Does instantaneous communication implies a preferrred Lorentz frame?

  • #126
atyy
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We feel that way because we feel that it's possible to change the future and impossible to change the past. Why do we feel this way? Because we have memories of the past and none of the future. Why is that? Because storing a memory is a process that increases entropy, and entropy is increasing towards the future. Why is entropy increasing? Because the universe started out in a low entropy state. Why did it do that? No one knows.
I thought it was erasing a memory that increases entropy?

I've naively been thinking that we can remember some of the future, in the sense that we can predict it. And the only reason we remember more of the past is that entropy is increasing, due to the initial conditions of the universe.
 
  • #127
atyy
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Dmitry67 and PTM19, it is not the question whether life itself is consistent with the second law. As you say, it is consistent.
The question is whether the EVOLUTION of life (in the Darwinian sense) is consistent with the second law. How evolution helps to increase the total entropy of the ecological system?
Evolution produces human beings who think up lots of nonsense, such as MWI, thus increasing entropy :tongue2:
 
  • #128
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I've naively been thinking that we can remember some of the future, in the sense that we can predict it. And the only reason we remember more of the past is that entropy is increasing, due to the initial conditions of the universe.
I agree. :approve:
 
  • #129
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So if you don't have a single model of how the universe works, why bother pretending that you had one?
Way to strawman the argument! I never pretended to have a SINGLE model for how the Universe works. Instead, I simply told you how I believe it works and how it does not "fry & sizzle" one's brain.

If i joined your 2 statements that you made in 2 separate posts, would they make sense and not be contradictory:
(Me) "As far as your question is concerned (i.e. where the Universe came from) it came from a singularity at the beginning of time: an initial uncaused state from whence the Big Bang emerged. No sizzle & fry here, I assure you! :eek:)."

(Me) "Not only does physics have A model for the Universe, it has MANY. Among these is the Big Bang (which has different "interpretations" within it as well), the many worlds interpretation, etc."

The fact that there are many models as to how the Universe works is not in itself a contradiction. These models need not be mutually exclusive and even if they were, one could simply pick one and be done with it.

The issue is a matter of philosophy only as much as we do not know how the universe works. That you believe a certain model is true in no way says that all the other models are wrong. It just means T-Boone believes a certain model of the Universe is correct.
Well, if it were just philosophy, then it might be just an opinion but it's not; it's actually much more than just an opinion. It's actually theoretical physics which isn't just philosophy and just an opinion. As I explained, the Big Bang model has more empirical evidence and less speculation than the rest.

Anyway, it is the task of physics to find the correct model(if there is one at all), not philosophy and it is work in progress. I referred you to realism in modern physics only to highlight that realism(objects having definite properties at all times) cannot be recovered, not to discuss philosophy.
Agreed: it is the task of physics to find the correct model and it is a work in progress. I'd like to add, that in all likelihood it will really never be 100% finished. If you think about it, considering that we've practically just come down from trees, I think we've done pretty good so far! But, as I'm sure you'd agree, there is much room for improvement & much more to be learned.

In post 118, you proclaimed this(and it strongly implies that "the Big Bang as the TRUE & ONLY model"):
(me)"As far as your question is concerned (i.e. where the Universe came from) it came from a singularity at the beginning of time: an initial uncaused state from whence the Big Bang emerged. No sizzle & fry here, I assure you! :eek:)"
That is one of the best examples of a non-sequitur I've seen in a while! No where in my quote do I state that it is the ONLY model. The only thing you can really say is that I am implying that it's true. Well, I'll say it explicitly: it's true! You can choose not to believe it; there are other alternatives, as I said previously. However, you are already keenly aware of this and I suspect that you only side with whatever model (i.e. supporting science) suits your point at the time; but I'll give you the benefit of the doubt.

If you're measuring photons polarization at 45 deg, those photons exit the polarizer in a superposition of H/V states.
Sure, although I was thinking more along the lines of electron spin but, whatever.

Before the measurement, a photon polarized at say 45 deg. to the horizontal is neither horizontally nor vertically polarized. It's in the act of measurement that determines the measured value(H/V).
I see that you have accepted the Copenhagen interpretation here...

