When people began to understand the material world, they put forward various views. Some philosophers in ancient Greece believed that all kinds of substances in the world were composed of some basic units that would never change and could not be separated. They call this basic unit atom. It was not until the second half of16th century that physicists confirmed the existence of atoms. Later, Italian scientist avogadro put forward the molecular theory, which supplemented Dalton's atomic theory. As a result, people have formed such a mode of thinking: matter is composed of molecules, molecules are composed of atoms, and atoms are inseparable.
By the end of19th century, the inseparable mode of atoms had been impacted, and American scientist Thomson discovered particles much smaller than atoms-electrons. Then scientists found that there is a small nucleus in the center of the atom, and some electrons move around the nucleus. By the 1930s, it was discovered that atoms were composed of protons and neutrons. Protons are positively charged and neutrons are electrically neutral, which is more than 1800 times heavier than electrons. Later, positrons, the antiparticle of electrons, were found in cosmic rays. They are as heavy as electrons but positively charged. It was later discovered that electromagnetic waves and light are also composed of particles called photons. In this way, people have discovered new levels deeper than atoms-positrons, neutrinos, muons, τ neutrons and so on. It belongs to three levels: proton, neutron and electron. People think that they have found the most basic unit that constitutes the material world, so they call it elementary particles, and think that they are the eternal and inseparable basic units that constitute various substances.
However, some phenomena discovered later show that elementary particles are not "basic", and there should be something smaller and more basic inside hadrons.
In this regard, Sakata Shyoichi, a Japanese physicist, put forward the famous Sakata model in 1956, arguing that hadrons are composed of three basic particles, such as protons, neutrons and λ hyperons, and their antiparticles. 1964, gherman, an American physicist, improved the Sakata model and kept three kinds of "elementary particles", but they are not protons, neutrons and λ hyperons, but are composed of an unknown and symmetrical thing-quarks.
Why is it called quark? There is another interesting story about the naming of quarks. In the novel Night Sacrifice at Launigan by the English novelist James Joyce, there are some poems like this:
"quarks ...
Quarks ... Quarks, "
Three or five seabirds straightened their necks and rushed at the gentleman Mark together.
Mark got nothing but three quarks:
Everything belongs to Mark except the goal he wants.
The supreme emperor hid in the clouds and peeped into the lower world, and could not help sighing again and again. Mr. Mark, it's ridiculous and pathetic:
Crying in despair in the dark-"My shirt, my shirt,"
In order to find muddy pants, I stumbled in the depths of the park and fell down step by step.
This novel describes Mr. Brown's life. He sometimes plays Mr. Mark. Quark refers to the chirping of seabirds, and refers to Mark's three sons. Mark always expresses himself through the actions of his sons. Gherman imagined that there were three unknown particles in a proton, so he casually named him "Quark". China used to call quarks "stratons", meaning particles lower than electrons, protons and neutrons.
Gherman's quark model points out that this particle has the characteristics of fractional charge, and assumes that there may be three kinds of quarks-proton quarks, neutron quarks and strange quarks. From 1974 to 1976, someone increased the quark family to six, namely charm quark, upper quark and lower quark.
Since quarks exist, where are they? Some people think quarks are locked in hadrons like prisons. Hadron is like a pocket. Quarks are locked inside. It can move freely in its pocket, but it is not allowed to leave it. If you want quarks to come out of your pockets, you must provide huge energy, but it is impossible at present.
Although quarks are still in the hypothetical stage, some physicists have begun to consider particles lower than quarks. De Rogella of CERN named the particles that make up quarks "Gehrig". Later, people put forward various sub-quark models with various names, such as sub-quark, pre-quark, pre-quark or early quark, and some named Ques and Alpha. 1974, American physicists Patty and Salam put forward such a subquark model: I taste: P, N, λ, X, spin S = 12Ii color atoms: R, Y, G, L, spin s = 0. They can form quarks ur = (pr), uy = (py), ug = (pg) and so on. There are leptons: E = (NL), Yu = (XL), μ (λ L) and so on. 1977, Professor Hideki Terazawa of the Institute of Nuclear Physics of the University of Tokyo, Japan, put forward a new model based on the above model: quarks = taste, color and generation, all of which are subquarks with spin. No matter how different the models are, it is believed that quarks have a next level, so subquarks are also called "sublayers" in China.
What exactly are quarks like? Do subquarks really exist? These are still inconclusive, and people are waiting to be revealed.