system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: What does the Weak Nuclear Force act on? When does the Weak Nuclear Force occur?

Weak Nuclear is one of 4 fundamental forces, the others being Gravity, Electromagnetism, and Strong Nuclear. Gravity pulls any objects with mass or energy together. Electromagnetism pulls opposite charges together and like charges apart. Strong Nuclear holds nucleons together. What is the Weak Nuclear force and on which objects and conditions does it act on?
gpt
The weak force's equivalent of mass, charge, and color charge (for gravity, electromagnetism, and the strong nuclear force respectively) is called *weak isospin*. 

But its behavior isn't as simple as gravity's "masses pull together" or electromagnetism's "like charges repel, unlike charges attract", in part because the weak force (unlike its cousins) is carried by particles with rather large mass, which limits its range. This mass means that unlike electromagnetism's potential energy (which is just 1/distance between the particles, more or less), the weak interaction's potential multiplies this value by an extra term of 1/e^(distance times mass of the force carrying particles). For electromagnetism this mass is zero, so all that e^whatever nonsense is just e^(0) = 1 and this term disappears. But for the weak force, the effect drops off very very quickly the further apart the particles are, which means the particles have to be in such close proximity that you need quantum mechanics to talk about anything that's going on. And once you involve quantum mechanics, you're going to need much heavier-duty tools than ELI5 is going to really allow.

All [known] fermions (a class of particle which includes the protons, neutrons, and electrons that make up the world around you) have non-zero weak isospin, so all of these particles interact with the weak force. The main distinguishing feature of the weak force is that it allows transformations in "flavour" - that is, from one type of a sort of particle to another. For example, the weak force can allow a down quark in a neutron to convert into an up quark, which transforms the neutron into a proton. This is the mechanism behind most radioactive decay, which is the weak force's main practical effect on day to day human scales.