Can we count light as matter?
Can we count light as matter?
I think the real trouble with your question is that matter is a bad concept. If matter means a type of particle predicted by a quantum fields theoretical framework, then definitely yes, light is matter. If by matter you mean anything that has mass, then in some situations it may have some properties that are mass-like from a physical perspective. One such example is trapping EM waves in a wave guide, as mentioned by David, so in this sense it can be matter. If by matter you mean anything that got mass and a volume, well, that’s more of a trouble. Technically photons have no volume. Or they do, if you count having a wavelength as spatial extension. But neither does electrons, quarks, or any other fundamental particle that composes what we call matter by intuition. So you got a bunch of zero volume stuff composing structure that have non-zero volume. They’re all represented by excitations of quantum fields and all have a wave-like behaviour depending on the scale you’re analyzing. Well, that’s not by itself a logical contradiction (to say so would makes us incur in a very well known reasoning flaw named the composition fallacy, the ideia that if something is composed by other things, then the composition cannot have any property that the constituents do not have), but it’s certainly not intuitive, and provoke us to revisite the utility and motivation for the concept we are trying to investigate. Are we really confortable in saying that electrons are not matter? What is the rationale for the concept again? Why can’t we simply dispose of it and do not think about nature in those terms?
If by matter you mean anything that got mass and a volume, well, that’s more of a trouble. Technically photons have no volume. Or they do, if you count having a wavelength as spatial extension. But neither does electrons, quarks, or any other fundamental particle that composes what we call matter by intuition. So you got a bunch of zero volume stuff composing structure that have non-zero volume. They’re all represented by excitations of quantum fields and all have a wave-like behaviour depending on the scale you’re analyzing. Well, that’s not by itself a logical contradiction (to say so would makes us incur in a very well known reasoning flaw named the composition fallacy, the ideia that if something is composed by other things, then the composition cannot have any property that the constituents do not have), but it’s certainly not intuitive, and provoke us to revisite the utility and motivation for the concept we are trying to investigate. Are we really confortable in saying that electrons are not matter? What is the rationale for the concept again? Why can’t we simply dispose of it and do not think about nature in those terms?
