Albert Abraham Michelson

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Albert Abraham Michelson

Albert Abraham Michelson was an American physicist known for his work on the measurement of the speed of light and for the Michelson–Morley experiment

Michelson invested in very high quality lenses and mirrors to focus and reflect the beam, this was twenty times more accurate than foucault. This was accepted as the most accurate measurement of the speed of light for the next forty years

The Michelson Speed of Light Experiment at the Irvine RanchAt the heart of the experiment (pictured in the shack and graphic above), an arc light was bounced off a rapidly rotating set of mirrors, back and forth down a mile-long tube and home, to the mirrors, which by then would have moved slightly. If the speed of the mirror, the angle of the bounce and the length of the tube are known, it is possible to calculate the speed of light.

In 1887, Michelson and Edward Morely used the interferometer to find out how light waves moved through the theoretical "ether" in the universe. According to the principals of classical physics, the movement of the earth through this mysterious substance affected the speeds of light rays moving through it. Michelson and Morely used the interferometer to bounce light waves out and back at right angles, expecting to see one of the beams lag behind. This did not work out, and ether did not exist.

While preparing a lecture demonstration of Foucault's method for determining the velocity of light, Michelson realized that if he collimated the beam he could get a much longer optical path-length and thus a great increase in sensitivity. He continued his experiment for the next two years.

Michelson was known as the finest experimental physicist alive

Diagrahm of Michelson's measurment of the speed of light

While still at Annapolis he first repeated and improved upon Léon Foucault's measurement of the speed of light, calculating the speed at 300,140 kilometers per second.


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