Why light can't travel more than 300,000 km per second? What is the hindrance or block it faces in vacuum ?
610852
Light exhibits the characteristics of a wave in some situations and the characteristics of a particle in other situations.  The wave theory asserts that light is a form of high frequency electromagnetic wave.  Basically, a changing magnetic field produces an electric field and a changing electric field produces a magnetic field resulting in a wave.  As far as the speed of light, the real question is how do you accurately measure something that is moving so fast?
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.
736786
because LIGHT travels faster than SOUND!!!\n\nSpeed of light:  186,282.397 miles per second\n\nSpeed of sound:  1238 km/h or 770 mph
297054
heres the info:\n\nNobody has ever managed to ride a beam of light, although Einstein in his youth imagined what it might be like to do so. Such thinking eventually lead to the special theory of relativity. Although it is still impossible for anyone to travel on a light ray, physicists have managed to stop a laser beam in its tracks! This amazing result builds on earlier work by a research group led by Lene Hau in which light was slowed to 38 miles per hour.\n     Light in a medium travels somewhat slower than 300,000 kilometers per second, its speed in a vacuum. This effect, known as refraction, is responsible for the bending of light in passing from one medium to another. In an ultracold gas of sodium atoms, the index of fraction varies significantly with the frequency of light. The gas is normally opaque, but when the sodium atoms are bathed with secondary "controlling" laser light of a particular frequency, the medium becomes transparent and light can pass through it. Due to the varying index of refraction, a primary laser pulse slows down when it enters the gas. It also becomes greatly compressed. A pulse with a length of one kilometer gets squeezed into a tiny unit one one-thousandth of a meter in length. When the light pulse exits the region of sodium atoms, it expands back to its original length zooming off at 300,000 kilometers per second again. \n     To bring the light to a standstill, Dr. Hau and her co-workers turn off the secondary controlling laser light after the impinging laser beam has entered the ultra cold sample. The medium becomes opaque. One would think that the laser pulse would be absorbed by the sodium atoms. Instead, the information about the light wave is encoded in the atoms. When the controlling laser light is turned back on, the atoms reconstruct the laser beam. It continues its propagation though medium and then out the sample. If the time during which the beam is halted is not too long, the shape of the reconstructed beam coincides to a high degree with the original shape.\n     Imagine a train one kilometer in length consisting of thousands of cars traveling at 300,000 kilometers per second. Suddenly, the track becomes rough, causing the front engine and subsequent cars to come to a screeching slowdown. With the train now moving at 38 miles per hour, the cars pile up and are crushed to the size of an ant. Then a magician snaps her finger and the train disappears but leaves an imprint on the dirt between the tracks. With a second snap of the finger, the imprint vanishes while the ant-sized train reappears and moves forward at 38 miles per hour again. Then the train encounters smooth track. The engine speeds off at 300,000 kilometers per second, and as subsequent cars enter the smooth track region, they too rapidly speed off so that the entire accordion-like structure unfolds. Remarkably, little damage to the train occurs.\n     "Impossible!" You say. Well, in the case of a train, it is impossible because the deformation of metal is an irreversible process. But light is more accommodating and can be stretched or compressed more readily. Still, Dr. Hau's team has done what seems to be magical. Why isn't the light absorbed and lost? How can the atomic information reconstruct the beam? Why isn't the beam greatly distorted when it leaves the sample? The answers to these questions reside in the miracles of quantum mechanics, the dynamics that control the microscopic world of atoms and their interactions with light.\n     A major technological breakthrough has occurred. If low cost means are found to manipulate light in the above manner, then computers and communications will be revolutionized. One can imagine using light instead of electrons to perform computational processes. Such photonic machines would calculate at many times the rate of current computers.
168923
>>>>why can nothing excede the speed of light?\n\nLots of things can and do exceed the speed of light.\n \nNo information or mass can exceed the speed of light. Why? Because the speed of light is our one reference point. If anything exceeded the speed of light it would arrive at its destination BEFORE it was sent.\n\nIt's exactly like recieving a letter the day before it is written. It's impossible and  it makes no real sesne to ask why it can't happen. Cause has to preceed effect.\n\n>>>>if radio waves are slower than light\n\nRadio waves are just electromagnetic radiation. They travel at lightspeed just like all other EMR.\n\n>>>>>then wouldnt gama and X rays be faster?\n\nNo, they also travel at C. They just have higher freqencies.\n\n>>> or do all waves travel at the same speed and the light >>> part is just a term\n\nWaves have all sorts of speeds. \nOcean waves travel at variable speeds, often les than 10  kms.hr. \nSound waves travel at a bit over 1000km/hr. \nLight waves travel at the speed of light.\n\n_______________\nInfinity said:"By the way, the quote "Lots of things can and \n>>>>>>do exceed the speed of light" is entirely false.\n\nI really, really wish people would do some basic research before attempting to adress points they clearly don't understand.\n\nThe expansion of the universe itself is faster than the speed of light (see the link below).\n\nAnd as wd5gnr and Hound both said it is perfectly possible for non-information bearing events to propagate faster than lightspeed. We recently had an in depth discussion on the experiments which have managed to produce pahse vlocities hundreds of times faster than light.\n\nAnd of course there are many many other events that travel at speeds well in excess of C.\n\nReally Infinity, you should at least take the time to do some research before correcting others. It saves you embarassment of this kind. More importantly it prevents you misleading others and spreading your ignorance.
