Thursday, May 31, 2012

Olbers Paradox

"Dark Night Sky: Olbers Paradox"," Professions could freely intermingle and overlap. His work on comets and asteroids earned him a fairly respectable niche in astronomy, still he continued to be a physician. Almost towards the end of this career he brought it in the open. Newton argued in its favor and explained why it should be so. He reasoned that if there were infinite number of stars, the sky would be covered with stars. Yet the night sky is dark. It turns out though that a Swiss astronomer Cheseaux had made the same observation half a century ago and had mentioned it in his book. He tried a couple of explanations but found them unsatisfactory. Later though it turned out that this explanation would not fit either. So the paradox remained unresolved. The answer to the question was: the sky is not dazzling bright because the universe is spending its energy in expanding. Whatever remains is so thinned out over the vast distance as to be negligible. Redshift is the term used for the shift of the frequency of light towards the red end of the spectrum due to the source moving away from the observer. The frequency emitted by a source increases if it is approaching and decreases if it is receding. In the case of visible light the two ends of the spectrum are blue and red. All distant galaxies show redshifts directly depending on their distance, which shows that the universe is expanding. WHAT'S UP   


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