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There are no particles, there are only fields (2012) (arxiv.org)
294 points by monort on Aug 28, 2016 | hide | past | web | favorite | 199 comments



This only clicked for me a few weeks ago, but it finally gave me an understanding of the Higgs field, and the Higgs-boson.

So the Higgs field is everywhere, like the electron field and the electromagnetic field (all elementary particles are thought to have their own field, as I understand it).

As excitations of one field (electrons etc) interact with the Higgs field, they experiance a kind of drag and this interaction gives them mass.

So how about this Higgs-Boson then? Well if you produce enough energy, like smashing two protons together at huge speeds, this energy is released and some of it ends up in the higgs field, producing an excitation of the field, which we detect as the Higgs Boson. It's unstable and quickly releases it's energy which dissipates into other fields, producing more excitations which we see as more particles.

Before I understood this, I was trying to work out how if the Higgs-Boson was responsible for mass, why it needed so much energy for it to appear. All makes sense when you think about it as a field.


The professor I wrote my diploma thesis at said to me: quantum fields and the corresponding operators are just mathematical crutches because that stuff can't be described otherwise.


If anyone is interested in the mechanics of the higgs field / basic quantum mechanics in general, I found this lecture to be an excellent explanation:

https://www.youtube.com/watch?v=JqNg819PiZY


And in another 100 years or so, this will finally make it to textbooks...

Quantum field theory is weird, but there are much more compelling analogies in classical world than particles. (Feynman was a fan of particles, but I presume he was aware of the problems with this representation).

When you speak of fields and wave packets, you eliminate the uncertainty principle, and double-slit experiment is no longer a paradox — no small feat to achieve.


> Quantum field theory is weird, but there are much more compelling analogies in classical world than particles.

As a teen I read a book by Robert Anton Wilson that made an interesting point. We have experiments showing wave-like and particular-like behavior but all we have is that data and we can accept it at face value without having to impose the idea of a wave or a particle on it. "Waves" and "particles" are, like you say, analogies.

There's no particular reason the phenomena can't behave like both, and, in fact, they do. It's only a paradox if we choose to analogize. We don't have to.

As Korzybski said "the map is not the territory." Trying to resolve wave/particle duality is trying to impose one of two maps from other territories to a new one.


Well, we still have the fact that e.g. light is quantized on emission (photoelectric effect) and yet behaves continuously in the double slit experiment. I don't think you need particular preexisting concepts of waves and particles for this combination to be surprising.


It's just the same issue at another level. There's no reason that something can't have both properties. The issue is that it jars our preconceptions, which are formed from the things we've encountered so far. We want to understand things in terms of what we've seen. That's a basis of analogical reasoning.

It's kind of like the "monad tutorial" problem in software. Everyone tries to reach for analogy for that computational structure. Although there are some decent ones, in the end, people who work with monads just have to accept the monad laws (sort of a parallel to the data that physics has on quantuum phenomena) and eventually they develop a sense of what they are independent of cafeteria trays and burritos ( http://codetojoy.blogspot.com/2009/03/monads-are-burritos.ht... )


> As Korzybski said "the map is not the territory." Trying to resolve wave/particle duality is trying to impose one of two maps from other territories to a new one.

As a CS graguate, I would call it the halting problem. A mathematician would refer to the Gödel's incompleteness theorems. No formal system without paradoxies can be used to prove all true statements.


Whilst that may be true until you can prove that that applies to this particular problem it doesn't provide any reason why the typical approach to resolving dualities should apply. Come up with a super theory that contains them both and shows them to be manifestations of a common phenomena.


That's not true. The paradox exists, and it's because particles behave experimentally like particles, and like waves, and the two models are both correct in certain circumstances, depending on intuitively irrelevant details like taking extra measurements of the phenomenon.


The paradox exists because of our choice of models, and would not exist in other models if different choices had been made.

In other words, as michaelfeathers said, "the map is not the territory."


Technically, then, there are no fields either - claiming that fields are real because the field model matches experiments better, commits the same mistake of taking the map as real, as when we said that particles are really there. As in Kantian noumena, we can't know the territory, we can just build more useful models.


Exactly. Thinking about it more. Imagine we came at it from the other direction. All we know are quantum phenomena and then we encounter this human-scale world. We would be amazed and stunned by things like billiard balls that behave only half like quanta.

I'm surprised this way of seeing the world isn't more wide spread. My opinion is that it should be among people who have a deep interest in science.



Yeah, I'm not sure why you got down-voted. In the 1890s people that everything was a wave but then phenomena like wave function collapse and the quantum Zeno paradox were hypothesized and observed. To combat this you can introduce mathematical tricks like delta functions but this more of a hack.

Perhaps, the biggest philosophical problem with waves are their integration requirements and the potential for such iterations to exceed cosmic speed limits. When the function is continuous a perturbation at one end must effect the other end.


He's downvoted because he doesn't seem to get what the entire discussion is about, which is on a higher level. Instead he is caught down in the "lesser models". Whenever you have a paradox, like wave-particle duality - but also the "French paradox" in nutrition, it's not because there really is a "paradox" in the universe, it's because the way you look at it is too limited, and if you find a better view you will see there is no paradox. That doesn't make the paradox-creating models untrue - in their context, but we have gone beyond them. That's the subject of the submitted link!


I think the down-vote happens, because he's argumenting too concrete for the question.

I don't know much about physics, but my take on this is:

First you model reality with waves and particles, then you see that particles can behave like waves and vice versa. The next step is to model reality with something different that can behave like a wave AND a particle and suddendly there is no paradoxon anymore.


That's how I feel about quantum physics. Just fuzzy waves interacting randomly with each other, exchanging some quantities and reshaping, sharpening or blurring each other.

The fact that some of the energy and momentum exchange are governed by similar rules as two billiard balls bouncing from each other is pure coincidence (or just effect of the fact that round macroscopic objects behave like very sharp quantum waves).


I tend to think of it as a big ball of pure state. The field has both wavelike behaviors and quantized interactions. And even then, a field is only a model of the underlying state. This is why we can meaningfully talk of different fields independently even though there's only one underlying state.


I tend to think of it as unlimited amount of compute efficient at random intervals. Infrastructure will never be perfect, but it can be somewhat predictable when it is.


however it is quite difficult to explain the photoelectric effect purely (or at least clearly) in terms of waves.


I must admit I can't see any particular difficulty which would make the photoelectric effect more difficult to describe in terms of waves than other quantum phenomena.


fair enough; merely pointing out it is difficult for many others - it is subtle enough that it 'fooled' both Einstein and Feynman.


It's just a photon wave interacting with electron wave that's wrapped around nucleus, exchanging portion of energy and momentum and reshaping electron wave (unwrapping it). Nowhere the is actual need for bouncing balls. Just part of this process is governed by bouncing balls equations and since we had Newton and Bohr earlier we'd rather think about it as bouncing balls behaving bit strangely than waves obeying some of bouncing balls laws.


The salient point here about the photoelectric effect is not a pre-existing mental image of bouncing balls, but being forced to explain the fact that decreasing the intensity (amount of light) of monochromatic light doesn't produce electrons with lower energy (only changing the light's color/wavelength does that). This cannot be explained with classical waves; less light waves would produce lower-energy electrons.

now we can start talking about wave-packets, but then we staring to blur the lines between what is the difference between a particle and a wave-packet.


Yup, neither particles nor waves fit the quantum world completely, but people chose to think about all this as strangely behaving particles, not strangely behaving waves which would be much easier because there would be no need for collapse of probability distribution to a particle and concept of same particle being in multiple places as waves could be naturally more blurred or more sharp.

Ultimately it doesn't matter because math is the same.


How does speaking of fields and wave packets eliminate the paradox in the double-slit experiment? Particularly, the part about how when detectors are placed on the slits there is no interference pattern.


The trouble with explaining the double slit experiment with spread out waves is the electrons hit the screen at points leaving you to explain how that works. Video of it happening https://www.youtube.com/watch?v=ToRdROokUhs


Because charge is quantized, and not splittable.

Once it interacts with something all of it gets "sucked in" to one spot, and the entire electron interacts. The exact place it does that is randomized with varying probability at different spots.

But once a place is "picked" all of the charge goes there.

It's the quantization that is fundamental, and it's the quantization that makes fields look like particles, not the other way around.


If I understand correctly, there's currently no explanation of how one electron gets picked out of all the gazillions of electrons available; am I correct? Would that just be considered a fundamental randomness in nature?


