system
Given the following post, respond as if you're commenting on Reddit:
human
Does charge come in discrete chunks smaller than the charge of a single electron or proton?

I know that the charge of an electron/proton ±1.602x10^-19 C.

But I was wondering if there's any subatomic particle that carries a charge less than that, maybe some configuration of quarks or something? Or is e^- truly the *fundamental* unit of charge?

I'm reading in my E&M book, and it claims that the permeability of free space is an exact number, rather than an empirical constant, which defines the ampere and then, in turn, the coulomb. But if it's the case that the charge of a proton/electron is truly fundamental, why isn't the coulomb defined in terms of a certain number of electrons/protons? Would that not make more sense?
gpt
Sort of. Quarks can come in +/- 1/3 or 2/3 of the  fundamental charge, but they are only found in groups where the total charge adds up to an integer value of e.

SI units are defined the way they are so that they are easily replicatable, not because they are inherently fundamental (there's nothing special about the kg brick in France). The ampere is defined based on forces between wires, which allows the magnetic constant to have an exact value. It is easier to measure this, than to try to count a gigantic but exact number of electrons.