Why time is not an observable in quantum theory?

[DevilsAvocado]

As to "what exists before" - this question belongs, in my opinion, to the Philosophy section, not to Quantum Physics. But, roughly, I think John Archibald Wheeler may have been right when he speculated that Nature somehow "observes (or 'measures') itself all the time" - this is http://en.wikipedia.org/wiki/Ouroboros" .

Hehe funny!

Maybe you misunderstood me. It’s not "what" existed before (BB), it’s "merely" a question if the wavefunction should be considered real or not (before measurement), and this leads to next "tricky" question: If YES, then Locality in EPRB gets a blow. If NO, then Reality (naturally) gets a 'universal' blow. (And in both cases, Einstein will be 'slightly upset'... )

... maybe this painting by M. C. Escher could symbolize the "creation operators" ...?

 

[yoda jedi]

if the wavefunction should be considered real or not (before measurement),

if not, then, we create things very precisely and ever the "the same" type of entities ! ...lol...


we ......creating ontological entities




.

 

[Maui]

Thanks for your answer. This is interesting. My "special interest" is EPRB and I’ve seen you & Demystifier touched the subject.

My question: In what 'camp' are you, Locality or Realism? (i.e. nonlocality/nonseparability)



I might have missed it, but I think you didn’t answer Demystifier’s question, and I also think it’s interesting:

Did you see post 56 in this thread:

https://www.physicsforums.com/showthread.php?t=450649&page=4

 

[Careful]

Thanks for your answer. This is interesting. My "special interest" is EPRB and I’ve seen you & Demystifier touched the subject.

My question: In what 'camp' are you, Locality or Realism? (i.e. nonlocality/nonseparability)



I might have missed it, but I think you didn’t answer Demystifier’s question, and I also think it’s interesting:

I really cannot give any details about my thoughts here so some of my comments will sound weird inevitably (but I might also just give you a dishonest straightforward answer without giving the impression that I am lying - but that would not be fair either). So the rule of the game is that you don't ask me for further motivation, ok? Observations allow for some part of physics to be non-local and another part should definitely be local (so I am in a split position here) - I am talking about the dynamics here, not the collapse postulate or so. Concerning realism, strict positivism a la Hawking is rather silly, so some hidden layer of reality might exist (hidden variables) but as I explained before, the creation operators in QFT are also very real for me. Concerning observation, that part is definitely non-local and non-physical too! It's a second layer of reality which one might call awareness: it really is inevitable.

 

[arkajad]

Hehe funny!

Maybe you misunderstood me. It’s not "what" existed before (BB), it’s "merely" a question if the wavefunction should be considered real or not (before measurement), and this leads to next "tricky" question: If YES, then Locality in EPRB gets a blow.

How anything that lives in an infinite dimensional Hilbert space may have the same kind of reality as a chair or a table that you can knock against your head off in our 3d space?

Of course wave functions are "real" - we calculate using them. They are as real as calculated trajectories of planets. But they are real in their own world. What they "mean" - that's a different and, I think, a relevant question.

 

[Careful]

How anything that lives in an infinite dimensional Hilbert space may have the same kind of reality as a chair or a table that you can knock against your head off in our 3d space?

Of course wave functions are "real" - we calculate using them. They are as real as calculated trajectories of planets. But they are real in their own world. What they "mean" - that's a different and, I think, a relevant question.

I don't know if you are aware of this but Sven and Diederik Aerts from the free university of Brussels have written a nice paper about this: you can find it in the book Quo Vadis Quantum mechanics.

 

[arkajad]

Do you mean this:
"Towards a General Operational and Realistic Framework for Quantum Mechanics and Relativity Theory, Diederik Aerts, Sven Aerts"?

 

[Fra]

Here comes my personal view.

Does anything in QM exist before measurement, "creation", or tracks in a bubble chamber, etc?

I know you didn't ask me, but fwiw my opinion is that this is an irrational question.

I don't mean that with pun, I mean it in the sincere sense that it's a question whose answer our behaviour is invariant with respect to. We don't need to raise it nor to answer it to make progress. It's only the expectations that count.

Again, this is not just a superficial statement about human behaviour. When taken seriously the implication is also that the action of any subsystem, is a function only of the systems expectation and local information about it's environment, not some ontological "reality". Therefore it seems that system A is deeply and physically indifferent to what state system B REALLY is in (whatever that means) in between interactions. A basically acts on it's own expectations, and has to adapt to any feedback.

As I see it, this is an abstracted precursor to the principle of locality - where the distance in locality refers to some distance metric in abstract information space, rather than ordinary space.

So I think the best answer to that question is rejection; next question please. The one thing though that I think IS interesting to discuss, is why this is so. And in what sense there are good and bad questions, and some questions are worth answering, some are not.

