I How Does Special Relativity Challenge Our Understanding of Absolute Time?

[name123]

Neural events simply don’t happen fast enough for the relativity of simultaneity to matter. Simultaneity in the relativistic sense can never cause anything so it also cannot cause “what you were experiencing”.

You seem to have avoided answering the question. You seem to have denied that what you are experiencing reflects the simultaneity of neural events, but haven't stated what you think it does reflect. Does it reflect something, and if so, what in the model interpretation that you favour?

Which brings me back to the point I made in post #92

But presumably it would be slightly significant else if you counted each ns step as equivalent to the next then when considering the sum of lots of such differences you would consider it to make no difference. In the sense that if e₁ = e₂ and e₂ = e₃ and e₃ = e₄ and so on such that e_n = e_n+1 then e₁ = e_n+1. I have ignored brain waves and the extent to which some of the firings might be "synchronised".

If you state there is no difference in experience between the slightly different neural events, then it is a slippery slope. If you state that there is no difference that you could distinguish (for example there are RGB numbers we cannot distinguish), then there still is a difference, just not one we can distinguish. And how can the difference not actually be different, how could e₁ = e_n+1 for example.

You also have the problem of not knowing what events would be distinguishable and when they would be distinguishable over time. For example if on RGB events, some R changed later than B in some perspective, maybe it would cross the distinguishable boundary..

Regardless you still haven't explained what your experience reflects.

 

[SlowThinker]

Well it depends upon what you mean by simultaneous. Let me put it another way. Are you thinking that the truth of what you are experiencing is relative or is there an absolute truth about the matter?

Maybe you're misunderstanding the "relativity" in Theory of relativity.

Let's imagine you and I go to view some play in a theater. Your seat is more to the left, mine is more to the right. We both see the same thing, yet it looks different. Both of our views are equally correct. There is no "the one correct" view of the play.

Can you use this example to explain what you mean?

 

[name123]

Maybe you're misunderstanding the "relativity" in Theory of relativity.

Let's imagine you and I go to view some play in a theater. Your seat is more to the left, mine is more to the right. We both see the same thing, yet it looks different. Both of our views are equally correct. There is no "the one correct" view of the play.

Can you use this example to explain what you mean?

Yes two people are looking at you and from their perspectives estimate your experience . If they have differing opinions can they both be right, is it relative, or is what you were experiencing absolute. Can there be experiential scenarios (perhaps put forward by observers moving relative to you at a high speed and an extreme distance) that were simply false. You never experienced those. Is the truth about what you experienced relative?

 

[PeterDonis]

You seem to have denied that what you are experiencing reflects the simultaneity of neural events

That's right; it doesn't. Causal influences can't travel faster than light, and whatever you experience is causally influenced by neural events.

What you experience is that some events in the outside world seem to be simultaneous with some other events. But all of those appearances are constructed by your brain based on information in your past light cone, i.e., information that traveled to you at the speed of light or slower. You never experience anything from events which are actually simultaneous with you, because those events are outside your past light cone and you can't have received any information from them.

 

[SlowThinker]

Yes two people are looking at you and from their perspectives estimate your experience . If they have differing opinions can they both be right, is it relative, or is what you were experiencing absolute.

Maybe one of them saw what's behind me, and neither I nor the other observer saw it.
If the two observers are somewhat intelligent, they'll undestand that they only view some part of the full truth. So do I. But their view may be more complete and more correct than mine.

 

[name123]

Maybe one of them saw what's behind me, and neither I nor the other observer saw it.
If the two observers are somewhat intelligent, they'll undestand that they only view some part of the full truth. So do I. But their view may be more complete and more correct than mine.

I suspect this thread is about to be shut down, as considering this seems verboten.

The point is that if there were two differing opinions about what you experienced, and you only experience one of them (or neither), are the claims about what you didn't experience equally as true as any (if there were any) about what you actually did experience?

 

[PeterDonis]

if there were two differing opinions about what you experienced, and you only experience one of them (or neither), are the claims about what you didn't experience equally as true as any (if there were any) about what you actually did experience?

You are failing to distinguish two different things.

One, the one @SlowThinker is talking about, is where different observers have different information about events. This can happen in relativity if the observers are spatially separated; each one has the information in their past light cones, but their past light cones are not the same.

