Harlow Shapley (November 2, 1885 – October 20, 1972) was an American astronomer.
Born in Nashville, Missouri, he studied under Henry Norris Russell at Princeton University and used the period-luminosity relation for Cepheid variable stars (discovered by Henrietta Swan Leavitt) to determine distances to globular clusters. He was the first to realize that the Milky Way Galaxy was much larger than previously believed.
He participated in the "Great Debate" with Heber D. Curtis on the nature of nebulas and galaxies and the size of the universe. The debate took place on April 26, 1920. Shapley argued against the theory that the Sun was at the center of the galaxy, and promoted the idea that globular clusters and spiral nebulae are within the Milky Way. He was incorrect about the latter point, but correct about the former.
At the time of the debate, Shapley was working at the Mount Wilson Observatory. After the debate, however, he was hired to replace the recently deceased Edward Charles Pickering as director of the Harvard College Observatory.
He served as director of the HCO from 1921 to 1952. During this time, he hired Cecilia Payne-Gaposchkin, who became the first person to earn a doctorate at Harvard University in the field of astronomy.
In the 1940's, Shapley helped found government funded scientific associations, including the National Science Foundation. He is also responsible for putting the "S" in UNESCO (United Nations Educational, Scientific and Cultural Organization).
Politically, Shapley was a liberal, and found himself one of the victims of McCarthyism.
In 1950, Shapley was instrumental in organising a campaign in academia against the controversial US bestseller pseudoscience book Worlds in Collision by Russian expatriate psychiatrist Immanuel Velikovsky.
In addition to astronomy, Shapley held a life long interest in myrmecology, the study of ants.
Harlow Shapley originally intended to study journalism at Princeton. When he learned that the opening of the journalism department had been postponed for a year, he decided to study the first subject he came across in the course directory. Rejecting archeology, which Harlow later explained he couldn't pronounce, Harlow chose the next subject, astronomy.
Named after him