It was a chilly, clear night in Eaton Canyon as the first Pacific rainstorm of the season approached. A light breeze rustled some Douglas Fir Pines on Mount Wilson while the skies overhead offered incredible views of the heavens. The moon was nowhere to be found. A large band of milky light dotted with secrets not yet discovered by humankind stretched high across the sky from one horizon to another. The year is 1923, and a certain astronomer on Mount Wilson is about to give all of humankind a reminder of just how small and insignificant we humans are.
Inside the brand new 101″ Mount Wilson Observatory Telescope, famed astronomer Edwin Hubble was peering into the night sky. He was aiming for a small cluster of light rising in the northeast over Mount San Antonio. On this night, Edwin Hubble was using a new method of measuring the distance of the stars called Leavitt’s Law. Its creator, Henrietta Swan Leavitt, was a scientist at Harvard who had studied a unique type of star called Cepheid variable stars. In 1908, she discovered that this type of star undergoes regular and predictable variations in brightness over time. By observing the period of a Cepheid variable star, astronomers could determine its intrinsic luminosity, and by comparing it to its apparent brightness, they could calculate the distance to that star. These stars have since earned the nickname “standard candles.”
All around the world, astronomers who caught wind of this discovery began searching for those stars to calculate the true distances to them from Earth. Over the next 15 years, it became clear that the Milky Way was some 20,000+ parsecs in diameter. Edwin Hubble was one of those astronomers, and on the night of October 6, 1923, he discovered something odd. This method of determining the distance of the stars was seemingly not working for the small inconspicuous cluster he was staring at. His calculations showed that the Andromeda Nebula was 275,000 parsecs from the Sun, much further away than any Cepheid variable star previously discovered. After further investigations and confirmations, it was determined that he was not in error. Upon this discovery at Mount Wilson, Edwin Hubble realized that the nebula he was looking at was in fact the Andromeda Galaxy, a galaxy both different from our own and 250 million light years away. Before this discovery, scientists only had proof that the Milky Way existed, and nothing else. Now, we have proof that the Universe is far, far bigger. Henrietta Swan Leavitt died in 1921, never getting the chance to see her work completely reshape our understanding of the Universe.
Eaton Canyon has a long history of water, homesteading, and tourism. However, its most significant contribution to the world is that it was here where we discovered the cosmos was incomprehensibly large. It was here atop Eaton Canyon that humankind once again was reminded that we are nothing against the grand scale of everything there is. In this age of fast moving headline news, pointless conflicts, and political drama, such a revelation is worth dwelling upon.
PBS produced a short documentary at Mount Wilson that you can view here.