The other, the one you are implicitly referring to, is an argument about what one particular observer, at one particular point on his worldline, with one particular past light cone, experienced. Such arguments are irrelevant here; in relativity we assume that an observer's experience at a given point on his worldline is determined by what is in his past light cone, so there can't be any argument or difference of opinion about what that one observer experiences at that one point.

 

[SlowThinker]

The point is that if there were two differing opinions about what you experienced, and you only experience one of them (or neither), are the claims about what you didn't experience equally as true as any (if there were any) about what you actually did experience?

No, false claims are not as valid as true claims.
What we discussed on the first 4 or 5 pages was all true claims.

 

[PeterDonis]

I suspect this thread is about to be shut down, as considering this seems verboten.

No, the point @SlowThinker made was valid; see my previous post.

It is true that this is a forum on relativity, not neurobiology or cognitive science, so questions about the details of how people's experiences are constructed by processes in their brain are not going to go very far here; if you're really interested in that part of it, you should start a separate thread in a more appropriate forum. Unfortunately we don't have one specifically for those topics; the Biology forum is probably the closest.

If you are only interested in the relativity part of it, then please read the last paragraph of my post #107 carefully.

 

[name123]

No, false claims are not as valid as true claims.
What we discussed on the first 4 or 5 pages was all true claims.

So if

there were two differing opinions about what you experienced, and you only experience one of them (or neither), are the claims about what you didn't experience equally as true as any (if there were any) about what you actually did experience?

 

[PeterDonis]

in relativity we assume that an observer's experience at a given point on his worldline is determined by what is in his past light cone

There is one additional technical point here: if we include an observer's choice of coordinates or reference frame in what they experience, then different observers at the same point in spacetime, and therefore with the same past light cone at that point--for example, two observers flying past each other in spaceships--will have different experiences, because of their different reference frames (due to their relative velocity--there are other further complications lurking here as well, but I'll pass over them). But it's still true that the observer's past light cone, plus their reference frame, determines their experience at that point in spacetime, so there still can't be any argument or difference of opinion about it.

 

[SlowThinker]

So if there were two differing opinions about what you experienced, and you only experience one of them (or neither), are the claims about what you didn't experience equally as true as any (if there were any) about what you actually did experience?

A claim that I didn't see a purple elefant is perfectly true.
A claim that I did is false.
I still fail to see what is your question.

 

[PeterDonis]

So if

He already answered your question. So did I, in posts #107 and #111.

 

[name123]

No, false claims are not as valid as true claims.
What we discussed on the first 4 or 5 pages was all true claims.

So if your experience doesn't reflect the simultaneity of your neural state what do you think it does reflect?

A claim that I didn't see a purple elefant is perfectly true.
A claim that I did is false.
I still fail to see what is your question.

Supposing that a value could be given to your experience, e.g. 1979873987492873498273498273498723984729472984729847298742974928742987
and that another claimed it was 1979873987492873498273498273498723984729472984729847298742974928742986

Can you not comprehend the theoretical issue? Can they both be true? Is the truth of the matter relative?

 

[SlowThinker]

So if your experience doesn't reflect the simultaneity of your neural state what do you think it does reflect?

Different observers won't agree on simultaneity, precisely because it does not affect anything. It's only a viewpoint.
My neural state is defined by neuron charges and dendrite weights. These are the same whether viewed by myself or some fast alien.

Supposing that a value could be given to your experience, e.g. 1979873987492873498273498273498723984729472984729847298742974928742987
and that another claimed it was 1979873987492873498273498273498723984729472984729847298742974928742986

Can you not comprehend the theoretical issue? Can they both be true?

If someone says that I saw something, they'll probably be wrong. In physics we usually talk about ideal conditions and perfect observers. Only in that sense they can argue that perfect me saw some clock in a train doing something.

Who exactly is claiming that I saw ...986 when I saw ...987?

 

[russ_watters]

The point is that if there were two differing opinions about what you experienced, and you only experience one of them (or neither), are the claims about what you didn't experience equally as true as any (if there were any) about what you actually did experience?

After weeks of discussion, I don't know where you would come up with such a wrong idea. If I see two lights flash simultaneously, someone else who isn't near me but knows were I and the lights are could calculate correctly that I saw the two lights flash simultaneously, even if he saw them flash at different times. There are no differing opinions about what I experienced. No conflict. No problem. There is only one truth about a set of events and everyone who understands how the relevant scientific laws work and has access to the proper information will agree on what it was, even if they didn't observe them the same. This idea of "relative truth" you have is just plain wrong and you really should understand that by now.

