Question

Recently, I saw a video by Minute Physics and heard a lecture by Michio Kaku about "How to break the speed of light". There was a backyard experiment where a person was shooting a strong laser to the moon's surface from earth and so there was this laser spot on the moon. Now what he does next is, he flicks his wrist and the spot on the moon moves instantly which implies that the spot on the moon traveled much faster than the speed of light.

Now my question is, since light is made up of photons. When we flick our wrist, new photons are released from the laser torch, (from this new angle we created) which travel all the way to the moon thus creating a new spot. So how is it that the spot on the moon traveled faster than the speed of light? It should have taken the same amount of time like the first time the laser was shot to the moon.

Answer 1

Yes you are right that new photons will take same time as when photons took time to reach there first time and created a bright area. So we can explain this phenomenon as , that when he puts his wrist in path of photons at beginning , that part part or say that angle of photons are stopped there and they will not go to moon but since already some phonots which left torch right before he put his wrist are still traveling to moon and hence there will not be a dark spot until last photon beam reaches there . We took this example as partial interference by wrist , same way can consider it for whole wrist and we can come to a conclusion that it will take time to create a dark spot in lighten surface of moon as much as photons will take time to reach surface of moon but it won't take time to move dark spot on the moon surface from one end to another end of lighten area .

* Also here shadow moves with higher speed than light speed but it doesn't violate any law of physics or say Einstein because shadow is nothing but absence of photons and also it doesn't carry any INFORMATION .

*Hope it will be helpful to clear your idea.