2006-11-12 08:10:53 · 13 answers · asked by ? 2 in Science & Mathematics ➔ Physics
about 300,000 m/s
2006-11-12 08:56:32 · answer #1 · answered by futureastronaut1 3 · 0⤊ 0⤋
The speed 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 (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, or almost one foot per nanosecond.
Through any transparent or translucent material medium, like glass or air, it has a lower speed than in a vacuum; the ratio of c to this slower speed is called the refractive index of the medium(the actual speed is not affected, the speed of light is constant, the fact that the light is reflected around inside the glass will make a greater amount of time necessary for it to reach the next point). Changes of gravity, however, warp the space the light has to travel through, making it appear to curve around massive objects. This gives rise to the phenomenon of gravitational lensing, in which large assemblies of matter can refract light from far away sources, so as to produce multiple images and similar optical distortions.
2006-11-12 08:45:24 · answer #2 · answered by snissari 2 · 0⤊ 0⤋
here's the fun part, photons (of which light is composed) don't travel at all, they simply attach to time. and TIME moves at C.
This is why time slows as you approach the "speed of light" you are catching up to time.
think of a train moving by at 100 miles an hour, it takes 60 seconds to pass. If you were in a car driving along at 50 miles an hour, it would take 120 seconds for the train to pass.
Not the greatest analogy in the world, but this is what happens if you travel at C/2, seconds would take longer to pass.
2006-11-12 08:29:12 · answer #3 · answered by disco legend zeke 4 · 0⤊ 0⤋
The speed of light is EXACTLY 299792458 m/s (http://physics.nist.gov/cgi-bin/cuu/Value?c|search_for=universal_in! ) because of a circular definition of the meter to be the the distance travelled in 1/299792458 of a second. http://physics.nist.gov/cuu/Units/meter.html
The second is defined to be "9 192 631 770 periods of the radiation corresponding to the transition between the two hyperfine levels of the ground state of the cesium 133 atom" http://physics.nist.gov/cuu/Units/second.html
2006-11-12 08:36:28 · answer #4 · answered by arbiter007 6 · 0⤊ 0⤋
It travels extremely fast through vacuum and transparent media like glass, water, oil etc
Light's speed through vacuum is 3 x (100,000,000) meter/second
For any transparent medium, of refractive index mu, the speed is (1/mu) times the vacuum speed
For glass placed in air mu is roughly 1.5,
so speed through glass will be 1/1.5 times 3 x (100,000,000) meter/second = 2 x (100,000,000) meters/second etc..
You can look up for mu of the other media and calculate the respective speeds for light in those media youself...Got it?
2006-11-12 08:30:20 · answer #5 · answered by usarora1 3 · 0⤊ 0⤋
a "normal" speed of 186,000 miles per second. a lightyear is the distance light travels in 1 year.
2006-11-12 08:17:51 · answer #6 · answered by heli_guy60 3 · 0⤊ 0⤋
In metric units, c 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, or almost one foot per nanosecond.
2006-11-12 08:13:48 · answer #7 · answered by gordon_benbow 4 · 2⤊ 2⤋
this is my favorite subject............186 thousand miles per second.......wow. and it only takes light from the sun about 8 and one-half minutes to reach the earth which is 93 million miles away from the sun. isn`t that wonderful?
2006-11-12 08:20:39 · answer #8 · answered by mommy2yeayea2 1 · 0⤊ 0⤋
The speed of light is approximately 186,282.397 miles per second, or 670,616,629.384 miles per hour, or almost one foot per nanosecond.
http://en.wikipedia.org/wiki/Speed_of_light
2006-11-12 08:15:23 · answer #9 · answered by Anonymous · 0⤊ 0⤋
It's not that fast I can beat it anytime in a race!
2006-11-12 08:57:28 · answer #10 · answered by Anonymous · 0⤊ 1⤋
E=mc^2, that's the formula.
2006-11-12 08:14:45 · answer #11 · answered by Webballs 6 · 0⤊ 3⤋