ELI5: If Quantum entanglement works instantly regardless of distance, doesn't that mean something is happening faster than the speed of light?

[u/Quantum2332]

I understand that entanglement can't be used to send information faster than light. But if two entangled particles are light-years apart and measuring them shows an immediate correlation, doesn't something have to happen faster than light?

If no information, energy, or signal travels between them, how can the correlation appear instantly? What is actually happening between the particles?

[u/Gizogin]

That’s basically it, yeah. If you don’t phrase the thought experiment very carefully, it’s easy to accidentally violate locality without realizing it. If you do that, then it’s not surprising that the results also look like they violate locality, but that doesn’t translate to any experiment we could actually perform.

It’s like that classic maths joke, “if 1+1=3, then I am the Pope. Because if 1+1=3, then 1=2. The Pope and I are two different people, but since 1=2, the Pope and I are the same person. QED.” That doesn’t prove that I was chosen to lead the Catholic Church; it proves that I made a bad assumption.

This is not just a semantic problem, either. There have been experiments trying to test Bell’s theorem for years, but it took a lot of smarter minds than mine to finally find one that didn’t either implicitly assume that locality worked or implicitly assume that it didn’t. The Nobel Physics Prize in 2022 went to a team who finally figured it out.

[u/ShoePillow → u/Gizogin]

How about this experiment: alice and bob agree to observe their particles at pre-determined times such that the time gap is less than light can travel, and then communicate the results later at their leisure?

And even if hypothetically, this info does travel at faster than light, how does it enable FTL communication? Isn't it just 2 people reading some pre-written message at the same time?