I won't debate on the wavefunction collapse

[Hurkyl]

The reason every scientific theory has to deal with measurement is because measurement is what gathers empirical data. If a theory doesn't relate to empirical data, then it's not scientific.

There is no similar argument that a scientific theory must relate to interactions that are not measurements.

In terms of familiar theories, taking interaction as a foundation lies somewhere between taking measurement as a foundation and taking stuff as a foundation.

 

[rewebster]

The reason every scientific theory has to deal with measurement is because measurement is what gathers empirical data. If a theory doesn't relate to empirical data, then it's not scientific.

There is no similar argument that a scientific theory must relate to interactions that are not measurements.

In terms of familiar theories, taking interaction as a foundation lies somewhere between taking measurement as a foundation and taking stuff as a foundation.

I have to slightly disagree--or more specifically---foundational theories are more built on a specific hypothesis about the measurements and stuff, eg --nothing travels faster than light---because nothing has ever been observed conclusively/scientifically to travel FTL.

 

[lightarrow]

I have to slightly disagree--or more specifically---foundational theories are more built on a specific hypothesis about the measurements and stuff, eg --nothing travels faster than light---because nothing has ever been observed conclusively/scientifically to travel FTL.

I don't agree on it. If you talk about SR, it's based on the empirical data (measurement) that light's speed doesn't depend on the relative speed between source and observer, more than the hypothesis "nothing travels faster than light".
I apologize in case this is not what you intended.

 

[Mentz114]

lightarrow:

If you talk about SR, it's based on the empirical data (measurement) that light's speed doesn't depend on the relative speed between source and observer.

What empirical data would that be ? I don't believe a laboratory experiment is feasible, and astronomical data has large error bars.

 

[meopemuk]

lightarrow:

What empirical data would that be ? I don't believe a laboratory experiment is feasible, and astronomical data has large error bars.

Check, for example,

T. Alvager, F. J. M. Farley, J. Kjellman, I. Wallin, "Test of the second postulate of special relativity in the GeV region", Phys. Lett., 12 (1964) 260.

They used the time-of-flight method to measure the speed of gamma quanta emitted by high-speed \pi^0 mesons from an accelerator. This was a direct and accurate confirmation that the speed of light does not depend on the velocity of the source.

Eugene.

 

[rewebster]

I don't agree on it. If you talk about SR, it's based on the empirical data (measurement) that light's speed doesn't depend on the relative speed between source and observer, more than the hypothesis "nothing travels faster than light".
I apologize in case this is not what you intended.

yes--there is more, of course--but, for example, one reason that relativity hasn't won a Nobel Prize may be, in that, it may be highly correlative and useful in some circumstances (as was the celestial model), it at it's core, is a speculation (a hypothesis) that hasn't been totally proven. Things such as energy conversion/equivalence may be just coincidentally close.

 

[Xeinstein]

But, in my humble opinion, this is simply replacing one mystery with another mystery. How does this "interaction" occurs? What is the physical process behind it? When does it occur? Etc etc.

saying that "hocus-pocus, the wavefunction of the particle becomes entangled with the the measurement device when we do the measurement" is as mysterious as saying "the wavefunction collapses".

I am not saying I disagree with your point. I do agree that a formalism in which the collapse never occurs is more satisfying than the collapse approach. I am just pointing out that saying this opens up as many questions as it answers, IMHO.

Agree, this wavefunction collapses just garbage,
as Gell-Mann said Niels Bohr brainwashed a whole generation of physicists into believing that the problem had been solved

 

[reilly]

So what has been totally proven?
Regards,
Reilly Atkinson

yes--there is more, of course--but, for example, one reason that relativity hasn't won a Nobel Prize may be, in that, it may be highly correlative and useful in some circumstances (as was the celestial model), it at it's core, is a speculation (a hypothesis) that hasn't been totally proven. Things such as energy conversion/equivalence may be just coincidentally close.

 

[Xeinstein]

I think it is dangerous to pretend that we know what happens to the system "in reality", i.e., while we are not watching. This is a sure way to logical paradoxes. The whole point of complex amplitudes in quantum mechanics is to refuse any statements about "reality" and concentrate only on (probabilities) of measurable outcomes of experiments.

Eugene.

Recent experiments have proven Bell inequality has been violated
So the viewpoint of "local reality" is wrong and incompatible with quantum mechanics

 

[Cthugha]

yes--there is more, of course--but, for example, one reason that relativity hasn't won a Nobel Prize may be, in that, it may be highly correlative and useful in some circumstances (as was the celestial model), it at it's core, is a speculation (a hypothesis) that hasn't been totally proven. Things such as energy conversion/equivalence may be just coincidentally close.

I disagree in several ways. relativity is not a hypothesis, but a theory.

And it is not the goal of science to totally prove things. If you read a bit about the philosophy behind science (Popper or the Quine-Duhem thesis), you will notice that science can only totally disprove theories. And even that just in a limited sense (see Quine-Duhem). Also, any experimental result might just be conincidentally close to theory.

