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Transcript
We have now completed the first step So where are we? The universe is a cooling expanding sea of photons and small pieces of slightly clumped matter. The Universe remains ionized as the electrons can not yet recombine with the protons to make neutral hydrogen. When the temperature cools to 3000K, recombination happens, the surface of last scattering is reached, and the radiation dominated era is over. Matter can now clump Element Formation Only H and He exist – to make heavier elements we need to make stars. Star formation occurs through the gravitational collapse of gas clouds. We have not container yet for gas clouds We must make the container. Growth of Galaxies Mostly still an unknown process Matter clumps around surviving density enhancements Eventually a network of clumps starts to gravitationally interact Somehow this process produced the highly clustered and filamentary galaxy distribution Galaxy Formation Many details of this process are still unknown although Hubble space telescope keeps finding the proto-galactic building blocks. Galaxies are containers for Life They Nurture the process of star formation Stars build heavy elements via fusion. And Heavier Elements This Process continues up until 56Fe Then weirdness happens Then a Miracle Happens Neutron Capture makes Uranium, Gold, Titanium, Rare Earths