644825
According to Special Relativity Theory, when you are transporting a mass at a speed near lightspeed, the energy needed to increase your speed rises to infinity. We can't provide the system with enough energy to reach the light of speed.\n\nEnergy, though, can travel at the speed of light because it has no mass. If we could transform a mass in energy (remember: E = m c^2) and re-create it at destination, travelling at lightspeed would be possible.\n\nBut, as Dark Helmet said, speed of light is too slow. We need ludicrous speed!
615996
You don't go 'back' because you can't get to that speed.  Time slows for you by the ratio of 1 over sqrt(1-v^2/c^2).\nYou have to get quite close to the speed of light before this is noticable at all.
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 ...
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)
648382
In the vacuum light can get the high speed.\nAfter that you have gas, liquid an then solid.\nThis is because the density of matter. The more dense the matter is the more athoms there are, making it harder for the light to pass.
193299
It would take infinite energy to accelerate you and your light fixture to the exact speed of light which would thus be impossible.  However, as you approach the speed of light, at ever greater fuel expenditure, your rocket ship would shrink in the direction of travel and you would become a "pancake" but not be aware of it.  When you turn on your light, the photons emitted straight ahead would travel at the speed of light, c.  Photons always travel at the speed of light in a vacuum.  it is not like shooting bullets ahead from a fighter plane where muzzle velocity is added to the speed of the plane.  Although Einstein's theories of relativity do apply to the plane and bullets as well as photons, the effects are almost undetectable at the very low velocities we ordinarily experience on earth.
223333
Light is a bit pardoxical in that it exhibits characteristics of both a wave and particle, depending how you test it.  In physics this phenomena is referred to as the wave-particle duality (see 2nd ref below) and will probably never be fully resolved until physicists succeeds in finding the long sought unified theory meant to bridge the gap between gravity and electromagnetics.\n\nTo answer your question the maximum speed of light in a vacuum is approximately 3 x 10^8 m/s
68058
Two of these answers were correct (the speed of light in a vacuum is exactly 299792458 meters per second), although the appropriate reference is not wikipedia but the Bureau International des Poids et Mesures (BPIM).  This is the internationally recognized "official" source.\nhttp://www.bipm.fr/en/si/base_units/\n\nThe speed of light in a vacuum is exactly known because the meter is defined (by the BPIM) as being the distance that light in a vacuum travels in 1/299792458 of a second\n\nThe answer from Trsmd is not quite correct in stating that the speed of anything can be measured by determining the distance in travels in a given amount of time.  Since our units of distance are defined in terms of the speed of light, the correct statement would be that distance can be determined by measuring the amount of time that it takes light to travel that distance.\n\nAlso notice the qualifier "in a vacuum".  The speed of light travels more slowly when it travels through something like air, water, or glass.  How much more slowly depends on the properties of the material (density, composition, temperature, etc.)
122048
Peple I know you want the points, but can you please not just make up answers out of whole cloth like that?\n\n>>>>>Massive objects cannot go the speed of light.\n\nYeah, they can. They can't accellarate to the speed of light but they can be created at lightspeed and continue on.\n\n>>>>>> However if they could, no you could not see, becuase the light could not go furthur then the builbs at the front of your car\n\nNonsense. The speed of light is constant for all frames of reference. From the FOR of the bulbs the light would be seen travelling away from it at lightspeed. \n\n>>>> You'd be seeing the light go by your side.\n\nNo, you would not be seeing the light by your side. You would still be seeing all light in the universe travelling away form you or towards you at the speed of light, just as you do at your current velocity\n>>>>>The light would not shine out in front of you because you are going the same speed.\n\nIncorrect. Light always sines out in front at lightspeed in the observers FOR. It makes no difference if that FOR is stationary or lightspeed itself.\n\nYou quite obviously made that answer up.\n\nws, this question seems to get asked here every couple of days. You can go back and have a look and see it answered quite well several times.\n\nIn brief,\n\nLight is funny stuff. Light always travels at the same speed relative to you, it doens't matter how fast you travel. \n\nIf you are sitting still and a person is going past you at light speed you can both look at exactly the same light beam, and it will be travelling at lightspeed compared to both of you.\n\nIf you are going at lightspeed and turn on the headlights the light will move away fomr you at lightspeed. If it strikes something it will be refelected back at lightspeed. If someone is sitting completely still beside you he will also see that light move away form him at lightspeed, and get reflected back at lightspeed.\n\nIt's weird stuff light, it doesn't behave like anything else. The answer to any question that asks how fast light is moving towards you or away from you is always "lightspeed". It doesn’t matter what else we add to the question, the answer is always 'lightspeed".\n\nSo if the light leaves the bulbs at lightspeed and gets reflected back at lightspeed does that mean you could see?\n\nProbably not. \n\nAlthough light doesn't change speed relative to the observer it does change wavelength. The faster you travel towards a light source the bluer it will look. \n\nAny object that your headlights strike will reflect the light back to you at lightspeed, that's OK. But because you are travelling towards the object at lightspeed the light will be shifted way, way towards the blue end of the spectrum. It would all be ultraviolet an X-rays. The human eye simply can't see those wavelengths. So plenty of light would be reflected back, but it wouldn't be visible to you. As a result it would all look dark.\n\n\n>>>>> if the interior light inside your car was on at\n>>>>> the time would you see that?\n\nYes. Because both you and it are travelling at the same speed it woulnd't be red shifted at all. Similarly because you and the interior of the car are travelling at the same speed you would be able to see the light reflected off that just fine as well.\n\nEverything in the universe that is travelling as fast as you will look normal.Everything outside will appear black.