I don't understand your question, can you rephrase?

In the experiment here they fire one electron at a time, so you don't have to pick one electron. Rather the final location of that electron is what's random.


When you fire a photon on a wall and see a blip, the blip is the location of the atom that had the electron that absorbed the photons energy (The electron that interacted with the photon).

Presumably there are gazillion photons. Presumably they all want that photons energy. Presumably the photon is stretched out in space so it sort of "touches" all of them. Yet, only that one electron got lucky.


That's the question: how is the location picked?

You roll a fair die, 1-6. It lands on 4 this time. Why 4, and not 5? How was the 4 chosen? In classical mechanics, it's a horrendously complicated but fundamentally simple computation. In QM, no one knows.


Why the need for full determinism? Unlike Einstein, I have no problem with God playing dice; this allows for free will, among other things (randomness is in the [computational] eye of the beholder).


Why allows it for free will?

Consider those two situations:

A: You know everything and decide about something based on all the facts known to you

B: You know everything and decide about something based on all the facts known to you plus the result of a random generator

Why is B more "free will" than A? In B there is simply another fact which is beyond your control which modifies your decision. That doesn't makes your decision more free than A, you simply have an additional "input" to consider.

One may argue that B is more free than A because in principle another person with the same knowledge as you would know what's your decision is in A but won't know it in B because of the influence of the random generator. But that doesn't makes B more "free", it only makes it a bit more unpredictable. But in reality it's impossible to always know all facts leading to the decision in A so both have similar unpredictability.

In fact I would consider only A as real "free will" because even if your decision is only determined by (external) facts, it's still all your reasoning based on your beliefs, experiences etc while in B there is a determining factor outside your reasoning you depend on which makes your decision less free (because you may have to decide for a sub-optimal outcome because you're forced by the random generator to do so).


The Many Worlds Interpretation plus Sleeping Beauty can directly explain this.


Pilot wave theory :)


Isn't that theory rooted in the particles view of the universe? It's totally at odds with this paper, it seems to me. Is it not?


aka Bohmian mechanics, aka the de Broglie-Bohm interpretation of QM. It definitely doesn't get enough serious attention IMO.


It's been getting more and more attention especially since many recent QM simulation experiments kinda show that pilot waves are a real phenomena.


"Classical" states (a single dot on the screen instead of an interference pattern) are created through the measurement process, which involves entanglement and dephasing: The small quantum system (the electron) first becomes entangled with the macroscopic system (the photo film and everything coupled to it), then the phase coherence between the individual eigenvectors of the electron gets lost due to the coupling with a large number of degrees of freedom in the measurement system.


Exactly! But how do you explain that to the public in a way that doesn't sound like a bunch of hocus pocus?


I know, it's difficult. I wanted to write an article about this for a while, guess I have to get up and just do it.


If I understand correctly, it interacts with an electron that's more or less locked into a small place around an atom.

It doesn't just hit that one point; the blip represents the location of the atom that had the electron that absorbed the photon.

Just my two cents


Calling an electron "a particle" presumes that it is always localized somewhere, and has a defined travel path. But it doesn't; when measurement happens, it is localized at some specific point, but that's all.

Something that can be localized only at interaction points, and not elsewhere, is not a "particle", it's something else. Perhaps "field excitation", like a hot spot in a microwave.


But thats the catch 22. Macroscopic objects are only classical because they have their hand in the river of interaction non stop. Only the smallest butterfly can manage to remain coherent and uncollapsed.


Each probability field ends up interacting with a single point on the screen.


This is just the copenhagen interpretation which says nothing about the physical ontology of the light before it ends up as a point on the screen. Unless you are saying the probability amplitudes are physical things-in-themselves rather than calculational models. (side note - Feynman did not think of a probability amplitude as a physical thing-in-itself)


But did Feynman think anything as a physical thing-in-itself? Feynman repeatedly argued that that physics is whatever the instruments measure, generalized by whatever computational models match the measurements, and he was happy to analogize to metaphorize whenever convenient to describe an aspect of a phenomenon ("photons jiggling")


One good thing about Feynman was he was always clear on what was experimentally observable and is what it is and what is theory where you can make up anything that fits the experiment.


It fixes other things as well. A point particle like an electron has an infinite charge and an infinite energy.

Except obviously it doesn't.

If you make the electron a field instead of a point all of that goes away.


What do you mean about the uncertainty principle? The article here still relies on it.


It reduces to the standard Fourier uncertainty: if you have an energy packet (gaussian e.g.) of a certain width and wavelength, the shorter the width, the more uncertain your wavelength will be.


I think he means if you model things as waves the uncertainty comes about naturally. For example if you send a wave through a small hole so you know it's position accurately on two axes then that causes it to diffract out so you don't know it's direction/velocity along those axes.

(sort of illustrated: http://physics.stackexchange.com/a/61475)


Sean M. Carrol always mentions this fact when he talks about QFT, which can be very entertaining like this one from 2013

"Particles, Fields and The Future of Physics"

https://www.youtube.com/watch?v=gEKSpZPByD0

(Audio starts at 19 sec, Lecture starts at 2:00)


Just read this post from him recently, which, along with the referenced paper, was pretty enlightening: "Space Emerging from Quantum Mechanics" http://www.preposterousuniverse.com/blog/2016/07/18/space-em...

paper "Space from Hilbert Space: Recovering Geometry from Bulk Entanglement": https://arxiv.org/abs/1606.08444


Sean Carroll is very captivating and entertaining speaker. Thank you for the link.


Interesting that the paper starts by attacking "quantum mysticism". Seems to me that the argument it's making renders quantum mysticism easier to believe rather than harder. The concept of particles, after all, appeals to our Newtonian "billiard ball" intuitions; particles are the essence of locality, and our intuitions suggest that a particle universe should be deterministic.

On the other hand, if particles are epiphenomenal, and everything is really infinite fields which only have a certain probability of interacting in certain ways, it seems like, intuitively, there's a lot more room for consciousness to influence those fields in a nonlocal manner. No?

Just playing devil's advocate here :-)


Not at all. Fields are a precise mathematical model that could, in principle, be simulated on a computer to arbitrary precision. There's no room for mysticism or "consciousness" nonsense.


>in principle, be simulated on a computer to arbitrary precision.

However, for any finite precision, the simulation is valid for only a finite time -- and the precision required to guarantee a certain accuracy for a given time increases exponentially:

http://en.wikipedia.org/wiki/Lyapunov_time

That means that finite-memory simulations are limited even in principle (even for a computer whose memory is as large as the Universe, there is a rather short limit on prediction!)


I don't understand the implicit relationship you see between the regularity observed in our reality and consciousness. Why can't one go with the other?

That consciousness nonsense has you reading a post and reacting to it.

The simulation argument is silly, because all it does is "postpone the explanation" as Alan Watts joked in "Time and the more it changes". If our universe can be simulated, then so what? It is the same puzzle with the Matrix as Jed Mac Kenna explained in his famous trilogy: in Matrix 2 or 3 (don't remember), Neo escapes from his "simulated" reality, only to find himself in another. What if the other one is simulated? The movie just stops there, and Neo isn't actually free. He just switched one reality for another.


Parent comment was talking about "quantum mysticism". Which is a set of quasi-religious beliefs that have no justification whatsoever in scientific theories and often misunderstand distort real science a great deal.


> Fields are a precise mathematical model

Let's not get ahead of ourselves here; unless you've solved a millennium problem!


Which one is it?


Agree with the first part but I also believe that physics can't explain the hard problem of consciousness.


Nothing can ever explain the "hard problem" of consciousness. It's nonscientific nonsense that's totally disconnected from reality.


That's a convenient way of dismissing the problem, but since you didn't make any coherent arguments, we can safely ignore you. The hard problem simply asks how, for example, our subjective experience of color comes about, and why we should have that experience at all rather than nothing. If that's disconnected from reality and nonscientific, then you don't understand the meaning of those words.


I don't need to make an argument, because there is nothing to argue against. I don't accept that "the hard problem" is a real problem, or even a coherent thought.

It seems quite obvious to me that "consciousness" is caused by complex algorithms being run by the human brain. But even if science shows that is false, there will always be another scientific explanation. Even if souls exist, they would have to interact with physical matter to work, and so, in principle, could be studied scientifically. Observed and experimented with. And in principle, we could deduce the logical rules that explains their behavior, and build artificial souls, or simulate souls on a computer. I think "souls" are an insanely unscientific belief, on the verge of flat Earthism, but at least it's possible in principle.

