Near Pasadena in Los Angeles County, California — The American West (Pacific Coastal)
Michelson Pier on Mount Wilson
Albert Abraham Michelson
measured the velocity of light by means of a
beam of light transmitted to
Mount San Antonio
and reflected back to this station
Location. 34° 13.353′ N, 118° 3.475′ W. Marker is near Pasadena, California, in Los Angeles County. Marker can be reached from Mount Wilson Road. Touch for map. Marker is within the grounds of Mount Wilson Observatory, on the left when traveling south on an unnamed service road. The marker is about 125 yards NNW of the astronomers’ residence (called the Monastery), and 25 yards north of one of the smallest observatory domes on the mountain. Marker is in this post office area: Pasadena CA 91107, United States of America.
Other nearby markers. At least 8 other markers are within 6 miles of this marker, measured as the crow flies. Benjamin Davis Wilson (approx. ¼ mile away); Harvard’s Mount Wilson Station (approx. 0.3 miles away); Adams Pack Station (approx. 2.8 miles away); World’s Largest Blossoming Plant (approx. 3.6 miles away); Mount Lowe Railway (approx. 3.7 miles away); Mount Wilson Trail (approx. 3.7 miles away); Christmas Tree Lane (approx. 5.3 miles away); Queen Anne Cottage (approx. 5.6 miles away). Touch for a list and map of all markers in Pasadena.
Regarding Michelson Pier on Mount Wilson.
The apparatus at Mount Wilson consisted of a rapidly spinning disk with 8, 12, or 16 flat mirrors equally spaced around the rim. Light from a powerful arc lamp bounced off this spinning rim, traveled from Mount Wilson to Baldy, was reflected back, and bounced again off another part of the same spinning rim. The deflection of the return beam was used to calculate the light-travel time for the round trip.
Michelson’s final value for the speed of light was 299,796 ± 4 kilometers per second, which compares quite favorably with today’s adopted value of 299,792.458 km/sec.
Michelson is even better known for the famous Michelson-Morley experiment of 1887. Although it failed to show the “ether drift” Michelson was looking for, it helped to pave the way for Einstein’s special theory of relativity (1905).
(The above details of Michelson’s apparatus are adapted from K. D. Froome and L. Essen, The Velocity of Light and
Also see . . . Albert A. Michelson - The Nobel Prize in Physics 1907. Life and work of A. A. Michelson. (Submitted on July 8, 2012, by Roger W. Sinnott of Chelmsford, Massachusetts.)
Categories. • Science & Medicine •
Credits. This page was last revised on October 14, 2017. This page originally submitted on July 8, 2012, by Roger W. Sinnott of Chelmsford, Massachusetts. This page has been viewed 562 times since then and 3 times this year. Photos: 1, 2, 3, 4, 5. submitted on July 8, 2012, by Roger W. Sinnott of Chelmsford, Massachusetts. 6. submitted on October 14, 2017, by Roger W. Sinnott of Chelmsford, Massachusetts. • Syd Whittle was the editor who published this page.