To the best of our knowledge today quarks are the fundamental building blocks of all nucleons. An unusual property of quarks is that they carry fractional electrical charges. One kind, the “up” quark carries at 2/3 the electron charge, and another kind, the “down” quark has -1/3 the electron charge. The name “quark”, inspired by a quotation from Finnegan’s Wake by James Joyce was chosen in 1963 by Murray Gell-Mann, who first proposed their existence.
Lighter particles like muons and electrons, and still lighter particles called neutrinos make up a class of six particles called leptons, which are not composed of quarks. At the present time the six quarks and the six leptons (and their anti-particles) are thought to be the truly elementary particles. The neutrino (“little neutral one”) is very hard to detect because they interact very weakly with matter. Thousands of neutrinos are flying through you every second of every day, and only occasionally, one or two times a year or so, does a neutrino or two interact with the matter of your body. But when they do, look out. Pesky as mosquitoes. Continue reading