The hard problem asserts the possibility of something much, much weirder than the existence of souls or physical laws we don't understand yet. It asserts the existence of a universe which is causally disconnected from our own. Meaning the things that happen in that universe, can never influence anything that happens in our universe in any way. And that our "consciousness" exists in that universe, and not in our own. More on the absurdity of that proposition here: http://lesswrong.com/lw/nqv/zombies_redacted/


>It seems quite obvious to me that "consciousness" is caused by complex algorithms being run by the human brain.

Why "consciousness" in quotes? You don't have it? Are you a bot? And where is the obviousness from? Just this is how problems usually go down, so you assume this one will go the same way?

>But even if science shows that is false, there will always be another scientific explanation.

I mean, science is pretty cool, and having some faith in it is fine, but why this much? Why say always when it doesn't have one now?

> Even if souls exist, they would have to interact with physical matter to work, and so, in principle, could be studied scientifically. Observed and experimented with. And in principle, we could deduce the logical rules that explains their behavior, and build artificial souls, or simulate souls on a computer.

Yes, if they do interact with the outside world, they can be studied by science as much as they do interact. But how do you study them where they don't, where they just provide qualia and the outside world doesn't look any different? Isn't science about reproducible empirical evidence, which qualia don't provide?

>hard problem is weird

Well, you using consciousness in quotes as a, hopefully, conscious person is also weird. I don't see how you avoid the disconnectedness when you see that no science can even know whether you're conscious or not.


>Why "consciousness" in quotes?

Because I'm not convinced "consciousness" is a meaningful concept that actually exists. No one has the slightest idea how to define it or what it really means, so it's a very vague non-precise term at best. But I accepted it for the purpose of this discussion.

>where is the obviousness from? Just this is how problems usually go down, so you assume this one will go the same way?

Because there is abundant evidence that the brain is the mind. Brain damage causes mental impairment, and we can observe it through fMRIs and interact with it through various experiments. We can reproduce some behavior from computer algorithms somewhat similar to biological neural networks, and I don't see why we won't eventually be able to reproduce all of it. Modelling the brain computationally is a huge field of research that has made a huge amount of progress in recent years. Not to mention neuroscience in general, which has produced a huge amount of knowledge.

But beyond that, it would be really strange if the physical laws that govern are universe are magically invalid in this one specific place. We know from evolutionary theory that humans aren't special. We are just the product of random mutation and natural selection, from the first accidental self replicators. There is nothing special at all about humans, we are just regular animals made of physical matter, that have been selected for intelligence.

Of course it's possible this is all wrong. It's also possible that the Earth is really flat, and evil gods are manipulating all our observations and distorting photos taken from space, etc. But anyone who believes that is crazy.

>Yes, if they do interact with the outside world, they can be studied by science as much as they do interact. But how do you study them where they don't, where they just provide qualia and the outside world doesn't look any different?

"Qualia" is also a vague imprecise term. If this "consciousness" stuff actually interacted with the physical world, then we would, in principle, be able to observe it. But if it doesn't, then it's irrelevant to us. Totally disconnected from anything you can ever observe or experience.

If you say "I am conscious", then some chain of events caused that event. Perhaps a thought formed in the neurons of your brain. In principle we could study your brain and see why it believes it is conscious, and what things are causing that behavior. If it's caused by "souls", then, at least in principle, we could study the behavior of the souls, and observe them interacting with physical matter to make you say words or think thoughts.

Seriously read the link I posted, it goes into that in great detail.


Evolution shows that there is something to consciousness that is beyond current physics, especially if we accept the world is not massively anthropocentric (biocentric?).


Evolution doesn't show that at all. I think it shows that we weren't created by some kind of god, but more of an accident. If that's the case, it makes it much less likely that there are souls or other supernatural-ish explanations for consciousness, and so we are much more likely to be simply physical matter.


Rocks and unicellular life are simply physical physical matter, and they are not conscious. We would not have evolved to be conscious, in a coherent manner too, if there was no benefit to it.


>Because I'm not convinced "consciousness" is a meaningful concept that actually exists. No one has the slightest idea how to define it or what it really means, so it's a very vague non-precise term at best. But I accepted it for the purpose of this discussion.

Pick your poison. http://plato.stanford.edu/entries/consciousness/#ConCon

If you deny that you experience qualia, well then the core proof for it is gone. At which point we might as well put the whole discussion in quotes.

Still, what makes the definition different from the definition of matter? Do you deny the existence of matter also?

>Because there is abundant evidence that the brain is the mind. Brain damage causes mental impairment, and we can observe it through fMRIs and interact with it through various experiments. We can reproduce some behavior from computer algorithms somewhat similar to biological neural networks, and I don't see why we won't eventually be able to reproduce all of it. Modelling the brain computationally is a huge field of research that has made a huge amount of progress in recent years. Not to mention neuroscience in general, which has produced a huge amount of knowledge.

You mean, abundant evidence than the brain seems to interact with the mind. I think it's inherently tied with the brain too, but I don't think there's anything that bridges the gap and makes the brain = the mind.

>But beyond that, it would be really strange if the physical laws that govern are universe are magically invalid in this one specific place.

Sure, and yet we experience the mind and it's nothing like the things we measure with science. Shouldn't that shake your faith in the universal intelligibility of all things under science?

>Of course it's possible this is all wrong. It's also possible that the Earth is really flat, and evil gods are manipulating all our observations and distorting photos taken from space, etc. But anyone who believes that is crazy.

We experience consciousness. Again, if you don't, then perhaps I'm talking to a bot, at which point I don't deny that I won't be able to show to you what consciousness is. It does have to be experienced.

Your comparisons with flat earth and manipulative evil gods are wholly uncharitable. Science supports the proposition of a round-ish earth; it doesn't of a flat earth. Science doesn't say anything about the existence or lack of existence of consciousness, your intuitions about the future progress of science do. Don't you see the difference?

If this invokes craziness for you, then perhaps you should think longer about what science is and what it says, and compare that with your intuitions about what you think it will be.

>"Qualia" is also a vague imprecise term. If this "consciousness" stuff actually interacted with the physical world, then we would, in principle, be able to observe it. But if it doesn't, then it's irrelevant to us. Totally disconnected from anything you can ever observe or experience.

Funny. It actually is just about the only thing we experience of the outside world. There are people working on the best definitions we have for qualia - if they're not satisfactory to you, do you propose we stop discussing them even though we experience them?

I mean, maybe we should stop discussing unexplored problems in science too.

>If you say "I am conscious", then some chain of events caused that event. Perhaps a thought formed in the neurons of your brain. In principle we could study your brain and see why it believes it is conscious, and what things are causing that behavior. If it's caused by "souls", then, at least in principle, we could study the behavior of the souls, and observe them interacting with physical matter to make you say words or think thoughts.

I mean, I get it, you think it's linked with the brain. It probably is, but we only get reports from people saying it is, that's one thing. The other thing is that even if it is linked with the brain, it doesn't mean that the brain = the mind.

Do you have a different source for the argument? No offense. Yudkowsky isn't an expert on philosophy of mind or philosophy at all, and I don't know of any philosophers who take him seriously. I skimmed it and I'd read it if it was not so long, but I'd prefer a SEP article or something else trustworthy in this case as it's such a long read.


> Science doesn't say anything about the existence or lack of existence of consciousness, your intuitions about the future progress of science do. Don't you see the difference?

I didn't say science said anything about conscious. I said that there is zero scientific support for dualism, or anything like it. Those theories are incredibly unscientific. You are making very strong claims that have zero evidence.

But even if dualism is true, my larger point is correct, that we could study the "souls" if they interact with physical matter. We could learn exactly how they work, and perhaps build artificial ones from physical matter. And if they don't interact with our universe, then they are irrelevant to us.

This discussion started about quantum mysticism and whether science could ever explain consciousness. To assert something is "beyond science", even in principle, is ridiculous.


>I didn't say science said anything about conscious.

Well you did say:

>If this "consciousness" stuff actually interacted with the physical world, then we would, in principle, be able to observe it. But if it doesn't, then it's irrelevant to us. Totally disconnected from anything you can ever observe or experience.

I mean, how am I to read it. It reads like you're denying what you yourself experience if it isn't registered with scientific techniques.

We are yet to receive an actual datapoint from someone's mind, and it doesn't even seem like we know how we could do that. So all of your talk about scientific and not scientific theories seems to me a category mistake.

