Olbers paradox

Suppose the universe is filled randomly with stars (galaxies) and is infinite. If this infinite universe is divided into concentric shells of some arbitrary thickness, the light received at the center from each shell is the same, since the number of stars in a shell is proportional to r² and the light intensity at the center is proportional to r ^-2. The night sky is therefore bright?! Wrong. The night sky is dark. Therefore we do not live in an infinite universe that is randomly filled with stars.

Thinking again - the universe may not be infinite, but it is certainly very large. Large enough to render the night sky much brighter than it appears. Hence the apparent paradox.

The paradox is not resolved by pointing out that light is absorbed by dark clouds of gas and dust [as the editor thought when he was 12]. Given long enough, the gas and dust will absorb and re-emit radiation. We must look elsewhere for an explanation - especially since the IB examiner expects students to know.

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