Today we have a special treat: Lots of your favorite and most urgent questions about elementary particle physics - you do have some, right? - answered by Nobel Laureate Murray Gell-Mann, who predicted the existence of quarks back in 1963 and gave them their silly name. We caught up with him recently as he promoted his new book, "The Quark and the Jaguar."
Question: OK, so why'd he call them "quarks," and not, say, "geeberdongers"?
Answer: He says he just liked the sound of "quarks." Later he found a literary reference. He was perusing James Joyce's "Finnegans Wake" and saw a reference to "three quarks for Muster Mark." Though he says the right pronunciation is not "kwark" but "kwork."
Question: Do these things like quarks really exist, in reality, or are scientists just coming up with a theoretical model to satisfy their craving to understand the universe?
Answer: They're real all right. Gell-Mann says it's possible to detect quarks by bouncing electrons off protons or neutrons. The pattern of deflection shows that a proton or a neutron is actually made up of three distinct particles. Those are the quarks.
As for whether this is reality or just a model of reality, Gell-Mann says, "People who have taken philosophy courses seem to be worried about this. I don't know the difference. We describe reality as best we can. As far as we know, it is reality."
Question: Why was it such a big hairy deal when scientists recently found the so-called top quark?
Answer: Because if it hadn't been found, the theoretical physicists would have had to join Amway or find some other form of employment. They've banked heavily on there being a top quark. "It has to be there," GellMann says.
In science, unlike, say, politics, it is not enough to simply declare that something is so. You must support your explanation experimentally and show why some other explanation isn't as good. (This is why psychoanalysis is suspect as a scientific enterprise.)
What particle physicists do these days, for the most part, is try to discover particles that no longer exist. Used to be, back near the beginning of time, there were all kinds of interesting doodads just lying around. Big particles, powerful particles, particles with chicken pox, etc. But the Big Bang ruined all that. The cosmos cooled down, particles decayed, now we're stuck with what Gell-Mann calls the dregs of the universe.
Basically all we've got left in the wild are electrons, photons, neutrinos, gravitons (predicted but never found), and two types of quarks, called U and D quarks, for "up" and "down." But in high-energy particle accelerators it is possible to cook up some of the types of particles that used to exist. Physicists had found another pair of quarks, which they named "strange" and "charmed." Then came the discovery of another quark, dubbed the bottom quark. Quarks always come in pairs. Thus for years physicists have searched for the top quark to go with the bottom quark. They found it. Theory triumphed.
Question: How do we know there's not something more elementary than a quark?
Answer: We don't. But Gell-Mann suspects there isn't. "I think it's clear that the quarks are as elementary as the electron," he says. If quarks are composites, electrons have to be composites. And electrons don't look like composites, because they're all exactly the same, a strong indicator that they are truly fundamental.
Question: Why do protons have a positive charge and neutrons have no charge?
Answer: You really want to know?
Question: No, but you want to be asked.
Answer: You're right. Here goes. A proton is two U quarks and a D.
A neutron is one U and two Ds.
The charge of the U is plus-2/3 and the charge of the D is minus-1/3. So for a proton, Gell-Mann tells the caller, the charge is plus-2/3 and plus-2/3 and minus-1/3 equals plus-1 - there's your positive charge - and for a neutron it's plus-2/3 and minus-1/3 and minus-1/3 equals 0. That's why the neutron is neutral.
Question: What does Gell-Mann say about recent allegations by Russian intelligence agents that Robert Oppenheimer, Enrico Fermi, Leo Szilard and other U.S. atomic scientists funneled secrets to the Soviets?
Question: Why hasn't Gell-Mann become as famous as his late colleague Richard Feynman?
Answer: Even in a field like elementary particle physics it pays to be good-looking and charismatic and play the bongos. "He was a little too much of an egotist for me. After a while, it got wearing. But I still liked him," says Gell-Mann.
Question: Why are physics geniuses always rumpled professors in baggy sweaters and sneakers and unkempt hair?
Answer: They're not. Gell-Mann, at 64, is a dapper fellow. He's also annoyed that the public image of Einstein is that of a disheveled old coot. Einstein did his great work, developing the theories of special and general relativity, as a sleek, groomed, well-dressed German professor. But he was later forced into exile in the United States and, after his wife died, didn't take good care of himself. By then Einstein was far out of the physics mainstream. "He never tried to put the electron in any of his calculations," Gell-Mann says.
Question: That sounds dumb.
Answer: It's all relative.
Howard M. of Alexandria, Va., points out that we were reckless to use such language awhile back as "three-dimensional circle" when describing what a sphere is: "A circle rotated about a line tangent to it would form a doughnut and a circle moved through space on a line perpendicular to its center, or not perpendicular, would form a right circular cylinder or an elliptical cylinder."
Dear Howard: You say "elliptical cylinder," we say "hot-dog-shaped."