There's no scientific support for dualism. There's no scientific support for physicalism. Science can inform them, but we don't have scientific datapoints supporting either one. We merely have rational, or, if you will, philosophical arguments for them. I think I have made arguments against physicalism, namely, that we have no scientific method of accessing the contents of a mind, and we have no idea how to go about doing it.

What I'm hearing from your arguments is just your intuition telling you that all things are or will be intelligible under science, and having faith is fine, but at this point you have to know that this is the most grandiose claim of all in this discussion.

And to be specific, if dualism is true then we can't study minds with science. Science is about corporeal bodies, minds under dualism aren't corporeal. We can study what they do to the physical world, and guess how and when they appear to be linked with it, but we can't pry into the actual contents of the mind, not with science at least. Because under dualism, they aren't physical.


People like you are part of the reason it takes science so long to move forward in areas that contain mysteries. You say there's nothing to argue against, yet you are making an argument anyway, proving that there is, in fact, something to argue about. You are arguing against a very strange and specific version of what is called "the hard problem". At the heart of the hard problem is a simple question: how can we causally explain conscious experience? It's very convenient to say "oh it's just complexity. Done." But that doesn't solve anything and it's not particularly helpful. It leaves many questions unanswered. Why does consciousness seem to be unitary? Why does only a small portion of the information reach conscious awareness? Whence the feeling of free will? You should feel free to ignore these and many more questions, but to dismiss the inquiry entirely is, bluntly, stupid.

I've never argued for souls or anything immaterial, I simply think we haven't fully understood or explained the nature of consciousness.


Ok my terminology may have been wrong, fine. But this thread started off about quantum mysticism and whether or not physics or science could ever explain consciousness. I strongly object to that. And the people that promote views like that are the kinds of people that talk about "the hard problem of consciousness". Materialists generally don't talk about it or find it that interesting.

You're right that I don't have a complete explanation of consciousness, and of course no one does. But if we stop talking about the really crazy theories like epiphenomenalism, the answer must be that it's some kind of algorithm. A lot of people reject that idea completely with really bizarre arguments, hence my hostility.


I understand where your hostility comes from, but dismissing consciousness on the terms that there are so many people who use that term to make stupid claims and crazy theories is just taking the easy way out.

Has any materialist seriously considered what exactly is this material they so take for granted? When you really scrutinise it, you see that it can't be found. All you can find are models - mental representations of what it is. Does that mean that nothing exists? Of course not - you know that's not the case. This knowing is the hard problem, and you are right that it will never be solved by science, but not because it doesn't exist, but because the ability to do any science at all requires an "observer" and an "observed", and consciousness precedes both these concepts. It is the knowing in which all models can be experienced - how could something that includes all ever be explained by anything within it?

I find it quite ironic that materialists are so opposed to dualism, while at the same time being so entrenched in it. Not in the sense of "mind vs. matter" or "soul vs. body" (they managed to outgrow that naive philosophy), but in a sense of "knowing" that everything is matter while overlooking the fact that a distinct and separate knower has to exist in order to see this matter. That's as dualist as it gets...


Well it is nonscientific, it's outside the bounds of science. Doesn't mean it's irrational.


What do you mean it's outside the bounds of science? Surely there can be a physical explanation that we simply haven't been clever enough to discover yet? That's all I'm saying.


I mean that there is no known empirical method for receiving a datapoint about the mind. We can know things about the brain, we can ask people to talk about their experiences, but we can't receive the actual contents of the experiences.

Maybe we'll figure it out someday. That is probably a long way away though, and for now, the problem is for philosophy of mind, only to be informed, but not solved by relevant sciences.


Someday may be closer than you think -- https://www.nextnature.net/2008/12/scientists-extract-images...


Consciousness exists. Science either can explain it, or it cannot.


Presumably you're not familiar with the term the 'Hard Problem' of conciousness [0]. It's a specific supposition that there's something special about 'qualia' of experience that can't be explained by a physical model (or scientific explanation as you term it) of conciousness. There is considerable dispute as to whether the idea makes any sense or not and therefore if the 'Hard Problem' is even a thing. Which IMHO it isn't.

[0] https://en.m.wikipedia.org/wiki/Hard_problem_of_consciousnes...


It is a thing. We know how to study correlations between brain activity and conscious experience. The hard problem involves figuring out how brain activity causes conscious experience. Once we explain it (or, as in physics, have a convincing theory) it won't be a problem at all anymore. Saying that something that everyone experiences all the time "doesn't exist" is not a convincing theory.


> It is a thing. We know how to study correlations between brain activity and conscious experience. The hard problem involves figuring out how brain activity causes conscious experience.

Actually the hard problem is figuring out how anything can cause conscious experience/qualia. The insurmountable difficulty is explaining how first-hand knowledge can be explained with only third-hand knowledge. The only resolution for something like scientific materialism is to deny that first-hand knowledge actually exists, and consciousness is a fully third-hand knowledge system giving the illusion of first-hand knowledge [1]

[1] http://journal.frontiersin.org/article/10.3389/fpsyg.2015.00...


Sure...brain activity is included within "anything". Since brains are the only thing we know of that do this successfully, it's where people start.

Graziano has thought about this a lot, but his view is one of many that all have about equal explanatory power. Why would materialism/physicalism require that first hand knowledge not exist? If consciousness is explainable in terms of physical processes, then first hand knowledge would exist and be part of that process. Can first and third hand knowledge not coexist?


> Why would materialism/physicalism require that first hand knowledge not exist? If consciousness is explainable in terms of physical processes, then first hand knowledge would exist and be part of that process.

You cannot describe first-hand facts using only third-hand facts. This is the core philosophical dilemma in the hard problem of consciousness. Consider something like Mary's Room. What sort of third-hand description of "what it is like to see red" would describe the first-hand experience of seeing red? How can you actually capture data describing "what it is like"?

The only solution seems to be to deny that "what it is like" is first-hand knowledge at all, and that it is actually a set of third-hand facts that merely yields the illusion of first-hand knowledge, and so the hard problem reduces to explaining how this illusion comes about.


My question was, why is "denying first hand knowledge" the only solution? As you might know, there are several lines of thinking. Nagle, for example, might say that first hand knowledge absolutely exists, but it is "off limits" to anyone but the organism experiencing it. In that sense it exists and does not require us to say that it is only "illusions of third hand knowledge". On the other hand Dennett might say that once we have a full scientific understanding (as Mary would), we could in theory understand how to extract the first hand knowledge in an organism's brain and either modify our own brains to experience it or describe it so fully that Mary would know exactly what to expect when seeing red for the first time. I'm not sympathetic to Dennet, but there are other options than first hand knowledge simply not existing within materialism.


> Nagle, for example, might say that first hand knowledge absolutely exists, but it is "off limits" to anyone but the organism experiencing it.

If physicalism is true, then all facts must be reducible to the physical.

If everything is reducible to the physical, then the experiences of the organism are also so reducible and must have a third-hand description.

If experiences are not so reducible, then physicalism is false and no amount of third-hand knowledge can produce first-hand knowledge.

These are exhaustive and mutually exclusive options.

> I'm not sympathetic to Dennet, but there are other options than first hand knowledge simply not existing within materialism.

The meaning of first-hand knowledge in physicalism is different from the meaning of first-hand knowledge in other metaphysics. In physicalism, first-hand knowledge must be reducible to third-hand knowledge, and so it doesn't have a privileged ontological status, just like we don't ontologically commit to the existence of cars in quantum physics.

So first-hand knowledge cannot really exist in physicalism except as a useful label describing a specific kind of third-hand knowledge.


You are implicitly drawing a distinction between brain activity and conciousness. But if the brain activity is the conciousness, then there is no distinction. I'm not saying that our experience of things isn't a thing. I'm saying that it's not a distinct thing that's separable from the brain activity.


You said that you don't think the hard problem is a thing. The "hard problem" is simply a general question: how can we explain our subjective conscious experiences in terms of physical processes? That's a question which is well formed, interesting, and probably has an answer which we simply haven't been clever enough to find yet.


There's more to it than that though. David Chalmers who formulated the Hard Problem does not believe that subjective experience can arise from physical processes. Really. He calls it the Hard Problem because he thinks it's distinct from the Easy Problem of explaining how physical processes can constitute a thinking being. We haven't solved either problem yet, but Chalmers is distinguishing between them before we know what the answer even looks like. It his position that you can solve one (the Easy Problem) but that won't and can't lead to a solution to the Hard Problem. I think it will.


You are the first one in this thread to say "doesn't exist", yet you put it in quotes.

