2006-12-28 13:30:37 · 8 answers · asked by KS 1 in Science & Mathematics ➔ Physics
The first to make a reasonable estimate of the speed of light was in 1676 by Ole Romer, studying the orbit of Jupiter's moon Io, the discrepancy between calculated and observed times of Io's eclipse by Jupiter explained by a finite speed of light. Later, in 1728, an improved estimate of the speed of light was calculated by James Bradley by the aberration of light from stars, a slight angular displacement due to Earth's motion. The first time it was measured by an apparatus was by Hippolyet Fizeau in 1849, using a rotating cog wheel and a mirror placed miles away. In this fashion, a crude "inteference" effect was achieved by adjusting the speed of the cog wheel, and the speed of light calculated therefrom.
2006-12-28 13:49:57 · answer #1 · answered by Scythian1950 7 · 1⤊ 0⤋
2 experiments to read about: as they will no doubt give a more detailed explaintion than I will. Leon Foucalt's rotating mirror experiment and his predecessor Louiz Fieau's experiment with mirrors.
The principal is rather simple: Take one mirror and make it stationary. Take another mirror and place it far away and this mirror will rotate in a large arc around the stationary mirror at a fixed rate. (known rate). You then shine a light at the stationary mirror and it bounces off the rotating mirror back to the stationary one and you can measure the light angles that are made from the bouncing and as those angles will be slightly different the speed of light can then be calculated.
Philo the guy above is giving you an experiment that was intended to prove that there is no propagation medium that light was thought to have travled thru in the universe. This experiment was not used to measure the speed of light as it was known before that.
2006-12-28 13:43:38 · answer #2 · answered by travis R 4 · 0⤊ 0⤋
Romer had the first ballpark measurement of the speed of light, by looking at shifts in the apparent orbital periods of Jupiter's moons.
It was the first demonstration that the speed of light is not infinitely fast. It was not an especially accurate result, since his value was about 2/3 of the actual value. They did not accurately know the size of the Earth's orbit or the velocity of the Earth at the time, which contributed to the error.
2006-12-30 00:55:27 · answer #3 · answered by genericman1998 5 · 0⤊ 0⤋
Ole Romer in 1676 observed Jupiter occulting its moon Io and saw the time vary with Jupiter's distance from Earth. See the link for details.
Michaelson and Morley, around 1900, shot a beam of light at a spinning octagonal(?) mirrow 20 miles away. By measuring the speed of the spin at the point where the light bounced back, they had a measure of the speed of light. They did this in 2 perpendicular directions and established that there is NO DIFFERENCE in the speed of light as a result of Earth's motion through space (the ether). This fact became the basis of Einstein's Theory of Relativity.
2006-12-28 13:43:13 · answer #4 · answered by Philo 7 · 2⤊ 1⤋
The first measurement of velocity of light - by Olaus Roemer - using occultation of the Jupiter's satellites - 1676 A.D.
The earliest fairly accurate measure came in - by Foucault - using rotating mirror method - in 1862.
Please see the reference URL for details.
2006-12-28 17:30:08 · answer #5 · answered by Inquirer 2 · 1⤊ 0⤋
The speed of light in vacuum, a constant, was not measured but calculated
2006-12-28 15:01:40 · answer #6 · answered by Z 1 · 0⤊ 1⤋
The exact speed of light was calculated. c is not a measurement!
2006-12-29 01:46:24 · answer #7 · answered by supermmm 1 · 0⤊ 1⤋
Maybe something to do with mirrors....glass...cut-outs...or water..don't know/remember.
TT
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2006-12-28 13:38:15 · answer #8 · answered by The Platinum Mage 2 · 1⤊ 1⤋