The balls in your example(being macroscopic objects) always have the same defined properties and obviously cannot be in 2 states at the same time(one ball will always be red and the other blue). In your balls example you were attempting to ascribe a rather common-sense macroscopic view on a phenomenon that is anything but intuitive and common-sensical.
Saying "there exists a strong correlation" does nothing to explain the phenomena, it is merely a label/designation to show that you are able to attach labels/designations to unexplained events.
I wonder if you would have told Schrodinger that his cat was macroscopic and not microscopic? Anyways, the analogy still stands as you do not know what the color is. That being the case, the color of the balls are in a superposition of red/blue and once opened, it collapses to one of the colors. However, this is getting off topic; I was just showing another interpretation of what could be going on with entangled pairs.

As an aside, the "strong correlation" term was originally posted by you in post #123. Regardless, entanglement cannot be used for FTL signaling.

(T-Boone: I disagree. There is no instantaneous communication occurring with entangled particles; at least not any FTL communication, which is what I think is being referred to here.)
...is very premature at best, and completely wrong at worst. Your certainty is naive and unwarranted. The fact that you cannot send information through entangled pairs, does not in any way signify there is no causal, nonlocal influence. In fact, the violation of Bell's inequalities demands that either locality or realism must be wrong(or both).
I maintain that there is no FTL communication occurring here as is explained in EVERY experiment: information nor matter never exceeds c. Furthermore, the experiments end after the first set of measurements because after that, their properties are no longer related.

Absence of free-will is the same as "reality is an illusion". In an anti-realist setting, all paradoxes disappear. Responding to your question.
I have no idea how that responds to my question. If reality is an illusion, then what is left to be talked about in any meaningful way? How is that an approach to describing how the Universe works?
 
  • #130
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I see what you are saying about the BB. You worded it too strong in your first reply and i presumed you were too hung up on the notion of scientific models always being correct. Honestly, that's how it sounded.



T-Boone said:
I maintain that there is no FTL communication occurring here as is explained in EVERY experiment: information nor matter never exceeds c.

Your statement assumes realism is true and realism is just a hypothesis. A hypothesis that is exceedingly hard to maintain.


I have no idea how that responds to my question. If reality is an illusion, then what is left to be talked about in any meaningful way? How is that an approach to describing how the Universe works?

It'd be naive to assume reality has feelings and cares if T-Boone or someone else is able to make sense of it or not. I never claimed humans could understand all of reality, if that is what you believe, you can be certain that it's an utopia.
 
  • #131
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I see what you are saying about the BB. You worded it too strong in your first reply and i presumed you were too hung up on the notion of scientific models always being correct. Honestly, that's how it sounded.
Fair enough. I am kind of partial to BB theory...and don't like the MWI; maybe that's why I sounded so harsh!

Your statement assumes realism is true and realism is just a hypothesis. A hypothesis that is exceedingly hard to maintain.
I am guessing that you are referring to:
"...scientific realism is the thesis that the unobservable things talked about by science are little different (in terms of ontological status) from ordinary observable things (such as tables and chairs)."-wiki
I guess, in the face of adversity (i.e. entanglement, etc.) it can be tough, but I am not alone. At least that is comforting thought, so I manage.

It'd be naive to assume reality has feelings and cares if T-Boone or someone else is able to make sense of it or not. I never claimed humans could understand all of reality, if that is what you believe, you can be certain that it's an utopia.
Well, like I said before (post# 129): "that in all likelihood it will really never be 100% finished." Meaning that I think we will never understand 100% of reality.

That being said, I am curious to know about this concept of "reality is an illusion." I don't understand how that can lead to anything profound for if all is an illusion, then what is left?

I presume you might answer "real reality" (as you mentioned in a previous post) but unfortunately one would have to conclude that that too is an illusion, for the same reasons. This is why I think that it leads nowhere.
 
  • #132
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Demystifier said:
Nonlocal entanglement of quantum mechanics suggests the existence of instantaneous communication between distant particles.
Instantaneous communication is a contradiction in terms.

