HN Theater @HNTheaterMonth

I always struggled with that too - I found this Veritasium video helpful

https://www.youtube.com/watch?v=WIyTZDHuarQ&ab_channel=Verit...

⬐ __s

Never heard of this, looked up whether there was some gap in the theory the video failed to mention, found a discussion on why this model isn't more pervasive: https://physics.stackexchange.com/questions/341400/why-would...

& one comment which specifically separates pilot waves from the bouncing droplet demo https://old.reddit.com/r/quantum/comments/7crdz6/whats_wrong...

Oil droplets can model quantum behavior too https://www.youtube.com/watch?v=WIyTZDHuarQ

⬐ mettamage

Note: while this has been submitted before, I'm surprised there has been no discussion about it.

⬐ mgsouth

It's been refuted. https://www.quantamagazine.org/famous-experiment-dooms-pilot...

I found this while following up on an excellent pilot wave (de Broglie-Bohm) theory video by Veritasium[1]. I never knew there were so many interpretations!

1. https://www.youtube.com/watch?v=WIyTZDHuarQ

Great video that showcases the Pilot Wave idea: https://youtu.be/WIyTZDHuarQ

I really do hope that we can find a way to make sense of everything in Physics, but Bohm's description of the infinite in the article is rather fascinating. Maybe there's no way out after all

suitable as a visual aid

Especially the somewhat related silicon droplet videos on youtube, e.g.: https://www.youtube.com/watch?v=WIyTZDHuarQ

Veritasium video about the topic https://www.youtube.com/watch?v=WIyTZDHuarQ

There is the silicone oil droplet phenomena which is a classical version of the pilot wave, and it does reproduce some quantum behavior, including the double slit. That a pilot wave has been discovered (granted at macro scale) does make one reconsider.

https://youtu.be/WIyTZDHuarQ

⬐ kkylin

As far as I know there is no analog of entanglement in these experiments. If someone has heard or read something in that regard, I'd be interested in a reference!

⬐ lisivka

Nobody even tried to entangle two walkers. AFAIK, uncharged non-magnetic particle without any inclusions (e.g. bubbles) has spin and phase of vibration only. How to entangle them?

Moreover, spin is 3d, walker is 2d, phase is 1d, while our Universe is 3d. It's like studying of 2d/1d projection of 3d world.

⬐ krastanov

It does not, really. The macroscopic realisation is not particularly surprising (although it is quite awesome and original). If you put a ball floating on top of a wave you will observe the predictions from a mathematical model of that system, which is exactly what the pilot wave theory is, and there is nothing surprising here. Moreover, the macroscopic model simulates something which by definition is an unobservable construction in the quantum model. It does not simulate any inherently quantum behavior (classical waves is a thing we already knew exists).

⬐ lisivka

Nobody tells that walkers are simulate all quantum behavior and doing that correctly. However, they helps to understand some of quantum puzzles. For example, droplets have spin. Can you predict behavior of the classical droplet spin in compare to the puzzling quantum spin?

⬐ krastanov

But you can do the same with classical setups that mimic some effects from the typical quantum mechanical formulations. Those classical experiments are indeed amusing and interesting, but they do not illuminate the "quantum puzzles", no matter whether they are modeled after pilot wave theory or after quantum mechanics. And very importantly, those amusing demonstrations do not scale! Sure, you can mimic with classical contraptions the pilot wave (or the wave function) of a single particle, but the nice intuitive demonstrations fail when you try to scale it up to more particles (or anything that would be exhibiting the interesting, nontrivial quantum behavior).

⬐ lisivka

So, your prediction for walker droplet spin is that walkers, in kind of Stern and Gerlach experiment, will behave like classical magnets, not like quantum particles, right?

⬐ krastanov

No, they would behave like a ball floating on top of a wave and given that there are waves involved there will also be interference patterns. There is nothing quantum here. Sure, in one particular way it looks like a quantum particle (to the extent of a cargo cult), but in all the important ways it does not (entanglement, computational power, generalisation to multiple particles).

⬐ lisivka

I asking about outcome of Stern and Gerlach experiment. It's binary thing. Make public prediction, please.

⬐ krastanov

Certainly, but then please first pose/define the question clearly. What do you call a macroscopic Stern-Gerlach experiment with balls floating on top of the waves of a fluid? It would be an amusing toy problem to work out if you define it for me. However, it does not change the main argument: there is nothing quantum in macroscopic experiments with water waves - interference does not imply "quantumness".

