We knew that it's about 186,000 miles/second years ago and I'm wondering if this number's precise enough for modern physics in the 21st century.
2006-10-08 22:10:24 · 7 answers · asked by Arigato ne 5 in Science & Mathematics ➔ Physics
The speed/velocity of light in a vacuum is an important physical constant denoted by the letter c for constant or the Latin word celeritas meaning "swiftness".
In metric units, c is exactly 299,792,458 metres per second (or 1,079,252,848.8 km/h). Note that this speed is a definition, not a measurement, since the fundamental SI unit of length, the metre, has been defined since October 21, 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.
Converted to imperial units, the speed of light is approximately 186,282.397 miles per second, or 670,616,629.384 miles per hour.
2006-10-08 22:21:40 · answer #1 · answered by Shushana 4 · 3⤊ 0⤋
In metric units, the velocity of light is exactly 299,792,458 metres per second (1,079,252,848.8 km/h). Note that this speed is a definition, not a measurement, since the fundamental SI unit of length, the metre, has been defined since October 21, 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. Converted to imperial units, the speed of light is approximately 186,282.397 miles per second, or 670,616,629.384 miles per hour.
2006-10-08 22:18:11 · answer #2 · answered by Anonymous · 0⤊ 0⤋
It depends on the medium in which it is travelling. In vacuum it is 186,282.397 miles per second or 670,616,629.384 miles per hour; in metric units it is 299,792,458 metres per second or 1,079,252,848.8 km per hour. Happy??
2006-10-08 22:28:08 · answer #3 · answered by ancalagon2003 3 · 0⤊ 0⤋
The velocity of lightis:3*10^8m/s.if u want to know the exact value once u have to meet ALBERT EINSTEIN.
2006-10-08 22:25:49 · answer #4 · answered by Naddi S 1 · 0⤊ 0⤋
186,282.397 miles per second
2006-10-08 22:14:12 · answer #5 · answered by holden 4 · 1⤊ 0⤋
http://csep10.phys.utk.edu/guidry/violence/lightspeed.html
2006-10-08 22:13:05 · answer #6 · answered by Anonymous · 0⤊ 0⤋
http://en.wikipedia.org/wiki/Speed_of_light
2006-10-08 22:18:59 · answer #7 · answered by dogpatch USA 7 · 0⤊ 0⤋