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- Why light moves sideways? 4 answers
The thing that I don't understand is, why does the light appear to be travelling at an angle for the observer outside the moving frame (the one containg mirrors)?
Physically speaking, what forces the light beam emitted by a moving source not to go simply straight up vertically, missing the upper mirror completely?
I am fully aware why this works in Minkowski spacetime; all observers must see the spacetime event of the beam hitting the upper mirror, and I understand relativistic aspects like relativity of simultaneity, time dilation and comparing discrete spacetime events in Minkowski spacetime diagrams.
But in this case I am confused:
- presuming there is vacuum between the plates, what properties of the "empty space" between these mirrors cause it to be slanted, once it leaves the emitter?
- is the light supposed to be treated like a particle, and it's actually affected by the train speed?
- is the light supposed to be treated like a wave radiating from the emitter, and the point where it hits the mirror is actually not the top of this sphere wave?
My confusion is deepened by the following statement by @JohnDuffield in this answer:
(OP's question:) The reason a wave such as sound would have the trajectory shown in this example is that the medium inside the rocket, air, is moving at the speed of the rocket and the sound wave would take on that velocity as it left it's source. Light does not use a medium to move.
Answer: It does. Have a look at Nobel Laureate Robert B Laughlin here: "It is ironic that Einstein's most creative work, the general theory of relativity, should boil down to conceptualizing space as a medium when his original premise [in special relativity] was that no such medium existed".
So, given the link to the wikipedia article on aether, this answer seems to imply that aether in fact not only exists, but is also being dragged by the train?