Olbers' paradox


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Olbers' paradox

(ol -berz) Why is the sky dark at night? Heinrich Olbers in 1826, and earlier J.P.L. Chesaux in 1744, pointed out that an infinite and uniform Universe, both unchanging and static, would produce a night sky of the same surface brightness as the Sun: every line of sight would eventually strike a star, a typical example of which is the Sun. This theoretical argument is obviously in disagreement with observation. The observable Universe is, however, neither uniform, unchanging, nor static and does not extend infinitely back into the past. The paradox is then resolved because the redshift of extragalactic radiation (i.e. the diminution in its energy) and in particular the youth of our Universe make the background radiation field at optical wavelengths very low indeed – less than about 10–21 times the surface brightness of the Sun.
Collins Dictionary of Astronomy © Market House Books Ltd, 2006

Olbers' paradox

[′ōl·bərz ′par·ə‚däks]
(astronomy)
If the universe were static, of infinite age, and the galaxies distributed isotropically, the distance attenuation of their light would be exactly balanced by the increase in number in successive spherical shells centered at the earth; hence the night sky would be of daylight brightness instead of dark.
McGraw-Hill Dictionary of Scientific & Technical Terms, 6E, Copyright © 2003 by The McGraw-Hill Companies, Inc.
References in periodicals archive ?
Yet it cannot be so old that it would violate Olbers' paradox; Poe anticipates an essential part of the modern resolution of the paradox when he offers this explanation of why the night sky is dark:
Heinrich Olbers, the astronomer most associated today with "Olbers' paradox," remarked about Biela's Comet in The American Journal of Science: "at some time the comet may pass at a very small distance from us, and even so near, that its atmosphere may be in contact with our globe.
The text is frequently cross-referenced to other chapters --for example, in Chapter 12, on asteroids, a statement about the discovery of an asteroid by Heinrich Olbers contains a reference to Chapter 61, where we learn about Olbers' Paradox, for which this astronomer is best known.
The fact that this argument doesn't work and that the night sky is dark became known as Olbers' paradox, although Olbers wasn't the first to ponder the mystery.
Wesson of the University of Waterloo in Ontario presents new calculations demonstrating that the finite age of the galaxies--rather than the expansion of the universe--chiefly accounts for the resolution of Olbers' paradox. Wesson tackled the question after discovering that a number of textbooks still erroneously attribute most or all of the effect to the expansion of the universe.
Elsewhere, a few "guest contributors" have provided articles (explaining Olbers' Paradox, for example).
Surprisingly, the first correct resolution to Olbers' paradox came not from an astronomer at a well-equipped European observatory but from a poet and writer in America.
It was Harrison who unearthed the Poe reference that correctly explains Olbers' paradox in Eureka, an essay written only a year before Poe died.
To Poe, God was a poet and the universe, as he wrote in Eureka, "the most sublime of poems." He explained Olbers' paradox as follows:
The farther they look, the further they peer into the past --a concept carrying religious implications that Harrison believes slowed the resolution of Olbers' paradox. "We can look back and wonder why it is people were being so obtuse about the whole thing, but it was a problem that was looked at within a cultural context," says Harrison.
Even though Olbers' paradox had a centuries-long history, it did not become famous until the 1950s.
This strategy, however, can detract from the importance in previous decades of many other controversial subjects, such as the immutability of the physical constants, Olbers' paradox (popularized by Bondi), and Mach's principle (popularized by Dennis W.