3887
It is impossible to actually go at the speed of light because in the formula for time dialation (That's right Velocity distorts time. The faster you go, the slower time goes for you. This effect is negligable unless you are going very close to the speed of light.) if v(velocity) were equal to c(the speed of light) you would have a zero in the denomonator.\nthe formula is:\nt'=t/sqrt(1-v^2/c^2)\n\nwhere t' is the time that has passed from a stationary observer, t is the time that has passed for you, sqrt means square root and ^2 means squared. As you can notice, when v is small, since c^2 is so huge, you get a miniscule decimal, and 1 minus that number is basically as small as 1.0000000000001 or something, and so time is not really affected. As v gets larger(it can never be the speed of light, then the denomonator would be zero) that fraction becomes closer to 1, so when you subtract it from one, the denomonator gets smaller and smaller, meaning t gets smaller(in order for t' to remain constant) this means that time actuall slows down for the object moving at such velocities. This formula is correct, it is part of Einstein's theory of relativity, and I have had to derive it myself from ordinary mechanics formulas. \n\nAlong with time, length contracts and mass expands by the same factor.  If you were to go close to the speed of light, your mass would increase and length would decrease. This means that the density of your body would increase more and more as you went faster and faster, and your blood eventually wouldn't be able to flow anymore and your cells would die of oxygen starvation.  Not that it really matters, because to even begin witnessing this effect, you would have to be going at least 90 or 95% or so the speed of light.  \n\nNow to answer your question in that is it actually physically possible to get close... considering they have particle accelerators stories high and miles long requiring tremendous amounts of energy in order to even get tiny protons and neutrons to move at such speeds, it doesn't seem like they're anywhere near accelerating something big anytime soon.  F=ma, meaning in order to get something that weighs one gram, like a paperclip to accelerate to the same degree as they do the protons, you would need about 2x10^24 times the force.  That notation just means a 2 with 24 zeros after it.  The reason for this is that that is how much more mass a paperclip has then a proton.  An actual human isn't going to get anywhere close for a very long time.
258719
The speed of light in a vacuum is the same for all colors, and this includes all electromagnetic waves outside the human visible spectrum, such as ultraviolet, microwaves, infrared, gamma rays, x-rays, and so on. \n\nIn materials, however, the speed of light is not only slower than in a vacuum, it's also different for each color.  This is why we have dispersion in transparent materials which is responsible for phenomena like chromatic abberation in lenses, rainbows formed by droplets of rain, and splitting of light into a spectrum by a prism.  If the speed of light was slower in a material than in a vacuum, but the same for all frequencies (colors) of light, we'd have refraction, but no dispersion.   \n\nAnd, while nothing can have a velocity higher than that of light in a vacuum, things can go faster than light in a transparent medium.  This causes the electromagnetic equivalent of a "sonic boom", which is called Cherenkov radiation.  \n\nAs for a light year being a "perfect unit of measure", well, it has a rigorous definition developed from basic units of nature on which everyone can agree.  But, so does the meter, or the second, and almost everything other than the kilogram.  \n\nHowever, if you were to send a beam of light into space, you'd find that depending on the frequency it may travel somewhat less than a standard "light year" in one year's time.  This is because space isn't actually a perfect vacuum, and so it does actually have an index of refraction. For many wavelengths, it will be a full light year distance traveled, but some frequencies will travel slightly slower due to the tiny amount of matter, averaging one hydrogen atom per cubic meter, that is present even in deep space.
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.