Physics: A question about the curvature of the universe?

[HeWhoFightsFurther]

If the universes is flat, then the speed of the expansion of the universe should approach zero. BUT the universe is accelerating. how come the general consensus is that the universe in flat? Shouldn't it be hyperbolic then? Has this been disproved or something? and what about the inclusion of dark energy and matter?

I...AM...LOST!

oh and uh, can someone explain what this 'cosmological constant' is? I dont really get it.

Thanks

[Green]

As far as I'm aware of, the Universe is not flat. Or at least according to General Relativity.

It may be flat according to WMAP Satellite data, but there are many unanswered questions and things that do not fit into this idea of "flat universe"

It could be spherical or at least curved in some manner.

I'm not sure what you mean by "inclusion of dark matter and dark energy", but if it's in relation to the topic, then I found this on a site that might help you:

"Einstein’s cosmological constant allowed for a uniform repulsive energy throughout the universe. Since Hubble discovered the expansion of the universe, most scientists have believed that the cosmological constant was zero (or possibly slightly negative). Recent findings have indicated that the expansion rate of the universe is actually increasing, meaning that the cosmological constant has a positive value. This repulsive gravity — or dark energy — is actually pushing the universe apart."

From: Link

Theres a section in that link as well to do with dark matter, if you intend on explaining it, you might have to get into a bit of String Theory.

The cosmological constant (as you probably know) is in Einstein's general relativity equation which acts as an "anti-gravity effect", or to simply allowed the universe to be stable/static. It's presented as Lambda, which you probably also know. However since there has been proof that the Universe is expanding, the cosmological constant is believed to be zero. The last thing I know about this is that due to the acceleration rate at which the universe is expanding, it is believed to be dark energy which is now related to the cosmological constant.

I think this should explain it nicely to you.

Thats a lot of theoretical physics you are dealing with.