The following glossary includes terms that are used in Student Text, Epoch Eight in our Evolving Universe. You will probably want to study the terms and their definitions before you read the student text.

Kelvin ('kel-v&n)
A kelvin is the SI unit (International System of Units) of temperature. Zero kelvin is considered absolute zero, the temperature at which all molecular motion ceases.

Gravity ('gra-v&-tE)
Gravity is the fundamental force produced by the mutual attraction of two masses. The force is directly proportional to the masses and indirectly proportional to the square of the distance between them.

Kinetic energy (k&-'ne-tik 'e-n&r-jE)
The energy that a body possesses as consequence of its motion.

Strong Nuclear Force ('stro[ng] 'nü-klE-&r 'fOrs)
The strong nuclear force is force holds that holds protons and neutrons very tightly together to form an atom’s nucleus. It is also called “chromoelectric” force, because the gluons that carry it have an assigned characteristic called “color.”

Plasma ('plaz-m&)
Plasma is sometimes called the fourth state of matter. It is gaseous and contains electrically-charged particles, like free electrons and positively- and negatively-charged ions.

Gluons ('glü-"än)
Gluons are massless carriers of the strong nuclear force, the force that acts between quarks to form protons and neutrons.

Structural epoch ('str&k-ch&-r&l 'e-p&k)
Another name for the Eighth Universal Epoch in which cosmic matter condensed to form solid structures‚the galaxies, clusters and superclusters of galaxies—that are part of our universe today.