Hubble, Edwin (1889-1953)

views updated

Hubble, Edwin (1889-1953)

American astronomer

Edwin Hubble was an American astronomer whose impact on science has been compared to pioneering scientists such as the English physicist Isaac Newton and the Italian astronomer Galileo. Hubble helped to change perceptions of the universe in two very important ways. In an era when the Milky Way was perceived as the extent of the entire Universe, Hubble confirmed the existence of other galaxies through his observations from the Mount Wilson Observatory in Pasadena, California. Furthermore, with the help of other astronomers of his time, Hubble showed that this newly discovered Universe was expanding, and developed a mathematical concept to quantify this expansion now known as Hubble's law.

Edwin Powell Hubble was born in Marshfield, Missouri to John P. Hubble, an agent in a fire insurance firm, and Virginia Lee James Hubble, a descendant of the American colonist Miles Standish. The third of seven children, Hubble spent his early childhood in Missouri, entering grade school in 1895. In 1898, John Hubble transferred to the Chicago office of his firm, and the Hubble family moved first to Evanston and then to Wheaton, both Chicago suburbs.

Hubble attended Wheaton High School, excelling in both sports and academics. He graduated in 1906 at the age of sixteen, two years earlier than most students. For his efforts, he received an academic scholarship to the University of Chicago, where he studied mathematics, physics , chemistry , and astronomy . In the summer, Hubble tutored and worked to earn money for his college expenses. In his junior year he received a scholarship in physics, and by his senior year he was working as a laboratory assistant to physicist Robert A. Millikan. Hubble graduated in 1910 with a B.S. in mathematics and astronomy. In addition to his academic career, the six-foot-two-inch Hubble was an amateur heavyweight boxer.

In 1910, Hubble was awarded a Rhodes Scholarship, following which he went to attend Queen's College at the University of Oxford in England. There he studied jurisprudence, completing the two-year course in 1912. He began working on a bachelor's degree in law during his third year, but renounced it for Spanish instead. He also continued his athletic endeavors, excelling in the high jump, broad jump, shot put, and running. In 1913, Hubble returned to the United States and began practicing law in Louisville, Kentucky, where his family was now living. Bored with his law career within a year, Hubble returned to the University of Chicago in 1914 to work towards his doctorate in astronomy.

At the time Hubble attended the University of Chicago, Yerkes was a waning institution that did not actually offer formal courses in astronomy. However, working under the supervision of Edwin B. Frost, the observatory's director, Hubble made regular observations on Yerkes'telescope and studied on his own. It is believed that Hubble's work at this time was influenced by a lecture he attended at Northwestern University. At the presentation, Lowell Observatory astronomer, Vesto M. Slipher presented evidence that spiral nebulae (in that era, the term nebulae was used to describe anything not obviously identifiable as a star) had high radial velocitiesthe velocities with which objects appear to be moving toward or away from us in the direct line of sight. Slipher found spiral nebulae that were moving at much higher velocities than stars generally movedevidence that the nebulae might not be part of the Milky Way.

During his term at Yerkes, Hubble also met astronomer George Ellery Hale, founder of the Yerkes Observatory and then the director of the Mount Wilson Observatory in Pasadena, California. Hale had heard of Hubble, and in 1916, invited him to join the Mount Wilson Staff once he received his doctorate. However, Hubble's acceptance of this offer was delayed by World War I, which he joined in 1917. Hubble attained the rank of major, and after his discharge in 1919, he finally began work at Mount Wilson. The observatory had two telescopes, a 60in (152cm) reflector and a newly operational 100in (254cm) telescope, the largest in the world at that time. It was here that Hubble began the major portion of his life's work.

Hubble's first notable achievement at Mount Wilson was the confirmation of the existence of galaxies outside the Milky Way. From observations made in October 1923, Hubble was able to identify a type of variable star known as a Cepheid in the Andromeda nebula (known today as the Andromeda galaxy). By using information about the relationship between brightness, luminosity (how much light a star radiates) and the distances of Cepheid stars in our galaxy, Hubble was able to estimate the distance to the Cepheid in the Andromeda nebula to be about one million light years. Hubble also discovered other Cepheids, as well as other objects, and calculated the distances to them. Since scientists knew that the maximum diameter of the Milky Way was only 100,000 light years, Hubble's figures established the existence of galaxies outside our own. Eventually, he determined the distances to nine galaxies. Consistent with scientific terminology of his time, Hubble called these "extragalactic nebulae." The results of Hubble's work were publicly announced at the December 1924 meeting of the American Astronomical Society, settling one of the great scientific debates of that era.

Also in 1924, Hubble married Grace Burke Leib. His personal interests included dry-fly fishing (his favorite fishing haunts were in the Rocky Mountains and in England) and collecting antique books about the history of science. He served as a member of the Board of Trustees of the Huntington Library in San Marino, California from 1938 until he died in 1953.

Hubble's work at Mount Wilson was interrupted during World War II, when he served as chief of exterior ballistics and director of the supersonic wind tunnel at the Ballistics Research Laboratory at Aberdeen Proving Ground in Maryland. He worked at Aberdeen from 1942 to 1946 and received a Medal of Merit for his efforts.

Returning to Mount Wilson after the war, Hubble continued his observations of galaxies. In 1925 he introduced a system for classifying them at a meeting of the International Astronomical Union; according to this system, galaxies were either "regular" or "irregular." In addition, regular galaxies were either spiral or elliptical, and each of these classes could be further subdivided. The system used to classify galaxies today is still based on Hubble's structure.

In 1927 Hubble was elected a member of the National Academy of Sciences, but another great achievement was yet to come. By combining his own work on the distances of galaxies with the work of American astronomers Vesto M. Slipher and Milton L. Humason, Hubble proposed a relationship between the high radial velocities of galaxies and distance. He systematically looked at a number of galaxies and found that except for a few nearby, all of the others were moving away from us at high speed. He discovered a correlation between this velocity and distance, and the result was a mathematical concept now known as Hubble's law. Simply put, Hubble's law states that the more distant a galaxy is from us, the faster it's moving away from us. Although Hubble didn't actually discover that the universe is expanding, he put the theory together in a coherent way. Today, the expanding universe is part of the big-bang theory of the creation of the universe.