Light

From Slackerpedia Galactica

Opposite of Heavy!

It's all astronomers really care about. Light can be thought of as a wave or a particle, which doesn't really make sense. The little particles are called photons, and they're something like baseball cards- very collectable and occasionally valuable.

Like ice cream, light comes in many flavors. The most popular is visible light- it's what your eyes are able to detect. But spending too much time analyzing visible light is like eating vanilla ice cream all the time, so astronomers will also sample infrared light, ultraviolet light, microwaves (the waves/photons, not the oven), radio, and gamma rays. Just like ice cream, a complete understanding of the world is impossible without trying all the flavors. Astronomers can also combine images made in different kinds of light to make one composite image, like Neopolitan ice cream.

The different flavors of light are determined by their wavelength, or alternatively, by the energy the photon carries. Each flavor is useful for studying different kinds of objects or objects at different distances and times.

Light moves at a finite speed. It's very fast. For all intents and purposes, it's infinitely fast. Except that for all intents and purposes, Astronomical Distances are infinitely far. And, Astronomers are almost only interested in objects that are Astronomically Distant.