What Are Quarks?
If you’ve dabbled in some elementary school science, you probably once learned that everything is made up of atoms. You were probably told that atoms are fundamental to everything and that you can’t break them up any further. And that was probably a happy explanation for 10-year-old you.
Then later in life, you might have learned that there actually are things smaller than atoms. But unless your career path took you into physics, you might not know much beyond that. Thankfully, we’re here to help.
In this post, we’ll be exploring the elementary particles known as quarks. What are quarks exactly? Why are they important? Why do they come in flavors?
The Quark Model
The atom was discovered before we could actually observe it; the same goes for quarks. Even now, we can’t really build a scale atom for us to understand, even though the modern model is pretty accurate.
Atoms look a lot like the cartoon you see whenever you look them up–just little orbs orbiting a cluster of bigger orbs. The orbiting guys are electrons, and the nucleus (the middle) is made up of protons and neutrons. However, if we want to be more exact, instead of electrons orbiting the atom, imagine a cloud of them buzzing around the atom at light-speed. The light-speed part is why modelling atoms is hard.
So, if it’s already hard to model atoms, imagine how hard it is to model the things that make up atoms. And this is where quarks come in. Quarks combine to create things called hadrons. That’s what protons and neutrons fall under. In fact, protons and neutrons are the most stable type of hadron. Protons have a charge of +1, and electrons have a charge of -1. (This will be important in later in the post.)
Any hadron not bound to an atomic nucleus is theorized to be unstable, and as such will decay into something else. This includes neutrons. A free neutron will decay in about 600 seconds. Free protons are an exception though, they either are stable or take a very long time to decay. By long we mean on the scale of “might see the latter part of the universe’s life” type long. Before you cry foul play, we promise this makes some logical sense.
If you remember how elements work, an element’s atomic number is exclusively determined by how many protons it has. So adding neutrons or electrons (was well as taking them away) from an atom won’t change what element it is. But changing the amount of protons will change what element you’re working with. Hydrogen has an atomic number of 1, which means you can boil its nucleus down to just a single hadron (a proton).
We’re kind of comparing apples and oranges here, but this is a decent way to rationalize the deal. If anything, at least you know protons are what determines an element.
Depending on how many quarks are in a hadron, you can get hadrons that aren’t protons and neutrons, like mesons and pions. That’s a totally different discussion that we’re not having today, though. Basically, quarks and their variations make hadrons.
Why Do Quarks Come in Flavors?
Before we do any more discussion of quarks and their flavors, let’s just list them all out for you.
- Up | +2/3 Charge
- Down | -1/3 Charge
- Charm | +2/3 Charge
- Strange | -1/3 Charge
- Top | +2/3 Charge
- Bottom | -1/3 Charge
If you were hoping the flavor part of this post would be a neat way for you to get some edible treats for reading, we’re sorry. The only treats we have on offer here are science.
We’re making a deal out of quark charges because of what we said earlier about protons. A proton is made up of two up quarks and one down quark. Add up those charges by list above, you get a charge of +1. Neutrons are also exclusively made out of up and down quarks as well. We didn’t mention electrons because they’re made of a different particle that’s kind of a quark analog (they’re called leptons, in case you were wondering).
Just to make things extra confusing, quarks can shift fairly readily between flavors. Granted, it’s easier to switch between up and down/strange and charm than from say up to top. We don’t have the best idea on what makes quarks what flavor, but we do know which ones are the most common.
We kind of implied it already, since protons and neutrons are exclusively up and down quarks. But yes, the up and down flavor make up the vast majority of the universe. Strange, charm, top, and bottom quarks existed in the very early fractions of seconds of the universe. We don’t really see them anymore unless we’re slamming things together in a particle accelerator. Which, you know, simulates the early fractions of seconds of the universe.
Think you know your quark flavors? Check your tastes here.