What is "Weak Force"

[18-Till-I-Die]

Simple question, could anyone just explain it to me. I know nothing about physics, so is there some way to simply say what it does.

For example i know it has something to do with something called Flavor, that apparently affects quarks...wut?

I think it affects nuclear decay somehow?

What does Weak Force actually do, since i actually find i understand the other three Four Forces and this one, being so abstract to me for some reason, i just cant get. Is there some kind of two paragraph synopsis as to what it is exactly?

[Kanastrous]

http://en.wikipedia.org/wiki/Weak_force

If you're impatient and don't want to wait for a custom response.

Although the opening paragraph feels weirdly edited and I suggest skipping most of it...

[Duckie]

http://en.wikipedia.org/wiki/Weak_force

If you're impatient and don't want to wait for a custom response.

Of course if you read it right now it's been edited by some idiot to explain his theory of the Weak Force, so it'd be best to check the history archives for right after a revert to make sure.

Edit: And nevermind, just like that wikipedia cleans itself up. Still, makes me leery of ever believing anything I read without checking the history and/or independent verification now. (Not that I ever trusted wikipedia)

[Kanastrous]

Yup. Makes *much* more sense, now.

[Kuroneko]

The short answer is that it doesn't do much but create certain forms of radioactive decay, although it's important in that it's likely the main reason behind the asymmetry between matter and antimatter (the weak force violates parity).

---

Let's back up just a bit. Gravity has one kind of charge, which is normally called mass. Electromagnetism has two charges, or actually just one if the anti-charge is not counted as separate (choose your own preference as to which is positive and which is negative). Thus, it has just one mediating particle, the photon.

The strong force is where things get a bit more complicated. It has three types of charge, labeled by the three (additive) primary colors of red, blue, and green. The baryons are color-neutral (rgb = "white"), but the force carrier particles, gluons, come as linear combinations of color+anti-color pairs. What they actually do is exchange color between quarks, e.g., a blue quark becomes red if it emits a blue+anti-red gluon.

The weak force has its own charge, aka flavor charge, of which there are two kinds. Their force carriers, however, are very massive, making them short-lived, and thus limiting the range of the weak force. Just as a colored particle emitting a gluon changes color, a flavored particle can also change its flavor by emitting a weak force carrier. For a common example, look up beta decay, in which a quark of the "down" flavor in a neutron (udd) changes to and "up" flavor, forming a proton (uud), and thus transmuting the atom.

[18-Till-I-Die]

If Weak Force controls, or at least affects, radioactive decay wouldn't that have to do with something like nuclear reactions too? Like in stars and nukes such? Or would that be some other force?

[Kuroneko]

Oh, good point. Since it can manufacture neutrons from protons, getting the elements from stellar fusion, etc., would have probably been outright impossible. I don't see any relevance to nukes, though.

[Gil Hamilton]

So neutrons are made of an up and two downs, and a protron is made of two ups and a down. That implies that ups have a charge of 2/3rds and downs have a charge of -1/3rd, right?

[Starglider]

So neutrons are made of an up and two downs, and a protron is made of two ups and a down. That implies that ups have a charge of 2/3rds and downs have a charge of -1/3rd, right?

Yes. The other four types of quark have the same charges but are more massive.

[Gil Hamilton]

Yes. The other four types of quark have the same charges but are more massive.

That's interesting. Those are the first particles I've heard of that aren't a integer of a fundamental charge in total (as opposed to moieties of molecules, which can be fractionally charged depending on how you do your bookkeeping).

[Starglider]

That's interesting. Those are the first particles I've heard of that aren't a integer of a fundamental charge in total (as opposed to moieties of molecules, which can be fractionally charged depending on how you do your bookkeeping).

I think it's more a case of 'protons and electrons should have been assigned +3 and -3, but we didn't find that out until 50 years later'.

[Surlethe]

Also, nature doesn't like quarks to exist by themselves. AFAIK, their existence has only been observed indirectly (shining high-energy electrons through atomic nuclei and observing diffraction); the strong force is so strong that when nuclei split apart quarks get slammed back together too quickly to see.

[Starglider]

the strong force is so strong that when nuclei split apart quarks get slammed back together too quickly to see.

Actually if you separate quarks far enough, the potential energy between them is converted into a quark/antiquark pair, such that confinement is maintained. AFAIK this is how mesons are produced in particle accelerators.

[Gil Hamilton]

I think it's more a case of 'protons and electrons should have been assigned +3 and -3, but we didn't find that out until 50 years later'.

Heh, there is always that. Physicists don't like changing their conventions once they made them.

[Fingolfin_Noldor]

Actually if you separate quarks far enough, the potential energy between them is converted into a quark/antiquark pair, such that confinement is maintained. AFAIK this is how mesons are produced in particle accelerators.

If I recall correctly, most interaction forces have a fair bit of pair production and annihiliation if the energies are high enough to produce them.