What is Olber’s Paradox?

Answer 1

Early astronomers such as Kepler and Halley wondered how is that there should be an infinity of stars, and yet the night sky looks dark? The name of the paradox is credited to Heinrich Wilhem Olber who in 1823 mathematically demonstrated that for an infinite space with an infinity of stars uniformly distributed, the night sky should not be dark. The poet Edgar Allan Poe was actually the first to suggest that perhaps that stars have a finite lifetime, and that would explain it. The Big Bang hypothesis further gave a stronger explanation, including the Hubble redshift which would further reduce the light energy influx from distant galaxies, and has become the standard resolution of Olber's Paradox. However, if the distribution of stars throughout space was a fractal, such as Cantor's dust, where the density of stars converges towards zero with ever larger volumes of space, then the paradox would be resolved as well. But because the Big Bang hypothesis is strongly supported by other evidence, it remains as the explanation for the paradox.

Answer 2

Olbers' Paradox asks why the night sky is dark. If we assume the universe is static and eternal there should be a star visible in every direction you look. Clearly the night sky is dark, so at least one of the starting assumptions must be wrong.

The wikipedia article has lots of detail

Answer 3

Um.. it's called a search engine? Type it into google or yahoo and poof! THere's the answer! What a shock!

http://search.yahoo.com/search?p=olber%27s+paradox&fr=yfp-t-429&toggle=1&cop=mss&ei=UTF-8

Answer 4

It is the originally postulated incompatibility with the assumption that the universe is infinite and contains an infinite number of stars (which we now know is not true) while not having a sky that is blindingly and uniformly illuminated -- i.e. that the sky is black would run against the assumption that, wherever you look, there would be a star right there at some distance, leaving no gaps.