Block Time & Action at a Distance

[InterestedParty]

TL;DR

Block Time and entanglement

Sorry, for the lack of correct terminology - this may be answered elsewhere on the forum, I haven't been able to find it.

If the Universe is in Einstein's 'Block Time', then does this provide a mechanism for 'action at a distance'? Rather than a particle being split and entangled, if viewed in Block Time it would look like one particle being stretched (a single line), not two separate particles. As such it always remain in contact with itself and account for the interaction.

 

[PeroK]

Summary:: Block Time and entanglement

Sorry, for the lack of correct terminology - this may be answered elsewhere on the forum, I haven't been able to find it.

If the Universe is in Einstein's 'Block Time', then does this provide a mechanism for 'action at a distance'? Rather than a particle being split and entangled, if viewed in Block Time it would look like one particle being stretched (a single line), not two separate particles. As such it always remain in contact with itself and account for the interaction.

Your question is based on a misunderstanding of block time. It supports neither action-at-a-distance, nor does it explain entanglement.

 

[InterestedParty]

LOL! Thanks for taking the time to respond, I appreciate it:)

 

[InterestedParty]

Could I just ask: if time *were* viewed as all future and past permanently existing in the same moment, is there a QM way of describing that as a concept?

 

[PeroK]

Could I just ask: if time *were* viewed as all future and past permanently existing in the same moment, is there a QM way of describing that as a concept?

That's exactly what block time isn't. See the bit I've highlighted. There's no sense in which the entire spacetime exists at a moment in time. Time itself is part of the block universe. Causality and the flow of time, as measured by the evolution of physical processes, is not affected by the concept.

In fact, the block universe raises philosophical questions rather than makes any meaningful difference to physics. Whether or not the universe is a block universe is not something that can be tested. It's more of a metaphysical interpretation of the theory of relativity and the nature of spacetime.

 

[PeroK]

PS The thing to learn from relativity is that the concept of a universal "now" is meaningless - which is what allows the block universe interpretation in the first place. The problems start when you then forget this and imbue an arbitrary "universal now" with some physical significance.

 

[InterestedParty]

Thanks again. I understand that that's what block time isn't, I was just wondering if there was anything like it in QM, but you've answered my question.

 

[PeroK]

Thanks again. I understand that that's what block time isn't, I was just wondering if there was anything like it in QM, but you've answered my question.

The lack of an absolute universal now is important for entanglement as follows:

If entangled particles are separated by a sufficient distance, then (*) it is not possible to say unambiguously which one is measured first. If someone proposes, therefore, a mechanism by which the particle that gets measured first sends a message to the other particle, then it's not possible even to say which particle is supposed to be sending the message.

(*) To be more precise, you can conduct the experiment in such a way that it is not possible to say unambiguously which one is measured first. Technically this means that the measurement events must be spacelike separated.

 

[InterestedParty]

Ahhhh, that makes sense, thanks, a good summation:)

 

[DrChinese]

The lack of an absolute universal now is important for entanglement as follows:

If entangled particles are separated by a sufficient distance, then it is not possible to say unambiguously which one is measured first. If someone proposes, therefore, a mechanism by which the particle that gets measured first sends a message to the other particle, then it's not possible even to say which particle is supposed to be sending the message.

Not disputing this, but pointing out an additional point: You can certainly unambiguously measure one before the other. But there is no observable difference possible from the predictions of QM. It is not possible to conclude that A causes B any more than you say B causes A : except by assumption.

@InterestedParty : There is an interpretation of QM that features elements of block time. That interpretation is best discussed in the PF subforum on quantum interpretations. The interpretation is called Relational BlockWorld (RBW), and is quite sophisticated. See this breezy 47 page intro: https://arxiv.org/abs/0908.4348

 

[PeroK]

You can certainly unambiguously measure one before the other. But there is no observable difference possible from the predictions of QM. It is not possible to conclude that A causes B any more than you say B causes A : except by assumption.

Good point. I've clarified that post.

 

[InterestedParty]

Not disputing this, but pointing out an additional point: You can certainly unambiguously measure one before the other. But there is no observable difference possible from the predictions of QM. It is not possible to conclude that A causes B any more than you say B causes A : except by assumption.

@InterestedParty : There is an interpretation of QM that features elements of block time. That interpretation is best discussed in the PF subforum on quantum interpretations. The interpretation is called Relational BlockWorld (RBW), and is quite sophisticated. See this breezy 47 page intro: https://arxiv.org/abs/0908.4348

'Breezy' indeed, thanks for the link and the directtion:)