The speed of light is, like said before me, C. Or a constant, hence the C.
299,792,458 metres per second
or also 1,079,252,848.8 km/h in vacuum that is!
Really fast :)
2007-03-12 03:01:00
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answer #1
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answered by Pim 2
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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". It is the speed of all electromagnetic radiation in a vacuum, not just visible light.
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 a transparent or translucent material medium, like glass or air, it may appear to have a different speed than in a vacuum; the ratio of c to the observed phase velocity (which may be both smaller or larger than c) is called the refractive index of the medium. 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.
2007-03-12 03:00:25
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answer #2
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answered by Anonymous
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The speed of light is 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.
2007-03-12 03:06:19
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answer #3
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answered by shalu 3
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Often referred to as C
In a vacuum the speed is 299,792,458 metres per second
2007-03-12 02:58:42
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answer #4
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answered by Anonymous
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For ease of calculations it is often specified as:
3 * 10^8 meters/second
A mathematician named Dwight,
Could travel much faster than light,
He took off one day
In a relative way
And returned on the previous night!
.
2007-03-12 03:04:09
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answer #5
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answered by Anonymous
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Hi, the speed of light today is: 299792.458 km/s.
declared by Einstein (1905): "The velocity c of light in vacuum is the same in all inertial frames of reference in all directions and depend neither on the velocity of the source nor on the velocity of the observer". Einstein's theory of special relativity says that the speed of light in vacuum is always the same (at 299,792.458 km/s) but this is true only for systems that are inertial, which means not accelerating. From Newton's second law: if forces exist implies acceleration exists; this means that special relativity is valid only when no forces are acting; thus it cannot be used when there is a gravitational force present. Albert Einstein himself emphasized this in his paper written in 1917: "The results of the special relativity hold only so long as we are able to disregard the influence of gravitational fields on the phenomena". Therefore for the results of special relativity to hold the systems should not be accelerating (no gravitational forces).In conclusion, the velocity of light in a gravitational field is not a constant, but rather a variable depending upon the reference frame of the observer; what one observer sees as true another observer sees as false. The only observers that can actually agree that the speed of light outside gravitational fields is 299792.458 km/s are those who are themselves outside gravitational fields.
By using classical orbital mechanics we discovered that all observers will see the speed of light outside gravitational fields equal to 12000 Lunar Orbits/Earth Day. An observer near a black hole for example sees the speed of light outside gravitational fields a zillion km/s, but still equal to 12000 Lunar Orbits/Earth Day! This means that if the speed of light outside gravitational fields (or the speed of any object) were defined in km/sec then it will appeare to vary for observers in different gravitational fields; however if this speed is defined in Lunar Orbits/Earth Day then it will never appear to vary to anyone because 12000 Lunar Orbits/Earth Day is common to all observers. It also turned out to be a constant forever.
1667 Galileo: at least 10 times faster than sound
1675 Ole Roemer: 200,000 Km/sec
1728 James Bradley: 301,000 Km/s
1849 Hippolyte Louis Fizeau: 313,300 Km/s
1926 Leon Foucault 299,796 Km/s
Today: 299792.458 km/s
299,792.458 km/s is the speed of light in vacuum. However, according to Einstein's theory of General Relativity, the speed of light appears to vary with the intensity of the gravitational field.
But 1400 years ago it was stated in the Quran (Koran, the book of Islam) that angels travel in one day the same distance that the moon travels in 1000 lunar years, that is, 12000 Lunar Orbits / Earth Day. Outside gravitational fields 12000 Lunar Orbits / Earth Day turned out to be the known speed of light!
2007-03-12 03:22:08
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answer #6
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answered by star 2
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3 x 10^8 metres per second
or 300,000,000 metres per second.
2007-03-12 03:00:39
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answer #7
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answered by Doctor Q 6
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It is approx. 186,282.397 miles per second. This is not a measurement, it is a constant used in calculations.
2007-03-12 03:04:51
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answer #8
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answered by Sky K 2
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299,792,458 metres per second
300,000,000metres per second
2007-03-12 03:09:56
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answer #9
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answered by Anonymous
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