how can u say that the universe is expanding?

[swaha]

is there any proof? actually gravitational force is attractive so it should be shrinking by the way if it had to. pls explain where i was wrong.

[Dudde]

I'm no astronomy expert by any means, but your post made even my head hurt. Perhaps it would be beneficial to start small and work your way up, the best learning one can receive can happen in ones own studies.

 

Wikipedia might be a good place to start a general inquiry, read up a bit and see if you understand more, you'll probably get a better response if you can address your question further.

 

just a suggestion

[swaha]

gravitational energy is actually a bound state one so why universe needs to expand i really dont get it. 2 things can separate if some repulsive force exists else why move leaving the bound state? actualy the place i stay asking questions to teachers is almost a crime so i really dont get any help regarding what i want to know. pls explain it.

[Dudde]

Did you check the link referenced? There is actually quite a bit of detail residing within, far more than I could give you personally. It's definitely a sad state if you aren't able to interact with teachers, but if you're approaching them by denying everything and telling them to prove it, that may contribute.

 

If you don't like wikipedia, you can always google:cool:

[Klaynos]

On a local scale, you are right gravity rules and there is no local expansion.

 

On a large scale (clusters of galaxies) gravity is weak and is overcome by the expansion.

 

You ask why it needs to, and the answer to that I don't think we really know, this isn't really my area of physics, but the expansion is a result of the big bang, why that happened, who knows. But the universe is expanding. There is evidence for this:

 

http://en.wikipedia.org/wiki/Metric_expansion_of_space#Observational_evidence

 

Even stranger is the fact that it is not just expanding but the expansion is accelerating.

[swaha]

well since we are accelerating without something stopping us can some day we reah the speed of light?

[Klaynos]

Relativity does not apply to universal expansion. Therefore it is not bound by the same speed limits, it is not a velocity as such but space actually getting bigger.

 

http://curious.astro.cornell.edu/question.php?number=575

 

Read that.

[One of the Few]

Here is my thought, contrary to Klaynos, gravity in its entiry is indeed quite monstrous it holds together the entire universe, while on earth a mere child can manipulate it. But here is an example of how I can prove its expansion, imagine this one can only register that which is confined to the speed of light, so in light of all this one can assume, that if we cannot see the edge of the universe either there is an object in the way or it is accelerating faster then light and thus we cannot visualize it. I would be delighted if you could offer a rebudle or even contradict me.

[Klaynos]

Gravity doesn't hold together the entire universe, that is why the expansion is accelerating. Observational evidence proves this.

 

This would also be true if the universe had expanded very very very quickly at one point in the past so that the "edge" was beyond the age of the universe in years * 1 light year. Which it certainly is even if there is anything that could be described as an edge.

[swaha]

whether the universe expands or the galaxies move away from each other at a greater speed of light the relative velocity remains greater than the speed of the light. does it mean the reference frame of those galaxies they are at our past?

[One of the Few]

"Gravity doesn't hold together the entire universe."

 

Alright I believe I used the term "universe" a bit loosely. By universe I meant all that which resides inside the universe eg. planets, moons, stars, solar systems etc.