Steven Elliot Koonin, born in Brooklyn, New York City, is an American theoretical physicist and environmental scientist. He graduated from Stuyvesant High School at 16, earned his Bachelor of Science from the California Institute of Technology, and his Ph.D.
from the Massachusetts Institute of Technology. In 1975, Koonin joined the faculty of the California Institute of Technology as an assistant professor of theoretical physics, becoming one of their youngest faculty members.