It takes a beam of light a single day to travel 16.1 billion miles, a distance known as a light-day. It'll take Voyager 1, the American spacecraft moving at 10.6 miles per second, more than 49 years ...

Before defining what a light-year is, we should define what a light-year is not: It is not a measure of time, but rather a measure of distance. The confusion arises from the “year” that comes at the ...