what is the difference between velocity and speed of light?
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)
13174
Hi Writholeen, the only flaw in JayNick's answer is the accuracy part. As per the National Institute of Standards and Technology, the exact value of Speed of Light in vacuum is 299,792,458 m/s. By exact, I mean there is no uncertainity till the last digit. \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)\n\nThese values are accurate to the 7th digit of decimal. \n\n\nFlaw in JayNick's answer:\n\nThe speed of light in kilometres per second is 279,600 kilometres/sec. Even if you approximate the actual value , 299,792.458 kilometer/second by round off the last three digit, the value would have been 300,000 kilometers per second.
843918
Speed.\nSpeed is only concerned with how fast your travel, and not with the direction.  (One example for velocity, by contrast, is that you drive 1000 miles east and then 1000 miles west in one day, but your velocity is zero, because you are at the same position, and the same reasoning can be applied to acceleration, as well as force).
1177822
The speed of light *in a vacuum* is constant. Light does slow down as it passes through a transparent medium, like glass or air.\n\nA black hole does not affect the speed of light. But the escape velocity of a black hole is greater than the speed of light, so once a photon enters a black hole's "event horizon," it will never come out.
753670
The speed of light varies depending on the medium the light is traveling through.  In a vacuum however, which is the fastest medium in which light can travel, the speed of light is 299,792,458 m/s.
344500
Yes the difference between the two are still the speed of light -- it's because at speed of light, or even just factions of the speed of light "normal" Neut on physics stops and only relativity theory explains what happens.  At speed of light time no longer move at the same rate, so the two object will not have same reference in time, and since speed is distance over time, the comparison make little sense to the normal perception of how things work.\n\nAn that ultimately explain why the difference between the two is not 1000 miles per hour.
301843
299 792 458 m / s ,approximately 300000 km/h=186000 miles a second or 700 million miles an hour.(all measures above are in vacum.not in the air! the speed of light reduces when it gets into areas like air or water.for example in normal pool water the speed of light is about 2/3 of the speed in vacum zone.for more info go to google.com and in search bar type:"speed of light"
269338
The speed of light is 3 x 10^10 cm/sec or 3 x 10^8 m/sec or 3 x 10^5 km/sec.\n\nWavelength = speed of light / frequency\n\nBe sure you use the right units.
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.
332266
The velocity of an object is simply its speed in a particular direction. Since velocity is defined as a vector, both speed and direction are required to define it.\n\n\nThe average velocity v of an object moving a distance d in a straight line during a time interval t is described by the formula:\n\n v=d/t\n\nPlease look at the below site for more details:\nhttp://en.wikipedia.org/wiki/Velocity
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.
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.
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
283556
The speed of light is a CONSTANT and has the symbol c in Science and is measured in meters per second.\n\nc (the speed of light) is equal to 3 times 10 to the power 9.\n\nNow 3x10*9 meters per second equals 3000000000 meters per second. (3 then nine zeroes!).\n\nc is important in physics because nothing can go faster than  c. \n\nNothing can go faster than the speed of light and as Einstein showed with the Theory of Relativity (a very important theory in physics) when an object (mass if you will) approaches c it gets bigger and bigger!! \n\nIf it gets to c then its mass will become infinite - this is impossible! An object with infinite mass! Hence it is impossible to reach the speed of light. \n\nHope this helps.
697320
newton....and u better take care,..its not just any velocity ^2 but the velocity of light^2 which is a constant\nhey,...just sum extra info...if u like\nAccording to Einstein, matter and energy are just different forms of the same thing. In Einsteins theory a mass cannot be accelerated to a speed greater than that of light, hence if a mass is traveling at the speed of light and energy is added it must be converted to mass, hence any mass can be converted to energy equal to that mass x velocity squared with Vc=1. this formulae shows a relationship of the quantities of mass and energy, A conversion factor. \n\nThis is actually a restatement of F=MV^2 with a special relativity to c to describe the equivalence of mass and energy.
71955
Here are two explanations (neither particularly satisfying I will tell  you in advance.)\n\nThe first is that the speed of light (in a vaccuum) is a property of the universe that is measured the same by everyone, regardless of their motion relative to anyone else. This is a true statement born out by experiment, but it implies some very weird stuff.  One is that distance and time are not measured the same by people in relative motion.  Another is that you can never get closer to a beam of light going away from you (i.e. go faster than the speed of light).  If you could, you would measure the speed of light differently than someone else, and you would be special.  The basic idea behind relativity is that, with regard to the laws of physics, no one is special.  \n\nThe second unsatisfying answer is E=mc^2.  In order to go faster, you have to accelerate.  Acceleration takes energy, and an accelerating body has more mass than a body in a constant state of motion (increase E in that equation m has go up, because c is the constant speed of light).  It just so happens that the mass doesn't go up in proportion to the rate of acceleration, but in relationship to how close you are to the speed of light.  Everytime you halve the distance between your speed and the speed of light, your mass doubles, and the amount of effort needed to get that next bit of acceleration doubles.  Getting to the speed of light would require infinite energy.
676715
The speed of light is the upper limit of speed in our space-time universe. Nothing here can be faster. And no car or any other macroscopic object can be equal to the speed of light. But the question is a thought experiment, hence, a good one indeed. Questions like this were raised by Einstein and Relativity became part of modern physical theory.\n\nSince the speed of light is an upper limit, the light from the headlamp of the relativistic car cannot be faster than the car. You won't see them in front.