How a janitor at the Mount Wilson Observatory measured the size of the universe
Milton Humason, a high-school dropout who worked as a mule driver and then a janitor at the Mount Wilson Observatory in California, worked his way up to become the assistant of Edwin Hubble, whom he helped to study the spectral redshift of hundreds of galaxies.
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Humason worked with Hubble, and later Hubble’s protege, Allan Sandage, to study the spectral redshift of hundreds of galaxies to determine how fast they were receding… their so-called “radial velocity”. Hubble (correctly) believed the radial velocity of a galaxy was related to its distance, a relationship now known as “Hubble’s Law”.Skip to next paragraph
Gallery Images from the Hubble telescope
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But these far-away galaxies had low surface brightness, and were notoriously hard to measure. So Humason developed techniques to optimize the photographic exposures and plate measurements. He determined the radial velocities of 620 galaxies, and helped set the distance scale and age of the universe. Much of Hubble’s success was attributed to Humason’s painstaking measurements.
In 2005, Humason’s life was the subject of the musical “The Expanding Sky” by the writer Stan Peal.
Brian Ventrudo blogs at One-Minute Astronomer.
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