No one is trying to tell you that consciousness doesn't exist. The question is whether the "hard problem of consciousness" is a thing: that is, a well-formed topic of scientific inquiry.


"Isn't a thing" is synonymous with "doesn't exist". Pedantry aside, the existence of the hard problem and the existence of consciousness entail the same questions. The general question is simply this: how can we explain our subjective conscious experiences in terms of physical processes?


We're getting off topic, but it is at least worth considering just why it's described as a "hard problem", which is that science involves the observation (via human consciousness) of things in relation to other things.

But because consciousness is the medium of observation, it can't be independently observed relative to other things, thus the ultimate nature of consciousness can only ever be postulated, not objectively proven.


Objectivity doesn't have anything to do with observation, it is orthogonal.


> Consciousness exists. Science either can explain it, or it cannot.

More specifically, people claim the existence of consciousness. It can't be held as an absolute irrefutable by investigation. To do otherwise would be violating several basic concepts of epistemology, science and thinking.


I mean, this sort of scepticism is applicable if you don't have consciousness yourself. Do you not see, hear, smell, think or otherwise perceive?

Surely experiencing that yourself adds more weight to others' claims?


> I mean, this sort of scepticism is applicable if you don't have consciousness yourself. Do you not see, hear, smell, think or otherwise perceive?

The OP is suggesting that experience isn't first-hand knowledge the way it appears to be. Certainly he agrees that we appear to have first-hand knowledge, but this appearance is only a cosmetic illusion, a trick that lends some adaptive advantage. Something like: http://journal.frontiersin.org/article/10.3389/fpsyg.2015.00...


Bingo.


Consciousness exists as much as the color blue or the soft hum of a clean sine wave — it's qualia.

Our interpretation of the physical world doesn't necessarily exist anywhere but in our minds.


Yeah, it's nonscientific, out of the scope of science. I'm an extremely sceptical and scientific-minded person but I'm also fairly sure about this.


The pythagoras theorem is also unscientific. Your point betrays ignorance of what science even is.


The pythagorean theorem could easily be tested empirically. In fact it was probably discovered through empirical observation as many ancient mathematical facts were.


Where do you put that test, though? The theory itself is not empirical, nor is the proof, nor is anything used in the theorem.

Even if the idea came through empirical means, the theory itself isn't empirical.


The pythagorean theorem predicts how long the hypotenuse of a right triangle will be, based on it's sides. That's quite easy to test empirically. You take a ruler out and draw a right triangle. It's nice that we have a solid mathematical proof for it. But if the axioms of geometry were somehow thrown into question, no one would question pythagoreans theorem because we know it works and have tested it countless times. It has more evidence than entirely scientific matters like the law of gravity.


And all that empirical stuff doesn't matter when it comes to the actual theorem. The proof does. As is the case with tons of math that don't have empirical evidence.

That's why it's math and not science.

My original point was that calling a philosophical problem unscientific is like saying this ice cream is nonelectronic. It wasn't meant to be, it doesn't mean it's not good. Or in the case of mathematical theorems or philosophical problems, insightful.


I think he means consciousness as a factor in QM, not generally. I don't know for sure tho.


<ironic> right... and you also can simulate initial conditions to infinitely arbitrary precision as well.


  in principle
You're missing the point, which is

  no room for mysticism or "consciousness" nonsense
not anything to do with the limits of computation.


This article did get published in the American Journal of Physics, and there was some back and forth discussion also published in the Journal. Unfortunately, the published version and the ensuing discussion is effectively inaccessible ... they want 30 USD from me to read each published response.



Is any of it available on Sci-Hub, or be made to be available there?


Sources say: yes.

But I found Art Hobson's website, which includes the published paper and the published commentary

http://physics.uark.edu/hobson/publications.html


Even better, thanks for that link!


Generally I think the field idea is more plausible than the particle idea. But I think there are some things that the field can't explain yet (to my satisfaction at least). Why, whenever we measure the charge of an electron, do we measure the same value? Why not one half, or one third of that charge sometimes? After all, if an electron is just a disturbance in a field, why might we not capture just part of that field in our measuring apparatus?

This is of course trivially explained by the particle idea.


I don't know anything about the physics, but here's something field-related that seems particle-like to me. On a smooth manifold (which is a space that is "locally Euclidean" in such a way that you can do calculus), there is a concept of a smooth vector field, which is a smooth assignment of a vector tangent to the manifold to each point. While there isn't too much to constrain a vector field, there is an invariant: if you take all the places where the vector field vanishes and compute something called the "index" there, and sum up all the indices, you get the Euler characteristic of the manifold. Index is an integer quantity, and it roughly corresponds to how many times the vector field spins around while going around the vanishing point once.

You can smoothly deform vector fields through time, and there are different features you can notice: zeros of opposite index annihilating each other, zeros of opposite index appearing out of nowhere, and other sorts of combinations of zeros combining and splitting.

For the surface of a ball, the Euler characteristic is 2, so the sum of indices must be two, so it seems spheres must be "positively charged," if index and charge are actually analogous. For a torus, the Euler characteristic is 0, so the "charge" is neutral. For a plane, on the other hand, the theorem I mentioned doesn't quite work because it requires a compact manifold, but a vector field could have any total index (though there will be a virtual zero at infinity which always has the opposite index).

If measuring charge corresponds to finding the total index in a region of space, then maybe that's why it's only ever an integer.


The idea of the charge being some topological quantity is interesting and I think the mostly likely explanation. There's something similar with the electron spin that I don't fully understand. (If you rotate an electron once its wavefunction is negated, twice to restore it, I might have the details incorrect there though)


Saying that particles explain why electrons all have the same charge presupposes that all particles are identical, but why should that be? Your particle theory has to explain why all particles of a given type have the same property; or rather, why there are types of particles.

The field idea, as discussed here, actually explains why all electrons are identical: because they're all quantized excitations of the same field. It's the quantization that really does the trick, but after all that's how we got started here.


That's a good point, we would have to consider all electron particles identical.

Regarding field quantisation - why should the electron field be quantised?


If I understand it a free particle is not really quantised; it can have pretty much any wavelength. But when it is confined by boundary conditions (e.g. within an atom) we then get interference and reinforcement in the wave equations.


Boundary-induced quantisation does explain the limited set of acceptable/stable wavelengths around e.g. an atom.

However, what it doesn't explain, is why the amplitudes of such wavefunctions should be what they are. For example, why should the integral of the squared norm of the wavefunction for an electron be 1, if it is not a particle?


In fluids, we sometimes get discrete but dynamic structures. Those structures would not be stable without a certain base energy. That could explain it. For example, suppose an electron is a vortex.


I have seem some papers discussing the idea of an electron as a ring or vortex of electromagnetic energy. I believe the idea is still purely speculative though.


It can be said to be speculative, but if the model can explain everything in the world of phenomena, including things that are not explained by particle physics, then, by the same token, so can particle physics. What we need is for the theory to be put to paper and then simply confirmed by a lot of people. Then people will start to develop new technology with the things that it can explain and by that point no one would say it's not confirmed. But I have found that there are societal and psychological issues which prevent many people's confirmation of the basis of my supposition.


That actually makes a lot of sense to me. What with E=MC^2, antimatter explosions, generating new particles from collisions, everything.


I've been told by a lot of physicists and engineers to write a paper. I'm pretty certain it's correct. The theory can go much further and explains gravity.


Why do gliders (https://upload.wikimedia.org/wikipedia/commons/9/96/Animated...) always have a 'weight' of 5 cells? Why not 4 or 6?


Space itself cannot be quantized into a grid because it totally fails under special relativity.


I seem to remember reading somewhere recently that you can in fact quantize space in a hexagonal grid in a way consistent with quantum mechanics, but I can't find a link now.


quantization consistent with QM is tautology; issue is this can't be made consistient with GR. see raattgift's comment in thread.


citation?


Special relativity is defined by invariants on the Minkowski metric ds^2 = dx^2 - dt^2 using general coordinates and setting c to unity. This is a generalization of the Euclid metric ds^2 = dx^2. (In Cartesian coordinates and in 2d, ds^2 = dx^2 + dy^2).

Just as the Euclidean metric fails on a gridded plane where one would instead use the Taxicab metric (ds = \sum _{i=1}^{n}|p_{i}-q_{i}|), and the problem persists to higher spatial dimensions, the 3+1 Minkowski metric of Special Relativity fails on a discretized spacetime, and one would have to use a metric appropriate for whichever dimension(s) is/are discrete. Assuming it's not just the timelike dimension that's discrete, the Taxicab metric is readily generalized to small patches of 3+1 spacetime, just like the Euclidean metric.

