AST201H5 Lecture Notes - Horizon Problem, Wilkinson Microwave Anisotropy Probe
Document Summary
Energy becomes matter = protons, neutrons, electrons. Antimatter should have been created, but we do not nd it now. This charged gas (= plasma) is opaque to light: fusion era - 0. 001 s to 5 minutes. Temperature drops from 1012 k to 109 k. Protons and neutrons fuse to create helium: nuclei era - 5 minutes to 380,000 years. Too cool for fusion, but too hot for atoms: era of atoms 380,000 years to 1 billion year. Protons and electron combine to form neutral atoms. Universe becomes transparent to light: era of stars and galaxies - 1 billion+ years. Gas had cooled enough for the rst stars and galaxies to form: tests of the hot big bank theory, cosmic microwave background (cmb) At 380,000 y, the universe was a dense gas with a temperature of 3000 k emitting thermal radiation (ch 5) The universe has expanded for more than 13 billion years.
