Although we have greatly expanded the reach of the idea, we still conduct our science by this same principle: that the laws of physics and chemistry are the same everywhere, and we now call the general thought the "Principle of Mediocrity."

If this is so — and after 400 years of observation and investigation, we have no reason to doubt it — then we cannot believe that there is anything special about the Earth or the life that inhabits it. If one earth exists, then there must be many.

The first extrasolar planet was discovered in 1995 by Michel Mayor and Didier Queloz of the Geneva Observatory, but we deeply believed in the existence of these planets long before their recent discoveries.

Mayor and Queloz's finding was soon confirmed by the team of Marcy, Butler, Fischer and Vogt and then greatly expanded upon. Marcy and colleagues have since discovered more than 110 planets. But in the intervening years since 1995, we have been surprised by the diversity of the types of solar systems we've found.

In September 2005, Geoff Marcy and Michel Mayor were awarded the $1 million Shaw Prize for their revolutionary discoveries. In referencing his award, Marcy said:

We now know that other planetary systems exist, but that their diversity renders our solar system just one type of many. The odd orbital shapes caused by the gravitational scattering of planets by other planets makes our solar system relatively peaceful by comparison. Perhaps life owes its existence here on Earth to the fortuitous, delicate arrangement of the planets in our system.

Marcy, like almost everyone else at the moment, expects that bacterial life should be common in the universe, but he is quite pessimistic about the presence of technological, "intelligent" life anywhere near us. Every observation of the night sky for the last two hundred years has been one more negative refutation its nearby absence.

— Wirt Atmar

About the Speaker

Geoff Marcy is well-known for discovering more extrasolar planets than anyone else, 70 out of the first 100 to be discovered, along with R. Paul Butler and Debra Fischer. He also confirmed Michel Mayor and Didier Queloz's discovery of the first extrasolar planet 51 Pegasi b.

Other achievements have included discovering the first multiple planet system around a star similar to our own (Upsilon Andromedae), the first transiting planet around another star (HD209458b), the first extrasolar planet orbiting beyond 5 AU (55 Cancri d), and co-discovered the first Neptune-sized planets (Gliese 436b and 55 Cancri e). He continues to discover and co-discover more every year.

Marcy and Michel Mayor received the $1 million Shaw Prize in astronomy in 2005 for their work.

Marcy has held teaching positions, first at the Carnegie Institution of Washington as a Carnegie Fellow from 1982 to 1984, then as an associate professor of physics and astronomy from 1984 to 1996, and then as a Distinguished University Professor from 1997 to 1999, both at San Francisco State University. Today he is an adjunct professor at San Francisco State University and a Professor of Astronomy at UC Berkeley.

Geoff is now the Director of the Center for Integrative Planetary Science at UC Berkeley.

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