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

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

During Epoch Three, quarks and electrons are free particles. They are also very hot!

The temperature of the plasma composed of quarks, gluons, electrons, and photons at the end of the epoch is about ten to the fourteenth kelvins.

At the beginning of the epoch it was about ten to the twenty-eighth kelvins.

What is even more remarkable is that this temperature change took place over a period of ten to the negative twenty-eighth second.

Notice that the size of the epoch box is smaller than the Epoch Four box was. That means that the plasma becomes even more dense while the temperature increases as we go back in time.