 

[PeterDonis]

if your experience doesn't reflect the simultaneity of your neural state what do you think it does reflect?

I already answered this: your experience reflects the information in your past light cone. "The simultaneity of your neural state" doesn't even make sense.

Supposing that a value could be given to your experience

Then this value would be determined by what's in your past light cone.

Can they both be true?

No. What is in your past light cone is an invariant.

Is the truth of the matter relative?

No.

 

[Janus]

I suspect this thread is about to be shut down, as considering this seems verboten.

The point is that if there were two differing opinions about what you experienced, and you only experience one of them (or neither), are the claims about what you didn't experience equally as true as any (if there were any) about what you actually did experience?

That never happens. Everyone will agree as to what happens to any given observer, though they might disagree as to the timing of some event that led to what that observer experienced.
For example, consider the following scenario.
You have an observer on the tracks and one in a railway car. Flashes of light are emitting by the the red dots and meet at the track observer just as the railway car observer passes him. Thus both flashes reach both observers at the same instant.
Here's those events according to rest frame for the tracks.

Here are the same events according to the railway car rest frame. ( please forgive the fact that I didn't include length contraction with this example)

In this frame, the light are emitted at different times, yet they still meet when the observers pass each other. Both frames agree as to each observer experiences while disagreeing on whether or not the flashes were initially emitted at the same time.

Or we could consider the traditional Train experiment.
The flashes are still emitted at the same moment and reach the the track observer at the same time, however now they are emitted at the moment that the train observer passes the track observer (according to the track observer frame.
Again first we look at the track frame:

Here the train observer runs into the right flash before before the left flash catches up to him. The right flash hits him when about a third of the way to the right red dot and the left flash catches up to him when he reaches the right red dot. The flashes reach the track observer when the rear of the train is about two car lengths away.
Now the same events according to the train.

A few things to note. In the last image, the train fit exactly between the red dots. But this was a "length contracted" train according to the Track frame. In the train frame, the train is its proper length and the tracks are length contracted. As a result, the train no longer fits between the red dots and the front of the train reaches the right dot before the rear of the train reaches the left dot.
The flashes are still emitted when the end of the train reaches a red dot. Thus the flashes are emitted at the different times. The right flash still hits the train obsever when he is ~1/3 of the way between track observer and right red dot and the left flash reaches him when he is next to the right red dot. the flashes still both reach the track observer at the same moment and when the rear of the train is about 2 car lengths away.
So while observers on the train and tracks disagree as to whether or not the ends of the trains reached the red dot at the same time or not and whether or not the flashes were emitted simultaneously or not, they are in perfect agreement as to what any observer on train or tracks directly experiences.

 

[Dale]

You seem to have avoided answering the question. You seem to have denied that what you are experiencing reflects the simultaneity of neural events, but haven't stated what you think it does reflect. Does it reflect something, and if so, what in the model interpretation that you favour?

It most certainly does not reflect simultaneity of neural events, because it would violate the laws of physics for simultaneity to cause anything. Whatever causes any observable (including experience) must be entirely within some past light cone, not on any surface of simultaneity. This is known as causality.

As for what it does reflect, I have avoided answering the question because we don’t know enough to answer the question. However, we are not completely ignorant. We do know some things, and they are not compatible with your suggestions.

If you state there is no difference in experience between the slightly different neural events, then it is a slippery slope.

It isn’t a slippery slope, it is hard data. For example, if there is a coherent visual and auditory stimulus (e.g. a movie), and if the auditory stimulus is delayed anywhere from 0 to about 100 ms, then the experience is the same. The experience is that there is no discrepancy. So it is a clear experimental fact that different neural states lead to the same experience. Any theory of experience that can not accommodate that is already falsified.

then there still is a difference, just not one we can distinguish.

If you can not distinguish it then it certainly isn’t “what you were experiencing”.

Regardless you still haven't explained what your experience reflects.

Along the lines of what I said above, we don’t have a “standard model” of experience yet. So we don’t know that yet and I won’t speculate. All we can do is place some physical and empirical constraints on it.

