Space-Time Boundary Inquiry

[Randolpin]

We are dwelling in this space-time reality. The question that I want to convey now is that"Does our space-time has a boundary?" Or an edge? Is it finitely or infinitely distributed? What is the position of science with regards to this inquiry nowadays?

[Lord Antares]

The correct answer is that no one knows. Some scientists think the universe is finite, while others say it's infinite. It's irrelevant because it's just a guess at this point anyway.

[Strange]

Our current models describe a universe that has no edge or boundary. It may be finite or infinite.

[geordief]

Our current models describe a universe that has no edge or boundary. It may be finite or infinite.

Fair to say that ,if a global boundary was ever discovered it would be perhaps the most revolutionary discovery in science?

 

The equivalent of the ability to look at ourselves "from the outside" -something which I would count as a self contradictory concept.

[Raider5678]

Fair to say that ,if a global boundary was ever discovered it would be perhaps the most revolutionary discovery in science?

 

The equivalent of the ability to look at ourselves "from the outside" -something which I would count as a self contradictory concept.

Yeah, we really have no idea.

For all we know, time could be atmosphere and the farther you go out form the edge the less and less time affects you.

[Deverebond]

Fair to say that ,if a global boundary was ever discovered it would be perhaps the most revolutionary discovery in science?

 

The equivalent of the ability to look at ourselves "from the outside" -something which I would count as a self contradictory concept.

Raider5678's PhotoRaider5678

 

I personally look at it like the game of risk. We can only see a part of the map until we explore past it. If there is a boundary, just by finding what we think is a boundary and look past it we redefine the boundary.

If the big bang theory is correct and as is theorised the speed of moving apart of galaxies is getting greater then there must be an edge of the universe but there must be something further than that to move into. I think that the question should be, what is outside the universe

[Mordred]

An infinite universe can still expand. Expansion does not mean the universe requires an edge.

[Strange]

If the big bang theory is correct and as is theorised the speed of moving apart of galaxies is getting greater then there must be an edge of the universe but there must be something further than that to move into. I think that the question should be, what is outside the universe

 

 

There is no edge to the universe in the big bang model.

[Pugdaddy]

If space is being created as is the theory, then nothing is required to move into. I recently watch a lecture where the expansion was explained this way. If you are at a point in space, and space is doubling in time. If you make a grid with our galaxy at the center of one grid and another galaxy is at the center of the grid next to yours and another galaxy is at the center of the grid next to that, every time there is a doubling of space, then every someone, including you, would see the others moving away from each other faster and faster the further away they were. The one that was in the next grid would be 2 grids away and the one that was 2 grids away would be 4 grids away and so on.

[Randolpin]

If space is being created as is the theory, then nothing is required to move into. I recently watch a lecture where the expansion was explained this way. If you are at a point in space, and space is doubling in time. If you make a grid with our galaxy at the center of one grid and another galaxy is at the center of the grid next to yours and another galaxy is at the center of the grid next to that, every time there is a doubling of space, then every someone, including you, would see the others moving away from each other faster and faster the further away they were. The one that was in the next grid would be 2 grids away and the one that was 2 grids away would be 4 grids away and so on.

Base on the Big bang model, space is being created. Thru this, I come up the reasoning that:

 

1. We can assume that space is infinite because before bigbang there is nothingness. But a question still arises, if space infinite, then it is instantly created as infinite in the very time of the moment of bigbang?

 

2. We can also assume that before big bang there is already space existing ( I call it ultraspace) so that the space created after bigbang is in the premise of ultraspace and it is finite & grows thru time.

 

This is only my suggestion.

Edited May 15, 2017 by Randolpin

[Lord Antares]

Base on the Big bang model, space is being created.

 

No it isn't. There is as much substance now as there was at any point after the big bang. Space is just expanding and matter is getting further apart.

 

 

1. We can assume that space is infinite because before bigbang there is nothingness. But a question still arises, if space infinite, then it is instantly created as infinite in the very time of the moment of bigbang?

 

Firstly, the first sentence is incorrect. Science doesn't know and makes no claims about anything before the big bang. I don't follow your second sentence. If there was really nothingness before the big bang, it would me lead to assume that space is FINITE, not infinite. But it's irrelevant since the premise is wrong.

 

 

2. We can also assume that before big bang there is already space existing ( I call it ultraspace) so that the space created after bigbang is in the premise of ultraspace and it is finite & grows thru time.

 

This point contradicts your point 1. And again, it's just a guess.

[MigL]

I believe the OP asked ' does space-time have a boundary ?'.

 

Of course it does.

What was there 'before' 13.7 bil yrs ago ?

There is an edge to the time axis at T=0 !

[Strange]

I believe the OP asked ' does space-time have a boundary ?'.

