This student text describes Epoch Two in our Evolving Universe. It is the eighth student text of the Tracing the Origins of Our Universe activity.

Feel the number Two in the upper left corner of the card. Place your Epoch Two Tactile Card to the right of the Epoch Three Tactile card on the table.

Epoch Two lasts only ten to the negative tenth second. During this time the temperature increases rapidly as we go back in time. At the end of the epoch it is ten to the twenty-eight kelvins. At the beginning of the epoch it is ten to the thirty-two kelvins.

The primal stew of hot plasma is now made up of quarks, gluons, electrons, photons and X particles—and all their corresponding antiparticles.

Antiparticles have the same mass as particles but have equal but opposite charges. Remember that positrons had the same mass as electrons but a positive charge.

The antiparticles that make their appearance during Epoch Two are the anti-quarks. They are shown in the Epoch Two cards as open “up” and “down” arrows.

If an “up” quark has a charge of plus two-thirds, then an “up” anti-quark has a charge of minus two-thirds. “Down” anti-quarks have a charge of plus one-third.

What are the X particles? They are thought to be particles that decay into quarks and anti-quarks as the temperature decreases during the epoch.

These quarks and anti-quarks destroy each other immediately upon contact, producing either two photons or an electron-positron pair, which, in turn, trigger further matter-antimatter destruction when they collide.

But, more importantly, the X particle decay resulted in the production of one out of a billion more quarks than anti-quarks. Not many, you say? But that excess is important! That was the source of the quarks that make up all matter in the universe today.