Can anyone tell me exactly how someone figured that out.
2007-02-25 15:54:14 · 3 answers · asked by Anonymous in Science & Mathematics ➔ Physics
The first successful measurement of the speed of light using an earthbound apparatus was carried out by Hippolyte Fizeau in 1849. Fizeau's experiment was conceptually similar to those proposed by Beeckman and Galileo. A beam of light was directed at a mirror several thousand metres away. On the way from the source to the mirror, the beam passed through a rotating cog wheel. (follow the link) At a certain rate of rotation, the beam could pass through one gap on the way out and another on the way back. But at slightly higher or lower rates, the beam would strike a tooth and not pass through the wheel. Knowing the distance to the mirror, the number of teeth on the wheel, and the rate of rotation, the speed of light could be calculated. Fizeau reported the speed of light as 313,000 kilometres per second. Fizeau's method was later refined by Marie Alfred Cornu (1872) and Joseph Perrotin (1900).
Leon Foucault improved on Fizeau's method by replacing the cogwheel with a rotating mirror. Foucault's estimate, published in 1862, was 298,000 kilometres per second. Foucault's method was also used by Simon Newcomb and Albert A. Michelson. Michelson began his lengthy career by replicating and improving on Foucault's method.
In 1926, Michelson used a rotating prism to measure the time it took light to make a round trip from Mount Wilson to Mount San Antonio in California. The precise measurements yielded a speed of 186,285 miles per second (299,796 kilometres per second).
2007-02-25 16:07:22 · answer #1 · answered by Joe M 2 · 3⤊ 0⤋
Joe M answered well with many details.
I will answer more intuitively and practically.
James Clerk Maxwell first described the elecromagnetic wave mathematically. His theory gave the speed of this wave to be 198,000 ft / sec.
Light was later measured to be this speed by the methods described in the earlier answer. this led to the realization that light was an "elecrotromagnetic" phenomena.
Michelson and Morley later illustrated that the speed of light is independent of the observer's speed, which confirmed the validity of Einstein's predictions.
the speed of light is one of the most perplexing concepts in modern physics !
2007-02-25 16:26:50 · answer #2 · answered by fullbony 4 · 0⤊ 0⤋
Most simple:
Set up a light detector of some sort and a light source a certain distance apart, then clock the time it takes the light to go from the light source to the light detector.
Speed or rate = distance/time
However, this would require extremely sensitive equipment, I imagine, to yield accurate results.
Who know?!
2007-02-25 16:07:31 · answer #3 · answered by harshama 1 · 0⤊ 2⤋