Wrt to just ftl (not instantaneous) propagations, they're not suggested or implied by quantum entanglement -- but rather are considered in connection with quantum entanglement and EPR-Bell tests because they're a cheap solution to the still open problem of the physical mechanism(s) underlying the correlations produced in those sorts of experiments.

Demystifier said:
What I push forward is the idea that it is causality (i.e., the principle that events can be ordered into "causes" and "consequences") that should be abandoned.
Wrt any set of spatial configurations of some frame of reference, there's an evolution (a preferred direction) in the order away from lower-numbered configurations. This preferred evolutionary direction is called the arrow of time, and its archetypal (idealized) form is that of an expanding 3D spherical wave shell.

The terms cause and effect are just relative placeholders in any time-indexed set of spatial configurations -- ie., by definition, causes happen before effects.

So, instead of pushing to abandon the idea of a preferred temporal order, why not take the radiative arrow of time as fundamental vis the adoption of its archetypal form as the fundamental wave dynamic?

Anyway, this seems to me to be conceptually preferable to taking calculational conveniences as literally corresponding to the real world.
 
  • #133
Fredrik
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RUTA sent me a question about the thought experiment I posted in #17 (and had to keep clarifying until #64), and I decided to clean it up a little and post a new version here. This is (my version of) the standard argument for why it can't be possible to send instantaneous messages in a special relativistic universe.

Imagine a computer that's doing inertial motion. We will call it "Alice". I want you to draw a spacetime diagram that represents the coordinates that the inertial coordinate system associated with Alice's motion assigns to the events I'm about to describe. Draw the 0 axis (time) in the "up" direction. Draw the 1 axis (position) to the right. Alice's world line coincides with the 0 axis.

I will write the coordinates (assigned by Alice's coordinate system) of an event as (t,x), not [strike](x,t)[/strike]. When I talk about the "slope" of a line, I mean dt/dx. This means that a horizontal line has slope 0 and a vertical line has slope ∞. The world line of an object moving with velocity v has slope dt/dx=1/(dx/dt)=1/v. The simultaneity lines of the inertial coordinate system associated with the motion of such an object would be drawn with slope v in this diagram. (This follows from the same synchronization argument that's used to associate an inertial coordinate system with an inertial observer. See any book on SR for an explanation of simultaneity and clock synchronization using light signals).

Now I want you to draw a straight line through the events (-4.5,0) and (8,10). Suppose that this line represents the motion of a second computer. Let's call it "Bob". The slope of this line is (8-(-4.5))/(10-0)=12.5/10=1.25, so Bob's velocity is 1/1.25=0.8. Draw another straight line, through the events (0,0) and (8,10). This line has slope 0.8=v, so it's the set of events that Bob considers simultaneous with (8,10).

Now suppose that both computers are hooked up to tachyon transmitters that can send and receive 1-bit messages, i.e. either "0" or "1". We assume that a tachyon emitted by one of these transmitters will move at infinite speed in the rest frame of the transmitter that emitted them. (It isn't necessary to assume that the speed is infinite, but it makes the diagram a bit easier to draw). Suppose also that Alice is running a program with the following instructions:

IF the message received at t=0 is "1" THEN send the reply "0" at t=8
IF the message received at t=0 is "0" OR if no message is received THEN send the reply "1" at t=8​

And suppose that Bob is running a program with these instructions:

IF the message received is "0" THEN immediately send the reply "0"
IF the message received is "1" THEN immediately send the reply "1"​

This leads to the following paradox:

If Alice receives 1 at (0,0), she replies by sending 0 at (8,0). When Bob receives that message at (8,10), he replies by sending 0 at (8,10), so Alice receives 0 at (0,0). If Alice receives 0 at (0,0), she replies by sending 1 at (8,0). When Bob receives that message at (8,10), he replies by sending 1 at (8,10), so Alice receives 1 at (0,0). So if Alice receives a message at (0,0), no matter what that message is, we get a contradiction. If she doesn't recieve a message at (0,0), she sends 1 at (8,0). Bob receives that message at (8,10), and replies with 1 at (8,10). So Alice receives 1 at (0,0), and we still have a contradiction. :bugeye:

