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Jun12-10, 08:13 AM
P: 2,284
Quote Quote by ABHoT View Post
I am thinking a clittle clearer now.

I have two sticks in space with light bulbs on the ends, say bulbs A & B on one stick, bulbs C & D on the other. Both sticks are straight and are the same length.

I hold both sticks upright, next to each other lining up bulbs A & C at the top and bulbs B, D at the bottom. I switch on bulbs A & C together and simultaneously drop the first stick so it is falling (or it was already moving and just flying past the other stick but the bulbs were level when the lights were switched on).

Light from A should reach B at the same time that light from C reaches D because both the top bulbs are stationary wrt to their bottom bulbs, both are level when it started and both sticks are the same length.

But stick one is falling and these are really long sticks, so by the time light reaches bulb B from A the sticks should no longer be level. To my thinking, at some point light from bulb A on stick one ought to pass bulb D on stick two before light from C has.

But how can this be if everything was equal and level at the start? Does SR make this possible?
It is the Relativity of Simultaneity.