The First Three Minutes

time Temp
[K] 		 Z
(redshift) 		 Radius
(?) 		 Density
[g/cc] 		 Stuff 
0:00:00.01  1011  3x1010  10 ly  4x109 
  • e+ , e-
  • photons, neutrinos
  • protons(p+) = neutrons(n) (1)
0:00:00.1 3x1010  1010  30 ly  3x107 
  • e+ , e-
  • photons, neutrinos
  • 62% p+ , 38% n
0:00:01 1010  3x109  100 ly  4x105 
  • e+ , e-
  • photons
  • neutrinos -- decoupled!
  • 76% p+ , 24% n
0:00:13.8 3x109  109  300 ly  3x103 
  • e- frozen out
  • photons, neutrinos
  • 83% p+, 17% n
0:03:02 109  3x108  1000 ly  40 
  • photons, neutrinos
  • 86% p+, 14% n
  • deuterium bottleneck (2)
0:03:42 9x108  ~3x108  ~1000 ly  26 
  • photons, neutrinos
  • 87% p+ , 13% n (in He)
  • deuterium now stable
  • -> 26% Helium (3)
0:34:40 3x108 108 3000 ly 0.10
  • e+ , e-
  • photons, neutrinos
  • 87% p+ , 13% n (in He)
  • trace 3He, 7Li, deuterium

Adapted from The First Three Minutes, by Steven Weinberg

1) antineutrino + proton <--> e+ + neutron
e- + proton <--> neutron + neutrino
2) proton + neutron <--> deuterium + photon
3) deuterium + proton --> 3He
3He + proton --> 4He