⬐ lisivka

Lets define experiment as following (excuse me my bad English, please):

- vibrating bath with non-conductive, non-magnetic, non-paramagnetic, non-diamagnetic fluid;

- vibrating bath is wide enough to avoid excessive interference with reflected waves from bath sides;

- vibrating bath has regular pattern on top of fluid, without any irregularities in space of experiment;

- small charged droplets of fluid on top of bath;

- north and south poles of a magnet are placed horizontally, without touching of bath fluid or droplets, e.g. at sides of bath, OR over fluid, OR under bath;

- an apparatus creates droplets of same size with random spin in all 3 dimensions;

- droplets are forced to walk through the batch, starting at center line between north and south pole and following that line;

- without magnetic field applied, droplets must walk straight;

- an detectors to measure decline of droplet path from center line must be installed at end of magnetic pole.

I expect that, when magnetic field is applied, droplets will slide completely to left or completely to the right, like electrons in Stern-Gerlach experiment.

It's not a quantum experiment, of course, but it can provide insight on nature of quantum spin.

PS.

Sorry, droplets must be charged, not magnetic. Updated.

⬐ krastanov

The main point of the Stern-Gerlach experiment was that the electrons hitting the screen were forming two distinct dots instead of a long spread out line, therefore proving that the angular momentum is quantised. In your example you will instead have simply a spread-out distribution because there is no quantisation of the angular momentum of your droplets.

The pilot wave usually refers to the spatial degrees of freedom, especially in these classical mock-ups with balls on top of waves. They do not properly addressed internal degrees of freedom like spin.

Unrelated to those macroscopic mock-ups, pilot wave theory actually has serious problems with the description of anything that is not a spatial degree of freedom.

You can still use pilot wave theory to describe the quantum behavior of the coordinates of a particle. But even then, the classical mock-ups we are discussing will not show anything inherently quantum - it will simply produce some interference patterns, that can be explained classically.

P.S. side note: An important part in the Stern-Gerlach experiment was that the magnetic field was not homogeneous, because it is the gradient of the field, not the field itself that causes the electrons to move.

⬐ lisivka

IMHO, Stern-Gerlach experiment demonstrates interaction of magnet field with guiding wave mediated via particle, so I expect that magnet will steer particle-wave into same spots, thus will demonstrate «quantum» behavior of particle spin at macro level.

⬐ krastanov

Without disrespect I insist that you are wrong about that. The spin degree of freedom is "internal", unrelated to the position of the particle. The pilot wave does not influence that spin, and if you have a big ball on top of a wave, that wave does not care about the angular momentum of the ball. The ball is big and classical, hence its angular momentum is (practically) not quantized.

The thread got a bit long, but if you are really interested in learning about this I would be happy to continue the discussion through email ([email protected]). You probably also need proof of some kind of qualification on my part - my online profile does prove that I work at a respected institute doing research on that topic.

A bit unrelated, but there's a possibility that quantum mechanics are not exactly probabilistic and that they're actually deterministic, while still being compatible with observed quantum phenomena. This video explains it well https://www.youtube.com/watch?v=WIyTZDHuarQ

"In the classical physics of Newton and Einstein, the vacuum of space is entirely empty, but the theory of quantum mechanics assumes something very different.

According to quantum electrodynamics (QED) - a quantum theory that describes how light and matter interact - it’s predicted that space is actually full of 'virtual particles' that pop in and out of existence and mess with the activity of light particles (photons) as they zip around the Universe."

So, does this mean that this explanation for Quantum mechanics https://www.youtube.com/watch?v=WIyTZDHuarQ has been vindicated?

i.e. the double slit with the fields being the cause of the oddity instead of... something that is hard to explain.. including the observer effect

⬐ tfgg

No. Quantum field theories and their vacuum state has nothing to do with pilot wave theory (PWT).

PWT is oddly popular amongst internet people, but is just a mathematical transformation of the Schrodinger equation, with some associated interpretation. It makes no additional predictions.

⬐ _0ffh

I wonder. In the Em-drive paper the NASA scientists seem to point to PWT for a possible explanation. If it didn't make a difference, then why should they have done that?

⬐ contravariant

>So, does this mean that this explanation for Quantum mechanics https://www.youtube.com/watch?v=WIyTZDHuarQ has been vindicated?

If anything the virtual particles are an alternative to the pilot wave theory. Instead of having quantum effects mediated by virtual particles the pilot wave theory uses a 'pilot wave'. Now as far as I know most phenomena caused by virtual particles can be explained by the pilot wave, but I'm not sure how easily.

Either way, results like these which seem to be in favour of the existence of virtual particles are weak evidence against the pilot wave theory.

⬐ rrauenza

...I thought the article implied the opposite -- against the pilot wave theory.

Can someone weigh in and put this article in the context of the pilot wave theory?

(Not a physicist!)

⬐ z92

It's against pilot wave theory. Pilot wave theory is another form of hidden variable theory, that has been proved wrong again and again.

Source: check wikipedia.

⬐ dangirsh

Pilot wave theory requires non-local hidden variables. Only local hidden variable theories have been shown to be impossible.

In non-relativistic situations, Bohemian mechanics (pilot wave theory) makes the same predictions as more mainstream interpretations of QM.

