I've heard that nothing can travel faster than the speed of light. Is that actually held to be a scientific truth, and if so what is the basis for that? The reason I ask, I was watching a video on relativity, and it illustrated a straight-line light beam traveling through space. Superimposed upon the beam was the electromagnetic sine wave that is a part of that light beam. In a way the whole thing looked like a ski boat traveling across a lake, with the skier cutting back and forth across the straight-line path of the boat (wake). I've skied enough back in the day to know that cutting back and forth across the boat's path makes the skier go at much greater speed than the boat, adding lateral movement to the forward movement. So, I'm wondering that, if the straight-line speed of a light beam is c, then isn't the electromagnetic wave that constantly crisscrosses it going at a speed significantly faster than c?