Eli5: What exactly are quarks…how many are there…and is there anything smaller?
In: 47
Quarks are what hadrons are made of, the hadrons are split into two groups, baryons and mesons. There are 6 that exist, up, down, strange, charm, top, and bottom. They can only exist in isolation in extremely high energy environments that haven’t existed since the first microseconds of the universe, so we only see evidence of their existing by smashing different baryons and mesons together.
Up, charm, and top quarks all have a charge of +2/3 e where e is the elementary charge (a proton has a charge of 1e and an electron has a charge of -1e)
Down, stange, and bottom quarks all have a charge of -1/3 e
Baryons are made of 3 quarks each, some you may be familiar with are uud (proton) and udd (neutron) any combination of 3 quarks works, and you will always end up with a charge of +2e, +1e, 0e, or -1e
Mesons are made of a quark and anti quark pair, and are important in high level particle physics, so we won’t go into these much. They always have a charge of +1e, 0e, or -1e regardless of how you combine them. Ie an up and anti down quark makes a pion+, which has a charge of +1e
We used to think there were only up and down quarks, until one day we found something that looked like a down quark, but had way more mass than it should. We thought this was strange, so we named it the strange quark. We were confused by this, so we kept looking until we found something to restore symmetry to the standard model of particles. This made everything look nice again, so we thought it was charming and named it the charm quark. We did some math and figured out that another pair of quarks should be possible, but anything beyond those two would take more energy than is in the universe, so since these two quarks would be the limit of what’s possible, we called them the top and bottom quarks.
At this time, we believe quarks to be fundamental particles, as well as the family of leptons (electrons and neutrinos) so wee can’t break then down any further without reducing them to pure energy.
[The standard model](https://www.pngfind.com/pngs/m/110-1103032_the-standard-model-of-elementary-particles-standard-model.png)
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