ASTRON 2B03 Lecture Notes - Lecture 20: Runaway Greenhouse Effect, Red Giant, Hittin
6 Nov 2015
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Journal: just under a month left to submit journals. Everyone should have made a few entries by now! Remember this is worth 10% of your grade! Earth the only location of life that we know of. There are a surprising number of astronomical conditions that need to be met! Message: we are here because of our connections with the outside universe (1) location, location, location. The (cid:2)goldilocks principle(cid:3): we are at just the right distance from our star, the sun not too hot, not too cold (cid:2)habitable zone(cid:3) An interesting twist: the habitable zone shifts outward as time goes on! A star evolves with time it gradually gets more luminous (brighter). So, a planet that was initially inside the habitable zone would later on find itself too hot (2) timing: not just any old star will do. It took the earth about 4 billion years for a diverse array of multicelled living things to develop.
