In science, alumni include astronomers Carl Sagan, a prominent contributor to the scientific research of extraterrestrial life, and Edwin Hubble, known for "Hubble's Law", NASA astronaut John M. Grunsfeld, geneticist James Watson, best known as one of the co-discoverers of the structure of DNA, experimental physicist Luis Alvarez, popular environmentalist David Suzuki, balloonist Jeannette Piccard, biologists Ernest Everett