It takes light, traveling 186,000 miles a second, eight minutes to reach earth, but it needs 100,000 years to cross our Milky Way galaxy containing some 100,000,000,000 stars.

Some astronomers estimate that there are as many galaxies in space as there are stars in the Milky Way. Radio telescopes have detected light coming from 10,000,000,000 light-yearsb away.