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Is light fundamentally a wave or a particle?

forbes.com

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Re: Is light fundamentally a wave or a particle?

#41

Post by robertlagrant »

danbruc wrote: post #24
misja111 wrote: post #8

Earlier quoted context omitted.

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 th…

It is decomposable; this doesn't affect that. It just means what we've decomposed it to cannot be modelled sufficiently with the current metaphors.

Re: Is light fundamentally a wave or a particle?

#43

Post by mhh__ »

tiborsaas wrote: post #38

I feel like this question is like asking a hexagon if it's a circle or a square. Let me summon the annoying physicist take on this by Sabine: https://youtu.be/kSG4Rfc9YIw?t=179

I assume it's ultimately in good humour but some of the things she does seem quite "out" for a physicist e.g. the annoying physicist things looks like position yourself towards outsiders.

I'm still a mere trainee so I'm basically neutral on her opinion of HEP and Accelerators, but I know enough that it looks a little weird for an academic.

Re: Is light fundamentally a wave or a particle?

#44

Post by lilgreenland »

Is nature made of waves or particles? The annoying answer is neither. The wave model and the particle model are approximations of nature that are each accurate for different conditions.

Quantum field theory describes reality with wave functions. In this theory there is a field for each type of fundamental particle spread across all of space and time. Regions of a field can evolve into a localized excited state. Particles are a useful mathematical approximation of these excited states.

For example, an electron is a region where the electron field has more amplitude, or bigger ripples. The electron field exists everywhere, but electrons are more likely to be measured where the field amplitude is larger.

Fields interact with other fields, and with themselves. These interactions can be approximated with a Feynman diagram, which treats everything as particles.

Using Feynman diagrams electron field interactions generally model well as particles. This is because the most complex electron interactions are weak enough to be mathematically canceled out. Quarks, the particles inside protons and neutrons, interact through the "strong force". This force has frequent complex interactions that don't cancel out, making the particle model less useful for calculations.

Re: Is light fundamentally a wave or a particle?

#47

Post by tiborsaas »

mhh__ wrote: post #43
tiborsaas wrote: post #38

I feel like this question is like asking a hexagon if it's a circle or a square. Let me summon the annoying physicist take on this by Sabine: https://youtu.be/kSG4Rfc9YIw?t=179

I assume it's ultimately in good humour but some of the things she does seem quite "out" for a physicist e.g. the annoying physicist things looks like position yourself towards outsiders. I'm still a mere trainee so I'm basically neutral on her opinion of HEP and Accelerators, but I know enough that it looks a little weird for an academic.

I dig her style, but don't subscribe to all her views either.

I linked this part in the video because it points out that it's quite common to try to categorize things in one box or another while it should really be given a new box even if that box contains one item only.

Re: Is light fundamentally a wave or a particle?

#48

Post by maxnoe »

the_other wrote: post #31
amelius wrote: post #29

Earlier quoted context omitted.

Because someone might come up with a problem that is a bit like X and a bit like Y.

That sounds like an excellent opportunity to test both the models, and perhaps to develop a third.

We already have, its called QED and is the most preise physical theory ever created and tested. Theoretical predictions agree with experiment inside the statistical uncertainties which are now at the 15th or so decimal digit.

The problem is, people still want to map the mathematical description of how light and particles behave of QED to common sense analogies and that just does not work.

There is no commonly known and understood thing that lends itself as a working analogy.

Re: Is light fundamentally a wave or a particle?

#49

Post by danbruc »

robertlagrant wrote: post #41
danbruc wrote: post #24

Earlier quoted context omitted.

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 th…

It is decomposable; this doesn't affect that. It just means what we've decomposed it to cannot be modelled sufficiently with the current metaphors.

What do you mean with it? The quantum state of a two particle system? In that case I am pretty sure - even though I am not a physicist - that you are wrong. The quantum state of a two particle system can not be decomposed into two states, one state for each particle, in the general case. You can find the density matrix for each particle which will tell you how each corresponding particle will behave in isolation but you will lose information about the system by doing so in the general case.

Re: Is light fundamentally a wave or a particle?

#50

Post by el_don_almighty »

amelius wrote: post #29
vanderZwan wrote: post #25

Earlier quoted context omitted.

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.

The French called this the "le principe Donny et Marie," based on some research from the mid 70's for some reason. Oooh la la, those hot pants!
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