There are no particles, there are only fields (2012)
arxiv.org
arxiv.org
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.
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.
(sort of illustrated: http://physics.stackexchange.com/a/61475)
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).
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.
Ultimately it doesn't matter because math is the same.
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
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.
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.
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.
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).
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.
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.
Except obviously it doesn't.
If you make the electron a field instead of a point all of that goes away.
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.
In other words, as michaelfeathers said, "the map is not the territory."
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.
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.
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.
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 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.
"Particles, Fields and The Future of Physics"
https://www.youtube.com/watch?v=gEKSpZPByD0
(Audio starts at 19 sec, Lecture starts at 2:00)
paper "Space from Hilbert Space: Recovering Geometry from Bulk Entanglement": https://arxiv.org/abs/1606.08444
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 :-)
in principle
no room for mysticism or "consciousness" nonsense
[0] https://en.m.wikipedia.org/wiki/Hard_problem_of_consciousnes...
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.
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.
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...
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?
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.
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.
Our interpretation of the physical world doesn't necessarily exist anywhere but in our minds.
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.
Surely experiencing that yourself adds more weight to others' claims?
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...
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.
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/
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.
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.
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.
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.
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.
I've never argued for souls or anything immaterial, I simply think we haven't fully understood or explained the nature of consciousness.
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.
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...
Even if the idea came through empirical means, the theory itself isn't empirical.
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.
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!)
Let's not get ahead of ourselves here; unless you've solved a millennium problem!
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.
But I found Art Hobson's website, which includes the published paper and the published commentary
This is of course trivially explained by the particle idea.
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.
Regarding field quantisation - why should the electron field be quantised?
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?
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.
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
(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.)
"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.)
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 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.
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.
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...
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.
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
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
(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.
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:
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.
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 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.
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?
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.
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.
>'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.
Here's Feynman talking about it.[1] "We interpret the intensity of the wave as the probability of finding a photon".
To me, QM is still in the former state, detailed equations looking for a soul.
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. ;-)
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.
the model is not Absolute, but it gives us a really, really good idea.
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...
Schrödinger's catnip?
> ...this idea that there is definitely no paradox...
> 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.
"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"
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.