Without defining the terms; the same reasoning suggests that time isn't a regular observable because it's not a rational question to just ask for time; since time is IMHO merely a parameterization of a sequential flow, or and expected flow. I see this flow in an entropic sense and then to just ask for pure time, is to ask for the "probability of a particular probability" in some absolute sense. I think this absolute sense doesn't exist, and there are only conditional probabilities in this flow. Time is like an ordering parameter, not a primary information. Without relational flows, there would be no time. This is why I think it makes no sense to say have expectations of time. Bcause somehow time is always "now", no matter when you check you always find yourself at the present moment - and it doesn't seem to be a conicidence ;)

Beyond that, "clock readings" is to me something different from this proper intrinsic flow of time that is tied to each observer.

/Fredrik

 

[Careful]

Do you mean this:
"Towards a General Operational and Realistic Framework for Quantum Mechanics and Relativity Theory, Diederik Aerts, Sven Aerts"?

Yes I do. I don't agree with everything they say but the paper contains a few useful ideas.

 

[DevilsAvocado]

...creating ontological entities

gotcha

 

[DevilsAvocado]

Did you see post 56 in this thread:

https://www.physicsforums.com/showthread.php?t=450649&page=4

Now I have. And I see "unusual" quarrel... rendering in locked...

 

[DevilsAvocado]

I really cannot give any details about my thoughts here so some of my comments will sound weird inevitably (but I might also just give you a dishonest straightforward answer without giving the impression that I am lying - but that would not be fair either). So the rule of the game is that you don't ask me for further motivation, ok? Observations allow for some part of physics to be non-local and another part should definitely be local (so I am in a split position here) - I am talking about the dynamics here, not the collapse postulate or so. Concerning realism, strict positivism a la Hawking is rather silly, so some hidden layer of reality might exist (hidden variables) but as I explained before, the creation operators in QFT are also very real for me. Concerning observation, that part is definitely non-local and non-physical too! It's a second layer of reality which one might call awareness: it really is inevitable.

Okay, fair enough. I interpret this as you’re "working on it", right?

Let us know when you’re ready to go public!

(I also suspect that our senses MIGHT play us a trick when it comes to "reality" and "layers". We know e.g. that (mixing) colors is something that "goes on" inside our heads solely. My personal guess is that EPRB might be the knob on the "Royal Door", but so far we have been trying to open it in the wrong direction... No-go push! )

 

[DevilsAvocado]

I know you didn't ask me, but fwiw my opinion is that this is an irrational question.

Thanks Fredrik for your feedback, interesting. It’s quite late over here, and even if time doesn’t really exist, my brain is dead sure it does and distresses me with "chemical inactive weapons"! :zzz:

I have to get back tomorrow.

 

[Careful]

Now I have. And I see "unusual" quarrel... rendering in locked...

It really was no quarrel. I just gave this guy sensible advise for his own good

 

[DevilsAvocado]

It really was no quarrel. I just gave this guy sensible advise for his own good

... something "unusual" must have happened to unusualname ... that’s not the same "usual guy" I used to debate ...

 

[Careful]

... something "unusual" must have happened to unusualname ... that’s not the same "usual guy" I used to debate ...

Ohw sorry, my usual mind-reading capacities were switched off here

 

[andrebourbaki]

In orthodox QM there has been a consensus that time is not an observable.
Nor charge. We don't measure time in the same way we measure position
or spin. Neither do we measure physical constants such as the speed of
light or the charge on the electron that way, so in threads on quantum measurement
we should restrict the meaning of the word 'measurement' to the type of
measurement envisioned in the axioms of QM.

This consensus has never been really logically justified, as can be seen by the differences of opinion between Wigner, Pauli, and the contributors to this thread.
Or maybe I should say merely that there has never been a consensus as to what the proper justification of the consensus is.

Feynman said in print that in his opinion, the reason quantum measurement gives rise to probabilities is because amplification is necessary for a macroscopic measurement apparatus to register a microscopic effect. From this, I would go on to deduce that since clocks are not amplifying devices,
then from this point of view, they do not accomplish quantum measurements, so time is not an observable. I find this deduction from Feynman's idea convincing.

I cannot speak to the big bang and curved space-time, but merely address the first edition of this question.

 

[Trifis]

An addendum regarding this continuously arising question of "what does QM suggests about ontological issues BEFORE measurement?"...
As far as existence is considered, REALISM and once again REALISM! The very moment we write: |ψ> with the condition: \exists r_0 : <ψ|r_0|ψ>≠0 for r_0 inside a "physical" space (whereby this condition is almost always implied), existence is presupposed. And by "existence" I mean the profound philosophical meaning of the word, on which the whole logical construction of science is based. So QM treats the objective observer independent existence of the material world axiomatically.
The question therefore is not addressed inside the scope of the theory and that's the way it should be. ANY claim (e.g. the rejection) with respect to a condition before the observation or if you prefer in the absence of a conscious mind, is by definition unfalsifiable and thus unscientific.
Intriguing as it may sound, Archibald's ouroboros is for the time being even philosophically redundant, let alone scientific. Obsolete idealists, theologians, mystics and several other "speculators" may feast on such science-motivated ideas though...