Bringo said:
Is the universe finite or infinite ?
If there is another thread discussing the question, please post the link.
Also any other link poiting to a relevant website is appreciated.
...
you might enjoy these two websites which have
cosmology FAQ
Ned Wright (teaches graduate and undergrad cosmology courses at UCLA)
http://www.astro.ucla.edu/~wright/cosmology_faq.html
Eric Linder (similar standing at Berkeley, college textbook on cosmology)
http://supernova.lbl.gov/~evlinder/umass/faq.html
At Linder's site, see his answer to the frequently asked question
"How could an infinite universe have been, say, the size of a golf ball?"
At Wright's site, he answers the FAQ
"How can the Universe be infinite if it was all concentrated into a point at the Big Bang?"
the main scientific observation is that the U does not appear curved at large scale
measurements using the microwave background indicate that the curvature is either exactly zero or very close to zero
it is so surprisingly flat that the simplest thing to assume is that it is exactly flat (but there is no way of being sure at present which is true, flat or within a percent or so)
if the U is flat (i.e. zero curvature) then by far the simplest model with that property is that it is infinite in spatial extent
this is consistent with the observations made so far, no reputable cosmologist will exclude the possibility and in fact it is the prevailing notion
(which is why Linder and Wright take care to explain it) BUT
it has not been proven
it is very difficult to distinguish, with telescopes and suchlike gear, between the case of an infinite uncurved universe and
the case of a very enormous universe with a very small positive curvature
where it goes out way way beyond the farthest we can see, so to us it looks flat, but then curves around and closes with itself so it is after all finite.
however you can't go wrong if you assume PROVISIONALLY that it is infinite because that agrees with the observations and is overall the simplest model
you are right, we have had several threads about this at PF
maybe you could find them by using the keyword search option at the top