Middlesboogie: The observation that the Universe will continue expanding forever has one crucial flaw: If it were true, there would not be enough gravity in the universe to hold Galaxies together. The fact that galaxies DO stay together means that there must be more matter out there than we can see, hence the search for Dark Matter [Neutrinos, WIMPs, MACHOs, VMOs, etc.]. The Observable Fact that galaxies stay together means that there
must be enough matter in the universe to cause it to fall back on itself. So, basing our theories just on observable facts, it is impossible for it to either carry on expanding forever or to collapse in on itself. Therefore there must be something that scientists don't know about, e.g. Dark Matter. Bleurgh, that was a longwinded way of saying that scientists haven't a clue...
Pinky, you keep asking for proof of the Big Bang, but when I give you it, you ignore it! I'm going to post this again, and this time READ IT:
Cosmic Microwave Background Radiation
There is observable radiation (in the microwave portion of the electromagnetic spectrum) left over from the big bang. It is considered [by sensible, reasonable, non-fundamentalist people] to be proof of the Big Bang.
Big Bang Nucleosynthesis
Lighter elements, such as Hydrogen, Helium and Lithium, were formed as a result of the big bang in a process called big bang nucleosynthesis. Scientists can calculate how much of which elements were formed, and the fact that
observation agrees with calculation is considered proof of the Big Bang Theory.
Hubble Expansion
It can be observed with telescopes [by measuring the Red-Shift] that all of the galaxies in the Universe (outside the local group of galaxies) appear to be moving away from us, implying that the Universe is expanding. The phenomenon was discovered by Edwin Hubble in 1929, and is generally considered to be proof of the Big Bang Theory.