One key physical constraint is that spacelike separated events cannot be causally related, so the experience cannot be a function of simultaneous neural states. Of course, given how slowly the experience changes and how small the brain is, this really is a non-issue and you can simply think of the brain as a point object wrt relativity and experience. However, even though it is a non-issue (as I have repeatedly shown) you continue to push it.

One empirical constraint is that the experience must be a many-to-one function of neural activity, with substantial “editing”. Another is the relativistically large time delay between the arrival of a stimulus and its experience. Another would be the time scales involved for experience.

For example if on RGB events, some R changed later than B in some perspective, maybe it would cross the distinguishable boundary..

That is simply not physically possible.

Can you not comprehend the theoretical issue? Can they both be true?

Can you not comprehend the answers? The question was answered already, multiple times by multiple people. No, they cannot both be true, therefore any correct model of experience can not depend on non-causally related events (e.g. simultaneous neural states)

 

[Ibix]

A point about the neural states thing - it may be true that I see two of your neurons complete a state change simultaneously while a passing alien does not. But it does not matter because the aluen and I will have different opinions about how fast the consequences of that change propagate, and the result will be that further neuron state changes will happen as expected. So if you have neurons A, B and C in a line, I might say that A and C activated simultaneously and their activation triggerred B to activate. The alien might say that A and C did not activate exactly simultaneously, but the signals of their activation still arrive at B simultaneously, so has no problem with it activating.

As Dale points out, the above is completely irrelevant because of the slowness of state changes. It's also irrelevant because you are at rest with respect to you. If I run towards you then you will appear slightly blue. Do you now expect to suffer anti-blue racism? No - because nothing about you changes because of my state of motion.

 

[name123]

That never happens. Everyone will agree as to what happens to any given observer, though they might disagree as to the timing of some event that led to what that observer experienced.

Thanks again for the diagrams they were really good. I think that the difference disagreements in simultaneity would get smaller the closer the events are, but there would still be differences. So if the person was lying on its back on the train looking up, there could be disagreements about whether two lasers simultaneously hit each of the person's eyes or not (if one was aimed at each. But I am going to stop responding to this thread after this set of posts, because thanks to those on this forum including yourself, the confusions I had have been cleared up, and I think the issues now are slightly philosophical, and so maybe a topic for the general forum or something, but not here. Thanks for the help.

 

[Janus]

Thanks again for the diagrams they were really good. I think that the difference disagreements in simultaneity would get smaller the closer the events are, but there would still be differences. So if the person was lying on its back on the train looking up, there could be disagreements about whether two lasers simultaneously hit each of the person's eyes or not

But no disagreement over what the person would "see". The nerve impulses created by the light hitting the eyes still has to travel to the visual cortex, and whether or these impulses arrive there simultaneously or not would not be in dispute.
Another example would be the person standing with his arms outstretched. The palms on his hands are pricked with a needle. According to his frame, this is done simultaneously, the nerves impulses travel along the arms to his brain and arrive simultaneously. He "feels" the needles poke his hands at the same time. He reacts, sending impulses back down the arms, causing his hands to flinch, again simultaneously.
In another frame, the needle pricks don't occur simultaneously. But the nerve impulses traveling along the arms are subject to the relativistic addition of velocities and so the speed at which they travel with respect to the arms is not equal. And event though one impulse starts before the other, they still both reach the brain at the same time and the person still "feels" the needle pokes at the same time. The reflex impulse leaves the brain at the same moment, but because of the same effect of velocity addition, arrive at each hand at different times causing them to flinch at different times.

 

[name123]

I am going to stop responding after this post, as the forum has helped out on the things I was confused about and the conversation would seem to be getting a bit philosophical now and so off topic. I would be happy to discuss it on another thread in another forum if anyone wanted to continue, but do not want to annoy people on this forum.

It most certainly does not reflect simultaneity of neural events, because it would violate the laws of physics for simultaneity to cause anything. Whatever causes any observable (including experience) must be entirely within some past light cone, not on any surface of simultaneity. This is known as causality.

I was assuming that most physicalists would think that what caused that surface of simultaneity, also caused the experience. That corresponding to the experience was some physical state that had been caused. That the experience was a property of that physical state, and that like other properties of that physical state, they are simultaneous to it.

I am not clear on what you are suggesting here. You seem to be suggesting that the experience will not be a property of some physical event but be something non-physical that is acted upon by physical events and that this acting upon takes time, such that the experience cannot be simultaneous to the physical events that acted upon it. Interesting, but I am not sure any physicalist would go for it, as what would be this entity in the ontology that is acted upon.

