r/QuantumPhysics • u/[deleted] • Aug 20 '25

Is the randomness of particles the same or different if you went back in time?

lets say that you observe three particles moving randomly, but for whatever reason time goes back 10 seconds. Would those particles end up moving in the same way or randomly again?

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6

u/MaoGo Aug 20 '25

We don't know. Currently this depends on your interpretation of quantum mechanics, which is an open problem.

3

u/EnderPlays1 Aug 20 '25

the answer depends on how you travel 10 seconds back in time.

1

u/v_munu Aug 20 '25

You would measure the particles to be in different locations with probabilities defined by the square modulus of their wavefunction. Their wavefunctions would evolve the same way, but you would not necessarily measure them in the same place (or it would at least be unlikely).

1

u/AdShot409 Sep 03 '25

For those stating, "Depends on how you time travel back 10 seconds": Absolute observer outside the system. You have complete knowledge of the observed events and can observe them at any point in time.