The following glossary includes terms that are used in Student Text, Epoch Two in our Evolving Universe.

Anti-quarks
Anti-matter particles that have the same mass as quarks but have opposite and equal electric charges.

X particles
The theoretical particles that are thought to have decayed into quarks and anti-quarks during the Second Epoch.

Big Bang
A scientific model that predicts that the origin of the universe was a very hot, very dense plasma.