Speed of light question?
828289
It is exactly that question that inspired Einstein to formulate his theory that nothing can ever travel faster than light. I am not saying the Einstein had a goal to make a theory saying nothing can travel faster than light. I am saying that the question made him think about how to explain what would happen in such a case and then the math lead him to a theory of motion in general which says nothing can travel faster than light.
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)
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.
263654
The speed of light is exactly 299,792,458 m/s.\nThe meter is defined in terms of the distance which light travels in a certain amount of time, that is how we know the EXACT speed of light....we defined it as so.
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.
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 ...
624995
Energy = mass x speed of light squared
227315
Speed of light in vacuum is given, but light travels at constant speed in any medium, but the magnitude of the speed might be different than any other medium. There was a discussion about that here before. You might wanna check that.
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.
532772
nothing but light can travel at light speed.  the faster you go, the more energy it requires to accelerate.  at speeds that are close to the speed of light, you would need what is basically an infinite amount of power to accelate.  with current technology, it is impossible.  the only reason light can travel that fast, is because when it is created it is already traveling that fast.  it doesnt have to accelerate.
555954
Updated 1997 by PEG.\nOriginal by Philip Gibbs 1997.\n\n\nI am driving my car at the speed of light and I turn on my headlights.  What do I see?\n\nSadly this question and all others about experiences at the speed of light do not have a definitive answer.  You cannot go at the speed of light so the question is hypothetical.  Hypothetical questions do not have definitive answers.  Only massless particles such as photons can go at the speed of light.  As a massive object approaches the speed of light the amount of energy needed to accelerate it further increases so that an infinite amount would be needed to reach the speed of light.\n\nSometimes people persist: What would the world look like in the reference frame of a photon?  What does a photon experience?  Does space contract to two dimensions at the speed of light?  Does time stop for a photon?. . .  It is really not possible to make sense of such questions and any attempt to do so is bound to lead to paradoxes.  There are no inertial reference frames in which the photon is at rest so it is hopeless to try to imagine what it would be like in one.  Photons do not have experiences.  There is no sense in saying that time stops when you go at the speed of light.  This is not a failing of the theory of relativity.  There are no inconsistencies revealed by these questions.  They just don't make sense.\n\nDespite these empty answers, nobody should feel too put down for asking such questions.  They are exactly the kind of question that Einstein often asked himself from the age of 16 until he discovered special relativity ten years later.  Einstein reported that in 1896 he thought,\n\n``If I pursue a beam of light with the velocity c (velocity of light in a vacuum), I should observe such a beam of light as a spatially oscillatory electromagnetic field at rest.  However, there seems to be no such thing, whether on the basis of experience or according to Maxwell's equations.  From the very beginning it appeared to me intuitively clear that, judged from the standpoint of such an observer, everything would have to happen according to the same laws as for an observer who, relative to the earth, was at rest.  For how, otherwise, should the first observer know, i.e., be able to determine, that he is in a state of fast uniform motion?  One sees that in this paradox the germ of the special relativity theory is already contained.  Today everyone knows, of course, that all attempts to clarify this paradox satisfactorily were condemned to failure as long as the axiom of the absolute character of time, viz., of a simultaneous, unrecognizedly was anchored in the unconscious.  Clearly to recognize this axiom and its arbitrary character really implies already the solution to the problem.''\n\nIn 1905 he realised how it could be that light always goes at the same speed no matter how fast you go.  Events that are simultaneous in one reference frame will happen at different times in another that has a velocity relative to the first.  Space and time cannot be taken as absolute.  On this basis Einstein constructed the theory of special relativity, which has since been well confirmed by experiment.\n\nQuestions of relative velocity in relativity can be answered using the velocity subtraction formula v = (w - u)/(1 - wu/c2) (see relativity FAQ: velocity addition).  If you are driving at a speed u relative to me and you measure the speed of light in the same direction (w = c in my frame), the formula gives v the speed of light in your reference frame as, v = (c-u)/(1 - u/c).  For any speed u less than c this gives v = c so the speed of light is the same for you.  But if u = c the formula degenerates to zero divided by zero; a meaningless answer.\n\nIf you want to know what happens when you are driving at very nearly the speed of light, an answer can be given.  Within your car you observe no unusual effects.  You can look at yourself in your mirror which is moving with the car and you will lo
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.
687262
Light doesn't accelerate to that speed, it just propogates at that speed period.  Besides, F = ma says you need a mass to have an acceleration, and light, or photons, have zero mass.
867201
nothing can go faster than the speed of light (in theory) so the answer is 3*10^8
11066
well first, read my other answer to your question about the speed of sound.  You would probably expect the answer to be the same, and the light to reach the other car, but this is a special circumstance because nothing can travel faster than the speed of light, not even light itself.  when a beam of light is shone ahead of a rapidly moving space vehicle, and is expected to be moving at the speed of light plus the speed of the vehicle, it is still only moving at the speed of light, which is puzzling.  Physicists have defined the speed of light to be the ultimate cutoff point for speed.\n\nAnd also, you wouldn't be able to travel at the speed of light anyway because time would probably stop since it does get slower and slower the faster you go.  Velocity warps time, the faster you go, the slower time moves for you relative to a stationary object.  I've read this, and it is definately true, we had to derive the formula in physics from, and calculate the time, lenghth(which decreases with speed), and mass (which increases with speed) distortion as well.  The effects of this are very negligable unless you are moving at speeds very very close to the speed of light, at least over 90% of the speed of light, and we haven't gotten anywhere close yet.  The denominator of this factor that time, length, and mass are distorted by actually is 1 minus the square root of the speed of light(c) over the speed in which the object is traveling (v), so the reason you can't go faster than the speed of light is because if v was greater than c, then that square root would be greater than one, meaning the denominator would be negative, meaning the factor would be negative, and the light would actually be travelling backwards in time...\n\nIf you find any of this interesting, I highly recommend "The Elegant Universe" by Brian Greene.
214684
No massive object can move at the speed of light, so the question is ill-posed. Sorry.\n\nAs a physicist, please let me give you a little advice: don't loose your time with this nonsense, try instead to focus on the mathematics of the relativity theory, that's the way to understand it. The rest is pseudo-science.
426747
The speed of light is a measurement of how fast light travels in a vacuum. The speed of light also known as "c" as in the famous Einstein equation E=mc^2. And its equal to 299,792,458 m/s or in U.S miles per hour is about 670million miles per hour!!!!!!! It would take light coming form the sun only 8 seconds to arrive on earth which is 92million miles away. Now say "WOW!!"