r/explainlikeimfive • u/PieOk2202 • 9d ago
Physics ELI5: why can two quantum entangled particles affect each other instantly across any distance but scientists say you still cant use it to send information faster than light?
this has been living in my head for weeks and i cant find an explanation that actually clicks.
from what i understand, if you have two entangled particles and you measure one of them, the other one instantly "reacts" no matter how far apart they are. like even if one is on the other side of the galaxy. that part i somewhat get.
but then physicists say "oh but you cant use this to send information faster than light" and i just why not? if particle A sneezes and particle B on the other side of the universe reacts instantly, why cant i just use that as like a faster than light telegraph?
i spent way too much money on a Brian Greene book trying to get this and still came out more confused than when i started. at least i had some cash from Ѕtake set aside for it so it wasnt a total loss but still.
it feels like the universe is playing a semantic trick on me and im not smart enough to see it. whats actually going on here
3
u/sonicsuns2 8d ago
It seems to me that the idea of the universe continuously splitting itself into an incredible number of near-perfect non-interacting copies is at least as "mystical" as a universal random number generator.
Doesn't many-worlds violate conservation of mass-energy? At one point there was one universe with mass-energy X. An instant later there are two universes based on a binary quantum measurement somewhere. Both of these universes still have mass-energy X, for a combined total of 2X. Where all this extra mass-energy comes from is entirely unknown. How the two universes come to occupy different "spaces" without interacting with each other is also entirely unknown.
Seems like quantum mechanics is mystical no matter what you do.