Question

THEORETICAL PHYSICS: If a person is running at the speed of the light and turns on a flash light in his hand, does any light come out of it?

Answer 1

This is a question that falls within the realm of Special Relativity. The correct short answer is yes, in your "inertial frame" light travels from the flashlight relative to you at the speed of light. But, from the reference frame of someone who you are traveling at the speed of light relative to, the light from the flashlight is still traveling at the same exact speed: 300,000,000 meters per second. In Newtonian mechanics, the inertial frame from which you are traveling at the speed of light relative to would in fact record the light from that flashlight traveling at twice the speed of light. However, in special relativity, light always goes the same speed from any given reference frame. As a result of this, combined with the principle of relativity (all inertial frames have the same laws of physics) time dilates and length contracts relative to different inertial frames. But the speed of light (though not the velocity) is always constant. This is a founding axiom of special relativity, the speed of light is constant