoctorBeaver (OP)]

I suppose a lot of this will depend on whether you believe that the universe is infinite or not.

Is the universe expanding or is the matter in it just moving further apart relative to other matter?


If the universe is infinite and the matter in it is moving further apart then no space is being created as the space is already there.

I don't believe the universe is infinite. Space may be curved enough that travelling far enough in a straight line will bring you back to your origin, but that's a different thing.

However, I do believe that the universe could be bigger than we think. In the oscillating universe scenario, any new space that was created by the first expansion could remain for further expansions to expand into.

I also believe if that is the case then there may be matter that is far enough away that it will keep moving away while the rest of the matter contracts to a singularity. If that is the way things are then the universe could be immensely bigger than we think, depending on how long it has been since the very first expansion.

I'm not saying that I think that is the case, but I certainly don't rule it out; and that's why I've asked this question. If matter contracting into a Big Crunch pulls space back in with it then new space is created with each expansion. If it doesn't, then the expansion we are in is expanding into space that was already there; no new space is being created.

[that mad man]

To be honest, I have recently decided like you when it comes to infinity. []

I now think that the universe is not infinite but bound and so large that we cant possibly measure or know its size. It may be that it could also be expanding. The difference here (I think) is if it is bound then that raises the possibly of a centre somewhere.

The problem I have though, is in believing that it could then contract into a big "crunch" as something must then be causing that to happen.

So for me its a case of what could cause that reversal?

[DoctorBeaver (OP)]

To be honest, I have recently decided like you when it comes to infinity. []

I now think that the universe is not infinite but bound and so large that we cant possibly measure or know its size. It may be that it could also be expanding. The difference here (I think) is if it is bound then that raises the possibly of a centre somewhere.

The problem I have though, is in believing that it could then contract into a big "crunch" as something must then be causing that to happen.

So for me its a case of what could cause that reversal?

I have a problem with the universe not having a centre. I know all about it expanding everywhere etc; but if it started from a singularity of some sort, then that is where it spread out from. Maybe it didn't expand uniformly in all directions, in which case it may be more accurate to refer to it as the point of origin rather than as the centre.

I just don't like the concept of infinity - I think it's a cop-out; although that in itself raises the question of what, if anything, is outside of our universe and what is beyond that etc.

[that mad man]

I just don't like the concept of infinity - I think it's a cop-out; although that in itself raises the question of what, if anything, is outside of our universe and what is beyond that etc.

Just a thought.

If space itself was infinite then we could be living in a "local" universe that is bound and expanding created by a singularity. It could then be possible to have other similar universes created in the same manner in that infinite space, not parallel universes but separate. Our universe could then be expanding quicker because of the gravitational attraction to other universes which are also expanding in the same way.

Do we know if the universe is expanding equally in an outward fashion?

Phew, my brain hurts! []

[maff]

To be honest, I have recently decided like you when it comes to infinity. []

I now think that the universe is not infinite but bound and so large that we cant possibly measure or know its size. It may be that it could also be expanding. The difference here (I think) is if it is bound then that raises the possibly of a centre somewhere.

The problem I have though, is in believing that it could then contract into a big "crunch" as something must then be causing that to happen.

So for me its a case of what could cause that reversal?

I have a problem with the universe not having a centre. I know all about it expanding everywhere etc; but if it started from a singularity of some sort, then that is where it spread out from. Maybe it didn't expand uniformly in all directions, in which case it may be more accurate to refer to it as the point of origin rather than as the centre.

I just don't like the concept of infinity - I think it's a cop-out; although that in itself raises the question of what, if anything, is outside of our universe and what is beyond that etc.

There cannot be a point of origin. If there was a point of origin then the CBR would lead you right to that point.

[Soul Surfer]

I prefer to use the physical term undefined for the total size of the multiverse/universe rather than the mathematical term infinite this avoids getting into tangles with the properties of the mathematical infinities (because there are different sorts of infinities in mathematics).

[Soul Surfer]

To get back to your original question beaver  if you are talking about the reversal of the space expansion process, logically you must mean a process that effectively destroys space, as opposed to the normal process of gravitational collapse  which has nothing much to do with the space it occupies until it detaches itself as a black hole.  alternatively do you see a black hole as something that is in some way destroying bits of space.

[DoctorBeaver (OP)]

To get back to your original question beaver  if you are talking about the reversal of the space expansion process, logically you must mean a process that effectively destroys space, as opposed to the normal process of gravitational collapse...

I was asking about both those scenarios. Would gravitational collapse (I don't see there could be any other cause for a contraction) cause space to contract or would space be left in situ?

[DoctorBeaver (OP)]

There cannot be a point of origin. If there was a point of origin then the CBR would lead you right to that point.

Not necessarily. If you put a ball of dough in the oven for it to expand, the inside looks uniform. If you were inside it you would not be able to tell where the centre is unless you knew where the boundary was. In the case of the universe, we do not know where the boundary is - or even if there is a boundary. The CBR, like the inside of the dough ball, will appear homogeneous.

In any case, if the universe was created from a singularity and expanded then it must have expanded from a point. That point is the point of origin.

[Soul Surfer]

I can't add much to what I said last time if curved space is contracted space OK.

I Think that you like me and a lot of other serious scientsts are reaching out for a better understanding of what "space" really is.  I personally have several mental models  that may or may not be compatible and/or in agreement with other more skilful thinkers.

These ideas really live in the new theories area associated with my evolutionary cosmology ideas to I will not mention them here

[DoctorBeaver (OP)]

...alternatively do you see a black hole as something that is in some way destroying bits of space.

I assume the volume of a black hole is equivalent to the amount of space it takes up, so I don't see that any space gets destroyed. However, it certainly gets slapped about a bit.

[Mw-theoritician]

Will the universe still actually be there but with only the singularity in the middle?

the way i see it is if all mass in the universe would be reduced to a singularity then it collapse in on itself and an explosion maybe,. the after effect of particles scattering throughout the empty univers would recreat all of which was destroyed,

[DoctorBeaver (OP)]

Mw-theoritician - welcome to TNS.

the after effect of particles scattering throughout the empty univers would recreat all of which was destroyed,

The universe is the way it is because of certain values - for instance gravity, the EM force, the weak force, the strong force, the speed of light, etc. If any of these values were changed by just a few percent then the universe would look very different. In fact, it may not exist at all.

We do not yet know why these values are what they are. If the universe contracts to a point and explodes again (the Oscillating Universe scenario), what guarantee is there that those values will be the same?

It has been theorised that these values are random quantum values and, as such, it is purely by chance that our universe evolved the way it did. If that is the case then it is highly unlikely that these universal constants will have the same value were the universe to oscillate.