2007-02-15 06:38:05 · 9 answers · asked by trlz71 1 in Science & Mathematics ➔ Physics
The speed of light in a vacuum is _defined_ as exactly 299 792 458 m/s. This is not a measured value since the metre is now (somewhat perversely, perhaps) defined in terms of the speed of light in the SI system of units. It's also about 1.8 terafurlongs per fortnight or alternatively one foot per nanosecond. The speed of light is not a simple speed limit; for example, no matter how fast two observers are traveling relative to each, they will observe the same light as going at the same speed relative to themselves, whereas with, say, a thrown ball, this would clearly not be the case.
As to whether the speed of light is different in different materials, it is not, since it neither gains nor loses energy on entering or leaving the material. Why it is observed as slower is... complicated. ;)
2007-02-15 14:14:54 · answer #1 · answered by Anonymous · 0⤊ 0⤋
Actually, the speed of light varies slightly with several factors among those are temperature and material (medium) either present or absent, through which it travels.
Accept: 186,600 mps as a close answer
2007-02-15 14:45:28 · answer #2 · answered by S. B 2 · 0⤊ 0⤋
it depends on the medium
In vaccuum 299 792. 458 km/s = c
In a matter with index of refraction n , the speed is v/c
in water n = 1.333 v = 225000km/s
2007-02-15 14:53:03 · answer #3 · answered by maussy 7 · 0⤊ 0⤋
Faster than you can turn off the light switch and hop in bed. It is about 186,000 miles per second.
2007-02-15 14:45:51 · answer #4 · answered by Kerry 7 · 0⤊ 0⤋
To the moon and back in 2 and a half seconds. To the sun in 8.3 minutes.(186,000 miles per second).
2007-02-15 14:53:37 · answer #5 · answered by John O 1 · 0⤊ 0⤋
Its really really really fast. Faster than a cheetah I'd bet.
2007-02-15 14:42:15 · answer #6 · answered by Anonymous · 0⤊ 0⤋
Approximately 186 000 miles/sec, or 300 000 km/sec.
2007-02-15 14:41:00 · answer #7 · answered by Anonymous · 0⤊ 0⤋
3x10^8 meters per second in a vaccum
2007-02-15 14:41:01 · answer #8 · answered by gramatron 2 · 0⤊ 0⤋
3 *10^8 m/s....
2007-02-15 14:44:24 · answer #9 · answered by rdx 1 · 0⤊ 0⤋