⬐ Filligree

Well, sort of.

Pilot wave theory, if simulated, still requires you to run all the same calculations as (say) the Many-Worlds interpretation, in order to know what the pilot wave is doing.

In fact, the pilot wave will still contain everything that MWI does: Multiple timelines, vast assemblies of nearly-independent universes, Earths beyond counting, etc etc. What PWT does is add in some nearly-epiphenomenal particles, and declare that only these count; that any observer described by the pilot wave is a philosophical zombie.

I have objections to this concept. :P

⬐ randomguy1254

That's not quite accurate. Local hidden variable theories have been proven wrong, but pilot wave theory is a nonlocal hidden variable theory. Bell himself was a proponent of pilot wave theory.

⬐ evanb

No. Vacuum birefringence is understandable from a perfectly conventional understanding of quantum field theory, and does not remotely require anything about the pilot wave idea to be true. Every quantum field theory, including QED, has a roiling vacuum of virtual particles, whether you hold an orthodox view or not.

Source: am physicist ;P

⬐ joantune

Got it, thanks!

The only thing it contradicts was already contradicted by Quantum theories which were some of the more classical Newton and Einstein's theories.

So this is exciting 'only' because it is a larger version of a man made in lab phenomenon, and seen occurring naturally.

Again, thanks

⬐ dschiptsov

Define 'virtual', please.

⬐ randomguy1254

Can you give me some hints on what virtual particles actually are if its not too complicated? I keep reading that they are not actually real particles, only useful for calculations/as a simple way to understand what is going on. How does something like Hawking radiation work if they are not real particles?

⬐ DavidPlumpton

In Many Worlds virtual particles are simply other universes (other parts of Hilbert space) that have electrons in different positions. They are nearby enough to contribute some amplitude to have an observable effect. Edit a word.

⬐ randomguy1254

Interesting, thanks!

⬐ Florin_Andrei

The main challenge in understanding QM is the fact that we are all intelligent animals whose brains developed in what is for all practical purposes a classic newtonian universe. When you were one year old, crawling on the floor at your parents' house, your brain was learning to operate within the realm of classic physics.

In such a universe, things are very clear-cut. An object must be either here, or there. Something must be either in this state, or the other. Particles behave like billiard balls, and waves behave like, well, waves. Things either exist, or they do not. Space and time have perfect accuracy, there's no "smearing" of coordinates either in space or in time.

The problem is, that is not at all the case at microscopic levels. You've learned what a marble is as a kid, and you think of electrons as little marbles racing around the nucleus - but that's utterly wrong. You've watched water waves on a pond and you think that's how a beam of light behaves, but that's ridiculously simplistic.

The fundamental reality at the quantum level is the awkwardly named wave function (awkward because there's no wave proper there). That's what electrons, and photons, and neutrons, etc, are. It's a function that describes a probability amplitude as a complex number. That's it. They're not little marbles - although sometimes they kind of behave like that. They're not little waves - although they kinda-sorta look like that. They are bundles of probability amplitudes smeared out over space and time intervals. This is not a metaphor. This is stark reality.

The familiar classic universe with crawling floors and marbles and water waves is just an epiphenomenon. It's a collateral that emerges on top of the quantum world if you zoom out a trillion-fold and ignore all the little details.

The "smearing out" of space, time, momentum and energy parameters at the quantum level simply means these are not the truly fundamental things you think they are on that level. Take energy and time; in a quantum system, you could measure energy with infinite precision, but then you can't say anything about the time intervals. Or you could measure time very precisely, but then you don't know anything about energy. That's not a limitation of your equipment. It simply means neither energy nor time are the precious snowflakes you thought they are - but their combination is.

A particle that does not exist has exactly zero energy and exists for exactly zero seconds. But wait, this is the quantum world. That means a deviation from zero energy is permissible, as long as it does not take place longer than a correspondingly short interval. The higher the energy deviation, the shorter the duration of the blip. That means, in completely empty space, you will be able to measure that particles seem to appear out of nowhere, exist a very short time (the more massive the particle, the shorter the time), then vanish.

But do those particles actually exist? In QM, that's meaningless. Remember, there's no such thing as a particle? Only bundles of probability density? Remember that? And those bundles obey the basic relations about energy/time and momentum/location. As long as you're talking about fluctuations the size of an electron, then yes, pure vacuum would seem to produce electrons continuously, but they only blip in and out of measurement for a very short time.

But are they "real"? If you can measure it, it's real. Full stop. But classic categories such as "it exists" or "it does not exist" get blurred at the quantum level. Anything could potentially, and does actually, exist - provided it does not violate basic QM relations.

---

So that "quantum fog" exists in a vacuum all the time. Usually it's completely chaotic. But magnetars have such strong magnetic fields, they impose a structure over those short-lived virtual particles. And then when light passes through, it interacts with that structure and gets polarized.

