Edwin Hubble made two major contributions to American science. At a time when it was believed that the universe ended with the Milky Way, Hubble proved the existence of other galaxies, and he showed that the universe was expanding. He developed a mathematical concept to quantify this expansion, known as Hubble's law.
Edwin Powell Hubble was born on November 20, 1889, the third of seven children. The family lived in Missouri until 1898, when they relocated to Chicago, Illinois . Hubble excelled in both academics and sports, graduating from high school in 1906 at the age of sixteen. An academic scholarship sent him to the University of Chicago, where he graduated with a bachelor's degree in mathematics and astronomy in 1910.
In 1910, Hubble traveled to England to study at Oxford University as a Rhodes Scholar. In addition to his law studies there, he continued to pursue his athletic interests. Hubble returned to the United States in 1913 and began practicing law. Boredom set in within the first year, and he returned to the University of Chicago to work toward a Ph.D. in astronomy.
Hubble began working under the supervision of the school's Yerkes Observatory director. During this time, he met astronomer George E. Hale (1868–1938), the founder of the Yerkes Observatory and director of the Mount Wilson Observatory in California . The director invited Hubble to join the Mount Wilson staff once he received his degree, and Hubble accepted the offer. After serving in the army in World War I (1914–18) and being discharged in 1917, Hubble began his work at Mount Wilson. He stayed at the institution throughout his career.
In 1923, Hubble observed galaxies outside the Milky Way. His discovery of the existence of other galaxies—he would eventually discover nine—was announced publicly in 1924. That same year, he married Grace Burke Leib. The following year, Hubble introduced a system for classifying these galaxies, which became the basis for the modern classification system used by astronomers.
Determining distance using Hubble's law
Hubble continued to study galaxies throughout the 1920s. During this time, he measured the distances of more than twenty galaxies. But 1929 would prove to be the year of Hubble's most important discovery.
For over a decade, scientists predicted that the light coming from distant galaxies might indicate that they were moving apart from each other and away from Earth. If they were speeding fast enough away from Earth, that motion would stretch the light waves emitting from them. This stretching was called the redshift because longer wavelengths make light take on a reddish hue.
Hubble's most famous achievement was to determine the redshifts for a large number of galaxies by measuring the wavelengths of light emitting from them. His measurements told him that distant galaxies did move away from Earth. He also learned that the farther away these galaxies were from Earth, the faster they moved. The relationship between a galaxy's distance and its speed eventually became known as Hubble's law.
Big bang theory
Hubble's observations gave scientists a place to start when trying to determine the age of the universe and how it began. Some experts, such as British astronomer Fred Hoyle (1915–2001), theorized that the universe existed in a steady state, without beginning or end. Others raised the possibility that the origin of the universe was a single point from which everything else—space, time, and matter—had expanded. Astronomers proposed that this expansion had begun with a huge explosion, called the Big Bang, a phrase coined by Hoyle.
Hubble refused to get involved in the argument. Instead, he viewed his role as one of observing and reporting. Instead of saying galaxies were moving, he claimed they appeared to be moving.
Hubble had become America's leading astronomer by the 1930s. He was in charge of the Mount Wilson Observatory and mentored an entire generation of younger astronomers who studied there. His work extended beyond Mount Wilson, however, and he was intimately involved in the planning and construction of a new 200-inch telescope at Mount Palomar observatory in southern California. The telescope was named the Hale, after Hubble's own mentor.
Hubble headed an army research department during World War II (1939–45). He had the honor of being the first to use the Hale telescope when it was completed in 1948. The esteemed astronomer continued to work at Mount Wilson and Mount Palomar until his death on September 28, 1953, of a stroke.