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lecture03-1

lecture03-1 - 1 Extraterrestrial Life Spring 2008 Why is...

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Unformatted text preview: 1 Extraterrestrial Life: Spring 2008 Why is carbon not formed in the Big Bang? Carbon is formed from the reaction: 4 He + 4 He " 8 Be 4 He + 8 Be " 12 C `Triple alpha process ’ Problem: beryllium 8 is unstable - decays with a half life of ~10-16 s… Reaction is possible: • given enough time (stars, not the Big Bang) • due to fortuitous resonance that favors the 2nd step of the reaction Extraterrestrial Life: Spring 2008 Anthropic Principle If the laws of physics were different (in some cases in quite minor ways) life might not be possible Astronomical examples: • if the Universe started off denser than it was, would have collapsed to a Big Crunch before life could have started • if the dark energy were stronger, Universe would expand too rapidly to form stars • possible to imagine nuclear physics such that heavy elements never form • planetary orbits with n > 3 dimensions?...
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lecture03-1 - 1 Extraterrestrial Life Spring 2008 Why is...

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