So do those virtual particles exist? Well, they changed the light, didn't they? But realistically - "exists", "does not exist", that's newtonian bullshit. At the quantum level, which is the basis of reality as far as we can tell nowadays, it's all about probability functions.

---

If you feel compelled to visualize this stuff, think of quantum particles as little "clouds" of probability. More dense in the middle regions, getting thinner and thinner towards the periphery - but basically it keeps going on an on, it's just a stupendously small value far from the thickness. Of course, this is just a poor visualization, but for some folks it's better than nothing.

⬐ SomeStupidPoint

You mix facts about the mathematics with opinions about interpretation and philosophical positions pretty freely, and that equivocation in science communication is what puts a lot of people off QM.

Scientists are too comfortable presenting philosophical positions or opinion as fact just because it's consistent with a model.

See the split between Copengahen, MWI, and Bohmian views about how to interpret the underlying calculations.

⬐ Florin_Andrei

Meh. It was just an intuitive description for laypeople, not a dissertation on the differences between Copenhagen and many-worlds.

Yes, I do take sides - but only for ease of explanation. The "sides" I'm taking are not even the ones I actually prefer.

Get people started first, then they can read rigorous analyses on their own.

⬐ randomguy1254

Thanks! That's a really nice explanation. I keep forgetting that particles don't really exist so much as a wave function does in the Copenhagen interpretation, so that gives me a new way to think about virtual particles, and helps tie it in with the article. Also a lot of other nice tidbits in this explanation for me to mull over...

⬐ halpiamaquark

>That's what electrons, and photons, and neutrons, etc, are. [...] They are bundles of probability amplitudes smeared out over space and time intervals. This is not a metaphor. This is stark reality.

Aren't you describing a representation of atomic particles, not the particles themselves?

Edit: I'm not looking to get into a discussion about what constitutes "existence". I am just wondering if you are conflating a scientific-mathematical model for a thing with the thing itself.

⬐ Florin_Andrei

> you are conflating a scientific-mathematical model for a thing with the thing itself

Bohm would say yes. Others would say no.

⬐ aroberge

(Apologies to Quantum Field Theorist for the gross simplification below.)

I'm going to assume you know about basic calculus and Taylor series; if not, I'll explain what these are in a subsequent answer if you are interested.

In Quantum Field Theory, we cannot do exact calculations ... only (better and better) approximations. The way we do these calculations is very much similar to doing a Taylor series in Calculus. However, the calculations involved many complicated multi-dimensional integrals

Feynman found out a way to represent these complicated mathematical expressions that occured in those approximate calculations as pictures (known as Feynman diagrams). In these pictures, one could represent (real) particles interacting as lines (straight, curvy, etc., depending on the rules) that end in open space..

As we increased the order of expansion in the approximation (think of powers of the variable in a Taylor series), the terms corresponded to more and more diagrams, each increasing in complexity with the order of expansion.

Well, it turned out that, using the Feynman rules for translating mathematical expressions into parts of a pictures, that lines (straight, curvy) similar to that of "real" particles appeared inside the diagrams; however, these lines were all connected to others and did not end in open space: they do not correspond to any particles that we can measure directly.

However, we can think of these lines as representing "virtual" particles, that we cannot probe directly.

One thing to keep in mind (and that many that mention the "virtual particle" explanations often forget to mention): these diagrams are, in a very strong sense, an artifact of the way we do calculations using the best approximation techniques we know. These are useful computational tools. But individual diagrams should not be thought of as representing an actual precise interaction that is taking place. And virtual particles are just a way to make a connection between what we think we know ("real" particles interacting) and what our approximative way of calculating things give us.

⬐ randomguy1254

Thanks! That's an interesting fact about Feynman diagrams. If we had a hypothetical machine which could perform these calculations with infinite precision, would the "virtual particles" disappear from the diagram, or is it impossible to know this?

⬐ aroberge

Let me answer your question first very obliquely. We know that we can represent the sine function near x=0 as the following Taylor series:

sin(x) ≈ x - x^3 / 6 + x^5 / 120 - ....

With more and more terms, we can can calculate it more and more precisely. Does this means that this function really contains all of these powers of x?

Well, suppose we want to calculate sin(pi/2) (angle in radians, which is required for the Taylor series). We know that it is exactly 1. There are no powers of (pi/2) appearing in "1". The Taylor series gives us a convenient way to calculate the value of the function (technically: inside a radius of convergence), but it is not the same as the function itself.

Now, to give an example from Quantum Field theory: let me quote from a wikipedia page [1]:

_In a perturbative approach to quantum field theory, such interactions may require the calculation of hundreds of Feynman diagrams. In contrast, twistor theory provides an approach in which scattering amplitudes can be computed in a way that yields much simpler expressions._

So, these hundreds of Feynman diagrams would lead us to think of many virtual particles describing an interaction. The Amplituhedron type of calculation is done completely differently, in a way that does not lead one to think of interactions through virtual particles.

