The lanthanides and actinides, the two rows at the bottom of the periodic table, make up the inner transition elements.

A small mass of ice and dust that revolves around the Sun in a highly elliptical orbit.

A procedure used to establish the age of ancient organic remains by measuring the concentration of 14C and comparing it to that of present-day organic remains.

The solar radiation received by the Earth and its atmosphere; incoming solar radiation.

A line on a weather map denoting locations with the same atmospheric pressure.

The continuous forward-flowing of events.

The change in velocity divided by the change in time; a = ?v/?t.

The change in velocity divided by the time for the change to occur.

The distance traveled divided by the time to travel that distance.

The change in displacement divided by the change in time; v = ?d/?t.