Milton Humason

Milton Humason. An American astronomer whose meticulous spectroscopic work was fundamental to the discovery of the expansion of the universe. With no formal education beyond the eighth grade, he rose from being a muleteer and janitor at the Mount Wilson Observatory to becoming a pivotal figure in observational cosmology. His decades-long collaboration with Edwin Hubble provided the critical radial velocity data that cemented the concept of an expanding cosmos, leading to the formulation of Hubble's law.

Early life and career

Born in Dodge Center, Minnesota, Humason moved to California as a youth and showed little early academic inclination, dropping out of school. He initially worked at the Mount Wilson Observatory site as a muleteer, helping to transport construction materials up the mountain via the Mount Wilson Toll Road. In 1917, after a stint as a janitor at the observatory, his keen interest and mechanical aptitude were recognized by staff, including astronomer George Ellery Hale. He was hired as a night assistant, operating the observatory's powerful telescopes, such as the historic 100-inch Hooker reflector.

Work at Mount Wilson Observatory

Humason quickly mastered the complex techniques of astronomical spectroscopy and astrophotography. His exceptional skill and patience at the telescope made him invaluable for long, difficult exposures required to capture the faint spectra of nebulae and distant galaxies. He worked under the directorship of Walter Sydney Adams and alongside noted astronomers like Francis G. Pease. Humason pioneered methods to increase the spectral sensitivity of photographic plates, allowing him to measure the redshift of galaxies farther away than previously possible, pushing the boundaries of the observable universe.

Collaboration with Edwin Hubble

This technical expertise led to a historic partnership with Edwin Hubble in the late 1920s. While Hubble focused on measuring galactic distances using Cepheid variables, Humason provided the complementary radial velocity data by analyzing galaxy spectra. His measurements, including that of the Virgo Cluster, showed a clear correlation between distance and redshift. This work, presented in a seminal 1931 paper, established the Hubble–Humason relation, the observational foundation for Hubble's law and the expanding universe model. Their collaboration continued for years, with Humason obtaining spectra for galaxies in the Coma Cluster and beyond, greatly extending the Hubble diagram.

Later life and legacy

Humason continued his research at Mount Wilson and later at the Palomar Observatory, contributing to the National Geographic Society – Palomar Observatory Sky Survey. He received an honorary Master of Science degree from Lund University in 1950. Despite his lack of formal training, he was elected president of the Astronomical Society of the Pacific in 1954. Humason retired in 1957 and spent his final years in Mendocino, California. His legacy is that of a consummate observer whose precise data underpinned one of the greatest scientific discoveries of the 20th century, transforming our understanding of cosmology and the Big Bang theory.

Category:American astronomers Category:Mount Wilson Observatory Category:1891 births Category:1972 deaths