The Fundamentals, Part 4: The Weak (but still really strong) Force

Our final interaction, and it’s a tough one. The weak force is probably the most subtle of the fundamental interactions; it’s responsible for beta decay, or the breaking down of particles like the neutron and proton through radiation. This kind of decay is the main force that powers our Sun, as well as making heavier elements possible. However, there’s a lot more to the weak interaction than meets the eye...

Analogous to the gluon powering the strong force, the weak force has three different fundamental particles to its name: W+, W-, and Z. Though these particles are only force carriers, they do have mass. In fact, each of them are at least 100 times heavier than either the proton or the neutron. This hefty weight really limits the distance they can move and interact with other particles before they themselves decay and disappear; the limited range of the weak force’s bosons is what makes it ‘weak’ in the first place. Yet if the distance is small enough (around .00000003 meters), the weak force becomes about 10,000 times stronger than the electromagnetic. That's crazy strong.

In addition, one of the most interesting parts of the weak force is its ability to change the flavors of quarks. Many of you probably know the weird names given to the six types, or ‘flavors’, of quarks. In order of lightest to heaviest: 

1. Up
2. Down
3. Strange
4. Charm
5. Bottom
6. Top

The weak force is the only known interaction that has the ability to turn one flavor into another. I’m sure you’re thinking, yeah, that’s really awesome, but what does it have to do with beta decay? I’m glad you asked. 

You always ask such good questions, you politically correct
group of students, you. 

In reality, the only difference between a neutron and a proton is the type of quarks that they’re made up of. A neutron has an Up and two Down, while a proton has a Down and two Up. They’re nearly analogous but for charge, and can actually turn into one another using, what else, beta decay. The difference between the two defined types of beta decay, β+ and β-, lies in what particle is decaying: β- involves the breaking down of a neutron into a proton, and β+ goes the other way. It’s the interaction of the bosons involved (W+ for β+, W- for β-) that makes the quark change happen, and allows the neutron/proton turn into the other particle.

Whew... everyone with me? 

The weak force, as seemingly limited as it is, actually does a lot for the universe. Like I mentioned earlier, the beta decay that takes place powers the nuclear fusion of the Sun. All of the hydrogen that the sun starts out with is compacted so tightly together that the weak force begins to have a significant effect on the atoms. All of the hydrogen atoms quickly turn into deuterium, and then into helium. The death of a star comes when so much of the hydrogen has turned into heavier elements that there’s nothing else to react with; it then either collapses in on itself, or violently explodes. 

Similar to their "Child Star" counterparts.

... and that’s the breakdown of the weak force. It’s a bit complicated, because unless you’re really tiny or inside the sun, you’ve probably never had to think about it. But, like every other fundamental, it does a lot to keep this universe up and running. 

ALSO: Little did you know that at the time the Universe was born, there was so much energy flying around that the electromagnetic and weak forces were one and the same. The electroweak force, as it’s called, has been scientifically proven to exist in post-Big Bang conditions, meaning that every photon from the electromagnetic force is actually related to a weak force boson. Cool, no? It just illustrates a key concept of science: that when one really thinks about it, one realizes that the universe is not some giant set of equations, full of conditions and exceptions, but rather one unified entity. This beautiful idea, that everything is connected, makes Physics the joy that it is.