Edwin Hubble: the Astronomer Who Discovered the Universe

The astronomer Edwin Hubble made one of the most profound discoveries about our universe. He found there is a much larger cosmos out beyond the Milky Way Galaxy. In addition, he discovered that the universe is expanding. This work now helps astronomers measure the universe.

Hubble's Early Life and Education

Edwin Hubble was born November 29, 1889, in the small town of Marshfield, Missouri. He moved with his family to Chicago when he was nine years old, and remained there to attend the University of Chicago, where he received a bachelor’s degree in mathematics, astronomy, and philosophy.

He then left for Oxford University on a Rhodes Scholarship. Due to the dying wishes of his father, he put his career in the sciences on hold, and instead studied law, literature, and Spanish.

Hubble returned to America in 1913 and spent the next year teaching high school Spanish, physics, and mathematics at New Albany High School in New Albany, Indiana. But, he wanted to get back to astronomy and enrolled as a graduate student at the Yerkes Observatory in Wisconsin.

Eventually, his work led him back to the University of Chicago, where he received his Ph.D. in 1917. His thesis was titled Photographic Investigations of Faint Nebulae. It laid the foundation for the discoveries that changed the face of astronomy.

Reaching for the Stars and Galaxies

Hubble next enlisted in the Army to serve his country in World War I. He quickly rose to the rank of major, and was injured in combat before being discharged in 1919.

Hubble went immediately to Mount Wilson Observatory, still in uniform, and began his career as an astronomer. He had access to both the 60-inch and the newly completed, 100-inch Hooker reflectors. Hubble effectively spent the remainder of his career there. He helped design the 200-inch Hale telescope.

Measuring the Size of the Universe

For years, astronomers had observed strangely shaped fuzzy spiral objects. In the early 1920s, the commonly held wisdom was that they were simply a type of gas cloud called a nebula. "Spiral nebulae" were popular observation targets, and a lot of effort was spent trying to explain how they could form. The idea that they were whole other galaxies was not even a consideration. At the time it was thought that the entire universe was encapsulated by the Milky Way Galaxy — the extent of which had been precisely measured by Hubble’s rival, Harlow Shapley.

Hubble used the 100-inch Hooker reflector to take extremely detailed measurements of several spiral nebulae. He identified several Cepheid variables in these galaxies, including in the so-called "Andromeda Nebula". Cepheids are variable stars whose distance can be precisely determined by measuring their luminosity and their periods of variability. These variables were first charted and analyzed by astronomer Henrietta Swan Leavitt. She derived the "period-luminosity relationship" that Hubble used to discover that nebulae he saw could not lie within the Milky Way.

This discovery initially met great resistance in the scientific community, including from Harlow Shapley.

Ironically, Shapley used Hubble’s methodology to determine the size of the Milky Way. However, the "paradigm shift" from the Milky Way to other galaxies that Hubble was a tough one for scientists to accept. However, as time passed, the undeniable integrity of Hubble’s work won the day, leading to our current understanding of the universe.

The Redshift Problem

Hubble's work led him on to a new area of study: the redshift problem. It had plagued astronomers for years. Here is the gist of the problem: spectroscopic measurements of the light emitted from spiral nebulae showed that it was shifted toward the red end of the electromagnetic spectrum. How could this be? 

The explanation turned out to be simple: the galaxies are receding from us at high velocity. The shift of their light toward the red end of the spectrum happens because they are traveling away from us so fast.

This shift is called doppler shifting. Hubble, and his colleague Milton Humason used that information to come up with a relationship now known as Hubble’s Law. It states that the farther away a galaxy is from us, the more quickly it is moving away. And, by implication, it also taught them that the universe is expanding. 

The Nobel Prize

Edwin Hubble was never considered for the Nobel Prize, but it was not due to a lack of scientific achievement. At the time, astronomy was not recognized as a physics discipline, therefore astronomers could not be considered.

Hubble advocated for this change, and at one point even hired a publicity agent to lobby on his behalf. In 1953, the year Hubble died, astronomy was formally declared ​to be a branch of physics. That paved the way for astronomers to be considered for the prize. Had he not died, it was widely felt that Hubble would have been named that year’s recipient (the Nobel Prize is not awarded posthumously).

Hubble Space Telescope

Hubble’s legacy lives on as astronomers continually determine the expansion rate of the universe, and explore distant galaxies. His name adorns the Hubble Space Telescope (HST), which regularly provides spectacular images from the deepest regions of the universe.

Edited by Carolyn Collins Petersen