Shapley was born on November 2, 1885, in Nashville, Missouri. He received the equivalent of a fifth-grade education and went to nearby Pittsburg, Kansas, where he took a business course. He became a reporter and, at the age of sixteen, moved to Joplin, Missouri, to become a police reporter. Later he enrolled in the Presbyterian Carthage Collegiate Institute in Carthage, Missouri, and graduated after a year and a half and went on to the University of Missouri in 1907, planning to enter the new School of Journalism. A delay in the opening of that school interfered, so Shapley became involved in astronomy almost by accident. He received a B.A. degree in 1910 and an M.A. in 1911, with honors in mathematics and physics.
After graduation, Shapley began working with astronomer Henry Norris Russell at Princeton University on eclipsing binary stars. The two men were able to gain a great deal of knowledge about the sizes of stars, using new computing methods. In all, they examined ninety eclipsing binary stars.
After completing his Ph.D. in 1914, Shapley directed his attention toward Cepheid variable stars, which fade and brighten at regular intervals, as if one star was eclipsing another. Shapley had proposed that Cepheids were single stars that slowly pulsed. As the star's size changed, its brightness changed as well. Arthur Eddington did the theoretical analysis that supported Shapley's claim.
When he was hired to a post at the Mt. Wilson Observatory in Pasadena, California, in 1914, Shapley began to study variable stars in objects called globular star clusters. Shapley discovered many new Cepheid variable stars and devised a method of calculating the distance to the clusters, based on the relationship between a Cepheid's brightness and its period of change worked out by Henrietta Leavitt. His results, in 1918, established a radically changed concept of the size of the Milky Way. It had been believed that the Milky Way was about 10,000 light years across, and that the Sun was near its center. Shapley deduced that the system was actually 300,000 light years across and the sun was 50,000 light years away from the center.
Others, such as Heber Doust Curtis (1872-1942), were not convinced at first. But in 1921 Shapley was appointed director of the Hale Observatory at Harvard, where he began a study of the two Magellanic Clouds. In 1924 he determined that the Clouds were not a part of the Milky Way; the Small Magellanic Cloud was as much as 100,000 light years away.
In February of the same year, astronomer Edwin Powell Hubble notified Shapley of his discovery of two Cepheid variable stars in the Andromeda nebula. Astronomers thought that the nebula was a part of the Milky Way system. But looking at the data provided by the Cepheid variables, Shapley realized the Andromeda nebula was an entirely separate star system, located at an extreme distance. Shapley's interests swung toward the nature of these distant nebulae, which he called galaxies, and he surveyed tens of thousands of them in the following years.
During the late 1930s, Shapley became active in human rights issues, rescuing European refugee scientists by bringing them to the United States. After World War II, he was involved in the formation of the United Nations Educational, Scientific, and Cultural Organization (UNESCO), and was one of the Americans sent to London to write the UNESCO Charter. He also hosted scientific and political conferences attended by Soviet delegates. As a result of these cultural endeavors, Shapley was accused of un-American acitivities during the anti-communist hysteria of the late 1940s and early 1950s. However, he was quickly absolved. Shapley continued as director of the Harvard Observatory until the fall of 1952. He remained active, traveling and giving lectures, through his 85th birthday. When his health began to fail, he retired to Boulder, Colorado, where he died on October 20, 1972.
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