Measuring one of the universe's building blocks

Electrons are everywhere. There are trillions of them around you as you read this. They help make your computer, TV, cell phone - even the universe - work.

Every atom boasts a thin cloud of them orbiting its core, or nucleus. When they jump from one orbit to another, they create the electric and magnetic forces that power the universe. Their behaviors in the most energetic orbits determine the chemical properties of everything you can think of.

Yet only a few people think deeply about electrons. One is Gerald Gabrielse, Leverett Professor of Physics at Harvard University. In the past 20 years, he has discovered new things about them, things that even Albert Einstein never knew. And he's trained a half-dozen young Ph.D.s in the business of how subatomic particles make the universe what it is.

Despite its role as a fundamental building block of everything, there are still some mysteries about the electron's size and character, its motion and magnetism, its energy and natural spin.

These mysteries are difficult to solve because, as you might guess, single electrons are hard to isolate and work on. First of all, they are among the smallest of particles, about 1,000 times smaller than the protons in the atomic cores they orbit, or much less than a trillionth of an inch across.

Also, electrons are the world's smallest magnets, and they carry a minute electric charge. This negative charge keeps them in orbit around the positively charged nuclei of atoms. You can't keep them alone in metal containers unless you find a way to neutralize their electricity and magnetism. They move with almost the speed of light at room temperatures. Gabrielse and other physicists have to cool them down to temperatures near minus 460 degrees Fahrenheit, or near absolute zero, a temperature at which electrons and other particles hardly move.

Gabrielse has earned himself a place in the history of physics for skillfully building exotic traps that hold single electrons at very low energies so they can be studied and measured (see Nov. 14, 2002, Gazette). In one of these traps, he and a student once carried electrons, delicately suspended in magnetic and electric fields, across the United States inside a truck.

In two papers about to be published in the scientific journal Physical Review Letters, he and his colleagues describe how they used such a trap to measure the electron's magnetism with an accuracy of more than one part in a trillion. That's a sixfold improvement over a historic measurement of electron magnetism made in 1987, a feat that later won a Nobel Prize.

"Peeking inside a particle as fundamental to us and our universe as the electron is an exciting and difficult undertaking," Gabrielse notes. "The puzzling electron seems to have no discernable size or substructure, yet it has intrinsic magnetism. We finally devised a way to peek inside it at a level of precision 10 times better than any other method used to date."