Szydagis' point 3: Interstellar travel is too hard

[John J.]

The pilot wave theory (and the like) treats the wavefunction also as a real wave which, however, guides particles along a certain probability distribution rather than turns into a particle

Good for the double slit experiment.

Serious question (for anyone who knows about QM); for the double slit experiment, after the double slit and before the detection screen or whatever, is it theorised that the mass of the (e.g.) electron is distributed across the relevant space?

I think I understand that a direct attempt at measurement would collapse the wavefunction and reveal a discrete particle.
Theoretically, would it be possible to measure the distribution of mass in a "closed" double-slit experiment?

 

[LilWabbit]

The pilot wave is just as un-detectable as the standard wave function.

As are all laws of physics except for their predicted observable outcomes (i.e. the predicted behaviour of particles at measurement in the case of the wavefunction). The non-observability of theorized entities/properties/laws that underlie observations (a basic fact of science) is not at issue when discussing the measurement problem, but rather the claimed magical effect of 'collapse' caused by the measurement which doesn't occur at all in the pilot wave interpretation. Whosoever has made people think the wavefunction collapse is an observed fact rather than theoretical claim by certain theories of quantum physics has done a great disservice to the popular inaccurate understanding of the quantum world. In pilot wave theory the hidden variables (another misleading term not used by pilot wave 'theorists' themselves) are nothing more and nothing less than the positions of the particles before measurement and after measurement (being also disturbed by the measurement whilst, however, not causing any collapse) which are unknown.

Pilot wave also has various issues to do with local realism.

Not at all. This misconception arises (often unwittingly) from an old trope by Copenhagenists based on a complete misunderstanding of the pilot wave interpretation which, in fact, satisfies Bell's theorem and fully accomodates nonlocality. Also, there's nothing about 'classical' physics that automatically hinges on local realism. Local realism was, rather, just a strong personal conviction of Einstein's whereby nothing (not even causalities) could go faster than the speed of light. Bell's inequality test proved otherwise. A faster-than-light causality is an observed fact by Bell's tests. Not a theory. Yet particles (matter) cannot be superluminal which sets all the constraints upon inter-galactic travel discussed earlier and which are valid constraints often skirted by ufologists.

Btw, I'm not a Bohmian (am very open to all well-formulated theories consistent with observations) but realize people commonly misunderstand the de Broglie-Bohm theory because of 'sciency' falsehoods spread about by those vehemently and often dogmatically opposed to any challenge to Copenhagen. Not based on actually studying Bohmian mechanics and its exact claims.

 

[LilWabbit]

Good for the double slit experiment.

Serious question (for anyone who knows about QM); for the double slit experiment, after the double slit and before the detection screen or whatever, is it theorised that the mass of the (e.g.) electron is distributed across the relevant space?

I'm not aware of such theories but know such a distribution is not an observed fact. In the standard (Copenhagen) intrepretation the electron's true quantum state is the wavefunction which is a mathematical description of a purely wave-like state having no mass like particles do. Hence the collapse dilemma for Copenhagenists as observations do not reveal any wavefunction but only particles most of which do have mass (some, like photons, don't). The particles do, however, appear on the screen in a wave-like interference pattern which adds credence to Bohmian mechanics (the pilot wave theory).

I think I understand that a direct attempt at measurement would collapse the wavefunction and reveal a discrete particle.

Read my previous response to Scaramanga. Wavefunction collapse itself is a theory, not an observed fact. Only discrete particles are ever observed and thereby casting doubt on any strong/dogmatic claim (such as Copenhagen) that those particles couldn't have existed as particles before measurement or after, but rather represent some 'collapses' of some mathematical differential equation (wavefunction) floating in the universe.

All in all, I think we've digressed enough from the main topic.

 

[Mendel]

Obviously you can't sell the movie rights to your golf game if nothing exciting happened—there's a bias in what gets made into movies.

"Scientists have calculated that the chances of something so patently absurd actually existing are millions to one.
But magicians have calculated that million-to-one chances crop up nine times out of ten."

― Terry Pratchett, Mort​

Actually, there's an analogy to the anthropic principle at play here:
if I'm in a movie, and the protagonists stake everything on that million-to-one chance, then the fact that I'm sitting in the cinema watching this now is a strong clue that they're going to be lucky.

When I'm dealing a deck of cards, the first hand I'm dealing is just as unlikely to come up as any other (including the fully ordered hand). But the fact that I dealt it and am looking at it now is proof that I beat near-impossible odds and dealt that exact hand.

 

[Mendel]

Serious question (for anyone who knows about QM)

is @Marcus still around? he's very good at explaining these things.

 

[LilWabbit]

Two informative clips from a great recent podcast discussion on the measurement problem between David Albert and Tim Maudlin:


Source: https://youtu.be/A59GMM8rHGA?si=-_mMABbrjWh5xy1Z



Source: https://youtu.be/Qyfxa74HBTw?si=6iCHHKHB176jV_bK

 

[FatPhil]

Good for the double slit experiment.

Serious question (for anyone who knows about QM); for the double slit experiment, after the double slit and before the detection screen or whatever, is it theorised that the mass of the (e.g.) electron is distributed across the relevant space?

I think I understand that a direct attempt at measurement would collapse the wavefunction and reveal a discrete particle.
Theoretically, would it be possible to measure the distribution of mass in a "closed" double-slit experiment?

This mass distribution is one of the questions that a quantum theory of gravity would hopefully answer. Just believe in the many worlds interpretation, and the problem goes away ;-)

 

[Scaramanga]

Read my previous response to Scaramanga. Wavefunction collapse itself is a theory, not an observed fact.

The wave function itself is a theory, or rather a mathematical tool, not an observed fact. Nobody has ever 'seen' a wave function. Indeed, Heisenberg and Born had to effectively invent matrix mechanics out of nowhere in order to have a tool to use. It would be more accurate to say the world behaves 'as if' this function were a real thing.

 

[Mauro]

The wave function itself is a theory, or rather a mathematical tool, not an observed fact. Nobody has ever 'seen' a wave function. Indeed, Heisenberg and Born had to effectively invent matrix mechanics out of nowhere in order to have a tool to use. It would be more accurate to say the world behaves 'as if' this function were a real thing.

But the same is true also of energy... it's a mathematical tool. Noone has ever 'seen' kinetic energy (for example), nor there's a way to directly measure it.

 

[FatPhil]

But the same is true also of energy... it's a mathematical tool. Noone has ever 'seen' kinetic energy (for example), nor there's a way to directly measure it.

The "1/2. mv^2" version of kinetic energy isn't even a mathematical tool, as it's a newtonian simplification. Special relativity's "mass energy" just gobbles up that term, it's no longer useful.