we know the speed of  light.But,what is the speed of darkness?
406703
the speed of light is c=3*10 at the 8-th power  m/s\ndark means 0 light
618284
light travels fastest than anyone in the world\nhis speed=1,079,252,848.8  kilometres per hour
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
1093142
Darkness is the absence of Light!....Same Speed?\n\nIf we are talking about 'How long it takes to go Dark',  then it depends on the time of year (whether the Sun is below or above the Equator, and to what extent), you level of latitude on the Planet..... Because, it changes nearer to the poles because, firstly the Earth is not a perfect Sphere (it is flatter at the poles), and secondly (and very important to our weather, etc), the Earth is inclined at an angle (10 degrees at Poles?) which results in the Tropical Zones...\n\nConclusion: Faster the further North in Winter, slower in  Summer!....... A friend says, blooody quick at the Equator, but never been there to see!
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.
126628
The speed of light in a vacuum is exactly 299,792,458 metres per second (or 1,079,252,848.8 km/h, which is approximately 186,282.397 miles per second, or 670,616,629.4 miles per hour; sometimes roughly 300,000 km per second). \nmeasured with a laser at a known distance x time
63049
Darkness has no speed. However if you could put a speed to darkness it would be amazing. If you could actually produce the absence of light, you would have created pure genious. As of right now, Darkness doesn't have a speed because it is nothing. That is like saying how much am i worth, if you don't have money. Technically you're worth $0 but am I trying to say that you are worth the absence of money. You don't have money so your worth nothing. Darkness isn't something that has a speed because it is the absence of light. I guess a better analogy would be: The absence of money has no worth.
43761
The speed of light in a vacuum is exactly 299,792,458 metres per second (or 1,079,252,848.8 km/h, which is approximately 186,282.397 miles per second, or 670,616,629.4 miles per hour; sometimes roughly 300,000 km per second). This value is denoted by the letter c, reputedly from the Latin celeritas, "speed", and also known as Einstein's constant. Note that this speed is a definition, not a measurement, in that the fundamental SI unit of distance, the metre, is defined 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.
983322
frequency = C / wavelength.  c is speed of light
195965
Darkness is limitless...Light has its limits...The speed of light is just as fast as speed in darkness...if there is such things....Our universe is nothing but darkness filled with little twinkling stars (sun) and dark planets..\nWith out sun our earth is nothing. \n1 In the beginning God created the heaven and the earth. \n2 And the earth was without form, and void; and darkness was upon the face of the deep. And the Spirit of God moved upon the face of the waters.  \n3 And God said, Let there be light: and there was light.  \n4 And God saw the light, that it was good: and God divided the light from the darkness.  \n5 And God called the light Day, and the darkness he called Night. And the evening and the morning were the first day.
1164047
The speed of light is only defined as a positive number.\n\nThere is no inverse of light speed - no "negative" light speed.\n\nThe speed of "dark" is undefined, since anything times nothing is undefined.  \n\nAll you can do is state how fast light moves out of a location once its source is discontinued.\n\n\nBy the way, saying that "everything has an opposite" is a false statement.\n\n\nHowever, I can see a case for considering that there may actually be a phenomenon of dark spreading at alarming speed, namely the Republican Party.
600967
No there is no 'summation' of speeds involved with light.  Light is Electro-Magnetic Energy, although light travels as particles as well as waves.  In this Universe the speed of light is a constant, roughly 186,000 miles-per-second, or 300,000 km/sec or 300 Mega-Metres / sec.  Unless some POWERFUL external force acts upon light, it cannot change speed.  This entails the gravity of black-holes and such. (Not even light can escape from them.)\n\nA vehicle might weigh somewhere in the neighbor-hood of 3,300 lbs. (Approximately 1,500 Kg, for those of you who have not learned to count properly, just yet ...)\nCheck out da' math ...\n\n60mph = 100 kmph = 27.77r mps. \n(1,500 Kg x 27.77r mps) / 9.81 mps = ~ 4,246 N\n\nI doubt, very seriously, that a little over 4,000 Newtons is enough force to even put a dent in the factor of light-speed.  For more info, look-up Einstein's Theory of Realtivity' (Although I believe 90% of it to be short-sighted ancient crap ...)  This subject is covered in it ...\n(umm covered in Einstein's Theory, not copvered in crap .. which err .. is the same thing at times ...
26330
There is an ambiguity in the question!\nIt is not told in which medium it is.\nThe speed of light is 299,792,458 in vaccum & it is almost the same in air.
13401
It's true that the speed of light is constant no matter what speed at which you or the source is moving.  This is a fundamental postulate of relativity, and there is no explination.  It's just accepted because our experiments indicate that it is true.  You used the formula "lights speed + X = actual speed"  this type of velocity addition is called "Galilean".  It turns out that speeds don't actually add that way.  Far out.\n\nWhere is the rest of the energy? Good question.  The frequency of the light you observe from the sun DOES depend on how fast you and it are moving.  The energy of each photon is given by E = hf, where f is the frequency of light.
474792
(m)\n\nThe 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", and also known as Einstein's constant. 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.
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
779931
The speed of light in a vacuum is exactly 299,792,458 meters per second (fixed by definition). Although some people speak of the "velocity of light", the word velocity is usually reserved for vector quantities, which have a direction.\n\n\nNothing has a speed greater than the speed of light.\n(except in Science Fiction stories)