how long is a light-year vs earth years
1 In one of the NASA Space Shuttles, about 76,526 earth years (38,263 earth years one way). 2  1 light-year is 5.8 trillion miles and the maximum speed of a NASA Space Shuttle is 17,500 miles per hour. 3  The fastest unmanned space craft traveled 157,000 mph.
Â­So to measure really long distances, people use a unit called a light year. Light travels at 186,000 miles per second (300,000 kilometers per second). Therefore, a light second is 186,000 miles (300,000 kilometers).