Recombination Chronology of the universe

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9 year wmap data (2012) shows cosmic microwave background radiation variations throughout universe our perspective, though actual variations smoother diagram suggests.


hydrogen , helium atoms begin form density of universe falls. thought have occurred 377,000 years after big bang. hydrogen , helium @ beginning ionized, i.e., no electrons bound nuclei, (containing positively charged protons) therefore electrically charged (+1 , +2 respectively). universe cools down, electrons captured ions, forming electrically neutral atoms. process relatively fast (and faster helium hydrogen), , known recombination. @ end of recombination, of protons in universe bound in neutral atoms. therefore, photons mean free path becomes infinite , photons can travel freely (see thomson scattering): universe has become transparent. cosmic event referred decoupling.


the photons present @ time of decoupling same photons see in cosmic microwave background (cmb) radiation, after being cooled expansion of universe. around same time, existing pressure waves within electron-baryon plasma — known baryon acoustic oscillations — became embedded in distribution of matter condensed, giving rise slight preference in distribution of large scale objects. therefore, cosmic microwave background picture of universe @ end of epoch including tiny fluctuations generated during inflation (see diagram), , spread of objects such galaxies in universe indication of scale , size of universe developed on time.








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