What is it you need to understand? The wikipedia extract you posted is pretty clear.

I find the raisin-bread model helpful. Imagine galaxies (or stars, whatever) as raisins in a bunch of bread-dough. As the bread is baked, the raisins get farther and farther apart, but without "moving" in their local dough, because the dough itself is expanding.

Some of the light that reaches from the past comes from things that were far, far closer when it left them, and the light hasn't had to travel the full distance, because part of the new distance between us and the galaxy is due to expansion (*behind* the wavefront) of space that the light "already traveled through."

I hope that was helpful at all.

To clarify, most of the time what's were doing is finding lower limits.
I.e. if I figure out a house is 13 years old, the Earth I found it in is probably at least 13 years old. So when we say the Universe is 13 billion years old, it means we think we've found something at least 13 billion years old, so the Universe has also got to be that old too.

The best way I can explain it is that to figure out how big the universe is, we find the farthest-away thing, assume it must have been travelling really really fast (near/at speed of light) and back calculate how long it took it to get there, and that kinda gives us a radius.

http://www.space.com/24054-how-old-is-the-universe.html

Actually, Valis, that's not really true. It's true that estimating the age of objects only gives lower limits. However, scientists can also estimate how long ago (/"far away") the Big Bang was, and since in current models that is the beginning of spacetime, that is the age of the universe (the UPPER, as well as lower limit).

The big bang age estimate is made using the cosmic microwave background radiation, the correlation function of galaxies, and type IA supernovae (standard candles). See e.g. http://en.wikipedia.org/wiki/Big_Bang

If you're asking why we think the universe is expanding, it has largely to do with Redshift, in which EM waves from space appear to have longer wavelengths than one would expect based on what they are comprised of. This is very similar to the Doppler Effect you experience when listening to a siren in a passing ambulance.

my question is the one semck tried to answer, and i think he succeeded, kinda. this still makes my head dizzy though.

stop smoking the hukka, you should clear up in a couple of hours

The incredible vastness of space-time, as best as we've come to know it, is amazing to you? What are you, an atheist or something??