2006-07-04 02:26:52 · 9 answers · asked by brownrabbit596 1 in Science & Mathematics ➔ Physics
Now-a-days, the speed of light is defined to be exactly 299,792,458 m/s, we treat it as a universal constant, not a measurement.
Back before we defined the speed of light, any number of methods existed to measure this value.
http://www.speed-light.info/measure/
2006-07-04 03:12:09 · answer #1 · answered by mrjeffy321 7 · 0⤊ 0⤋
The speed of light in a vacuum is denoted by the letter c for constant or the Latin celeritas (speed). The speed of light through a transparent medium (that is, not in vacuum) is less than c; the ratio of c to this speed is called the refractive index of the medium.
In metric units, c is exactly 299,792,458 metres per second or 1,079,252,848.8 kilometres per hour. Converted to imperial units, it is approximately 186,282.397 miles per second, or 670,616,629.384 miles per hour. Note that this speed is a definition, not a measurement, since the fundamental SI unit of length, the metre, has been defined since 21 October 1983 in terms of the speed of light—one metre is the distance light travels in a vacuum in 1/299,792,458 of a second.
2006-07-04 02:30:48 · answer #2 · answered by Anonymous · 0⤊ 0⤋
In light years. In other words, the amount of space travelled by light in a year.
Typically used for measuring the distance between solar systems or planets.
If you are asking how did we find out how fast it is? As incredible as it seems I think they originally used mirrors on mountain peaks and a stopwatch.
2006-07-04 02:30:43 · answer #3 · answered by Anonymous · 0⤊ 0⤋
yow!!!...all those answers are wrong.......originally light's speed was measured by michelen's experiment..in which (well got no time to explain it..)...light's speed was measured to be 2.99797 * 10^8....he did it 10,000 times and took the average....thats why the answer is that much accurate with 5 no. beyond the point....believe it or not!!!!
2006-07-04 04:15:07 · answer #4 · answered by becks 2 · 0⤊ 0⤋
E=hf where h=Plank's constant and f is the frequency of emitted light.
f=1/t where t is the period of light wave.
d=ct where c is the velocity of light and d is the distance from the source of light to measuring point. then,
c=d/t this is the velocity of light.
Please note that physically, the word speed means the Vectorial amount of velocity, the correct word is the VELOCITY OF LIGHT>
2006-07-04 02:40:47 · answer #5 · answered by Anonymous · 0⤊ 0⤋
See
2006-07-04 02:30:46 · answer #6 · answered by IT 4 · 0⤊ 0⤋
Not sure... maybe by time dilation?
The faster you move, the slower time goes. The speed of time is inversely proportional to the speed at which you are moving at.
2006-07-04 02:31:12 · answer #7 · answered by Anonymous · 0⤊ 0⤋
In light years how fast it travels in a year
2006-07-04 02:33:25 · answer #8 · answered by xr5turbo 3 · 0⤊ 0⤋
By the Doppler Effect.
2006-07-04 02:31:12 · answer #9 · answered by Aria 4 · 0⤊ 0⤋