In 1907, at the age of 22, Harlow Shapley went to study journalism at University of Missouri. When he learned that the opening of the School of Journalism 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.
Post-graduation, Shapley received a fellowship to Princeton University for graduate work, where he studied under Henry Norris Russell 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, and that the Sun's place in the galaxy was in a nondescript location.
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, where he had been hired by George Ellery Hale. 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.
From 1941 he was on the original standing committee of the Foundation for the Study of Cycles.
In the 1940's, Shapley helped found government funded scientific associations, including the National Science Foundation. He is also responsible for the addition of the "S" in UNESCO (United Nations Educational, Scientific and Cultural Organization).
In 1950, Shapley was instrumental in organizing a campaign in academia against the controversial US bestseller pseudoscience book Worlds in Collision by Russian expatriate psychiatrist Immanuel Velikovsky.
Named after him