Archive for Sunday, October 27, 2002

KU theoretical physicist studies shape of proton

October 27, 2002


The proton one of those spherical things buzzing around inside the atom is having an identity crisis.

A quick physics review. The simplest atom, hydrogen, is just one electron spinning around one proton. Get rid of the electron and you can actually taste the proton. Vinegar and lemonade get their flavor from hydrogen atoms stripped of electrons. Protons taste sour. But the identity crisis of protons involves their shape, not their flavor. It seems they may not be spherical after all.

Kansas University theoretical physicist John Ralston did some math a couple years ago that indicated the proton might instead be oblong.

Or it might have a hole in the middle, like a Life Saver. Or maybe, he says, the quarks that constitute the proton are laid out like the rings of Saturn.

Recently, Ralston's sense that the proton is out-of-round received some experimental support. A team at Jefferson Laboratory in Virginia, headed by a College of William & Mary physicist, Charles Perdrisat, shot a high-energy electron beam at a target full of protons. Then they studied the protons knocked loose.

If a proton is round, it should be hard to flip over. But, Ralston says, "When a proton is nonround, when it has a 'handle' on it, so to speak, then it will flip more easily." And that's what happened in the experiment.

Before you get worked up about the all-new oblong proton, please realize the idea is still controversial among physicists. Not everybody interprets the ease with which the protons were flipped as evidence that they're out-of-round. Besides, even if the proton isn't a sphere, that leaves a whale of a lot of possibilities. These do not include a cube-shaped or egg-shaped proton, says Ralston though a hot-dog shape isn't out of the question.

Of course, all the speculation about the proton's shape would cease if only we could see it directly, which is tough. The proton is a hundred thousand times smaller than an atom. Nevertheless, Ralston is feverishly at work on the mathematics of how to see a proton. Because of the nature of the equipment used in physics experiments, it actually may be easier to see a proton directly than to see a large molecule directly, Ralston says.

Today, in order to "see" molecules, scientists have to crystallize substances containing them. Even then, determining their structure involves guesswork. "It's an absolute jigsaw puzzle," Ralston says. "You can come up with the correct structure but have it twisted the wrong way."

So even as he theorizes about how to see the proton directly, he "agonizes" that's his word, not mine about how to see molecules directly. If that were possible, he says, "You could do everything on the planet. You could discover drugs, know how genes are regulated, answer every unknown question in biology just by looking at the molecules."

As we wait for that, here's my question: What earthly difference does it make if the proton is out-of-round?

Ralston answers by remembering Michael Faraday.

Faraday was the guy who discovered the physical laws that made it possible to tame electricity. At one point, somebody asked, "Mike, why should we care? What are folks going to do with electricity anyway?"

Faraday answered: "What use is a newborn baby?"

Right now, the oblong proton is Ralston's baby. If it survives ... well, it's an idea with all the potential of any newborn.

Roger Martin is a research writer and editor for the Kansas University Center for Research and editor of Explore, KU's research magazine Web site, which can be found at Martin's e-mail address is

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