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.
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.
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.
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
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.
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).
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).
"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.
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.
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 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.
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.