Michelson was born in Strzelno,Poland, on December 19, 1852, his family moved to the United States when he was only 3 years old. Landing in New York, the Michelson clan soon traveled westward, eventually settling in San Francisco, California where the elder Michelson became a successful merchant. At the age of 17, Albert Michelson entered the United States Naval Academy and excelled in his studies of the sciences, although he was a less than admirable sailor. Graduating in 1873, he began teaching science at the Naval Academy in 1875 and remained in the position for four years.Michelson was an instructor in physics.He had to do a lecture demonstration of how Foucault measured the speed of light(he measured the speed of light using Foucault's method).It was years since Foucault made his measurements.When Michelson was seeting up his demonstration, he saw how it could be improved to give a much more accurate measurement.The distance between the wheel that Foucault used and his mirror was 60 feet.Michelson put the very high quality(expensive) mirror 2 000 feet from the toothed wheel.He also had very high quality lenses to focus the beam onto the mirror.His final measurement was 186,355 miles per second.This measurement had a possible error of around 30 miles per second.Foucaults speed of light with an accuracy of about 1,000 miles per second.
Michelson, Morly and the interferometer
In 1887 Albert Michelson and Edward Morley determined if there was any difference in the speed of light, based on the direction it travelled in.They built an interferometer that send out two light beams: one beam of light was pointed along the direction of the earth's motion, the other light beam was pointed at a 90 degree angle relative to the first light beam. The beams were reflected by mirrors and focussed at a common point where they could interfere with each other. The light beam travelling along the direction of the earth's motion around the sun was expected to travel at a different speed compared to the light beam travelling at 90 degrees compared to this light beam.They did not encounted any interference that suggested these two beams of light travelled at even slightly different speeds. They would have been able to measure a difference in speed if there was one. They could not detect any difference in speed between these two light beams. In 1958 Froome used a microwave interferometer and a Kerr cell shutter to measure the speed of light to be 299,792.5 km/s.
