In quantum mechanics, it's a wave function. Wavelike, but not a wave; particle-like, but not a particle.
Is light fundamentally a wave or a particle?
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Re: Is light fundamentally a wave or a particle?
#22I found Scott Aaronson's explanation very helpful (and I'm a physicist, I think it might make even more sense to computer scientists and engineers).
Re: Is light fundamentally a wave or a particle?
#23Earlier quoted context omitted.
Two coherent beams of light will absolutely interfere.
Electron beams interfere in ways that light beams don't, though. If they cross in vacuum, they deflect each other due to the electric charge carried by electrons. Light beams can only deflect each other in media with non-linear response to electromagnetic fields, i.e. the response to one beam modifies the response to the other beam.
Technically speaking even the vacuum is nonlinear, according to current theories (although it hasn’t been observed yet).
Re: Is light fundamentally a wave or a particle?
#24I think the tendency to see everything as discrete units is a very human thing. Would love to see how alien species with fundamentally different perceptions approach these concepts.
I'm not so sure that other intelligent life could have evolved without having the same way of reducing complexity as we do. It is the essence of modelling: when you are interested only in certain aspects of an environment you try to categorise and classify your subject accordingly.
Which was helpful till now but there is no a priori reason that this must always be the case. And we might actually have reached to bottom in this regard with quantum physics where splitting things into pieces, studying them separately, and putting them together again does not really work anymore. A system of two or more quantum particles is not just the sum of those particles, the combined system can be in states that are not decomposable, i.e. the particles can be entangled.
Splitting the universe into galaxies, those into star systems, things in them into cells and molecules and then atoms and eventually elementary particles and all the success we had with this might give the impression that reductionism, that decomposing and reassembling things, is the only way that the world can be and that this will always work, but this is not true. And there is no a priori reason that the universe should be easily decomposable all the way down.
Re: Is light fundamentally a wave or a particle?
#25This was linked recently: https://www.lesswrong.com/posts/hc9Eg6erp6hk9bWhn/the-quantu... > An electron is not a billiard ball, and it’s not a crest and trough moving through a pool of water. An electron is a mathematically different sort of entity, all the time and under all circumstances, and it has to be accepted on its own terms. > The universe is not wavering between using particles and waves, unable to make up…
Why not say "when solving problem X, we can approximate it as a particle" or "when solving problem Y, we can approximate it as a wave"?
Re: Is light fundamentally a wave or a particle?
#26Earlier quoted context omitted.
Single beam of electrons diffracts like single beam of light, but otherwise electrons behave very differently than light: two electron beams interfere with each other, while two light beams do not.
Am I right that thinking of everything as waves isn't a bad mental model? If everything is a field, then light is simply a three dimensional wave in that field. This makes the double slit experiment seem much easier to grasp: A single photon (which is a wave with a discreet amount of energy) travels through both slits at the same time. This causes the wave to interfere with itself and when it hits the wall it registe…
"When it hits the walls it registers as a single point" is pretty vague and seems to me to be where you're kinda glossing over a lot of the not-just-a-wave complexity.
Im fairly certain you could make an experiment where one photon went through some apparatus and two specks of light appeared at the photo detector (with new wavelengths of course). What mechanism in your wave-only theory describes this split? Why do these waves sometime split or fuse and other times stay as single particles? The 'it stays as one particle cause it started as one particle' explanation would lead to a very monochromatic universe!
Re: Is light fundamentally a wave or a particle?
#27In each of the many-worlds it is a particle. The wave behavior is caused by the interaction of the many-worlds.
Re: Is light fundamentally a wave or a particle?
#28Earlier quoted context omitted.
Single beam of electrons diffracts like single beam of light, but otherwise electrons behave very differently than light: two electron beams interfere with each other, while two light beams do not.
Am I right that thinking of everything as waves isn't a bad mental model? If everything is a field, then light is simply a three dimensional wave in that field. This makes the double slit experiment seem much easier to grasp: A single photon (which is a wave with a discreet amount of energy) travels through both slits at the same time. This causes the wave to interfere with itself and when it hits the wall it registe…
Thinking of them as waves helps your intuition for entry-level QM phenomena like the dual-slit experiment and other lab-scale interferometry experiments.
Unfortunately, I would say it doesn't help (and could actually block you) when you want to build intuition around QFT and high-energy processes.
In your mind, you would still then think of a photon as a wave running around interacting with electronwaves that then oscillate and produce new photon waves.. and you'd think for example that "hey, I can just solve the wave equation and I solve the experiment".
While it's really so much more messy, as you'd note when you start considering the number of degrees of freedom involved required in your simulation to approximate reality. It's not classically interacting waves timestepped forward in time, it just looks like that in the most trivial situations.
Re: Is light fundamentally a wave or a particle?
#29This was linked recently: https://www.lesswrong.com/posts/hc9Eg6erp6hk9bWhn/the-quantu... > An electron is not a billiard ball, and it’s not a crest and trough moving through a pool of water. An electron is a mathematically different sort of entity, all the time and under all circumstances, and it has to be accepted on its own terms. > The universe is not wavering between using particles and waves, unable to make up…
Why not say "when solving problem X, we can approximate it as a particle" or "when solving problem Y, we can approximate it as a wave"?
Because someone might come up with a problem that is a bit like X and a bit like Y.
Re: Is light fundamentally a wave or a particle?
#30This was linked recently: https://www.lesswrong.com/posts/hc9Eg6erp6hk9bWhn/the-quantu... > An electron is not a billiard ball, and it’s not a crest and trough moving through a pool of water. An electron is a mathematically different sort of entity, all the time and under all circumstances, and it has to be accepted on its own terms. > The universe is not wavering between using particles and waves, unable to make up…
Why not say "when solving problem X, we can approximate it as a particle" or "when solving problem Y, we can approximate it as a wave"?
How do you know a priori which kind of problem it is?
Wave or particle are interpretations we attach to the results of applying the Schrodinger equation.