The other part of Special Relativity is important here: the fundamental actions that are invariant under translations, rotations and boosts -- Poincaré invariance -- is impossible to fully recover from a spacetime that does not admit the Minkowski metric; the best we can do with a metric on discretized spacetime is where the discrete steps are extremely small.

The firm upper limit, from experiment and astrophysical observation, on discretization approaches the Planck length. [0]

There is plenty of literature about violations of the full Poincaré symmetry under discrete spacetime (especially violations of Lorentz invariance; the Lorentz group is a subgroup of the Poincaré group). example at [1]

Essentially, the problem is that in a discrete spacetime a boosted observer could see a Lorentz-Fitzgerald contraction acting on the minimal length, further contracting it. The ways around that are either extremely shaky as there is lots of conflict with experiment (e.g. fixing a preferred rest frame) or extremely subtle (e.g., UV corrections to the smooth Lie groups of the Standard Model or replacements for them that reproduce existing IR results e.g. by replacing the metric with an operator (but see also [0] again vs [3]).

Some further detail on Sabine Hossenfelder's blog: http://backreaction.blogspot.co.uk/2016/04/dear-dr-b-why-is-...

[0] http://arxiv.org/abs/hep-ph/9812418 [1] https://arxiv.org/abs/hep-th/0112090 but for contrast [2] http://arxiv.org/abs/1406.2610 and http://arxiv.org/abs/gr-qc/0405085 which shows that in a toy 2+1d model with a discrete spacetime, Lorentz invariance can be recovered by introducing non-local interactions; it is only suggestive with respect to our 3+1d spacetime, however. [3] http://arxiv.org/abs/gr-qc/0205108


Thanks for taking the time to type that up, the bits I understood were interesting and the bits I didn't have enough detail for me to do some reading. :)


Thanks for the great comment!


Are you suggesting an electron is a glider? :)


Well, sorta. I'm suggesting it's a stable pattern (like a standing wave) in some (maybe-)discretized field resulting as a natural consequence of simple locally applied rules. Its properties (mass/energy, charge etc) are fixed by the properties of the field.


The probably is continuous, but the actual 'coming into being' is quantized. The question thus becomes 'Why are things quantized?' and the answers to that are either 'because they are' or unscientific in their nature.


Quantisation does not have to be axiomatic however. Some things are naturally quantised, such as the frequency or wavelength of standing waves in a chamber of a given length, and likewise the energy levels of an electron in a harmonic oscillator potential or an atomic potential.


Here another physicist challenges Hobson for not respecting realism, and he has a pretty good come back:

http://physics.uark.edu/hobson/pubs/13.09.a.AJP.pdf


That was eye-opening, and not just with regard to the titular subject. I'd never thought of energy stored in fields as a consequence of energy conservation.


The abstract already lost me: "Thus the Schroedinger field is a space-filling physical field whose value at any spatial point is the probability amplitude for an interaction to occur at that point." But the wave function lives on the configuration space of the system: if you have $N$ particles, the wave function lives on $R^{3N}$. In what way is this a "space-filling physical field"? Admittedly I haven't had time to do more than skim the article; perhaps it's explained more carefully later on.

(Off-topic, but since this has come up a number of times on HN: this point is also where Bohmian pilot wave theory has never been wholly satisfying for me. If you accept the pilot wave picture, then the double slit loses a little bit of its mystery, but many-body theory still seems just as weird as before.)


If there are no particles, then how do you know what $N$ should be?


From the paper, at the top of page 10 of the PDF, at the end of section A:

"Some authors conclude, incorrectly, that the countability of quanta implies a particle interpretation of the quantized system. Discreteness is a necessary but not sufficient condition for particles. Quanta are countable, but they are spatially extended and certainly not particles. Eq. (3) implies that a single mode's spatial dependence is sinusoidal and fills all space, so that adding a monochromatic quantum to a field uniformly increases the entire field's energy (uniformly distributed throughout all space!) by hf. This is nothing like adding a particle. Quanta that are superpositions of different frequencies can be more spatially bunched and in this sense more localized, but they are always of infinite extent. So it's hard to see how photons could be particles."

As mentioned above, you can take linear combinations of these different single particle states at different energies and come up with various energy/location spreads. Doesn't one such combination have a spatial spread of zero? This would correspond to a single quanta at a single location in space.

My physics may be a bit rusty since I have been out for a while. Combining the different frequency components from the different field configurations is not _exactly_ the same as simple Fourier analysis, on the face of it. However, the individual contribution from a given field configuration (meaning a single frequency) is very small since there are so many different field configurations contributing (an infinite number). I believe the Fourier result does apply to the expectation value of the particles location here.

If I am thinking correctly this seems to be a very critical error in the paper. Someone correct me if I am wrong.

* * *

EDIT: I believe I said something incorrectly. Where I said "I believe the Fourier result does apply to the expectation value of the particle's location here." I meant to make a stronger statement, "I believe the Fourier result does apply to the effective value of the particles wave function in this location in this case." (The expectation value being zero would not bean the field does not extend to that location.)


(Not a physics person, but) As I read it, he is just arguing against the implication that Countability implies Particles. So he is saying that adding a quantum that is monochromatic has an effect across all space (which is clearly a non-particle like effect). Then he admits that you can get localization through superpositions of quanta.

Since he is arguing against a logical implication he only needs to show a counterexample exists.

The problematic part in choosing a single mode like this is that it can lead to a non-normalizable integral at some point (ie, it won't be a member of the Hilbert space).

QFT always made more since to me. Everything flows more naturally than in QM, where out of the blue, they introduce wave packets.

The paper does feel a bit shaky though especially as it is essentially taking a pedagogical point (start teaching from a QFT viewpoint) and making it into an argument about the foundations of physics. The non-relativistic QM view point is taught because it represents a smooth departure point from classical thinking without requiring the full mathematical complexity of field theory.


I think the general assumption is that QFT is true, it is just whether you can call the physics it creates as being particles. At least that is how I interpret it. QFT is QM, but it just has a lot more degrees of freedom (infinite) than what you are talking here about when you say QM. You can write a Schroedinger's equation for a field. Rather than the wave function being a function of X, the wave function is a function of F(X) where F(x) is a field configuration over space.

I would say some of his argument comes down to semantics because by his definition in order for something to be a particle it can't have spatial extent. I think a lot of people don't include this in the definition of a particle. They do associate the number of "Quanta" with the number of particles, at least in a field theory.

What I was saying above is that I believe you can create an object by the "Quanta" definition in QFT that has no spatial extent. His argument is based on the fact that this is not possible.

Adding these Quanta together to form a zero extent object is similar to saying in Fourier analysis you can take a number of different frequencies (like the quanta at different wave lengths) and create a delta function (which has no spatial extent). The thing is, even though we are dealing with adding a bunch of frequencies together, it is not exactly the same as a Fourier series because we are adding them together in a different way.

You make a good point about people first teaching the simple Schroedinger's equation of particles because it is a lot easier. I think what is so hard about quantum mechanics is relating it to the real world, and not the axioms themselves. The simple form is much easier to relate to the real world.


Yeah, I just meant QM as meaning the semi-classical version. Making QM work with SR requires moving to QFT/"second quantization".

You can presumably create particle-like quanta with a creation operator that creates particles in position space vs momentum space. The particle then won't have a definite momentum in that case, so there's still an extent problem at least in configuration space. If there is an ultraviolet energy cut-off then you end up with problems as well.

I think we perceive living in a position space more than we feel we live in a momentum space. We would prefer things to have a definite position more than we care about them having a definite momentum. The fact that they are conjugate observables is the troubling part.


I suppose the whole crux and beauty of the article is that we can talk about physics without numbers. As soon as numbers enter the picture, we have discretized something that is beyond discretization.


Particles is just result of [self-centric] human perception bias and the resulting naive concept of matter or a substance as perceptual conditioning, evolved in a certain physical environment (everything what we are, including our mind and consciousness is shaped by the environment, and our perception of reality, in turn, is shaped by our mind, conditioned by perception).

We think that there are solids and atoms - grains of matter - basic building blocks. This model corresponds to what our sense organs give us. It is hard to convince oneself that there is no matter at all, only energy and our perception grossly zoomed out of what is really going on.

