# Relativity of simultaneous?

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So I was thinking: you have one measuring device "A" which contains an entangled particle, another measuring device "B" which contains a particle entangled with that of A and C, and of course the implied third measuring device which contains entangled particle "C". A is kept on Earth, B is in the vacuum of space, and C is put near the event horizon of a black hole with at least 5 solar masses A measurement is made, technically the disentanglement is "instantaneous", but you can't have a universal "time" that something happens, so how do we get around this dilemma?

Let's say device B made the measurement. Could device B say that it happened at the same time both on Earth and near a black hole? I don't see how, but I don't see how it wouldn't.

Edited by SamBridge
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I'm not sure what your question is. I posted this in another thread:

Imagine you have two balls: one red and one blue. The balls are, without you watching, put in separate boxes so that you can't tell which ball is in which box. Now, if you were to open one of the boxes and discover that the ball inside was red, you would immediately know what the color of the ball in the other box is. It doesn't matter how far apart you separate the boxes before you open one of them. That's sort of what entanglement is like. No information is transferred in this process.

The analogy isn't perfectly accurate (Bell's inequalities, etc.), but gets the idea across.

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I'm not sure what your question is. I posted this in another thread:

The analogy isn't perfectly accurate (Bell's inequalities, etc.), but gets the idea across.

I'm already completely aware of that analogy and the nature of correlation vs causation, but good try I guess. Besides that analogy doesn't completely make sense anyway because that would imply there is a chance the outcomes were already determined.

Edited by SamBridge
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I'm already completely aware of that analogy and the nature of correlation vs causation, but good try I guess.

Well, as I said, I'm not really sure what your question is. I thought the analogy might be relevant.

Besides that analogy doesn't completely make sense anyway because that would imply there is a chance the outcomes were already determined.

Yes, I believe I mentioned that.

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Well, as I said, I'm not really sure what your question is. I thought the analogy might be relevant.

The questions is how can something be instantaneous across different frames of reference including extreme variation of time dilation?

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You should better ask NASA why they don't use entanglement to transfer commands to devices or satellites on 2nd end of Solar System such as Voyager and pictures or movies from them back to Earth, if it really allows transfer of information instantaneously at so big distances.. What for waiting for radio waves minutes, or hours?

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You should better ask NASA why they don't use entanglement to transfer commands to devices or satellites on 2nd end of Solar System such as Voyager and pictures or movies from them back to Earth, if it really allows transfer of information instantaneously at so big distances.. What for waiting for radio waves minutes, or hours?

Simple. Entanglement does not allow for instantaneous transmission of information.

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Simple. Entanglement does not allow for instantaneous transmission of information.

That's...not really what I'm talking about.

Information isn't being transmitted because as per entanglement all the particles act as the same particle so there are no separate components to transmit information between, however the disentanglement is the correlation that the particle no longer has those components and instead becomes separate components, but saying it's truly instantaneous in the manner I'm describing would be like saying there is a frame of reference that can measure them all happening at the same time, regardless of time dilation and relativity, which doesn't seem to make sense.

Edited by SamBridge
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What, exactly, do you think is "simultaneous?"

Perhaps this analysis will put you at ease:

A neutral pion at rest decays into a positron and electron. The pion had spin-0, so due to conservation of angular momentum we know that one of the remaining particles must be spin-up and the other spin-down. We have two detectors set up in opposite directions which will tell us the spin state of each particle. Say detector A (which will measure the electron) is a bit closer to the original location of the pion, so in the center of mass reference reference frame the electron's spin state is measured first. Let's say the electron turns out to be spin-up. Now we automatically know that the positron is spin-down, which can be confirmed after it is measured and the two observers compare data. Even though the particles themselves didn't know which state they were going to be in once measured, as soon as one of them is measured you immediately also know the state of the other particle.