 

Of course it does.

What was there 'before' 13.7 bil yrs ago ?

There is an edge to the time axis at T=0 !

 

 

Not necessarily. It could have existed in some sort of metastable state for an infinite time before then. Or (as she attempt to medal quantum gravity show) it could have existed for an infinite time getting asymptotically denser. Or it could be the result of a "big bounce". Or ...

[MigL]

If the metastable state wasn't large enough to support geometry, or if the previous geometry, prior to a bounce, came to an end and then restarted in our Big Bang, it would still be a discontinuity, and therefore an 'edge'.

[Lord Antares]

I see what you mean. A finite universe makes much more sense to me than an infinite one but we are dealing with a complicated subject so that's nothing more than an opinion.

[Randolpin]

 

No it isn't. There is as much substance now as there was at any point after the big bang. Space is just expanding and matter is getting further apart.

 

 

 

Firstly, the first sentence is incorrect. Science doesn't know and makes no claims about anything before the big bang. I don't follow your second sentence. If there was really nothingness before the big bang, it would me lead to assume that space is FINITE, not infinite. But it's irrelevant since the premise is wrong.

 

 

 

This point contradicts your point 1. And again, it's just a guess.

 

 

First I want to have a clarification as to why space is not being created during the big bang. As I understand big bang, this is the time when the univese (all - spacetime and matter) begins out of nothing.

 

Secondly, the 2 reasoning I suggested is not an argument but rather it is the 2 possible ways either space is finite or infinite. I can agree with you that space is finite because it has an origin during the bigbang and it seems to me that it is impossible to be infinite because it must be instantly created during the bigbang. But what I am curious, is again as what I pointed already, why you say that space is not being created?

[Strange]

First I want to have a clarification as to why space is not being created during the big bang. As I understand big bang, this is the time when the univese (all - spacetime and matter) begins out of nothing.

 

 

No. The big bang model describes the evolving state of the universe from an earlier hot, dense state. It says nothing about creating anything from nothing.

[Lord Antares]

 

 

No. The big bang model describes the evolving state of the universe from an earlier hot, dense state. It says nothing about creating anything from nothing.

 

This. I don't know who downvoted you, but it's correct.

 

OP, think of inflating a baloon. The borders of a baloon are getting further apart in diameter, but they are getting thinner. So the surface of a baloon isn't really getting bigger in volume, it's just being spread out over a larger distance.

 

Space acts like this, except there is no evidence that it's material or quantized, so the point about density isn't applicable as far as current physics is concerned.

But the point is, there was as much space and matter in the singularity before the big bang as there is now and as there always will be, according to theory.

[Randolpin]

If space expands thru time, therefore it must be expanding with respect to something. Let's assume the balloon represents spacetime. The balloon expands because there is space outside. Obviously, it can't expand if there is no space outside (e.g. it is trap inside a container). Therefore, spacetime reality expands because there is space outside of it.

[John Cuthber]

53 minutes ago, Randolpin said:

If space expands thru time, therefore it must be expanding with respect to something. Let's assume the balloon represents spacetime. The balloon expands because there is space outside. Obviously, it can't expand if there is no space outside (e.g. it is trap inside a container). Therefore, spacetime reality expands because there is space outside of it.

No, all that shows is that, if there was a container that enclosed the universe it might stop it expanding.

The other side of the argument is that, since there is nothing outside the universe then there is nothing to stop  it expanding.

How would "nothing" get in the way and stop the universe expanding?

[Itoero]

Science can never prove an infinite universe. ..you can't prove the absence of a 'boundary'.

I'm inclined to believe in a finite universe because infinity throws open all possibilities.

[Tub]

Is it possible that infinite space has always existed, without time, and what is expanding into that space is the finite matter that had a beginning, with time, and will, according to entropy, eventually come to an end? 

[swansont]

3 hours ago, Randolpin said:

If space expands thru time, therefore it must be expanding with respect to something. Let's assume the balloon represents spacetime. The balloon expands because there is space outside. Obviously, it can't expand if there is no space outside (e.g. it is trap inside a container). Therefore, spacetime reality expands because there is space outside of it.

Apply that reasoning in two dimensions only. The surface of the balloon. What is it expanding into?

[Strange]

4 hours ago, Itoero said:

Science can never prove an infinite universe. ..you can't prove the absence of a 'boundary'.

These are not necessarily related. The usual model of the universe is that it is either finite or infinite but in either case has no boundary.

Edited July 24, 2017 by Strange

[Itoero]

2 hours ago, Strange said:

These are not necessarily related. The usual model of the universe is that it is either finite or infinite but in either case has no boundary.

Why does a finite universe have no boundary? I don't mean an edge where you can fall of.