Earlier this month ZapperZ posted a wonderful essay about the scientific meaning of words like theory or hypothesis and common misconceptions:
https://www.physicsforums.com/showthread.php?t=149923

Anyway, enough of that. This is getting slightly off topic.

 

[peter0302]

Isn't the "wavefunction collapse" nothing more than the wavefunction CHANGING?

Take two "free" electrons, non-entangled, defned by Y1(x,t), Y2(x,t). The probability of them interacting at some space 'x' and time 't' is a function of both wavefunctions: |Y1*Y2|(x,t). If the interaction occurs, the particles are subsequently defined by new complementary wavefunctions Y3(x,t) and Y3'(x,t) and, thus, entangled. Interaction gave the particles new wave functions. Then, once entangled, a further interaction/change in one particle's wave function causes a complementary change in the other.

The "collapse" language was introduced to ease the minds of people afraid of spooky action at a distance, i.e., accepting that change (even a statistical one) can be caused by something nonlocal.

Personally, I'm convinced that if it were possible to trace the wave function of every particle since the big bang, we would find the apparent "non-local" influence to be nothing more than a consequence of the infinite complexity of the entanglement of every particle with one another. But I won't even try to prove that. ;)

 

[AspectProteus]

I'm new to the forum. While not being ‘technically’ informed and having more of a visual-type understanding (as limited, and limiting to technical discussion as that is) I find QM (QFT whatever) extremely fascinating.

Now, if I were claiming to ‘understand/know’ any of this, I'd not be posting here with my occasional query. That said:

Take two "free" electrons, non-entangled, defned by Y1(x,t), Y2(x,t). The probability of them interacting at some space 'x' and time 't' is a function of both wavefunctions: |Y1*Y2|(x,t). If the interaction occurs, the particles are subsequently defined by new complementary wavefunctions Y3(x,t) and Y3'(x,t) and, thus, entangled. Interaction gave the particles new wave functions. Then, once entangled, a further interaction/change in one particle's wave function causes a complementary change in the other.

Personally, I'm convinced that if it were possible to trace the wave function of every particle since the big bang, we would find the apparent "non-local" influence to be nothing more than a consequence of the infinite complexity of the entanglement of every particle with one another. But I won't even try to prove that.

My previous understanding, was that the degree/extent of 'entanglement' depends upon the nature(?) length(?) of the interaction. Is this not so? If it is so, what indicates, to you, a causal linkage (through entangled wavefunctions) to the degree you've suggested above, i.e. 'finding the apparent "non-local" influence to be nothing more than a consequence of the infinite complexity of the entanglement of every particle with one another.'

Just curious. It’s provoked a few tangentially similar thoughts.

 

[peter0302]

Oh, I'm not claiming to understand/know any of this either. ;) Nonetheless -

They are indeed entangled to the extent of their interaciton. If the interaciton is a "classical" collision between two massive particles, for example, their momentum and spin would be entangled. If the interaction is, say, absorption of a photon by an electron, then the photon ceases to exist entirely and the electron has more energy (you could say the electron and the now non-existant photon are entangled). If the interaction was between two photons, they might constructively or destructively interfere. If the interaction was beta decay of a neutron, then the electron, proton, and neutrino would all be charge / mass / momentum entangled.

Now take the case of entangled photons where one goes through a lens. Everyone likes to simplify the problem and assume the photon going out is the same one going in, but we all know that's not what happens. The photon gets absorbed by an atom in the lens; for an instnat, the atom is entangled with the now-non-existant photon and its twin on the other side of the lab. It might be a "loose" entanglement, but it is still there. An instant later, the atom emits a new photon, which is partly entangled with the atom in the lens, and partly entangled with its original twin. And so forth, until the final atom in the lens emits a photon at the other end, in which case the new photon is still entangled with its twin to a degree, e.g., it's still polarization-entangled, but no longer direction-entangled - it's been "bent". Then there's that one last atom in the lens that's still entangled with that last photon - largely, in fact, for an instant. But then the other atoms in the lens all rapidly influence that last atom to such a large degree as to, on any perceiveable scale, render completely negligible the photon's influence on the atom. But the history of the interaction is still a part of that atom's wave function, no matter how small a part. It never "collapsed" - it just became infinitely small. But that infinitely small influence propagates through the entire lens, the surrounding air, the earth, the solar wind, etc. Thus, every interaction between any two particles alters the wave function of the entire universe at an infinitessimal level.

Hence, my statement that everything is entangled in an infinitely complex way, and my hypothesis that if one could model a huge number of particles interacitng and entangling as such, always obeying the laws of nature locally, the chaos that would ensue would, I believe, entirely mimic the quantum observations without the need for non-locality. Or put another way, my hypothesis is that any chaotic system appears to exhibit quantum-like effects when viewed at a sufficiently large scale.

Sorry for the overtly metaphysical babble.