Light Year – How far is it? Name ___________________________ date ________ period ____ Score ______

Distances in space are so enormous that a special unit of measure is used. The light year. It is defined as the distance light travels in one year.

Light is the fastest thing we know. It moves 186,000 miles a second! It moves so fast that when we turn on a light bulb it instantly glows. Light moves so fast that it could travel from New York City to San Francisco 62 times in one second!

Even at that speed the light from distant stars takes hundreds thousands and even millions of years to reach earth. For that reason when we look up into the night sky we are gazing into the past. The closest star to Earth other than the sun is 4.3 light years away. This means it takes 4.3 years for the light from that star to get to Earth. If something were to happen to that star we would not know if for 4.3 years.

Calculate the number of miles in a light year. One light year = the distance light travels in one year (use 365 days). Show your work below!

To get you started remember that light travels at 186,000 miles per second. How many seconds are in a minute? Minutes in an hour? Hours in a day? Days in a year?