Matter is an appearance to perception. A wrong model due to limitation of the sensory system. There is no matter when there is no observer, only states of energy, or fields, which is a better concept, but still mere concept. We could say that atoms are "stable" fields, but it is much better to do not apply "human" predicates to the nature.

Particles is a good-enough model, which allowed us to sequence a genome or build a CPU, but it is only a crude model nevertheless.


Total aside and this may be too late into a crowded thread for anyone to notice this. But have physicists ever rigorously examined the idea that quantum "duality" is explained by computational complexity?

I know it's more metaphysics/interpretation, but that's what we're talking about here. I also know that universe-as-simulation is a very popular notion among laypeople (particularly programmers) who look at physics. I'm just wondering if any physicists have rigorously studied the idea, and if there are falsifiable propositions we could make about this.

In game programming, one often cannot compute every detail of every component of a simulation. So, what you often do is focus more precise computation on areas around a player, or what the player is actually observing. The rest are often modeled stochastically or via computationally efficient functions. This has always mapped well in my (very surface-level, entirely layman) understanding of QM and QFT.

Note that there are, in my mind at least, two different notions here. One is actually the concept of a simulation with observer-dependencies directing the fidelity of the simulation. The other doesn't imply a "simulation" nor is it directly dependent on any "observer": perhaps computational complexity is related to the fundamental physics of the universe and nature prefers to use imprecise probability estimates wherever possible and it is only when precise interactions need to be resolved that more precise or definite calculations are performed.

I know these are sloppy notions as presented here and I'm not taking the time to phrase these questions very well, or very precisely. Busy atm, sadly. Just wondering if any well-reputed physicists have studied this possibility rigorously, or if it has been rejected for an obvious reason, etc.


I always enjoy a discussion about semantics, but only when both parties are very clear about the fact that it's semantics they're talking about, and not fundamental nature of existence. I'm very wary of people trying to use physics to further an ontology, as physics almost by definition allows for multiple, completely equivalent descriptions of reality. That's not to say I think physics teaches us nothing about how the universe really works, but I don't think you can conclude from his interpretation of the mathematics of QFT that particles (whatever they are) don't exist, just as much as the Fermat principle[0] doesn't imply that light has a sentient mind which seeks out the shortest path. There exists a consistent, fully equivalent interpretation of (non-relativistic or relativistic) quantum mechanics that includes particles at the core of its ontology, Bohmian mechanics[1]. I'm personally not an adherent of it, but it shows that by nature, it's very hard to use physics to show what something fundamentally is.

Besides, the article doesn't define clearly what it means by particle, which is a priori just an English word, nor does it justify it well. I don't share the authors' problem with the excitations of a field being spread out all over the universe (by virtue of them being momentum-eigenstates). It's discrete, has a mass, has a momentum, and energy and interacts as a whole. The article calls these properties necessary but not sufficient, but doesn't explain why this doesn't suffice.

Particles are at least a useful abstraction. They emerge naturally at the classical level, interactions between fields are even at extremely high energy levels still very localised, electrons "scatter" a lot like they're bouncing off other particles, they leave neat tracks in bubble chambers, excitations of fields are discrete even at the lowest level, ... Feynman diagrams[2] are extremely handy, even if they don't "actually" happen, but are just a term in the series expansion of an interaction Hamiltonian between two fields.

What's the use of contorting oneself to the limit to fit every observation in a single mold, a field. Sure, classical particles are nothing like what we see at the quantum level, but classical fields are absolutely nothing like the fields in quantum field theory either. Why pick one term over the other?

0: https://en.wikipedia.org/wiki/Fermat%27s_principle 1: https://en.wikipedia.org/wiki/De_Broglie%E2%80%93Bohm_theory 2: https://upload.wikimedia.org/wikipedia/en/f/fb/Feynman-diagr...


I think it's been proven fairly comprehensively that particles don't really exist in QFT in any useful sense. See e.g.

http://arxiv.org/pdf/1304.7469.pdf

http://www.sciencemag.org/news/2016/07/massive-neutrino-expe...

Particles may be a useful abstraction, but they're also a very misleading one.

It looks a lot as if what really happens is best described by a Two State Vector/Transactional interpretation.

Which is very weird, because those are both time symmetric. And that's not a feature you'll find in any particle-oriented theory.


Particles are very useful concept, used seriously also in elementary particle physics. That the concept does not fit mathematics of quantum fields is an incompatibility of the two approaches, not evidence that particles 'do not exist'. The articles you've linked do not even attempt to prove that particles do not exist. Sure, explaining wave behaviour of light with particles is almost impossible and field theory (wave theory of light) is superior. That still leaves the possibility that electrons, protons and neutrons are microscopic particles; currently known to be smaller than 1E-14 m.


Newbie question: if there are no particles, then why are there quantized packets of energy such as photons?


Light-particles seem like they exist for two reasons:

(1) when you detect things at high sensitivity, you get discrete events.

(2) Quantum fields have a thing called a number operator. When you "measure" it (whatever that means) you get an integer.

Now your language of "quantized packets of energy" comes from Einstein, who got his Nobel prize for noticing (1) in the form of the photoelectric effect. But that paper, though brilliant, was wrong. Classical fields (with quantum electrons) are enough to derive the photoelectric effect.

At first sight (2) seems to back Einstein up, since the number of photons seen on an (ideal) detector is pretty much the measured value of the number operator for the light beam.

But while that works in practice, it doesn't work in theory. The number operator is only really defined for monochromatic fields. It seems like you should be able to Fourier transform things until you had one for time-limited or space-limited situations. But I could never make that work.


> (whatever that means)

That (implied) question has an answer: measurement is the mutual entanglement of a number of degrees of freedom. See:

http://www.flownet.com/ron/QM.pdf

Or the movie version:

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


I'm am not a physicist, but interested in QM. Photons behavior cannot be completely explained by treating them solely as particles. The simples counter example (one you can perform yourself with a laser pointer), is the double-slit experiment. If photons behaved classically (like billiard balls) they'd never interfere with themselves.

If you'd like a good intro to QM, youtube is full of great material. Here are some of my favorites:

NOVA - The Fabric of the Cosmos: https://www.youtube.com/watch?v=NbIcg0XsbFQ

The Secrets of Quantum Physics: https://www.youtube.com/watch?v=VgDlzGZAPcY

Particle Fever: https://vimeo.com/125987472


Particles can interfere with themselves in the double-slit experiment if they are being guided by a wave. This explains wave behavior and particulate events as in Bohm's theory.

Sadly, there are issues with photons as particles as their wave equations do not seem to allow for an easy particle interpretation unlike, say, electrons. Of course, the flexibility of QM allows for electrons to have a particle existence and photons to not: http://arxiv.org/abs/quant-ph/0404134 (I am a coauthor of that paper)

And some videos to answer questions about BM: http://www.bohmian-mechanics.net/videos_faq.html


Yes, I'm aware of that, but how are fields quantized (divided into fixed-size packets of energy)?


A photon is a wave packet.


> fundamental nature of existence

> as physics almost by definition allows for multiple, completely equivalent descriptions of reality

> it's very hard to use physics to show what something fundamentally is.

There's no such thing as fundamental nature of existence. We just have mental models (like quantum mechanics) to describe the patterns of our observations. The idea that there is some fundamental underlying matter makes no sense, we only have perceptions and mental models do describe them. Like you said, there might be multiple physical models, as long as they give the same predictions, they're all correct.


"There's no such thing as fundamental nature of existence."

Of course there is. Or are you suggesting that there is not a reality?

There are models with more explanatory power that others. Those models map better to reality ergo they are more fundamental.

Otherwise, what it means to say that a model is better than other, if not that is more close to what really there is out there?


When people say "fundamental" they usually mean "the basic elements of which everything else is made of". The ancient Greeks thought those basic pieces existed and called them atoms, but it is not clear that reality has such indivisible basic elements.


Maybe they do, but I don't think this is the case here.


Maybe I shouldn't comment because I only read the abstract. My reaction was, "This isn't anything new. This is exactly how fields are interpreted." I appreciate the comment here because this is just a matter of semantics, at least from the reading of the abstract.

I am sure the author knows the subject very well. I see it is written in the area of History and Philosophy of Physics, so I assume it is there to clarify this for the non-experts, which includes many physicists who are not into the philosophy of quantum mechanics. I think that is why they wrote this article. I believe it is not intended as a physics discovery.

Quantum mechanics is very complex, at least when you try to relate it to the real world. I think the language in the early years of learning is to help gradually introduce the subject to students, and it can possibly be misleading as to what is meant by a particle. At a higher level, meaning someone who really studies quantum mechanics like an older theoretical physics graduate student, how quantum mechanic works is more clear.