Also even with events in the past light cone, there can be a difference in opinion over whether they were simultaneous or not.

It isn’t a slippery slope, it is hard data. For example, if there is a coherent visual and auditory stimulus (e.g. a movie), and if the auditory stimulus is delayed anywhere from 0 to about 100 ms, then the experience is the same. The experience is that there is no discrepancy. So it is a clear experimental fact that different neural states lead to the same experience. Any theory of experience that can not accommodate that is already falsified.

There is a difference between the experience being the same, and not being able to distinguish between the experience. For example consider the experiment you just quoted. The subjects might not be able to distinguish between which of two identical visual presentations had a time delayed audio. But that does not mean the experience is the same. If you were to play the audios together, and one was time delayed by a 100ms then you could clearly hear the difference. So in retrospect you could tell that the experience wasn't actually the same even though you couldn't distinguish which had time delayed audio. And that was my point. Sometimes though you might not even be able to tell the difference between two experiences when they are presented at the same time. Consider an RGB colour on your computer. You could compare two which are only 1 value apart, and you might not be able to distinguish them. That does not mean they are all the same though (though possibly on some the brain would encode them in the same way). You might keep increasing the colour values by 1 and then go back and compare to the original and find that there is quite a difference even though you did not notice it when slowing increasing the value. But like with the auditory, it doesn't mean that they are the same just because you do not notice the difference. Otherwise as I pointed out if you said that e₁ = e₂ and e₂ = e₃ and so on, then you would be saying e₁ = e_n regardless of the value of n, but with the RGB values it is easy to tell that that claim is wrong, and that for some at least there must have been a difference.

One key physical constraint is that spacelike separated events cannot be causally related, so the experience cannot be a function of simultaneous neural states. Of course, given how slowly the experience changes and how small the brain is, this really is a non-issue and you can simply think of the brain as a point object wrt relativity and experience. However, even though it is a non-issue (as I have repeatedly shown) you continue to push it.

Well presumably this is up for debate given "spooky" action at a distance. But ignoring the "spooky" action, and quantum mechanics, presumably all simultaneous finite points are considered to have spacelike separation. And each simultaneous point will have its own past light cone. I don't know whether you are expecting the answer regarding experience to depend on which point was chosen, or whether it would rely on some overlap of past light cones. But then I am not sure what you are thinking what the contents of those past light cones are having an influence on to give rise to experience. As I mentioned it doesn't seem as though you are envisaging it to be something physical.

The point is that whether in a past light cone or not, presumably the relative timing of the relevant events will have an influence on the experience, and while you may not consider the influence to be significant (as the difference in timing could be very small), it does seem to me that there would be a difference, however small. Unless perhaps you were considering the influence to be the influence at some particular point. I was not considering whether it would make any pragmatic difference, only that however small the difference in accounts were by observers, whether there can be multiple true answers to the way it was for you (however close they were), or whether there is only one true answer for how it was.

Anyway, if you want to continue, perhaps let me know and start up a thread in a different forum. If not, then thanks for the help and the time you have taken, I appreciate it, and thanks to the others on the forum that have also helped.

 

[PeterDonis]

I was assuming that most physicalists would think that what caused that surface of simultaneity, also caused the experience.

No, physicalists would say that a surface of simultaneity is not a physical thing to begin with; it's an arbitrary abstraction like a coordinate system. That is the fundamental point that you keep missing in this discussion.

even with events in the past light cone, there can be a difference in opinion over whether they were simultaneous or not.

Yes. So what? Simultaneity is not a physical thing anyway, and can't cause anything or be the effect of anything. It's just an arbitrary human convention.

presumably this is up for debate given "spooky" action at a distance.

No, it isn't. Quantum phenomena still obey relativistic causality.

presumably the relative timing of the relevant events will have an influence on the experience

If by "relative timing" you mean the order in which causal influences from different places arrive at some particular place, yes, of course this will have an influence on experience. But this has nothing to do with simultaneity. The order in which signals arrive from elsewhere at a particular location is a relativistic invariant; it doesn't depend on your choice of coordinates or simultaneity convention.

 

[Ebeb]

No, physicalists would say that a surface of simultaneity is not a physical thing to begin with; it's an arbitrary abstraction like a coordinate system.