Now to answer your question: I do believe that, if we were smart enough to find a way to compute things exactly, "virtual particles" would not appear as intermediate steps of computations. But, then again, to be perfectly honest, the same would likely be of "real" particles which are just a convenient way of thinking of excitations in quantum fields ...

[1] https://en.wikipedia.org/wiki/Amplituhedron

⬐ randomguy1254

Very interesting, good analogies and information for me to think about.

I highly recommend to watch this video first: https://www.youtube.com/watch?v=nsaUX48t0w8 , to get the idea.

Then this: https://www.youtube.com/watch?v=WIyTZDHuarQ , for explanation.

No need to read long books.

⬐ highd

Please don't suggest fringe views to people with no experience in the field.

⬐ lisivka

IMHO, it's better explanation than God or half-dead cat. If you have better explanation, then film it, please — it will be very helpful.

⬐ highd

http://home.basu.ac.ir/~psu/Books/%5BRamamurti_Shankar%5D_Pr...

⬐ lisivka

Book describes double-slit experiment but does not explain it. I read that when I was student 20 years ago.

So, WHY single particles are developing interference pattern when sent one by one?

Shut up and calculate is not an answer: https://en.wikipedia.org/wiki/Double-slit_experiment#Copenha...

Just by looking at video, it's clear that interference pattern appears because of interference of particle wave with itself. It's also clear that speed of sound in water is constant regardless of speed of particle, particle cannot reach speed above speed of sound in water, speed of particle affects particle itself, and so on.

⬐ tedsanders

The pilot wave interpretation of quantum mechanics is not a consensus, or even mainstream view. It is not helpful to blankly suggest that these videos illustrate the answer.

⬐ phest

It's an interesting theory though. What makes it less mainstream than other interpretations? (And is any interpretation of quantum mechanics a consensus?)

⬐ jfoutz

Can't say i can explain it, but the words you're looking for are "local realism".

I really like the pretty pictures from walking droplets, and it makes the thing seem very intuitive. But they're a little disingenuous. It's easy to imagine, or just see a drop of water bouncing in the air on a wave of water. But all this stuff happens in 3d. There's (as far as i know) no separation like air and water. It's more like a sound wave expanding out in all directions.

How do you surf on a sound wave? Not saying it can't be done, it's just that the pretty picture has to be a lot more complicated for the particle to have something to bounce off of. Maybe there are some weird hard thin shells that hover around particles. Who knows? For sure i can say 'not me'.

⬐ lisivka

Yep, you are right — 3D version will be very different. Why not to conduct such experiment in space, where 3D version can be constructed with ease?

Moreover, electromagnetic waves are very different from sound waves, so physic process involving them will be very different. Can you imagine an experiment, which will be closer to reality?, e.g. spinning eccentric charged particles in space.

⬐ semi-extrinsic

We have, at this point, strong evidence [1,2] against the straight-forward version of pilot wave theory. Thus pilot wave theory is forced to add more and more epicycles. This, IMO, is part of the reason why it's not becoming more mainstream today.

[1] http://journals.aps.org/prl/abstract/10.1103/PhysRevLett.115...

[2] http://journals.aps.org/prl/abstract/10.1103/PhysRevLett.115...

⬐ lisivka

Can you explain it in plain English, please?

⬐ fdgdasfadsf

When any theory has to add more and more complexity to explain the data it tends to be an indication that there is something wrong with the theory and that another theory may be more supported.

Occam's razor.

⬐ lisivka

Of course. Can you provide an explanation of double-slit experiment using Standard Model of QM?

⬐ fdgdasfadsf

No idea not a physicist I was merely providing a translation of the GP into plain English.

⬐ lisivka

Thanks for your service then.

⬐ om2

Can you explain how these are evidence against pilot wave theory? It's entirely compatible with Bell's inequality and indeed makes all the same predictions as other, more popular interpretations of QM, so it's not clear why these papers would be evidence against it.

⬐ Osmium

> (And is any interpretation of quantum mechanics a consensus?)

There is, broadly speaking, a consensus view. Whether this is because the consensus best matches reality or whether it's dogmatic is probably up for debate, but I don't personally know any professional scientists who believe pilot wave theory (Bell's theorem largely disproved it).

⬐ lisivka

As you may already known, paradigm shifts in science happens when old generation dies.

⬐ lisivka

Quote from https://www.quora.com/Why-dont-more-physicists-subscribe-to-...

