Nobel Causes

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The Cosmic Cartographer: George Smoot

George Smoot didn't set out to be a weather reporter or a mapmaker. But in 1992, he made cartographic history when he created the first map of the young universe by charting slight variations in the temperature of 14-billion-year-old radiation. Variations in this "cosmic microwave background," or CMB, give astrophysicists clues about how complex structures like galaxies formed.

A physics professor at the University of California, Berkeley, Smoot shares the Nobel Prize in physics with John Mather of NASA Goddard Space Flight Center for work on the CMB, whose existence supports the big bang theory.

Angelica de Oliveira-Costa, now a research scientist at MIT's Kavli Institute for Astrophysics and Space Research, joined Smoot's lab at Berkeley as a graduate student the year after Smoot announced his map. She says part of what makes him a first-rate physicist is that "he has a good eye for good ideas and is not afraid of change."

Smoot was always attracted to cosmology, but he did his graduate work in particle physics and took a job with Luis Alvarez, a Nobel laureate in that field at Berkeley. Between projects, Alvarez told his staff to take a few months off and look into fertile new areas of research. Smoot seized the opportunity to move into cosmology, adopting Alvarez's philosophy as his own: "When you finish an experiment, don't just automatically do the next one. You should see if there is some new discovery or technology that will enable you to make measurements in an area that's promising."

For Smoot, the study of the cosmic microwave background was just such an area--alluring and wide open. He says he had "the intuition that whatever you measure there is going to be a fundamental measurement," and he was right. De Oliveira-Costa says of her three years in Smoot's lab, "Scientifically, it was one of the best times of my life. Every tiny discovery you made was new."

Discovered in the 1960s, the CMB had been predicted by the big bang theory. The radiation comes not from a place in the universe but from a time soon after the universe's formation. "When we look back at the radiation, we're looking back to a time in the universe when everything was hot and dense like the plasma in our sun," explains Edmund Bertschinger, head of the MIT physics department's astrophysics division. As the universe expanded, it cooled, and so did the CMB, which is now only about 2.7 degrees above absolute zero. "We're seeing that afterglow in our radiotelescopes billions of years later," he says.

The photons of the CMB provide something like a photograph of the universe about 370,000 years after the big bang, when it cooled to about 3,000 °C, releasing particles to form the first atoms. Until then, the universe was an opaque, high-energy plasma; photons were caught up in heated and intimate conversation with subatomic particles like electrons. When the universe cooled and atoms formed, photons--including those that make up the CMB--could for the first time move freely.

When Smoot started working on the CMB, its exact spectrum was unknown, and it appeared to have completely uniform energy. This uniformity suggested an early universe where energy and matter were distributed homogeneously--a scenario apparently incompatible with today's varied and complex universe. How could stars grouped into galaxies grouped into clusters of galaxies surrounded by large voids emerge from an early universe where matter was spread out as smoothly as icing on a wedding cake? For the big bang theory to hold up, the early universe would have to have had lumps upon which quantum-mechanical forces and then gravity could act, eventually causing galaxies and other structures to form.