The Universe Adventure - Glossary: U to Z

Glossary: U to Z


Universe- All of space and time along with all the matter and energy in it.

Vacuum Energy- Energy that has been theorized to exist everywhere in space. It arises from quantum mechanics.

Variable Stars- Stars which brighten and dim, some with precise timing. For Cepheid variables (one type of variable star), their period allows us to find their brightness, and from that we can determine their distance.

Velocity- The speed of an object and the direction in which it is moving. It tells how fast and in what direction an object's position changes.

Visible Mass- Mass that can be detected or seen. We see it by detecting the electromagnetic radiation that it gives off. It is also referred to as ordinary (baryonic) matter or luminous matter.

Visible Universe- The part of the entire Universe close enough for light to have had enough time to reach us in the age of the Universe. Currently, it includes everything less than 13.7 billion light years away.

Wavelength- The distance between two peaks of a wave. Usually designated by λ (lambda), it is the distance it takes a wave to make a complete oscillation. For visible light, this is on the order of 500 nanometers.