may some one tell me  light speed is?
462491
The speed of light in a vaccum (any space with no matter to interfere) is 299,792,458 metres per second.  Light travels slower through fluids like our atmosphere, and water, and through translucent or transparent matter like lenses.
647799
You can't go at the speed of light. It's a theorical limit, so it's unreacheable. Only the light can reach it.\n\nIf C is the speed of light, the fastest you can get is C*0.999999999... (insert as many '9' as you want). When you turn on the headlights, they will be somewhat faster: they'll reach the speed 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.
1103100
Here's the equation T = T' / sqrt[1- (v^2/c^2)]\n\nT is time measured by an observer at rest.  T' (read: T prime) is time measured by a moving observer.  v is the moving observer's velocity and c is the speed of light.\n\nThe speed of light is very fast.  So if v is 100 mph or 10 000 mph when you divide it by a number like c (186000 mps that's miles per second so a huge amount of miles per hour)  the v^2/c^2 value is zero and T = T'/sqrt (1) which is T = T'/1 so there is no measurable difference.  \n\nBut plug in 9/10 c for v.  That means an object going 9/10 the speed of light.  You get T = T' / sqrt[1-(9/10c)^2/c^2]\n\nc^2 cancels out and you get T = T'/[sqrt 1-(81/100)] T would be 2.2 times T'.  More time transpired for the non moving observer.\n\nHow did we get the equation?  Einstein was really smart.
972241
Firstly, please allow me to substitute your term "speed" for the more accurate term "velocity".\n\nAll particles and waves have an intrinsic velocity  in a vacuum.  The subatomic particle which makes up light is the photon.  The photon travels at an average maximum velocity of 3x10^8 m/sec in a vacuum.  For the exact numerical speed, here is a good source\n\nhttp://en.wikipedia.org/wiki/Speed_of_light\n\nbut for the purposes of almost all calculations, 3x10^8m/sec is used.  There are physical forces which can slow down the speed of light, and the chief force is gravity.\n\nDarkness is the absence of light, and therefore, the absence of any photons. Therefore, the concepts of speed and velocity are not applicable.\n\nP.S.  There is only one particle theorized to be faster than the speed of a photon, or more aptly put, faster than the speed of light.  That subatomic particle is the "tachyon".  It is further theorized that , because it is travelling faster than the speed of light, it is also travelling backward in time.\n\nP.P.S.  Many of the theories in physics are derived from solutions to various "so-called" unsolvable problems derived from math theory.  In this sense , physics and math go hand in hand.  Therefore, many physics theories are simply supported by math equations until a real life proof can be generated, characterized properly, qualified, and quantified.  The problem here is that just because a math equation may have a solution , it alone BY NO MEANS is proof in and of itself of the existence of subatomic particles and physical phenomenae.  It can only be used as a measuring stick,of sorts,  in order to look for the existence, and therefore, FORMAL PROOF of such phenomenae.
183503
For instance, astronauts have attached a mirror to a rock on the moon; scientists on earth can aim a laser at this mirror and measure the travel time of the laser pulse--about two and a half seconds for the round trip, which gives about 3.00E8 m/s for the speed of light.\n\nIts speed can also be derived from Maxwell's equations for the speed of propagation of electromagnetic fields in vacuum.
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)
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.
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
697180
Which previous question are you talking about???\n\n3e8 is the speed of light. (3 x 10^8 meters per second)\nThe symbol for the speed of light is usually  "c".\n\nPerhaps they meant Velocity of Propagation??
226867
The speed of light. 186,000 miles per second.
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 ...
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)
61325
the Flash @ speed of light ;)
410856
Engery\nMass\nc is the speed of light (why c? I don't know does anybody else?)
24125
Lights speed is a constant that can be derived, but the constants upon which it hinges (eg permitivity constant) needed to be measured.  Einstein's relativity came as a theory when he saw that the speed of light came directly out of Maxwell's equations for electromagnetism.
624995
Energy = mass x speed of light squared