The public symposium, "The Cosmic Thread: From Stars to Life," will take place from 9 a.m. to 5:35 p.m. at UC Berkeley. The main lecture hall, Pimentel Hall, has already sold out, but a new hall has been opened with a high-quality audio/video feed. Tickets are $20 through pre-registration or at the door.

"The list of speakers is stellar," said Alex Filippenko, professor of astronomy at UC Berkeley and president of the society. "We chose people who are truly experts in their field but also excel at communicating scientific concepts to the public."

Among the speakers is Geoffrey Marcy, UC Berkeley professor of astronomy and the world's No. 1 planet hunter. He and his colleagues have discovered nearly two-thirds of all known planets outside our solar system. He will discuss "The Prospects for Life on Other Planets."

Two scientists from the SETI Institute, Jill Tarter and Seth Shostak, will give talks about the search for signals from space, and what we would do if we actually detected signals from another civilization. UCLA astronomer Ben Zuckerman will counter their optimism in a talk entitled "The Search Is Futile: Intelligent Life Is Rare," while Chris Impey of the University of Arizona asks the question, "Why Are We So Lonely?"

Two scientists from NASA's Ames Research Center, Chris McKay and David Morrison, will discuss the origins of life and cosmic influences on biological evolution.

Filippenko will begin the day-long program with a survey of the universe, from the Big Bang to the formation of galaxies, planets and chemical elements.

A panel discussion will follow the lectures, during which the speakers will take questions from the audience and debate issues brought up in the talks.

The lecture series is co-sponsored by the Astronomical Association of Northern California and by UC Berkeley's Department of Astronomy.

The non-profit Astronomical Society of the Pacific was founded in 1889 in San Francisco, and has since grown into an international society whose members include professional and amateur astronomers, science educators of all levels, and the general public. The organization publishes the bimonthly Mercury magazine for its members and a technical journal for professional astronomers.