It has been stated that photons move at the speed of light,but isnt photon a substance called light?
487618
In quantum physics, the photon (from Greek φως, "phōs", meaning light) is the quantum of the electromagnetic field (light). That is to say, electromagnetic fields are made up of large numbers of photons, and the electromagnetic interaction is mediated by the exchange of virtual photons. The term photon was coined by Gilbert Lewis in 1926.\n\nThe photon is one of the elementary particles. Its interactions with electrons and atomic nuclei account for a great many of the features of matter, such as the existence and stability of atoms, molecules, and solids. These interactions are studied in quantum electrodynamics (QED), which is the oldest part of the Standard Model of particle physics.\n\nIn many circumstances, a photon acts as a classical particle, for instance when registered by the light-sensitive device in a camera. In other circumstances, a photon acts like a classical wave, as when passing through the optics in a camera. According to the so-called wave-particle duality of quantum physics, it is natural for the photon to display either aspect of its nature, according to the circumstances. Normally, light is formed from a large number of photons, with the intensity related to the number of them. At low intensity, it requires very sensitive instruments, used in astronomy or spectroscopy, for instance, to detect the individual photons.\n\nIn many cases, people may say a photon "sometimes acts like a wave and sometimes acts like a particle". This is slightly misleading, because a photon always acts like both. For example, when shooting single photons through a slit, a detector can detect each photon when it hits — but over time, the detector will detect the same diffraction pattern as it would if the photons were given off all in one burst. This is because any given trajectory the photon could take has a certain probability that is dictated by the properties of an electromagnetic wave.
923435
light travels as fast as it always travels, no matter what it shines through. Things block light, but it doesn't slow it down.
7228
Ther are two natures assigned to light\n1.It is made of particles called photons\n2.It is an electromagnetic wave.
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"...What makes the light go so fast?..." Asking why light travels as fast as it does is a useless question because there's no answer. Light behaves as it does because that's just the way it worked out in our universe.\n\n"...What exactly is the definition of light?..." Light is electromagnetic radiation in many forms. For example radio signals, radar beams, lasers, visible light, xrays, etc.,. Light can behave both as a series of waves (..sort of like sound waves), or as a stream of individual particles. Light is said to be invariant, that is it moves at only one velocity regardless of how fast its source might move. The carrier of light energy is the 'photon' which has a tiny mass, but only when its not moving, and since light is never motionless under usual conditions it actually has no mass.\n\n"...Is only one single atom or electron going at 186000 miles per hour considered as light?..." No! Atoms and electrons and other subatomic particles all have mass, and nothing with mass can move at the speed of light.
188402
You don't need a force to enable something to travel, it's quite the opposite! Remember the Newton's First Law: an object in motion tends to stay in motion with the same speed and in the same direction unless acted upon by an unbalanced force.\nOf course Newton's Laws doesn't directly apply to light, which is best described by quantum mechanics as a flow of photons. However, I'm referring to it because its rationale holds also for photons and its formulation is very intuitive (opposite to quantum mechanics).\nOnce photons are emitted by a light source (for instance, electrons changing energetic level within an atom), they "just go", with no need of energy other than the energy that produced them in the first place.
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When light moves from one medium to another with different optical properties (effectively means something in which the speed of light is different). Can even be the same medium but different desity! Ever heard of mirage in deserts?\n[if you are wondering abt speed of light, yes its different in different mediums. The constant c is only for vacuum. In physical mediums, electrons can be made to travel faster than light!]
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The photon has zero mass (it does, however, have rest mass - as in M=E/C^2). \n\nLike all quanta, the photon exhibits wave and particle properties. \n\nIt is important to remember that mass and energy are equivalent. A photon is only referred to as a particle because of certain properties that light exhibits - the "particle" is actually no more than a quanta of pure light energy - and, as such, is indeed dimensionless in the conventional sense of density and volume.
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No. Photons are not particles but may behave like particles in certain circumstances. The most commom interactions are photoelectric, Compton, and pair production in the higher energies. And like visible and near-visible light in the lower energies.\n\nParticles have none of these characteristic mechanics except their collisions which are similar to Compton collisions.
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.
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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.
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.
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Most physicists (like Feynman) will tell you it's definitely a particle.  I think they're full of crap, and it's a wave.  The fact that it can only be absorbed and emited in discrete packets doesn't necessarily mean that it really travels as a particle, and the notion of a particle flies in the face of the double-slit one-photon experiment.
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The answers already given are generally correct for light travelling in a vacuum. However, the speed of light slows down when it travels through any material substance (the exact amount depends on the material).
146790
Photons do not just have a very small, negligible mass, they have zero mass.\nA photon does however have momentum due to the fact that it is traveling at the speed of light.\n\nYou cannot apply a force to a massless object, therefore, Newtons 2nd law is of no use here.\n\nIt might also help to remember that a photon is just one way to look at the nature of light.  Not only is light a particle, it is also a wave, an electromagnetic wave, and you surely cannot apply a force to a wave.\n\nhttp://math.ucr.edu/home/baez/physics/ParticleAndNuclear/photon_mass.html
39110
There is no such thing as a "molecule" of light. However, there are packets of light energy called photons that sometimes behave like waves, and sometimes behave like particles. We can measure their effects. For example, in the photoelectric effect, photons bump electrons out of their position  around atoms and create electric current.
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Its a myth that thought is particularly fast- We can measure the speed that signals travel along nerves, in the spinal cord, brain, etc, and it's around 20-60 meters/second.  Not nearly as fast as light (186,000 miles/second).  Photons don't "accelerate" to the speed of light-that speed is a stable property of photons, thus they are going that speed at the instant they are created-they dont start from motionlessness and speed up.\n*edit* Mich is right-light can be slowed and accelerated, but again, a photon upon creation does not accelerate to it's maximum speed (whatever that is given the medium that it's in)-it starts life going at that speed.  All light does *not* travel at 186,000 miles/sec- that is the speed of light in a vacuum-the speed varies with the medium that light is traveling through.  The speed of light through normal clear glass, for example, is around 120,000 miles/sec.
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Believe it or not, we already have it and use it everyday. I want to answer this in detail, but I cant disclose the true nature of how light travels until I publish.\nI will say that light that is propagated within a closed system can and does move at superluminal speeds relative to a location outside the closed system.\n\nI know-Everybody has a theory, but I can also explain why light bends at every instance without once referring to the fabric of space/time.\n\nWhat if Einstein was WRONG...errr...ok... (just so I dont offend anyone) not completely correct? What if light actually didnt travel by propelling itself into the electromagnetic field created by....itself? What if there was no such thing as a pure vacuum with zero atomic content? (by the way, there is no such vacuum.)\nResearch it, its true, there are always atoms left over to fill the space left by the vacated ones.\nDon't you find that at least a little interesting?  No such thing as a pure vacuum?