How fast does light travel? What could you do to find out? One natural thing to try is to have someone send some light your way and see how long it takes to reach you. How about if you got a friend to shine a flashlight at you from a distant hill, exactly at midnight? With your stopwatch you start counting the seconds until you see the light. Learn more on this Moment of Science.
Since time slows down the closer you get to the speed of light, if alien spaceships could travel at light speed, wouldn't they take longer to get places?