In
physical cosmology the
quark epoch was the period in the evolution of the early universe when the
fundamental interactions of
gravitation,
electromagnetism, the
strong interaction and the
weak interaction had taken their present forms, but the temperature of the universe was still too high to allow
quarks to bind together to form
hadrons. The quark epoch began approximately
10-12 seconds after the
Big Bang, when the preceding
electroweak epoch ended as the
electroweak interaction separated into the weak interaction and electromagnetism. During the quark epoch the universe was filled with a dense, hot
quark–gluon plasma, containing quarks,
leptons and their
antiparticles. Collisions between particles were too energetic to allow quarks to combine into
mesons or
baryons. The quark epoch ended when the universe was about 10
-6 seconds old, when the average energy of particle interactions had fallen below the
binding energy of hadrons. The following period, when quarks became confined within hadrons, is known as the
hadron epoch.