John Bell himself, the original author of one of the impossibility theorems, recognized its irrelevance, but he was systematically misquoted, misunderstood, or ignored as he tried to call attention to it. Ironically, he was then portrayed as being against Bohmian mechanics, despite the fact that he was its prime supporter during his lifetime.He said:

“But in 1952 I saw the impossible done. It was in papers by David Bohm. Bohm showed explicitly how parameters could indeed be introduced, into nonrelativistic wave mechanics, with the help of which the indeterministic description could be transformed into a deterministic one. More importantly, in my opinion, the subjectivity of the orthodox version, the necessary reference to the ‘observer,’ could be eliminated…

But why then had Bohm not told me of this ‘pilot wave’?... Why did von Neumann not consider it? More extraordinarily, why did people go on producing “impossibility” proofs, after 1952, and as recently as 1978?... Why is the pilot wave picture ignored in textbooks? Should it not be taught, not as the only way, but as an antidote to the prevailing complacency? To show us that vagueness, subjectivity, and indeterminism, are not forced on us by experimental facts, but by deliberate theoretical choice?”

John S. Bell, "On the impossible pilot wave". Foundations of Physics 12 (1982)

⬐ acqq

AFAIK it simply doesn't matter:

https://www.reddit.com/r/AskScienceDiscussion/comments/3py2d...

"Bohmian mechanics is an interpretation of quantum mechanics (other popular examples are the Copenhagen and the Many-World interpretation). They try to explain the origin of the weird behaviour of measurements in QM. The problem is that these interpetations don't actually make predictions, so you can't do an experiment that tells "Bohmian is right and Copenhagen is wrong". That's why physicists don't research a lot in this area, it is more at the boundary between physics and philosophy. Copenhagen is easy to understand, so in most cases that's being taught (despite its issues)."

⬐ lisivka

Quote from https://www.quora.com/Why-dont-more-physicists-subscribe-to-...

The rest of the story as to why Bohmian mechanics is not currently favored as the mainstream interpretation of quantum mechanics can be traced back to orthodox philosophical intransigence. Those that fail to comprehend, or factor in, the ontological advantages that come from the determinism and mathematical clarity of Bohmian mechanics often attempt to downplay the formalism by pointing out that it “doesn’t make any predictions that differ from those of ordinary quantum mechanics.” Technically, that’s not much of an objection because we could equally argue that empirically “the standard theory doesn’t go beyond Bohm’s theory.”

⬐ acqq

As soon as I read "those that fail to comprehend, or factor in, the ontological advantages" I roll my eyes and stop reading. It matches my quote: "it is more at the boundary between physics and philosophy." So, again, for physicists, it still doesn't matter.

http://www.keepcalm-o-matic.co.uk/p/shut-up-and-calculate-3/

Whenever I read the texts of philosophers and see the "ontology" mentioned as argument, I just conclude "one more guy who wants to find the proof that his god exists." Or remain being paid for something close to the religious thinking which is not called so.

I enjoyed watching the videos with the drops jumping above the waves, it is nice and visual, but the things the physicists have to work with in QM still aren't drops but the measurements and the formulas. If you like to imagine the waves visually, you're free to do it, but it's still not physics.

https://www.youtube.com/watch?v=_MmpUWEW6Is

Feynman: "I think it's much more interesting to live not knowing than to have answers which might be wrong. I have approximate answers and possible beliefs and different degrees of uncertainty about different things, but I am not absolutely sure of anything and there are many things I don't know anything about, such as whether it means anything to ask why we're here. I don't have to know an answer. I don't feel frightened not knowing things, by being lost in a mysterious universe without any purpose, which is the way it really is as far as I can tell."

⬐ lisivka

I had good teacher of physics. He always told to us that we must fully understand what happens at physical level, and only then start to calculate. „Shut up and calculate“ is not an answer for me.

I also don't feel frightened not knowing things, but now we know more than before. It's hard to imagine that particle must go through all slits and then God must play dice when you saw above video at least once.

General Relativity is based on assumption that speed of light is constant regardless of direction, and tests, done with 1E-17 accuracy, are proving that. But tests done with 1E-21 accuracy shows that speed of light is not constant, so whole theory was built on wrong assumption, but it still accurate to 1E-17, which is huge accuracy, much more than we need in practice.

⬐ acqq

I don't know what you talk about, if you give some links, maybe it would help. You are free to believe whatever you will, and these "god playing dice" arguments I don't even want to discuss, I'm curious just about the seriousness of this light "tests" you claim, given that the speed of light in vacuum is by definition now fixed -- it is the basis "meter" for the other things to measure. Thanks.

⬐ lisivka

It's hard to discuss with someone, which don't want to discuss. :-)

About "light" claims: I'm talking about "non-null effect": http://vixra.org/pdf/1105.0030v2.pdf .

⬐ acqq

The paper of the guy who can't even publish it on arxiv because he's banned there (it seems that's why it's on vixra instead)? And not because of what he writes but because it is below the necessary scientific literacy level. Arxiv's standards aren't particularly high. Is there any physicist in the world taking his papers seriously?

