Quantum Entanglement vs. Now Slices (Relativity)

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Discussion Overview

The discussion revolves around the relationship between quantum entanglement and the concept of "now slices" in relativity. Participants explore how movement and distance might influence the perception of simultaneity in quantum states, questioning the implications of these phenomena on each other.

Discussion Character

  • Debate/contested
  • Conceptual clarification

Main Points Raised

  • One participant suggests that movement can affect the "now" of distant places, potentially conflicting with the principles of quantum entanglement.
  • Another participant asserts that there is no global "now," emphasizing that multiple valid time slices exist in the universe.
  • This second participant challenges the initial understanding of quantum entanglement, proposing that it is fundamentally about consistency rather than simultaneity.
  • Questions are raised about whether the spin of an entangled particle can be measured independently of the other particle's state, with a later reply affirming that measuring one particle reveals the state of both.

Areas of Agreement / Disagreement

Participants express differing views on the nature of simultaneity and the implications of quantum entanglement, indicating that multiple competing perspectives remain unresolved.

Contextual Notes

There are limitations in the understanding of how quantum entanglement interacts with the concept of "now slices," and the discussion reflects various interpretations of these complex topics.

DrSammyD
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So I watched this video talking about now slices, and how it seems that across vast distances of space, movement can affect what is actually the now of places far away.

https://www.youtube.com/watch?v=

This seems to be in direct conflict with what I've heard about quantum entanglement.

Let's say we move an entangled particle across such a distance. If we start moving away with our particle at very fast pace, the entangled particle on the other side will be affected in the past, where as if we start moving towards it, it will be affected in the future. But from what I've heard, entangled particles change "simultaneously" without regard to which "now slice" is happening.

Am I describing this correctly? Is anybody researching how these two phenomenon relate?
 
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There is no such thing as a global "now". Or, perhaps more accurately, there are many perfectly-valid slices of the universe that can be thought of as having equal time values. What's incorrect here is your understanding of quantum entanglement. But that's understandable, as quantum entanglement is a very strange effect that is frequently described incorrectly.

Here's a (hopefully) better way to think about it: quantum entanglement is, fundamentally, about consistency. If we have a quantum-mechanical system that splits into two particles, one whose spin is always opposite the other's, then any measurement of particle A's spin will be opposite of particle B's spin. That is, if I measure spin "up" on my particle A, and particle B travels towards you, then you will necessarily measure spin "down" on particle B. It does not matter if we measure the particles at the same time, or one before the other. The timing is irrelevant. The only thing that is relevant is that the two particles have spins that are consistent.
 
Can the spin of the particle be measured without knowing what the other particle's spin is?
 
DrSammyD said:
Can the spin of the particle be measured without knowing what the other particle's spin is?

Measuring one tells you the state of both.
 

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