Site Glossary

the common centre of mass around which two objects orbit.

The scientific model describing the Universe as having expanded from an extremely hot, dense early state about 13.8 billion years ago.

The scientific model describing the origin and early evolution of the Universe from an extremely hot, dense state.

a proposed scenario in which cosmic expansion reverses into contraction.

a scenario in which expansion continues and the Universe becomes increasingly cold and dilute.

a hypothetical scenario involving increasingly extreme accelerated expansion.

possible evidence of biological activity.

A region of space where gravity is so strong that nothing, not even light, can escape.

shift toward shorter wavelengths.

The distance travelled while a vehicle slows under braking.