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Superluminal worldlines are space-like: 'Time' on an FTL-spaceship would have to be measured with meter-sticks instead of clocks. This is just one of the issues with tachyons (hypothetical superluminal 'particles'). Others are a failure to be properly localizable, processes with endpoints of the same intrinsic type on both sides (emission-emission, ...


The collapse is a non-unitary operation. It cannot be reversed (undone). Typically, we establish contact between the studied system and a macroscopic body (apparatus) that we are unable to describe by a wave-function. Also, we are not able to describe rigorously the process that follows this contact. The projection transformation done by such an apparatus on ...


Basicaly in generaly we explain entropy as "the disorderness of the system" we measure it on the large scale for macroscopic objects not for microscopic objects.


The reasoning in the question is correct. If you have a box with gas particles placed in half of a box but otherwise uniformly random and with random velocities then it is overwhelmingly likely that it entropy will increase with time, but if reverse the velocities, you will still have randomly distributed velocities and the same argument will apply. By time ...

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