View the Earth from outta space :)

[LV 4 26]

I am sure I read somewhere that they are tracking gases on the edges of galaxies and they know that they are expanding, But expanding into what?

And I am sorry but there are no black holes in the universe cause it is only a theory ( planets circling black mass).

That was a cheap one wasnt it.

 

[KitsuneAndy]

Originally posted by Robbo
I think if you subscribe to the idea of there being a 'big bang' (which I think is now generally uncontested) then I'm afraid it predetermines the universe to being finite doesn't it?

But at the same time, if it's expanding at the speed of light, and it's impossible to travel faster than that speed then you could never reach the edge of the universe and therefore we could consider it infinite.

 

[Skeet]

As an aside...I think one of the greatest examples of one perception of teh Universe, comes at teh end of "Men In Black"...where teh camera zooms out from the Earth, through ouur Solar system, into teh Milky Way, ou and out...until it ends up as a marble, being rolled into another, by a alien looking being...and eventually, plopped into a marble bag!
Brilliant!

 

[KitsuneAndy]

Yeah, I remember that

But what was the aliens universe inside?

 

[Mario]

Originally posted by Skeet
by a alien looking being...and eventually, plopped into a marble bag!
Brilliant!

alien? i thought that was piper on a bad day...?!?

 

[Robbo]

Originally posted by AndyDane
But at the same time, if it's expanding at the speed of light, and it's impossible to travel faster than that speed then you could never reach the edge of the universe and therefore we could consider it infinite.

Andy, you need to think clearly here mate, I don't know that it is expanding at the speed of light, is it?

And just because you couldn't ever go that fast to catch it up (if it in fact were going that fast) this doesn't mean it's infinite at all, it just means you can't catch up the expansion horizon.

The expansion horizon is the leading edge of space time as I understand it and as such it must be finite because if you run the clock back, the mass of the universe will be of finite size a fraction of a second prior to big bang.

I hope this is slightly clearer.

 

[Skeet]

Surely, it cannot be expanding at teh speed of light...obviously..., when teh Big Bang occured...everything was forced outwards, at very high velocity (one would imagine)...but...they do say that the planets in our solar system, are getting further apart...one would assume that, as teh Planets (as they are getting bigger as well, certainly Earth at least), got bigger as teh gas clouds contracted to form the planets, tehy would have slowed down..or would they..they would need gravity to slow them down...hmmm...so, I guess as they became one mass (a planet), it would have slowed down, due to teh gravitational pull of, teh other, new and hence close by, planets.

This isnt something I know a great deal about, so can only speculate.

I have to stop typing, as Mrs Skeet wants pizza, and says whoever im typing at can wait...I retorted, that "Robbo waits for no man"...but apparently he will wait for her, or so she tells me!

 

[Revolt]

Ive only done adv higher physics at school which is like 1st year uni physics

my opinion is that atm the universe is constantly expandin and is infinite in size, although those 2 statements could contradict each other

 

[KitsuneAndy]

Originally posted by Robbo
Andy, you need to think clearly here mate, I don't know that it is expanding at the speed of light, is it?

And just because you couldn't ever go that fast to catch it up (if it in fact were going that fast) this doesn't mean it's infinite at all, it just means you can't catch up the expansion horizon.

The expansion horizon is the leading edge of space time as I understand it and as such it must be finite because if you run the clock back, the mass of the universe will be of finite size a fraction of a second prior to big bang.

I hope this is slightly clearer.

I'm not sure, I think a popular theory was that it was expanding at the speed of light, but my memory is a little hazy on the subject.

Also, Hubble's law says that some objects are travelling away from us at a rate greater than that of the speed of light.

Skeet, it's possible because the theory of special relativity is talking about the 'spacial' movement of an object. Whereas if space itself is expanding an object is not actually moving although it's relative position with regards to other objects may be changing.

Objects that are fairly local to each other are held within each others gravitational fields and may be static in relation to each other or even getting closed together, such as the Milky Way and Andromeda. But the distance between each group of local galaxies will be expanding over time.

Pete: aren't there several theories as to how the universe is shaped? And depending on which you follow the opinion of it being finite/infinite changes? (the theory of the universe being flat with infinite radius of curvature?)

I've actually applied for some course material from the Open University now, going to do a physics course, something I wish I'd done when I went to uni. Instead of getting drunk, dropping out and working for an insurance company, lol

 

[Skeet]

Well yes, they do contradict.
If it is expanding, then it has to have a finite size, at any one moment....perhaps it has teh potential to expand for ever...but then...that would defy teh fact (or known fact) that energy, cannot be created or destroyed, only transferred...so...potentially...its expansion, should run out of steam at some point.