Q&A: Cosmology

Q:
How long would it take something to travel 1 light year or 30 million light years?

A:
A particle of light (called a photon) would take exactly one year to travel a light year. This is the definition of a light year. Thus, in order to calculate the distance traveled by light in one year, we must first know how fast light travels. It travels approximately 300,000 kilometers per second. Then we must know how many seconds are in a year - approximately 32,000,000 in one year. So, multiply 300,000 kilometers per second by 32,000,000 seconds, which gives you about 9000 billion kilometers.

It is easier for astronomers to measure distances in light years, because the Universe is so huge!