Superior Beauties: The Discovery of the Speed ​​of Light in the San Gabriels

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I always think of Michelson as the Science artist. His greatest joy seemed to come from the beauty of the experiment itself and the elegance of the method used … – Albert Einstein, on the Centenary of the Birth of Albert Michelson, 1952

The interaction between art and science was always complementary to the life of the American physicist Albert Michelson. A talented painter from his days as a cadet guardian in the United States Navy, Dr. Michelson had a deep fascination with both the aesthetic and physical properties of light. He excelled in the field of optics at the United States Naval Academy, and was especially engrossed in the challenges of measuring the speed of light. He eventually graduated in 1873. He chose to pursue a career in science above art. “I confess that the aesthetic side of the subject is by no means the least appealing to me,” he stated about the artistic appreciation of light in a lecture. at the Lowell Institute in 1899. However, he was more compelled to capture light through the faculties of reason, not the senses, to “perceive the even higher beauties that attract the mind.”

Michelson’s decision to pursue “superior beauties,” as he referred to the laws of nature, led him to the mountains of St. Gabriel to conduct one of the most famous scientific experiments in human history.

From left to right: Dr. Albert Michelson, Dr. Albert Einstein and Dr. Robert A. Millikan, president of the California Institute of Technology, at the California Institute of Technology in the 1920s and 1930s | Photo courtesy of the Los Angeles Public Library

During his career, Michelson had developed precision optical instruments to discover the effect of Earth’s motion on observed speed and to show that light travels at a constant speed in all inertial reference systems. His instruments and research had earned him the Nobel Prize in Physics in 1907, making him the first American scientist to receive the coveted prize.

By 1922, Michelson was determined to surpass the previous 44 years of his life he had spent trying to calculate the speed of light. Its goal was to reach a measure with no more than a possible error of 0.001%. This definitive measure, he said, could be achieved by drawing up an elegant but daunting plan: a beam of light would be launched from a Mount Wilson Observatory station, traveling 22 miles to a station containing a mirror back on a ridge of Mount San Antonio, called Lookout Mountain, and retrace the path back to Mount Wilson. The return beam would impact against a rotating mirror driven by compressed air, and by measuring the minute-by-minute angle of the mirror during a round trip, the speed of light could be measured.

Arrangement of Michelson's light experiment between Mount Wilson and Lookout Mountain near Mount San Antonio  Source: "Measurement of the speed of light between Mount Wilson and Mount San Antonio"

Arrangement of Michelson’s light experiment between Mount Wilson and Lookout Mountain near Mount San Antonio Source: “Measurement of the speed of light between Mount Wilson and Mount San Antonio”

Lookout Mountain today, showing the station's remaining concrete docks.  |  Photo: Daniel Medina

Lookout Mountain today, showing the station’s remaining concrete docks. | Photo: Daniel Medina

In order to ensure the accuracy of the experiment between Mount Wilson and Mount Lookout, the exact distance between the two peaks had to be verified. Since uneven mountainous terrain made it difficult to obtain an accurate reading, the U.S. Coast and Geodetic Survey intervened to triangulate the distance of a baseline they developed at the base of the foothills of the San Gabriel Valley. When completed, it was reported in the survey “An unusually high geodetic measurement of accuracy” that the line error between the two peaks was approximately 1 in 5,000,000. ”The report added : “The length of this line is believed to have been determined with greater accuracy than any triangulation line in this or any other county.” The experiment, animated with this precision, was about to begin. in 1924.

Michelson Triangulation Diagram |  Source: "A geodesic measure of unusually high accuracy"

Michelson Triangulation Diagram | Source: “A geodesic measure of unusually high accuracy”

 Measuring the baseline.  |  Source: "A geodesic measure of unusually high accuracy"

Measuring the baseline. | Source: “A geodesic measure of unusually high accuracy”

The baseline is measured to pass through the window at each end of the house.  |  Source: "A geodesic measure of unusually high accuracy"

The baseline is measured to pass through the window at each end of the house. | Source: “A geodesic measure of unusually high accuracy”

For the next two years, Michelson conducted his unprecedented experiments, alternating sizes and rotational speeds of the mirror on Mount Wilson. Each time, the beam of light rushed on the 44-mile round trip in much less than an instant.

Fortunately, by then Michelson, 73, ran his big experiment in San Gabriels. After collecting his data, he found that the final result of the speed of light, as published in the Astrophysical Journal in 1927, was 299,796 km per second. Modern measurements of the speed of light in a vacuum are 299,792 km per second; the calculations of the Mount Wilson-Lookout Mountain experiment were surprisingly accurate for their day.

Michelson became the first person to accurately measure the speed of light, the critical value “c” in Einstein’s energy equation “E = mc2” that would pave the way for the development of the revolutionary Relativity theory. This universal constant proved so crucial that Einstein reiterated in a speech at Caltech in 1931: “Without your work, this theory today would be almost more than an interesting speculation.”

After his advance, Albert Michelson had only a short term left on earth to enjoy the accolades and cheers that rained down on him. He died in 1931, the same year his California landscape watercolors were exhibited at the Pasadena Art Institute. There is no doubt that he must have loved this particular honor that came from outside the realm of physics. His legacy was now added to the arts and sciences, a final demonstration of his reverence for the intricate wonders of light.

mountain viewpoint

A geographic marker on the remains of a concrete pier at Lookout Mountain marks the summit of Mount Wilson | Photo: Daniel Medina

broken glass in the mountain viewpoint

Fragments of glass from Lookout Mountain Station are scattered over parts of the summit. | Photo: Daniel Medina

viewpoints mountain remains

Remains of concrete docks at Lookout Mountain | Photo: Daniel Medina

ruins on the mountain viewpoint

A sign marks the summit of Lookout Mountain Photo: Daniel Medina

Top image: Mount Wilson Observatory at dusk. | Screenshot of UCLA Mount Wilson Cam