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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 classi
by atemerev 10y ago
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.
- andrewflnr 10y agoWhat do you mean about the uncertainty principle? The article here still relies on it.
- tim333 10y agoI 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 http://physics.stackexchange.com/a/61475)
- dnautics 10y agoIt 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.
- scotty79 10y agoThat'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).
- platz 10y agohowever it is quite difficult to explain the photoelectric effect purely (or at least clearly) in terms of waves.
- kirrent 10y agoI 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.
- platz 10y agofair enough; merely pointing out it is difficult for many others - it is subtle enough that it 'fooled' both Einstein and Feynman.
- scotty79 10y agoIt'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.
- platz 10y agoThe 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.
- tim333 10y agoThe 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 https://www.youtube.com/watch?v=ToRdROokUhs
- maxerickson 10y agoEach probability field ends up interacting with a single point on the screen.
- platz 10y agoThis 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)
- srtjstjsj 10y agoBut 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")
- tim333 10y agoOne 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.
- hasenj 10y agoIf 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
- ars 10y agoIt 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.
- michaelfeathers 10y ago> 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.
- srtjstjsj 10y agoThat'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.
- deleted 10y ago[deleted]
- twblalock 10y agoThe 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."
- StefanKovachev 10y agohttp://inwhy.net/quantum.jpg http://inwhy.net/quantum.jpg <- THEY EXISTS!
- amatic 10y agoTechnically, 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.
- nwah1 10y agoHow 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.