Decoupling of Radiation and Matter

This movie illustrates the decoupling of radiation and matter in the early Universe, which occurred several hundred thousand years after the big bang when the temperature had dropped to several thousand K. The decoupling transition made the Universe transparent for the first time, since photons could now travel long distances without scattering off free electrons. This transition was also essential to the formation of structure, since matter coupled to photons could not form structure because of continuous interaction with the photons in the hot plasma. Usage: The animation begins when the movie loads. Click "Play" to move from the "Before decoupling" scene to the "After decoupling" scene. "Home" returns to the beginning.