Washington State University

Ask Dr. Universe

First you take three quarks…

January 6th, 2012

Dear Dr. Universe,
Can you tell our Science class about quarks?
Thank you.
Mrs. Brauchi and Mrs. Briere
Glendale, Arizona

In the beginning was the quark.

Actually, it was NEAR the beginning, and it was actually a very hot quark-electron soup, says Phil Deutchman, a theoretical physicist at the University of Idaho. He says that, according to current theory, the quarks in this early Universal soup condensed to form the nuclei of hydrogen, helium and lithium around 100 seconds after the Big Bang.

You realize that with a history like this we can’t cover everything about quarks in a newspaper column. But you’ll get a pretty neat glimpse. So, just to get us started,

Three quarks for Muster Mark!

Sure he hasn’t got much of a bark

And sure any he has it’s all beside the mark.

That’s a passage from James Joyce’s 1939 novel Finnegan’s Wake. It so happens that Murray Gell-Mann, the physicist who proposed the idea of the quark in 1964, is also one of the few people who actually RE-read Finnegan’s Wake. Though it is about language and dreams and mankind, I suspect that if you understand Finnegan’s Wake, you might also have a real knack for particle physics!

Regardless, says Professor Deutchman, you have to understand quarks historically. Even though they couldn’t see them, Greek philosophers, such as Democritus 2,400 years ago, figured everything was probably made of atoms—and that’s as small as things got. In fact, “atom” is from the Greek word for “indivisible.” However, it took over 2,200 years for someone to prove that these atoms existed.

Once that happened, though, other scientists joined in to completely screw up the idea of atoms being “fundamental,” or indivisible. In 1911, Ernest Rutherford and two of his students managed to reveal the existence of the atomic nucleus. So for a while it was just the nucleus and electrons. Then someone figured out the nucleus was made up of protons and neutrons, so THESE became “fundamental.” But, of course, that wasn’t the end of it.

Accelators are machines that hurl atoms and parts of atoms at each other at such high speeds that they break up. As the accelerators got stronger, scientists discovered more kinds of particles. Pretty soon it got out of control. There were suddenly so many fundamental particles (pions, kaons, lambdas, about 200 of them) that some people wondered, well what’s so FUNDAMENTAL about that?

So some of these people, including Gell-Mann, started suspecting there must be something MORE fundamental than fundamental particles. Maybe, just maybe, there was something smaller inside those neutrons and protons. Maybe there was a pattern.

The problem with trying to figure this out, says Professor Deutchman, is that there was no periodic chart for these particles, no family tree with which to relate them. And the abstract quantum numbers used to describe things at the subatomic level don’t exactly connect to your everyday experience.

In spite of this serious weirdness, however, Gell-Mann finally saw a pattern. He proposed that at least 200 of these particles could be reduced to fundamental(!) particles called quarks.

Well, okay, it wasn’t QUITE that simple. The quarks come in different varieties, or flavors, and combine in different ways. The first three quarks were named “up,” “down” and “strange.” This is not the world as you previously knew it.

Then the “charm” quark was discovered. Then the “bottom” quark, bringing the total to five. However, calculations showed there had to be a sixth quark. According to “The Standard Model,” everything in nature is made up of different combinations of six types of quarks and six of “leptons,” which include electrons and neutrinos.

Sure enough, scientists at the Fermilab, a huge accelerator in Illinois, found the “top” quark in 1995.

So is that it? Have we explained things? Is the quark truly fundamental?

No, says Professor Deutchman. It’s the first step inside. And it looks like maybe quarks have a structure, which means there’s something smaller!

One possibility for the smaller things inside the quark is “strings,” the core of Superstring Theory, yet another take on HOW THINGS WORK.

Superstring Theory holds that everything is made up of tiny (about one millionth of a billionth of a billionth of a billionth of a centimeter!) one-dimensional strings, and that particles as we know them are determined by how the strings vibrate. You may be glad to know that one thing Superstring Theory does away with is the idea of the infinitely divisible particle. The string is as small as it gets. Sound familiar?

Actually, it’s not, but that’s another story.

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