There are of course a few implicit assumptions in this scenario, and the contradiction we found implies that (at least) one of them must be false. These are some of the possibilities:

  • Tachyons do not exist.
  • Tachyons exist, but reliable tachyon transmitters do not. So they will sometimes send the wrong message or misinterpret the message they received. (I'm not sure if that's sufficient to avoid the paradox).
  • Tachyons and reliable transmitters both exist, but the time it takes to detect a tachyon is greater than vL, where v is the speed of the detector in the emitter's rest frame and L is the distance it has traveled since it was emitted. (This is for infinite speed tachyons. The formula would have to be modified for slower ones. We should also be talking about the time it takes to emit the tachyon, but I'm not attempting to give the complete answer here. I'm just trying to explain the basic idea).
(I'm sure there are other possibilities, but these are the ones I know).

Edit: I'm adding a quote from one of my posts that links to this one.

Since this leads to nonsense results, the most natural conclusion is that there are no particles that move faster than light.

There are a few other possibilities, for example: 1. The time it takes to emit and/or detect an FTL particle grows at least linearly with the distance it travels. (This would prevent the recipient of the first message to send a reply that reaches the sender of the original message before he sent it). 2. The equations of motion of the matter in the universe doesn't have any solutions that describe someone who both chooses to carry out an experiment like the one I described in the post I linked to, and succeeds. (Yes, this one is even weirder than the first one).
 
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  • #134
dx
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  • #135
Fredrik
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Yeah, but my tachyons are faster. :tongue:

Thanks for posting. The difference between that diagram and mine is that (if we rotate the whole page clockwise so that we can read the text easier) the "tachyon outbound" line would be horizontal, and the "tachyon inbound" would be parallel to the t'=0 line. (Again, I only chose infinite speed to make the diagram slightly simpler. This diagram clearly shows that we get the same paradox even with finite speed tachyons).
 
  • #136
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I read a paper from an author named Riff from UFRJ, Brazil where he shows that in one reference frame you will in a certain situation observe instantaneous communication experiment. In other reference frame the same physical situation will exemplify a delayed choice experiment, In a third reference frame, the same experiment will be captured as an example of Bell experiment.

I think this has to do with your OP.

Best Regards,

DaTario

P.S. sorry for not having here the exact reference, but you may look for Mr. Ryff in UFRJ web site and search for his e-mail address.
 
  • #137
Demystifier
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There are of course a few implicit assumptions in this scenario, and the contradiction we found implies that (at least) one of them must be false. These are some of the possibilities:

  • Tachyons do not exist.
  • Tachyons exist, but reliable tachyon transmitters do not. So they will sometimes send the wrong message or misinterpret the message they received. (I'm not sure if that's sufficient to avoid the paradox).
  • Tachyons and reliable transmitters both exist, but the time it takes to detect a tachyon is greater than vL, where v is the speed of the detector in the emitter's rest frame and L is the distance it has traveled since it was emitted. (This is for infinite speed tachyons. The formula would have to be modified for slower ones. We should also be talking about the time it takes to emit the tachyon, but I'm not attempting to give the complete answer here. I'm just trying to explain the basic idea).
(I'm sure there are other possibilities, but these are the ones I know).
My favored one:
  • If tachyons exist, then one cannot built a machine which would lead to inconsistencies you described. That's because such a machine is not a global solution of the equations of motion describing the behavior of matter interacting with tachyons. (Of course, a similar machine with the difference that it does not interact with tachyons can be built.)
 
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  • #138
Fredrik
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And suppose that Bob is running a program with these instructions:

IF the message received is "0" THEN immediately send the reply "0"
IF the message received is "1" THEN immediately send the reply "0"​
Typo. (Thanks to RUTA for finding it). This one was supposed to be

IF the message received is "0" THEN immediately send the reply "0"
IF the message received is "1" THEN immediately send the reply "1"​
 
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