But relativity tells us that with an instantaneous "interaction" (I use the word interaction loosely) we will be able to find a valid reference frame in which the positron was actually measured first. So in this frame the positron's state is measured, and we find that it's spin-down. In this frame we automatically know that the electron's state is spin-up. But this scenario is entirely identical to the original, in which the electron was measured first! Nothing changed from changing the order in which states were measured. Since the scenario is symmetrical it does not violate relativity in any way.

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What, exactly, do you think is "simultaneous?"

Perhaps this analysis will put you at ease:

A neutral pion at rest decays into a positron and electron. The pion had spin-0, so due to conservation of angular momentum we know that one of the remaining particles must be spin-up and the other spin-down. We have two detectors set up in opposite directions which will tell us the spin state of each particle. Say detector A (which will measure the electron) is a bit closer to the original location of the pion, so in the center of mass reference reference frame the electron's spin state is measured first. Let's say the electron turns out to be spin-up. Now we automatically know that the positron is spin-down, which can be confirmed after it is measured and the two observers compare data. Even though the particles themselves didn't know which state they were going to be in once measured, as soon as one of them is measured you immediately also know the state of the other particle.

But relativity tells us that with an instantaneous "interaction" (I use the word interaction loosely) we will be able to find a valid reference frame in which the positron was actually measured first. So in this frame the positron's state is measured, and we find that it's spin-down. In this frame we automatically know that the electron's state is spin-up. But this scenario is entirely identical to the original, in which the electron was measured first! Nothing changed from changing the order in which states were measured. Since the scenario is symmetrical it does not violate relativity in any way.

But definition of simultaneous is that it happens at the same "time", so you can see where the dilemma is when you have time dilation which makes time flow slower. How can something happen at the same "time" when there is extreme time dilation?

Edited by SamBridge
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But definition of simultaneous is that it happens at the same "time", so you can see where the dilemma is when you have time dilation which makes time flow slower. How can something happen at the same "time" when there is extreme time dilation?

What exactly do you think is happening "at the same time?"

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What exactly do you think is happening "at the same time?"

I don't know, I don't know how you can have a same time across frames of reference with different flow rates of time.

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I don't know, I don't know how you can have a same time across frames of reference with different flow rates of time.

Who said you have the "same time" in different frames? What do you think is going on that would require several frames to share ideas of simultaneity?

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In absolute terms “happening at the same time” is the simultaneity of the two opposite reference frame of an absolute phenomenon- which is not subject to time dilation. While in relative terms’ “happening at the same time” is the simultaneous
coordination and regulation between these two opposite reference frames-which is subject to time dilation.

The questions is how can something be instantaneous across different frames of reference including extreme variation of time dilation?

And If you can make the coordination and regulation of its concerned reference frames instantaneous; then their will be simultaneity.

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Who said you have the "same time" in different frames? What do you think is going on that would require several frames to share ideas of simultaneity?

I think "instantaneous" may, and I don't know what's going on that's why I'm asking about it.

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It seems that you are assuming the measurement of any one particle tells you the precise states of the other two. It's not clear to me this is true in three-particle entanglement. Do you have a source for this?

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It seems that you are assuming the measurement of any one particle tells you the precise states of the other two. It's not clear to me this is true in three-particle entanglement. Do you have a source for this?

Well let's make it two then. If one near the black hole measures a particle, how can it know at the same "time" what the other entangled particle must be if it discovers a specific spin state?

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Simple. Entanglement does not allow for instantaneous transmission of information.

I have to ask... I have read and been told a great many times that entanglement is something weird, counter intuitive, i think it was Einstein who was quoted as calling it spooky action at a distance... Simply knowing one thing because the other has to be the only other option is not counter intuitive in any way and is simple logic... Why is this so obfuscated?

