Nobel Prize for Physics Honors Subatomic Breakthroughs

Mason Inman
for National Geographic News
October 7, 2008
Three researchers from the U.S. and Japan will share the 2008 Nobel Prize in physics for their contributions to work that helps explain why the universe exists.

Yoichiro Nambu of the University of Chicago won half the 10-million-Swedish-kronor (1.4-million-U.S.-dollar) prize for being the first to predict spontaneous symmetry breaking.

Nambu's theories, developed in 1960, have been crucial in building the standard model of particle physics, a set of theories that describe all the fundamental forces of nature, with the exception of gravity.

Japanese physicists Makoto Kobayashi, of the High Energy Accelerator Research Organization in Tsukuba, and Toshihide Maskawa, of the Yukawa Institute for Theoretical Physics in Kyoto, will split the remaining half of the prize.

The pair is being honored for explaining in 1972 how symmetry breaking works among subatomic particles known as quarks.

Their work "provides a framework for understanding why matter vastly dominates over antimatter in our universe," said physicist Curtis Callan of Princeton University, who is vice president of the American Physical Society.

Frank Close, of the University of Oxford in England, added that the deficit of antimatter is "believed to be central to why there's something rather than nothing."

Matter Annihilation

Ordinary matter has an "evil twin" known as antimatter, which is made of particles of similar mass but of the opposite electrical charge.

Negatively charged electrons, for example, have antimatter counterparts called positrons, which are positively charged particles used in medical imaging.

When matter and antimatter collide, they annihilate each other in a burst of energy.

During the big bang—the violent explosion that kick-started the universe about 14 billion years ago—matter and antimatter should have been created in equal amounts.

But in the visible universe, we see mostly matter, and no one has been able to account for the "missing" antimatter.

This imbalance is what allows us to exist—had there been precisely equal amounts of matter and antimatter in the early universe, they would have quickly destroyed each other.

Physicists therefore think there must have been some tiny breaking of symmetry that made matter win out over antimatter.

This symmetry breaking is all around us in nature, noted Close of Oxford.

"If you freeze water, you get the beautiful six-fold symmetry of a snowflake," he said (see snowflake photos).

But liquid water is symmetric in all directions, and its molecules have to rearrange to form snowflakes.

"So when you freeze water, that symmetry [in all directions] disappears," Close said.

Predicting Quarks

Kobayashi and Maskawa's work was also recognized by the Nobel committee for predicting at least three families of quarks—particles that combine to form protons and neutrons, which make up the nuclei of atoms.

Particle colliders, which smash atoms together at high speeds to break them into their components, were able to create these short-lived quarks in the 1970s and 1990s.

The theorists' work later motivated the construction of two huge particle colliders in Japan and California that have since confirmed the researchers' precise predictions of how often exotic particles known as B-mesons would show symmetry breaking.

Oxford's Close noted that Nambu's work directly relates to understanding the Higgs boson, a theoretical particle that might give all other particles their mass.

Researchers hope the Higgs boson will appear for the first time in experiments soon to start at the recently launched Large Hadron Collider near Geneva, Switzerland.

Last year's physics Nobel went to two European researchers, who had discovered the electromagnetic phenomenon that made possible the massive hard drives used in modern computers, cell phones, and music players.

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