If the speed of light 1000,000 km/s, what is the speed of dark?
543697
Dark is the absence of light.  It has no speed.
35130
Zero....Illumination is tracked by the speed of light but the lack of illumination means that nothing is moving.
329962
Here is the correct answer....the speed of light is constant IN A VACUUM.  Light is most certainly slowed down by matter, and can be shifted by gravity.
932886
the speed of light = 299 792 458 m / s or 1079252848800 M/H\ncircumference = 2*Pi*R \nso 2* 3.14159*R= 107925848800M/H\n1079252848800/(2*3.14159)=R\nRadius= 1.71768571 × 1011(<--- times 10 to the 11th power) meters
229632
The speed of light pertains to E&M waves... You can have a wave on a rope for example... it will not be travelling at the speed of light.  To generalize, just state it as 'velocity'\n\nwavelength = velocity/frequency\n\nfor units in this case, x millimeters = (y millimeters/second)/(z cycles/second)
799573
speed of light in vacuum: c = 3.00 x 10^8 m/s\nThe speed of light is typically represented in m/s.\n\nThe speed of light in a vacuum should not be the same as the speed in a non vacuum.\nhttp://cord.org/step_online/st1-1/st1-1ei3.htm
727511
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.\n\nand everything about speech of light in this site\nhttp://en.wikipedia.org/wiki/Speed_of_light
402996
Light travels at 186,000 miles per second, or 300,000 kilometers per second.
755656
Light, as we know it, is a rush of photons.  As the photons go along, they would leave a darkness behind the last photon that would follow along at the speed of light.\n\nSince darkness is the absence of light (light would be something like the force acting upon or going through the dark), then by itself, dark has no speed.  It just is.
570639
As the speed of light is approached time slows.\nThis is given by the formula Sqrt(1-v^2/c^2) where\nv=velocity\nc=speed of light\n\nAt the speed of light time stops Sqrt(0) = 0\n\nFaster than the speed v exceeds c so v/c >1\n\nsqrt of a negative is imaginary.\n\nThe only thing you can see when traveling faster than a light is a snuffleupagus. (Because their IMAGINARY. or least they used to be back in the good old days.)
1169043
The speed of light in a vacuum is exactly 299,792,458 metres per second or 1,079,252,848.8  kilometres per hour. Converted to approximate imperial units, it is 186,282.397 miles per second, or 670,616,629.384 miles per hour.
271084
Speed of darkness is unmeasurable itself, It can only be measured as the speed of the exiting of light. So in short, just as fast as night, just when there is no light, there's darkness instead. More of a concept than a tangible thing.
344154
Scientists have defined the speed of light in a vacuum to be exactly 299,792,458 meters per second (about 186,000 miles per second).\n\nThis definition is possible because since 1983, scientists have known the distance light travels in one second more accurately than the definition of the standard meter. Therefore, in 1983, scientists defined the meter as 1/299,792,458, the distance light travels through a vacuum in one second. This precise measurement is the latest step in a long history of measurement, beginning in the early 1600s with an unsuccessful attempt by Italian scientist Galileo to measure the speed of lantern light from one hilltop to another.\nMicrosoft ® Encarta ® 2006. © 1993-2005 Microsoft
339050
The speed of light in a vacuum is exactly 299,792,458 metres per second (or 1,079,252,848.8  km·h-1, which is approximately 186,282.397 miles per second, or 670,616,629.4 miles per hour). This value is denoted by the letter c, reputedly from the Latin celeritas, "speed". Note that this speed is a definition, not a measurement, since the fundamental SI unit of distance, the metre, has been defined since 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. 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.
68058
Two of these answers were correct (the speed of light in a vacuum is exactly 299792458 meters per second), although the appropriate reference is not wikipedia but the Bureau International des Poids et Mesures (BPIM).  This is the internationally recognized "official" source.\nhttp://www.bipm.fr/en/si/base_units/\n\nThe speed of light in a vacuum is exactly known because the meter is defined (by the BPIM) as being the distance that light in a vacuum travels in 1/299792458 of a second\n\nThe answer from Trsmd is not quite correct in stating that the speed of anything can be measured by determining the distance in travels in a given amount of time.  Since our units of distance are defined in terms of the speed of light, the correct statement would be that distance can be determined by measuring the amount of time that it takes light to travel that distance.\n\nAlso notice the qualifier "in a vacuum".  The speed of light travels more slowly when it travels through something like air, water, or glass.  How much more slowly depends on the properties of the material (density, composition, temperature, etc.)
6671
The exact speed of light is 299,792,458 m/s\n\nTo be precise, what we usually call the "speed of light" is really the speed of light in a vacuum (the absence of matter). In reality, the speed of light depends on the material that light moves through. Thus, for example, light moves slower in glass than in air, and in both cases the speed is less than in a vacuum. However, the density of matter between the stars is sufficiently low that the actual speed of light through most of interstellar space is essentially the speed it would have through a vacuum, so we don't make much error by ignoring the difference.\n\nTo make it easier for you to convert, here is the speed in alternative units :\n\n(1) 983,571,056.4304461 foot/second\n(2) 11,802,852,677.165352 inch/second\n(3) 1,079,252,848.8 kilometer/hour\n(4) 299,792.458 kilometer/second\n(5) 582,749,918.3585312 knot\n(6) 880,991.0899527 mach\n(7) 670,616,629.3843952 mile/hour (mph)
48947
Darkness is just the absence of light. Darkness is always there. But in theoritical sense, it should be as fast as light  because when the light goes off suddenly, darkness can creep in immediately.\n\nBelow is an interesting thread i found online in an australian website.\n\n"If the speed of light is known, what is the speed of darkness? The two opposing schools of thought that have developed are:\n\n1. Darkness does not move, it is always present, and light is layed on top of it. (As an analogy, consider a table as being darkness, a tablecloth as being light: when you pull the tablecloth off, the table itself (darkness) doesn't move).\n\n2. Darkness moves at the same speed as light, and it meets the laws of motion in that Darkness is the equal and opposite reaction for the action of the movement of light. "\n\nCourtesy:- http://www2.abc.net.au/science/k2/stn-archive1/posts/topic1942.shtm