The three families

The three families of particles are shown in the Standard Model. Image: Fermilab

Did the title make you think of powerful people and wonder who the second and third families are? This is a science corner, and these families are elementary particles. When I told my girlfriend (long ago) I was studying elementary particles, she asked when would I progress to studying advanced particles. But elementary means that they are not made out of anything smaller, as far as we know.

Amazing fact: all known matter is made of just three tiny particles called up quarks, down quarks and electrons. They stick together to make atoms, which stick together to make you. We call them the “first family.”

It’s like letters put together in different ways to make words, sentences and then stories. Except that nature uses just three letters, and scientists discovered many rules about allowed combinations.

The lightest atom is hydrogen, made of (u+u+d)+e. I lumped the quarks together, because that’s what nature does to make a proton. All the different elements are more of these stuck together in different ways. For example, a carbon atom has (18 u’s and 18 d’s) and 6 e’s. Just saying. And then carbon atoms can be stuck together in different ways to make coal, diamonds and graphite. Complexity arising out of simplicity.

But there’s more! In addition to that “first family,” physicists discovered a second family they whimsically named the charm quark, the strange quark and the muon. These are all heavier than their first-family cousins, and all are very unstable, decaying so fast that they are not in normal matter. Then a third family was discovered, the top quark and bottom quark, at nearby Fermilab, and the tau (Greek letters!) at Stanford, California.

Each of these three families of particles has a fourth member called a neutrino. Neutrinos do not stick to the others, and are much lighter, zipping along at nearly the speed of light, mysteriously changing from one family to another. Experiments at Fermilab are trying to understand these weird particles. They come from the sun, from radioactivity, nuclear reactors, supernovae and the cosmos.

Astronomers discovered stuff out in space called “dark matter.” Like all matter, it feels gravity and is probably made of unknown particles. Like neutrinos it does not stick to normal matter, but there is about five times more of it out there!

The more you know (and we know a lot!) the more you realize how much you don’t know, as the frontiers of knowledge expand. Long may it continue!

This is a version of an article that appeared in Positively Naperville.