The set of simultaneous events I consider occurring 'now' is the 3D world I consider existing 'now'.
If a set of simultaneous events does not represent anything physical, then which 3D world do physicists consider physical?

 

[Dale]

If a set of simultaneous events does not represent anything physical, then which 3D world do physicists consider physical?

No 3D world is physical. The physical world if 4D. Didn’t we have a really really long conversation about this already?

 

[Ibix]

The set of simultaneous events I consider occurring 'now' is the 3D world I consider existing 'now'.
If a set of simultaneous events does not represent anything physical, then which 3D world do physicists consider physical?

The usual model is to treat spacetime as a 4d whole. You can select any 3d plane passing through your worldline "now" and call that "the universe now", but there's no significance to any particular choice. All are arbitrary 3d subsets of the 4d whole.

We're not saying that the 3d subsets don't exist. Just that there are infinitely many ways to pick a subset and no good reason to prefer one choice over another.

 

[PeterDonis]

If a set of simultaneous events does not represent anything physical, then which 3D world do physicists consider physical?

None. As @Dale and @Ibix have said, the usual model is to consider 4D spacetime as "real". An alternative is to consider the events in your past light cone as "real". The latter is the most parsimonious view IMO, since the actual evidence we have is all information in our past light cone.

 

[Dale]

I was assuming that most physicalists would think that what caused that surface of simultaneity, also caused the experience.

A surface of simultaneity isn’t something that is caused, it is merely arbitrary defined. It has no physical significance, neither as a cause nor as an effect.

That corresponding to the experience was some physical state that had been caused. That the experience was a property of that physical state, and that like other properties of that physical state, they are simultaneous to it.

All good until that last phrase.

You seem to be suggesting that the experience will not be a property of some physical event but be something non-physical

I did not suggest any such thing.

The subjects might not be able to distinguish between which of two identical visual presentations had a time delayed audio. But that does not mean the experience is the same.

I disagree. If two stimuli are subjectively indistinguishable then the experience is the same. The experience is not the stimulus, it is the subjective conscious experience that results from the stimulus. So if you cannot consciously distinguish two stimuli then the experience is the same.

Consider an RGB colour on your computer. You could compare two which are only 1 value apart, and you might not be able to distinguish them. That does not mean they are all the same though

Yes, they are not the same, but the conscious subjective experience is the same. You seem to be confounding the stimulus with the experience.

Otherwise as I pointed out if you said that e1 = e2 and e2 = e3 and so on, then you would be saying e1 = en regardless of the value of n,

No. When there is a threshold then at some point a small change makes a subjective difference. So (using what I am guessing your notation means) if e1=e2 that does not imply that e101=e102 even if all of the increments are equally small.

For example, if the numbers represent ms of delay and if the threshold for a given person is exactly 100 ms then subjective experience e0=e95 but e95$\ne$e105, even though the objective stimuli are closer. This is what a threshold response means. Small differences in input near the threshold lead to large differences in the outcome. There is no slippery slope involved, such mathematical functions are perfectly legitimate, although they can be numerically difficult.

Well presumably this is up for debate given "spooky" action at a distance.

No, it isn’t a matter of debate at this point. QFT is fully relativistic and respects causality as described above. In QFT this is enforced by the commutation relationship of spacelike separated events.

The point is that whether in a past light cone or not, presumably the relative timing of the relevant events will have an influence on the experience,

Certainly, but the distinction between the past light cone and the surface of simultaneity is important. If an experience is caused by a surface of simultaneity then it violates all known laws of physics. If experience follows the known laws of physics then it must be caused by the past light cone and, since all reference frames agree on the past light cone then all reference frames would agree on what was experienced (given a perfect theory of experience). The “truth of your experience” would therefore be frame invariant. Which was your question that started rhis whole tangent.

 

[name123]

One key physical constraint is that spacelike separated events cannot be causally related,...

Well presumably this is up for debate given "spooky" action at a distance

No, it isn't. Quantum phenomena still obey relativistic causality.

I wasn't going to respond to the philosophical stuff, but since this is directly to do with physics I will.

Are there not experiments where entangled particles are separated and they then subsequently have certain properties tested such as their spin for example, and that even if they are tested within a time frame which wouldn't allow for any causal effect from the testing of one even if traveling at the speed of light to have influenced the testing of the other, the spins for example are always opposite?

