Does light have mass.?
604389
Light doesn't have a rest mass, that is an inherent mass that it would have it it were at rest relative to you, but it does have a mass equivalence due to its energy. \n\nE=MC^2 gives the relationship between mass and energy, so you can rearrange this to M=E/C^2 to find the mass equivalence of a given amount of light.  The energy of light can be calculated a number of ways, and then this number can be plugged into the mass-energy equation.  Needless to say, it takes a whole lot of light to add up to a significant amount of mass.\n\nEdit:  Sorry, Mathematician, you're incorrect.  Light does have mass and it can be calculated using the mass energy equivalence.  Your argument is basically circular since you're using the definition of light not having a *rest*\n mass to say that it has no momentum, and the statement that it has no momentum to claim that it therefore has no mass.  You're right in that it has no rest mass, but that's not the only kind of mass there is.  If you've ever seen a radiometer work you've seen direct evidence of the momentum of light.
229775
light has mass....light is made up of photons....light has both wave and particle properties...rest mass of photon is zero and that the effective mass of photon is about 5.42MeV in the symmetric nuclear matter at the saturation density ρ0 = 0.16fm-3 and about 2.0MeV at the surface of }238U.
554379
light.\n\nlet me refer you to e=mc2...light has mass energy and inertia.\na light is a wave and a particle.\nIt is in motion, and objects in motion have inertia and thusly power.\n\nThe true absence of light would exist in a vacuum. There is no pwer in a true vacuum. Even if the absence of light was "massive", that word you chose is a relative term, which is to say that massive CAN NOT imply mass, inertia, etc. The absence of light is NOT measurable because there is nothing there to exist.
1071433
Considering that weight is really mass, and mass can be converted to energy, -and darkness, by this definition is void of either mass or energy, then no darkness does not have weight.\n\nBut if in the middle of night you get out of bed, and it's dark and you hit your foot on a chair, then yes, darkness does (have) (include) weight.
119352
All is clear once you understand the difference between mass and weight.\n\nIf you are not sure, look here:
203282
I think so. Because, existence of space-time is not directly connected to mass. However, presence of mass in space-time will give rise to curvature of space-time menifested as gravitation. If you consider Photons, they do not have rest mass but they have energy and motion in space-time.
302853
Because your mass increases as you get close to the speed of light, at the speed of light, you'll have infinite mass. And all the energy in the universe couldn't move something that has infinite mass.
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.
159391
We say that a photon is massless because it is in the usualy meaning of the word.  A photon has zero rest mass.  However, since it obviously has energy, it has a momentum.\n\nRead through this site and some of the related articles, I think it explains it very well,\nhttp://math.ucr.edu/home/baez/physics/ParticleAndNuclear/photon_mass.html
1049398
light is a wave-particle duality, and as such does not have 'mass'...
895733
Energy=Mass * (speed of light)^2
704770
Actually, any massive object has its mass increase the faster it goes, by the time it reaches the speed of light, its mass is supposed to be infinite (which is why a massive object cannot reach the speed of light, it would take all the energy of the universe and then some to get it there).\nAt the other end, there are photons and their mass at rest is zero. What is zero times infinity?  It is an indeterminate.  This means the result is actually a function of something else, namely the energy of the photon, which is a function of its wavelength (or conversely its frequency).  Since energy is mass times the speed of light squared, energy is mass and vice versa. The result is that light DOES have a pressure, but it is extremely small.  Solar sails are envisioned as a way of moving space probes about, but the size needed is extraordinarily large, owing to the very limited "push" light gives.  For instance, at high noon, the pressure given by the light from the Sun is, at the surface of the Earth, 4.6 micro Pascal. That is 4.6E-6 Newton per square metre. That is about the weight of a small short hair on 5 square metre (one hair on a surface 7 feet by 7 feet, about a large bed sheet).  One hair on a complete sheet is hardly a crushing force, and people simply do not notice that pressure.
624995
Energy = mass x speed of light squared
492443
It is theoretically possible, but highly impractical.  Think about the equation E=mc^2.  C is the speed of light - 186000 meters per second.  So from that equation, you can see that a tiny bit of mass is the equivalent of a huge amount of energy.  Conversely, it would take a huge amount of energy to make even a tiny amount of mass.
593336
http://math.ucr.edu/home/baez/physics/Relativity/SR/light_mass.html
21872
Any mass will attract light. The effect is called a gravitational lense and has been observed (and indeed used by astronomers) around our sun.\n\nInterestingly enough, a black hole is thought to radiate "Hawking radiation" (i.e. a continuum of light).
1102544
No.  Molecules with any kind of mass cannot achieve it, we'd have to be weightless, like photons.  \n\nMaybe you can ask photons how they did it.