How the speed of light is measured?

Answer 1

At work, lecture demonstrations had just been introduced at Annapolis. Sampson suggested that it would be a good demonstration to measure the speed of light by Foucault's method. Michelson soon realized, on putting together the apparatus, that he could redesign it for much greater accuracy, but that would need money well beyond that available in the teaching demonstration budget. He went and talked with his father in law, who agreed to put up $2,000. Instead of Foucault's 60 feet to the far mirror, Michelson had about 2,000 feet along the bank of the Severn, a distance he measured to one tenth of an inch. He invested in very high quality lenses and mirrors to focus and reflect the beam. His final result was 186,355 miles per second, with possible error of 30 miles per second or so. This was twenty times more accurate than Foucault, made the New York Times, and Michelson was famous while still in his twenties. In fact, this was accepted as the most accurate measurement of the speed of light for the next forty years, at which point Michelson measured it again.

Answer 2

The speed of light in vacuum c is not measured. It has an exact fixed value when given in standard units. Since 1983 the metre has been defined by international agreement as the length of the path travelled by light in vacuum during a time interval of 1/299,792,458 of a second. This makes the speed of light exactly 299,792.458 km/s. Since the inch is defined as 2.54 centimetres, the speed of light also has an exact value in non-metric units. This definition only makes sense because the speed of light in vacuum is constant; a fact which is subject to experimental verification (see relativity FAQ article Is the speed of light constant?). Experiments are still needed to measure the speed of light in media such as air and water.
www.math.ucr.edu
Best wishes and good luck

Answer 3

The speed of light is measured in Light Years.
The normal speed of light in vaccum is 3*10^8 m/s
(where *implies multiplication sign and ^ implies
to the power of)

Answer 4

One of the earliest methods of measuring the speed of light by measuring the time taken by the moons of Jupiter when they were eclipsed by the planet Jupiter.It was remarkably an ingenious method for those times and the result though not very accurate by todays standards proved that the speed of light was finite and was incredibly high.today we measure speed of light by laser interferometry,or even by sending a laser beam to moon and timing the reflected beam's arrival.we take advantage of a laser beam's coherence to do this,as simple as apple pie,isn't it!!

Answer 5

speed of the light is measured by light year. one light year is the distance travelled by light in one year.on light year=9.467 x 100000000000km.

Answer 6

light year