Does Bell's Inequality theorem not indicate that there could be no local hidden variables responsible?

Obviously the issue isn't whether the experiment proves there is spooky action at a distance (there is Everett's theory for example), just whether a case can be put forward for there being such spooky action.

 

[A.T.]

...the issue isn't whether the experiment proves there is spooky action at a distance...

If it doesn't then why conflate the two?

 

[name123]

If it doesn't then why conflate the two?

I did not think I had. I thought I was making a distinction between something being debatable, because there are differing opinions on the matter, and something being proven. Perhaps you can point out where you think I did.

 

[A.T.]

I thought I was making a distinction between something being debatable

But the statement you quoted is not debatable:

Quantum phenomena still obey relativistic causality.

 

[name123]

But the statement you quoted is not debatable:

Quantum phenomena still obey relativistic causality.

You quoted the wrong statement, the statement was:

One key physical constraint is that spacelike separated events cannot be causally related,

I pointed out some issues in post #130 which I thought indicated it was debatable.

 

[A.T.]

I pointed out some issues in post #130 which I thought indicated it was debatable.

How do those issues indicate that?

 

[weirdoguy]

I pointed out some issues in post #130 which I thought indicated it was debatable.

Do you know what 'spacelike separated' means?

 

[name123]

How do those issues indicate that?

Well I think those experimental results have been interpreted as being the measurement of one particle causally influencing the measurement of another particle even though the events were spacelike separated, and so have been interpreted as contradicting the statement "spacelike separated events cannot be causally related".

 

[name123]

Do you know what 'spacelike separated' means?

Roughly that the distance between the events was greater than light could travel in the time. Though I looked it up and I also saw the definition "Spacelike separation means that there exists a reference frame where the two events occur simultaneously, but in different places." Both seem to me compatible with what I was writing, so I am not sure why you asked.

 

[Herman Trivilino]

Well I think those experimental results have been interpreted as being the measurement of one particle causally influencing the measurement of another particle even though the events were spacelike separated, and so have been interpreted as contradicting the statement "spacelike separated events cannot be causally related".

No. Let one event be the detection of the spin of one member of an entangled two-particle system. Let the other event be the detection of the spin of the other member. Moreover, suppose those two events have a spacelike separation. If you are present at the first event it is true that as soon as you know the outcome of the first event you also know the outcome of the second, but you cannot send knowledge of that outcome and have it arrive at the location of the second event before that second event occurs.

 

[name123]

No. Let one event be the detection of the spin of one member of an entangled two-particle system. Let the other event be the detection of the spin of the other member. Moreover, suppose those two events have a spacelike separation. If you are present at the first event it is true that as soon as you know the outcome of the first event you also know the outcome of the second, but you cannot send knowledge of that outcome and have it arrive at the location of the second event before that second event occurs.

So what if you can't "send knowledge of that outcome and have it arrive at the location of the second event before that second event occurs"? The issue was whether the two events can be interpreted as being causally related.

 

[PeterDonis]

Are there not experiments where entangled particles are separated and they then subsequently have certain properties tested such as their spin for example, and that even if they are tested within a time frame which wouldn't allow for any causal effect from the testing of one even if traveling at the speed of light to have influenced the testing of the other, the spins for example are always opposite?

Does Bell's Inequality theorem not indicate that there could be no local hidden variables responsible?

Yes, there have been experiments verifying that quantum phenomena violate the Bell inequalities. No, that doesn't mean relativistic causality is violated. As I've already said.

 

[Ebeb]

The usual model is to treat spacetime as a 4d whole. You can select any 3d plane passing through your worldline "now" and call that "the universe now", but there's no significance to any particular choice. All are arbitrary 3d subsets of the 4d whole.

Looks fine to me.

We're not saying that the 3d subsets don't exist. Just that there are infinitely many ways to pick a subset and no good reason to prefer one choice over another.

Great.

No 3D world is physical. The physical world if 4D.

No 3D world is physical?
If the physical world is 4D, then 3D as a part of 4D has to be physical too.

Didn’t we have a really really long conversation about this already?

Yes, and I gave up because we couldn't get on the same wavelength.
Maybe we disagree on the meaning of physical.
As far as I understand Ibix, the events as such are indeed physical entities. If we consider an event 'car hits tree' then there is definitely car and a tree at a spacelike distance. There are physical object(s) at spacelike distance, hence the 3D world of simultameous events is physical.
And because there is no preference for a simultaneous collection, all 3D are physical. Which makes 4D physical too.

