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Fraser
2016-Nov-04, 11:01 PM
When was the first time that the Universe cooled down enough that light could finally move around?
The post When Was the First Light in the Universe? (http://www.universetoday.com/131809/first-light-universe/) appeared first on Universe Today (http://www.universetoday.com).


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Solfe
2016-Nov-05, 04:12 PM
I thought it was March 23, 1999. ;)

trinitree88
2016-Nov-07, 10:04 PM
Fraser. When the Big Bang plasma began to cool, the helium would have released light first. The ionization energy of the first electron in helium is almost twice that of hydrogen, and the ionization energy of the second electron being removed...is over 4 times that of neutral hydrogen. So, kind of like charging up a battery, if you spend the energy to charge it up, you ought to get most of it back as you discharge it.....(first law of thermodynamics)....and, as the temperature drops, the bare helium nucleus grabs the electrons while hotter than the hydrogen can, emitting line spectra from the edge of the plasma. I believe Sunyaev, and Chluba wrote a few papers on this circa 2009, and predicted a sensitive search should show it in WMAP, Planck data, though separating signal from noise might prove vexing. pete



SEE:https://arxiv.org/abs/0909.2378


SEE IONIZATION NRG Chart:https://en.wikipedia.org/wiki/Ionization_energies_of_the_elements_(data_page)