Within a second or two after the Big Bang, protons and neutrons start
to combine into atomic nuclei (hydrogen, helium, and traces of lithium,
beryllium, and boron). Roughly 300,000 years later, the Universe became
cold enough for electrons to combine with atomic nuclei and form atoms.
At the same time, the Universe became more transparent, enabling photons
to travel more freely.
SSP scientists study the interactions between photons and matter.
When atoms form during recombination, we learn about the conditions
in the early Universe before the formation of stars and galaxies.
Cosmic Background Explorer
RECFAST: CMB recombination code
Wilkinson Microwave Anisotropy