Here is the way I view fields and particles: a wave function for the field (not to be confused with the field itself) has a number of energy eigenstates. These eigenstates correspond to the existence of a number of particles. The simplest example is a simple harmonic oscillator in Schroedinger's equation. The discrete energy states correspond to: 0 particles for the ground state, 1 particle for the first excited state, 2 particles for the second state, and so on. This simple harmonic oscillator is also an example of a field theory where space has only a single point. Normal field theory corresponds an equation like this at each point in space (an infinite number of points). It includes an interaction between neighbouring points. This version of a harmonic oscillator at each point in space corresponds to a simple scalar field with a mass. This field theory can be solved exactly using Schroedinger's equation, though this is seldom done. I find this calculation to be very instructive.

The idea of "particles" in the simple harmonic oscillator is very trivial, with a one to one mapping between the number of particles and the energy state. In a non-interacting field theory, there are many different states related to a single particle, with the momentum being involved. Particles are less clear in an interacting theory. We usually only consider the states where the particles are far apart and effectively non-interacting. When particles are close together, meaning the wave function has a significant contribution from the interactive terms in the field equation, we have trouble understanding this and we consider it transient states that we call the interaction (or collision in particle accelerator).

Obviously I am not capable of describing this in a simple sentence or two. I am sure others could. But to me at least it is a complex idea.


Oops, there is an important omission in my above comment. I spent a lot of time talking about what a particle is and didn't say what a field is. Whereas particles are related to energy eigenstates, the field is related to eigenstates of the field value. These are two very different things and I think they are both valid, depending on what you are considering.

To me this is what it means to be both a field and a particle. At the same time, speaking of semantics, you can say particles don't exist because they are not a physical thing like a field value is.

Here is an aside that I just thought about while writing this which I hadn't considered before - Particles versus fields is similar to the Pauli Exclusion Principal. The Pauli Exclusion Principle basically states that energy/momentum can not be specified at the same time as position, and this is because they are eigenstates of different operators (energy/momentum operator and the time/position operator). You can't be in a pure state of both at the same time. In the particles versus field case, particles are related to eigenstates of the energy operator and fields are eigenstates of the field operator. These two values also can not be specified at that same time, for the same reason as in the Pauli Exclusion case.


as water waves are 'epiphenomena'/emergent from the underlying form, are the 'waves' that are used to describe light also epiphenomena (i.e. emergent) or are light waves the EM field exactly ? If the latter, I don't see how to interpret the photoelectric effect.


All phenomena are emergent. That word means nothing.

The photoelectric effect is not complicated any way you slice it. An atom absorbs some quantum of energy from the field. This doesn't require any understanding of what model you use to describe the energy in the field. The interaction is quantized either way.


not quite. 'emergent' in theoretical physics typically means 'arising from a composition of the more fundamental physical state'. 'All phenomena are emergent' with this definition of the word would mean you could always represent something with something else that is more basic, ad infinitum - I don't think that is the accepted view among physicists.


I'm not sure the term "emergent" is a term in theoretical physics. I've certainly never seen it.

>'All phenomena are emergent' with this definition of the word would mean you could always represent something with something else that is more basic, ad infinitum

No, what it means is that at some point, you've broken your model down into something that is not 'phenomena' in any meaningful sense. Which is something physicists do all the time.


The day I understood this, it was a awe moment. The realization that if we zoom in very very deep, we will not see marble-like particles, rather we will see nothing. Its only through the interaction of the excitation in these fields do our pseudo-particles form.



There is only the mathematics. "Shut up and calculate", as one physicist put it.

Here's Feynman talking about it.[1] "We interpret the intensity of the wave as the probability of finding a photon".

[1] https://www.youtube.com/watch?v=_7OEzyEfzgg


I feel this approach is flawed. In theory it'd have been possible to come up with Relativity by recognizing the Lagrangian transforms that match experimental outcomes and say "That's just how it is". Einstein provided an insight as to why that's far more enlightening.

To me, QM is still in the former state, detailed equations looking for a soul.


Nothing new. This guy published a book about it in 2006: http://transfinitemind.com/tapestryindex.php


"Physicists are still unable to reach consensus on the principles or meaning of science's most fundamental and accurate theory, namely quantum physics. An embarrassment of enigmas abounds concerning wave-particle duality, measurement, nonlocality, superpositions, uncertainty, and the meaning of quantum states. After over a century of quantum history, this is scandalous."

What is also scandalous that in this age of systems that do this work for you automagically (e.g. Tex) typesetting and microtypography in scientific publications seem to deteriorate. This one is a fine example of this trend. ;-)


Can someone ELI5 or possibly 15 on this for me?


the map is not the territory.

the model is not Absolute, but it gives us a really, really good idea.


Platonism and Kantianism are still alive and strong in Western thought.


What's wrong with Kantianism?


Its just a modernized version of Platonism.


I never understood why interpretations of QM which violate non-locality like pilot wave theory are frowned upon. Fields are non-local by definition.


is this essentially a reminder that the materialistic view of the universe / reality is outdated, or am I reading too much into it?


It's either this, or something like objective collapse really does happen, physically, which seems less likely.


Anyone who's studied beginning grad level physics should know that. I don't get why it's trending on HN


Yeah I'm being taught QFT in my undergrad. Any theoretical physicist would be expected to know this concept well. I guess people here aren't theoretical physicists though! However I do think the quality of physics commentary here is generally quite poor. I see a lot of crackpot theories or just ignorance in general. Especially with anything involving quantum mechanics, that seems to drive people crazy. I don't think that many people realise that in physics we don't talk about the philosophical implications at all, we're just trying to find good models, that's it...


I agree that many people who are not experts often misunderstand quantum mechanics. It is a very difficult field to learn. It takes a long time. I disagree about physicists not talking about philosophy. At least some people do in theoretical physics. That is probably why this paper is published in the area of "History and Philosophy of Physics".


I mean in general. Of course there are physicists at some universities that write about philosophy, but not a single one in my theory department.


> that seems to drive people crazy

Schrödinger's catnip?


Perhaps for those few of us who are a bit rusty on beginning grad level physics.


One of the points he makes in the paper is that none of the 36 quantum mechanics textbooks he found in the library held that fields were fundamental.

"30 implied a universe made of particles that sometimes acted like fields, 6 implied the fundamental constituents behaved sometimes like particles and sometimes like fields"


The theory behind the LHC experiment that led to the discovery of the Higgs Boson is based on the unanimously-accepted concept that particles are just quantized localizations of fields. Even in quantum mechanics, problems are solved by assuming that it is impossible to tell the difference between two or more of the same particle - which suggests that they are somehow the same thing. They are different parts of the same field.


It's interesting that the authors aren't clear about fields being fundamental, it's not even controversial.

I noticed that he looked for books with the words "Quantum Mechanics" in the title. The subject he should be investigating is called "Quantum Field Theory". But regardless, anyone qualified to write a text book on QM should be well versed in QFT.


Most of us haven't studied grad level physics?


It's presented as if it's a new discovery. If someone's interested in Physics, they should study Physics. It doesn't help much for one to jump right in the middle of a subject and act like they know what they're talking about. Which is exactly what linking to this scientific paper on HN encourages. In this case, anyone who could understand the paper would very likely have encountered the information already.

I've seen too many programmers act as if there's nothing they don't know or can't understand after a weekend's worth of study. That kind of arrogance is what separates scientists from pragmatists. It leads to situations like this:

http://academia.stackexchange.com/questions/9602/rediscovery...


My grade-school and freshmen physics texts contradicted the article and said there was a paradox caused by duality. Wikipedia 2 slit article still gives this general impression. Hobson is first time I have seen this idea that there is definitely no paradox and just fields. I think its like he says, there is a lot of lag in the mainstream basic education.


    > ...this idea that there is definitely no paradox...
Yes, it depends on what one means by "there are", ones own perspective or a much more abstract take, which I wrote somewhere else earlier:

    > Whenever you have a paradox, like wave-particle duality - but also the "French paradox"
    > in nutrition, it's not because there really is a "paradox" in the universe, it's because
    > the way you look at it is too limited, and if you find a better view you will see there
    > is no paradox.
Since you, especially as a human being, can't look at a phenomenon without having a point of view (models) paradoxes are real are not real - at the same time, depending on your models. I claim there always is a (higher) POV where there is no paradox.




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