Can light spot move faster than light itself?
Give 10 points to Kirchwey. Imagine a laser that spins around like a lighthouse. Point it so that once every revolution, its would point at the moon. Given that the moon's distance from earth is ~1.25 lightseconds, all the laser needs to do is exceed a speed of 1/ (2π *1.25 seconds) = 0.127 revs/second or once every 7.8 seconds for an observer on earth to say the dot on the moon was exceeding the speed of light. If you were on the moon, you would also conclude that the dot exceeded the speed of light, but you have to take into account the speed of light to make that calculation. (I only answered because you have different answers from two reputable people).
Sure, but that in no way means that any wave or particle exceeds the speed of light. Think of a point source of light at the center of a spherical shell. After it's turned on, the light reaches every point on the inside of the shell simultaneously. Is this infinite-speed motion? No. It's just an extreme version of the garden-hose example, in which the point of impact of the water stream moves much faster than the water particles do, giving the illusion of rapid motion of the water. But it's only our vision and brain that interpret it that way.
Hi guys, I agree with FGR. The problem here is that there is no monolithic light spot in physics. FGR's rotating lazer brought to vision the following thought experiment: A rotating source of photons inside a cylinder of infinite-resolution photographic film. After one revolution we shut off the source and inspect the film. Photon-energy dot density is proportional to the period of revolution. We conclude that each dot (photon) did not move. It was deposited. Nice answers by three excellent contributors.
The theoretical light spot will...but, the real visual light spot will not. It will have a lag...just like when watering your garden with a jet of water, and you suddenly twist the jet sideways, that you get a lag of the splash location since it isn't replenished as fast as it needs to be to have no lag.
