Quarks are one type of matter particle. Most of the matter we see around us is made from protons and neutrons, which are composed of quarks.
There are six quarks, but physicists usually talk about them in terms of three pairs: up/down, charm/strange, and top/bottom. (Also, for each of these quarks, there is a corresponding antiquark.) Be glad that quarks have such silly names -- it makes them easier to remember!
Quarks have the unusual characteristic of having afractional electric charge, unlike the proton and electron, which have integer charges of +1 and -1 respectively. Quarks also carry another type of charge called color charge
In order to make their calculations work, the quarks had to be assigned fractional electrical charges of 2/3 and -1/3. Such charges had never been observed before. Quarks are never observed by themselves, and so initially these quarks were regarded as mathematical fiction. Experiments have since convinced physicists that not only do quarks exist, but there are six of them, not three.
How did quarks get their silly names?
There are six flavors of quarks. "Flavors" just means different kinds. The two lightest are called up and down
The third quark is called strange. It was named after the "strangely" long lifetime of the K particle, the first composite particle found to contain this quark.
The fourth quark type, the charm quark, was named on a whim. It was discovered in 1974 almost simultaneously at both the Stanford Linear Accelerator Center (SLAC) and at Brookhaven National Laboratory.
The fifth and sixth quarks were sometimes called truth and beauty in the past, but even physicists thought that was too cute.
The bottom quark was first discovered at Fermi National Lab (Fermilab) in 1977, in a composite particle called Upsilon
The top quark was discovered last, also at Fermilab, in 1995. It is the most massive quark. It had been predicted for a long time but had never been observed successfully until then.
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