if photons have the same speed in all reference frames according to GR, why do slomo films of light beams exist?
In: Physics
If you mean videos that appear to show light propagating through a medium, you’re probably looking at precisely timed still photos of separate beams.
Set up everything. Turn on laser for x nanoseconds. Take a picture as you turn it on.
Repeat, this time taking the picture 0.1 nanoseconds after you turn the laser on. A nanosecond is enough time for light to go about 30cm/one foot, for a frame of reference.
Now do it again with the picture at 0.2 nanoseconds.
And so on. If you don’t change anything else about the setup and the laser itself doesn’t harm the target material, each laser beam would behave the same as the last, so by stacking up a sequence of images you’re basically doing stop-motion animation with light.
Latest Answers