Campus & Community

Radcliffe’s Super Cluster Lecture Series debuts:

3 min read

How old is the sun? … and other questions are addressed

How does the sun shine? John Bahcall, visiting professor of astrophysics at Princeton University and Richard Black Professor of Natural Sciences at the Institute for Advanced Study in Princeton, N.J., will explain on Wednesday (Dec. 11) at 4 p.m. His talk is the first in the Super Cluster Lecture Series at the Radcliffe Institute for Advanced Study

Bahcall will address the intertwined questions of the age of the sun and the origin of solar energy in “How Does the Sun Shine?” a lecture that takes us from debates on evolution to underground neutrino laboratories. The journey begins in the 1850s with the controversy over the sun’s age among physicists, geologists, and biologists, whose differing theories on evolution influenced their calculations. The tale weaves from there to the discovery of natural radioactivity; Einstein’s Theory of Relativity; nuclear fusion; and the use of neutrinos, massless particles produced by the sun as it burns hydrogen into helium, as a way to “see” into the solar interior.

Bringing us to the modern era, Bahcall will summarize historical developments across two centuries and discuss the implications of recent discoveries. He also will talk about his own experiments, which led to the building of underground laboratories in the 1960s and ’70s in Japan, Russia, and Italy to detect and measure neutrinos as proof that the source of energy radiated by the sun is the fusion of hydrogen nuclei in the solar interior. In this early work, fewer neutrinos were observed than predicted by theoretical models, however: a mystery that persisted until 2001, when new experiments provided a dramatic solution.

Bahcall received his A.B. in physics from the University of California, Berkeley; his M.S. from the University of Chicago; and his Ph.D. from Harvard University. He has been a member of the Institute for Advanced Study in Princeton since 1968 and a visiting lecturer with the rank of professor in astrophysics at Princeton University since 1971. He is a member of the American Astronomical Society and the National Academy of Sciences; has won the national Medal of Science and the Bernhard Lecture and Medal from the Royal Swedish Academy of Science, among dozens of other awards; and was a member of the Hubble Telescope Working Group for 20 years.

The Super Cluster Lecture Series brings to the public the work of cosmologists, astrophysicists, and earth and planetary scientists.

John Bahcall’s lecture is at 4 p.m., Dec. 11, at Jefferson 250, 17A Oxford St. It is free and open to the public and will be preceded by a reception at 2:30 p.m. in the Jefferson Library.