The comment of his previous work:

http://www.abovetopsecret.com/forum/thread1021214/pg134#pid1...

"I'm serious --- the writing appears to be that of a very intelligent schizophrenic who was trained in physics. It alternates between true statements and nonsense like rap rhymes. A key symptom is the various forms of "holistic fields" or what not that connect to DNA and brains --- this is part of the schizophrenics search for the origin of his internally-created hallucinations and delusions and feeling of "understanding the Universe"."

Regarding the paper you quote: it is... weird... and had he really found anything that would disprove the Michelson-Morley results (what he tries to claim between the lines) he'd already be famous and with his Nobel prize or just wait to get it.

You know "Extraordinary claims require extraordinary evidence"? It appears he doesn't even know (or doesn't want to know) what the necessary evidence for his claims would be.

Is your name by any chance Stoyan Sargoytchev (or B.M. Quine)? If not, where have you even heard/read about that paper?

Edit: (the answer to the response) thanks for answering with "I used first link with keywords similar to what I expected to find. I read linked articles and they are crap, so let dismiss this paper. Sorry." Regarding your question: "Can you accept, after confirming of gravitational waves, that there is field, called „gravitational field“, which affects speed of light, at least temporary?" the answer is: no, it seems you don't understand the basics of physics -- that is, the issues that were known before Einstein and the way he solved them, making the testable predictions. As the Michelson–Morley experiment was performed around 130 years ago, and confirmed many times since, it's really a lot that you miss, so I'm not going to continue the discussion.

⬐ lisivka

I tried to Google article I want to show, but I'm not able to find it, so I used first link with keywords similar to what I expected to find. I read linked articles and they are crap, so let dismiss this paper. Sorry.

Article, I looking for, is about experiment conducted using Sagnac interferometer for more than year to detect deviations of predicted Sagnac effect, from Earth rotation, during year, from actual measurement. They tried to account everything they know and still had small anisotropic variations across year. I'm not able to find that article, so I will try to use LIGO observation of gravitational wave as argument.

Can you accept, after confirming of gravitational waves, that there is field, called „gravitational field“, which affects speed of light, at least temporary?

PS.

It's looks like we cannot continue discussion because of larger delays between posts, so just thanks you for your replies — they were helpful. I will try to prepare better for next time.

⬐ acqq

Thank you too for answering my questions. And to answer your last: You can imagine that what is measured with LIGO is the change of the space itself as the wave hits the detector. The speed of light remains constant. But please let's not discuss it more in this thread, I also prefer continuing somewhere else on some other occasion.

⬐ lisivka

I found papers: they are calibration results of LIGO detectors. I read them years ago, so I forget anything except that they found systematic temporal variations across day and year, and they are using long 2km arms. Their latest paper: https://arxiv.org/pdf/1608.05134v1.pdf . Systematic error is still there.

Speed of light will remain constant, no doubt, so observer need to be far away to feel difference, otherwise it will be affected by wave, with his instruments and clock. It's why 2-4km arms are able to pickup temporal signal, while smaller setups are able to pickup thermal noise only.

PS.

Not sure that I will survive for so long, because of war with Russia — next week will be hard for me. :-)

⬐ acqq

It's a LIGO paper that you link now but it doesn't support any of your old claims, sorry. I still have an impression that you don't understand the physics, especially as you claimed before the "variable speed of light," it looks that you throw around something you remembered but never understood. So I'm more interested what's that "war with Russia"? Why next week? Is there a new conscription wave in Ukraine going on? I thought this was the latest state, only professionals:

http://www.worldbulletin.net/world/179487/ukraine-removes-la...

⬐ lisivka

English language is foreign for me and physics is my hobby, so you can safely assume that I'm noob in physics and use plain English and simple explanations. I need much more time to read in English that in my native language, especially in areas I'm not familiar with. I cannot just look at page and understand it, like in my native language.

Yep, it was not LIGO. LIGO uses Michelson inteferometer, while I'm looking for Sagnac interferometer results. As far as I remember, I started with that article: https://arxiv.org/pdf/gr-qc/0401005v3.pdf , then started searching of articles about rotation sensing mentioned in the article. It looks like that it: http://porto.polito.it/2460498/1/G_GranSasso_18.pdf (or a newer paper).

I looked at FIG. 10: The rotation rate of the Earth measured with the G ring laser as a function of time. Averaging over 2 hours was applied to a corrected dataset, where all known geophysical signals have been removed

But their measurements were done with up to 1E-11 accuracy, which is just not enough, because (IMHO) signal will be 10-100x weaker than gravitational wave, so, IMHO, 1E-21 accuracy is required. So my comment, which started that discussion, is just wrong. :-(

About war: war is still here. We are switched to professional army (hence no new conscription) and situation is stable enough (1-7 killed, 3-15 injured every day). Crimea is still captured. Next week will be hard because I will have meeting with my killers. But, after 2 month of preparation, I forgot about one small but important detail, so I am basically unprepared now. Unfortunately, I cannot stop my play because I want to free Crimea next year, and lot of people are already involved, and contact with Russians is important in this case, so I will try to improvise, like before, when I was unprepared. I will delete that text tomorrow.

