Ok, here goes blitzzen’s theory #542… Most of you know I hope that if you were on a train going, lets say, 100mph, and you threw a baseball in the direction the train is going(suppose you threw it at 20mph) Then the baseball is actually going 120mph. I know that for a fact, dont get me wrong. But lets say you were in the same position but you had a flashlight and you shined it straight forward, would it technically be going faster than the speed of light? Or consider: If it was possible to travel at the speed of light and you shined the flashlight straight forward, woulf the light beam be going at “warp 2” or 2 times the speed of light?
Nope. In fact, this is exactly what is the cause of all of relativity’s weirdnesses. One of Einstein’s postulates was that the speed of light is constant, regardless of how fast you’re moving with respect to the light source. This has been experimentally confirmed.
What happens instead is that the light gets blueshifted (if you’re moving toward the light) or redshifted (if you’re moving away). You have to think of light as a wave in this case. I’m sure more detailed explanations will be quickly forthcoming.
Uncle Cecil addressed this very question in: If you turn on your headlights while driving at the speed of light, what happens? This column originally appeared in Return of the Stright Dope, available at bookstores everywhere.
He also has addressed the similar question, If I fire a gun while near light speed, will the bullet EXCEED light speed?, which originally appeared in More of the Straight Dope, and which is also available at bookstores everywhere.