Evolution: A Scientific American Reader
From the Scopes “Monkey Trial” of 1925 to the court ruling against the Dover Area School Board’s proposed intelligent design curriculum in 2005, few scientific topics have engendered as much controversy—or grabbed as many headlines—as evolution. And since the debate shows no signs of abating, there is perhaps no better time to step back and ask: What is evolution? Defined as the gradual process by which something changes into a different and usually more complex and efficient form, evolution explains the formation of the universe, the nature of viruses, and the emergence of humans. A first-rate summary of the actual science of evolution, this Scientific American reader is a timely collection that gives readers an opportunity to consider evolution’s impact in various settings.
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The hydrogen molecules would then start to cool the densest parts of the gas by emitting infrared radiation after they collide with hydrogen atoms. The temperature in the densest parts would drop to about 200 to 300 kelvins, ...
Dust grains and molecules containing heavy elements cool the present-day clouds much more efficiently to temperatures of only about 10 kelvins. The minimum mass that a clump of gas must have to collapse under.
At these densities the hydrogen molecules collide with other atoms before they have time to emit an infrared photon; this raises the gas temperature and slows down the contraction until the clumps have built up to at least a few hundred ...
The standard wisdom of the past 40 years holds that prebiological organic molecules formed in a so-called reducing atmosphere, with energy sources such as lightning triggering chemical reactions to combine gaseous.
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