Monday, June 27, 2011

Olbers' paradox

Hunting through the internet to find something about Hubble's constant I found something on Olbers' paradox.  The Wikipedia article is not bad (but I have never disputed Wikipedia's generally good coverage of non-soft subjects).  The paradox is that a static, infinitely old universe with an infinite number of stars distributed in an infinitely large space would be bright rather than dark.  For if there were an infinite number of stars, evenly dispersed, the then for any angle of vision, the number of stars would be proportional, but the intensity of light inversely proportional to the square of distance. The two effects would cancel out thus, with an infinite number of stars, the sky would be uniformly bright, which it isn't.

The article says that Olbers was not the first to describe the paradox, without mentioning any earlier description. I remember reading a similar paradox by the English logician (and hymn writer) Isaac Watts (1674–1748), I shall look for his book tonight, and report back.

Meanwhile - and this is really a philosophical question - why is Hubble's constant a constant? 

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