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So I was thinking: you have one measuring device "A" which contains an entangled particle, another measuring device "B" which contains a particle entangled with that of A and C, and of course the implied third measuring device which contains entangled particle "C". A is kept on Earth, B is in the vacuum of space, and C is put near the event horizon of a black hole with at least 5 solar masses A measurement is made, technically the disentanglement is "instantaneous", but you can't have a universal "time" that something happens, so how do we get around this dilemma?

Let's say device B made the measurement. Could device B say that it happened at the same time both on Earth and near a black hole? I don't see how, but I don't see how it wouldn't.

The distance between A and B is measured in Rindler coordinates (or, you might say 'freefall coordinates') as is the distance between B and C. A (near the black hole) collapses the wave, which B learns a certain time later. The time between the collapse by A and the observation of the collapse by B, as measured by B, is the distance in Rindler coordinates divided by the speed of light. The time between B being informed of the wave collapsing and C's observation from B that the wave has collapsed is again 'the distance divided by the speed of light' time later.

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Well let's make it two then. If one near the black hole measures a particle, how can it know at the same "time" what the other entangled particle must be if it discovers a specific spin state?

If you measure the state of particle A then you immediately know the state of B. Since the two measurements are non-local, you can only confirm that B is in the state you expect when the two observers come together to compare results. It doesn't matter "when" each observer did the measurements because the results always agree. Indeed you can find valid frames in which the order of measurements is reversed and the results still agree. "When" the states of each particle were measured has no bearing on the measurements.

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If you measure the state of particle A then you immediately know the state of B. Since the two measurements are non-local, you can only confirm that B is in the state you expect when the two observers come together to compare results. It doesn't matter "when" each observer did the measurements because the results always agree. Indeed you can find valid frames in which the order of measurements is reversed and the results still agree. "When" the states of each particle were measured has no bearing on the measurements.

I know that aspect of it, but that doesn't seem to answer the question, but it seems like if you were near a black hole the measurement at the black hole should have happened some time in the past compared to the measurement you made. You know what the other one is when you measure it, but is that the same "time" that the one near the black hole would measure it?

Edited by SamBridge
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I have to ask... I have read and been told a great many times that entanglement is something weird, counter intuitive, i think it was Einstein who was quoted as calling it spooky action at a distance... Simply knowing one thing because the other has to be the only other option is not counter intuitive in any way and is simple logic... Why is this so obfuscated?

The counter-intuitive part is that each particle was in an indeterminate state prior to the measurement. If you measure a spin-entangled particle as spin up, that does not mean it was spin up the whole time prior to the measurement.

Well let's make it two then. If one near the black hole measures a particle, how can it know at the same "time" what the other entangled particle must be if it discovers a specific spin state?

A single observer only has one time. If that observer measures a spin state, that observer knows the other spin state as well, at the same time.

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The counter-intuitive part is that each particle was in an indeterminate state prior to the measurement. If you measure a spin-entangled particle as spin up, that does not mean it was spin up the whole time prior to the measurement.

Since you are rarely wrong and I have no clue I am going to assume you are correct but if the spin states are only two possibilities and they have to be different then how is it relevant they are unknown until you check them, the different colored balls are unknown as well until they are checked...

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The counter-intuitive part is that each particle was in an indeterminate state prior to the measurement. If you measure a spin-entangled particle as spin up, that does not mean it was spin up the whole time prior to the measurement.

I have no idea why you would think that as it was not what I was saying, that was more of what other people were saying.

A single observer only has one time. If that observer measures a spin state, that observer knows the other spin state as well, at the same time.

But can both observers agree that they measure disentanglement at the same "time"? And if not, how does that translate to in layman terms? If I measure disentanglement "now", does that mean it happened now for another observer some amount of time in the past due to time dilation?

Edited by SamBridge
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But can both observers agree that they measure disentanglement at the same "time"? And if not, how does that translate to in layman terms? If I measure disentanglement "now", does that mean it happened now for another observer some amount of time in the past due to time dilation?

"Now" is a local concept. It has no meaning for separated observers near different gravitating bodies.

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