First off, a car can't travel at lightspeed since it has mass, but a theoretical massless light source could. the answer is that the beam would travel at the speed of light relative to any observer in an inertial frame, but in the frame in which the source is moving at c the source will move forward as fast as the light it emits - if it were heading toward the observer it would arrive at the same time - he wouldn't "see it coming".
|