None. As @Dale and @Ibix have said, the usual model is to consider 4D spacetime as "real".

None? If the usual model is to consider 4D spacetime as "real", then the 3D collection of events is real too, see above, i.o.w. your -quote-" None" -unquote- cannot be correct.

I think Name123 too is a bit lost with above discrepancies. That's why he struggles with 'post topic Relative truth'.

 

[PeterDonis]

The issue was whether the two events can be interpreted as being causally related.

No, the issue is whether relativistic causality is violated. It isn't.

Asking whether two spacelike separated measurement events themselves are "causally related" is a different question. The strict answer to it if we take the viewpoint of relativistic causality is that the question has no meaning, because relativistic causality does not tell you which events can be "causally related". It just tells you that spacelike separated events have to commute--i.e., what happens at them does not depend on their ordering. The fact that the events commute does not prevent what happens at them from being correlated.

 

[PeterDonis]

If the usual model is to consider 4D spacetime as "real", then the 3D collection of events is real too

No, if the model considers all of 4D spacetime as real, then you cannot pick out any particular 3D collection of events as "real" while the others aren't. But you were implicitly saying that just one 3D collection of events was "real" and the others weren't.

If you're willing to say that "all 3D worlds are real", including 3D worlds that only contain events billions of years in our past here and now, and also 3D worlds that only contain events billions of years in our future here and now, then yes, you can say that. But then you can't draw the conclusions you are trying to draw from "3D worlds are real".

 

[Ebeb]

No, if the model considers all of 4D spacetime as real, then you cannot pick out any particular 3D collection of events as "real" while the others aren't. But you were implicitly saying that just one 3D collection of events was "real" and the others weren't.

I never said that. How can you pretend this after reading what I said about Ibix post? see #142

If you're willing to say that "all 3D worlds are real", including 3D worlds that only contain events billions of years in our past here and now, and also 3D worlds that only contain events billions of years in our future here and now, then yes, you can say that. But then you can't draw the conclusions you are trying to draw from "3D worlds are real".

No. You didn't understand me. I'm talking of 3D worlds or 3D universe 'now' as 3D sections made of simultaeous events.
What's you point of view on Ibix post #127 ?

 

[name123]

Yes, there have been experiments verifying that quantum phenomena violate the Bell inequalities. No, that doesn't mean relativistic causality is violated. As I've already said.

I never said it did mean relativistic causality is violated.

Dale had written:

One key physical constraint is that spacelike separated events cannot be causally related,

I had replied:

Well presumably this is up for debate given "spooky" action at a distance.

And then you wrote:

No, it isn't. Quantum phenomena still obey relativistic causality.

Though presumably you knew that quantum phenomena being interpreted as indicating that spacelike separated events can be causally related didn't imply that they were being interpreted as not obeying relativistic causality. So I found it slightly strange that you made such a switch on what I thought was supposed to be an educational site.

You seem to understand that many do interpret the experiments as indicating that spacelike separated events can be causally related and thus a claim that they cannot be is debatable. As I mentioned.

 

[name123]

No, the issue is whether relativistic causality is violated. It isn't.

No that was not the issue. That was what you tried to change the issue to as explained above in post #146

 

[PeterDonis]

I'm talking of 3D worlds or 3D universe 'now' as 3D sections made of simultaeous events.

Yes, but why pick out "now"? And why pick out your particular "now" (the events simultaneous to "here and now" in your rest frame), as opposed to someone else's "now" (the events simultaneous to "here and now" in someone else's frame)? Unless you want to give "now" some special status, there is no point to even mentioning it. And if all of 4D spacetime is real, then "now" has no special status.

What's you point of view on Ibix post #127 ?

See my post #128.

 

[PeterDonis]

I never said it did mean relativistic causality is violated.

Good. Then what have we spent the last hundred or so posts discussing?

You seem to understand that many do interpret the experiments as indicating that spacelike separated events can be causally related

I understand no such thing. I already explained what I understand in post #143.

 

[PeterDonis]

And if all of 4D spacetime is real, then "now" has no special status.

And similarly, if you take the alternative viewpoint I described in post #128 (that what is in your past light cone is what is "real"), then again "now" has no special status, so again there's no reason to even mention it.