⬐ lisivka

I cannot edit previous message, so let discuss a bit further. I'm sick, has high body temperature and unable sleep anyway.

To develop intuition, first you must understand that we are not moving through space, we are propagating through space, because we are waves. Actually, nothing is moved, hence no drag between material objects and space.

I will use video above as example. If you measure speed of sound in water between waves around droplets, you will found that speed of sound is constant, regardless of speed of droplet, because water is not moving at all. Water is contracting and expanding in place. We can perceive «lower» speed of sound in water in case of really big waves, because distance to travel will increase slightly. This is how gravitational waves are caught. Otherwise we are out of luck: we are counting waves to measure distance and time, and that count is not changing when space contracts and expands.

So the only two solutions I see to prove that space is real thing, like water, using waves only, is to:

1) cool vacuum below 0K — cooled vacuum will have slightly different speed of light (someone in USA is already working on that, shortly after discussion about „frozen vacuum“ at HN ;-). It's possible to cool or heat water using acoustic, but we are propagating through space, so cooled vacuum will be left in place while we will propagate away. Hard task. Can be done in interstellar space if ship will be able to stand at same place, or if large enough setup will be used quickly.

2) measure tiny asymmetry of front vs back of pilot wave using Sagnac effect to show that there are small deviations between predicted values and actual values, which are varying over year, as direction of movement and our position in Solar system changes (Solar system already had that asymmetry as measured by Voyagers). I saw (or I think that I saw) paper with exactly that information: experiment with large Sagnac interferometer conducted for over year with high precision which was focused on these deviations, but I still cannot find it. :-(

⬐ lisivka

Notes to myself: Lense–Thirring field, GINGERino project.

⬐ TheOtherHobbes

The "Doesn't matter" argument is nonsense.

Of course it matters. Your ontological beliefs define the questions you feel you're allowed to ask and the kinds of experiments you will design.

Copenhagen is just as much "at the boundary between physics and philosophy" as any other interpretation is.

The foundation of QT has been stuck for almost a century now. There's been a lot of detail filled in, but no truly fundamental movement towards answering the hard questions - what does quantum collapse really mean in physical terms, and how do you get from QT to relativity and back again?

What's so terrible about supporting alternative views that may shed some light on those questions?

Physics is ontology. There is nothing else involved. If you're going to pretend the true nature of reality is either irrelevant to physics or is somehow mystically unknowable, you may as well stop doing science altogether.

⬐ acqq

I'm very sure that as soon as you make any useful prediction from your favorite interpretation you'll get a Nobel prize (and then it would be a real discovery in physics and not a philosophic talk) but nobody produced anything from these interpretations up to now, except maybe getting paid for doing a non-physics work. To me it sounds only like a philosophy question when you write "what does quantum collapse really mean in physical terms" and that "really" exposes it. To compare, there's no "real meaning" in the existence of atoms, electrons and them making molecules, but we still know it makes calculations of chemical reactions obvious. What does it "really" mean? It doesn't matter, they exist, and behave as they behave. What does it "really mean" that the electrons exist can be pushed through the conductors? It doesn't matter if you formulate the question like that, but without them existing, I wouldn't be typing this on the computer, I wouldn't even be sitting on my chair etc. Even more profound, without the electromagnetic force existing there would be no stars and no galaxies. We know that because physics. You can talk about the "meaning of it" but you won't make any discovery unless you actually do some physics.

⬐ lisivka

It's looks like we are talking about differences of use of physics in practice versus advancing of physics as science. No doubt, if I will need to calculate something, being paid for that, I will use proven formulas. Totally agree with you at that point.

However, current major theories are in stuck, they cannot explain what we see, because now we have more data. So it is better to look for something else, which will explain everything we know already and more.

⬐ acqq

The theories aren't stuck, the existing ones cover everything we can measure, and that is amazing. Once the experiments make any new discovery which wouldn't match with the current theories the changes will be needed. So if you want the faster progress, support the experimental physics and the advancement in astronomy, don't repeat the talk of philosophers who do the equivalent to "how fairies really dance on the pin."

But don't forget: Einstein didn't disprove Newton, Newton's formulas are just a good approximation under the circumstances that were easier for us to observe. So most of what we now know will also remain as a "set of simpler models", as it is based on the valid experiments.

⬐ lisivka

Yep, field is covered by formulas with pretty high accuracy. AFAIK, the only practical field when correction is needed is GPS satellites, but correction is extremely low. However, our vision is moot. Video above just opened my eyes.