everyone knows roughly what the "Speed of light" is. Therefore, what is the "Speed of dark"???
359909
This is absolutely an unanswerable question. You have got  great thinking power. It really makes you to think for a moment. Nice way to put brains on work.
475201
velocity is just a term that means "speed" - the distance traveled per time unit \n\nthe "speed of light" is a number - the actual speed (velocity) that light travels, usually reported in meters/second (distance/time)
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.
219832
The speed of light is indeed a constant.  What's important is that it is a constant to every observer.  If you are traveling toward a light source at 1000 m/s, you will measure the light's velocity at 300,000 m/s.  If you are traveling AWAY from the light source, it will still measure 300,000 m/s.\n\nLight IS the absolute speed limit. (Of this universe anyway)
588349
The speed of light is invariant---no matter how fast or slow its source is moving, the speed of light remains unchanged (...please don't ask 'why?' because nobody has the vaguest idea) If you're in spaceship going at 99% the speed of light and shine a light outward in any direction, that light will move away from you at the speed of light, no faster, no slower.\n\nWith regards to the answer given that mentions the Doppler effect. The FREQUENCY (wavelength) of light is affected by the speed of the light source (Doppler effect), but frequency has nothing to do with the actual velocity of the light itself.
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.
54308
As you travel faster and faster, time for you slows down, and length contracts. From your point of view, when you measure the speed of light, it will always be the same. An observer standing still with respect to you and the beam of light could measure your speed at 185000 mps and the speed of light as 186000 mps, and say the difference in speed is 1000 mps. But that is relative to them. The speed of light will always be the same for whoever measures it, no matter how fast they are moving.\n\nSee the website below for more about relativity.
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.
619887
How can I answer that?  If I didn't know then how could I tell you what I didn't know?\n\nHowever, the ten thing that I do know that I think are interesting are:\n\nThe speed of light is constant no matter the respective velocities of the source and the observer.\n\nThe rate of time passage is not constant.\n\nHot water will freeze faster than cool water.\n\ne=mc^2\n\nWhen you stand still, you are moving in 8 different directions.\n\nL’ = L sqrt(1-v^2/c^2)\n\nM’ = M/sqrt(1-v^2/c^2)\n\nAbsolute Zero (not my physics grade, but close)\n\nClarke's Orbit\n\nAvagadro'w number\n\nPlanket's Constant\n\nThe Big Bang\n\nBlack Holes\n\nString Theory\n\nGravity Bends Light (not really, but the effect is the same)\n\nNeutrinos\n\nGirls (Ok, that's biology not physics, but I am listing more than 10 anyway)\n\nThe expanding universe\n\nrefraction of light\n\nSpectrograms\n\nAnd, I could go on and on.  When you look deep enough to understand things, it is all interesting.
161669
You've got it right! "c" is the usual way the speed of light is notated. .37 c would be 37% of the speed of light.
144613
light rays do not move faster or slower than the speed of light.  the speed of light is the speed of light, period.\n\nthat said, light often travels *slower* than c, which is a constant defined as the speed of light IN A VACUUM, approximately 3x10^8 m/s.  here is a way you can actually observe some honest-to-god light traveling slower than c:\n\nstep 1.  find a window.\nstep 2.  look at it.\n\ncongratulations, you have observed light traveling slower than c.  in ANY medium (air, glass, water - you name it) the speed of light is slower than the speed of light in a vacuum.  \n\nin fact, the so-called index of refraction (n, which equals 1.4 for glass) is defined as the ratio of c to the speed of light in that material.  generally, denser materials have a higher index of refraction, and people have been able to make light go REALLY slow by making some very dense materials.  all of this is perfectly consistent with general relativity.\n\nas for FASTER than c:  under certain conditions, it is possible to make photons with a "phase velocity" that is greater than c.  however, when people speak of the speed of light, they usually refer to the "group velocity".  the distinction between phase velocity and group velocity is kind of technical; but phase velocity refers to the speed at which the individual phase fronts propagate through space.  \n\nit is possible to make these phase fronts go faster than c; but because the energy or information or whatever carried by the light travels at the group velocity, the actual speed (as far as stuff like general relativity is concerned) is still less than c.\n\nanyway, all of these results are entirely consistent with general relativity.  in fact, i don't know of any published results of a scientific experiment which are not consistent with GR.  \n\nthe fact that einstein's theory, largely concocted out of the blue from basic principles and logical reasoning, has stood the test of time for so many years is a testament to the genius of the man's work.\n\nhere are some links to learn about phase velocity, group velocity and the speed of light:\nhttp://en.wikipedia.org/wiki/Group_velocity\nhttp://physicsweb.org/articles/news/4/7/8/1
426222
The speed of light is the same no matter where it is. It is 299,792,458 meters per second.
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.
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.
1063272
I like your question :-)\n\nWell, i think that "darkness" doesnt exist in itself but is a human limited concept, a pure product of our mind.\n\nSo: speed of darkness = speed of thought.\n\nHuh?
974250
This page gives a very nice table listing who, when, how, how accurately the speed of light has been measured including the first time when Olaus Roemer did it in a really neat way 330 years ago!\n\nhttp://math.ucr.edu/home/baez/physics/Relativity/SpeedOfLight/measure_c.html
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.