Why is it that the speed of light is constant, and not even affected by gravity? Also...logic dictates that if you shoot a gun from a moving car, the bullet moves at it's normal speed, plus the speed of the car. However, I've heard this isn't true for light; that the speed of light is 186,000 miles per second. Is that true? If so, why is that? If this is too difficult to explain in a post, I apologize. I'll read whatever links you can post, if that's the case.