Naked Science Forum

Non Life Sciences => Physics, Astronomy & Cosmology => Topic started by: ukmicky on 25/05/2007 22:45:14

Title: Current theory
Post by: ukmicky on 25/05/2007 22:45:14
What evidence do they have for the current theory of a boundless universe.

Surely that is one theory which can never be tested to the level required by science.
Title: Current theory
Post by: DoctorBeaver on 25/05/2007 23:38:55
It depends what you call "boundless". The topology of the universe could be open (saddle-shaped); therefore it could be boundless but still of finite size. If we can figure out the topology, we could determine whether it is, indeed, boundless.

That brings in the question of density & total mass but I think there are other posts about that sort of thing.
Title: Current theory
Post by: ukmicky on 25/05/2007 23:53:03
But we can't figure out anything in regards to what the universe really is and yet the theory of a boundless universe is accepted by most cosmologists as how things are .

Also for a boundless universe to be finite in size wouldn't that then mean there could be an outside, meaning beyond the universe there could be something else possibly containing more universes ,which is another big no no :)
Title: Current theory
Post by: another_someone on 26/05/2007 00:15:56
Is the universe assumed to be boundless, or merely to be larger than the event horizon we see (i.e. larger than about 13 billion light years)?
Title: Current theory
Post by: ukmicky on 26/05/2007 00:21:49
Boundless and infinite , In other words it goes on forever with no edge.

Title: Current theory
Post by: another_someone on 26/05/2007 00:41:23
Boundless and infinite , In other words it goes on forever with no edge.

Where is this stated?

As you say, I cannot see how we can even begin to speculate about what might be beyond our event horizon, so how can anybody say it is, or is not, infinite beyond that point.

I suppose it is reasonable to say it is boundless, insofar as one might say that if there is a boundary, there must be something on the other side, and this leaves a problem as to what one calls the things on the other side.
Title: Current theory
Post by: _Stefan_ on 26/05/2007 05:50:06
The universe might be infinite in such a way that if you moved long enough in one direction you would be looped round and arrive at your starting point. Is this possible?
Title: Current theory
Post by: another_someone on 26/05/2007 13:10:55
The universe might be infinite in such a way that if you moved long enough in one direction you would be looped round and arrive at your starting point. Is this possible?

Such a model is possible, but it is not infinite (it is like the surface of the Earth, only in higher dimensions, and nobody would regard the surface of the Earth as infinite, although it is unbounded, since one never reaches a boundary).
Title: Current theory
Post by: _Stefan_ on 26/05/2007 15:41:35
Ah, I see :)