If energy is proportional to mass, how come photons (which are massless) have energy?
>>7977925
http://math.ucr.edu/home/baez/physics/ParticleAndNuclear/photon_mass.html
>>7977925
Energy is proportional to mass and other things. E=mc^2 is a simplification. The "complete" equation is E= sqrt[ (m0 c^2)^2 + (pc)^2 ], p being momentum.
>>7977925
All mass is energy, not all energy is mass
>>7977925
photons have momentum
https://en.wikipedia.org/wiki/Energy%E2%80%93momentum_relation
>>7977961
Not OP, but does something having momentum equate to displacement of mass?
>>7977965
Short answer:
In classical physics, momentum (and energy) are properties of bodies with mass, so you are correct. But in special relativity, to account for the difference between different observers, energy and momentum are redefined as different quantities (that are conserved in special relativity)
The new, relativistic definition of momentum and energy allow massless particles to have momentum and energy, but they have to move at the speed of light. See:photons
>>7977965
>what is a reference frame
You're thinking that e=mc^2, and thus as they have no mass, their energy must be 0.
However this equation is incomplete:
the full equation is
e^2 = (pc)^2 + m^2c^4 and thus as they have relativistic momentum - p, they have energy.
The simplified version you're probably thinking of is for rest mass - ie; non-moving objects
>>7977945
>False. All energy act like mass(cause gravitational pull)
Mass doesn't couple to the gravitational field, the stress-energy tensor does. The SET contains information about energy and momentum.
>>7977925
Energy is not proportional to mass for moving objects.
Photons are not a pure wave or a pure particle. The have traits of both and exhibit behaviors of both depending on the situation. Physics can't explain it all yet. We have a pretty good idea but there is still a lot we have to learn.
The dual slit experiment is one of my favorite physics experiments. A single photon can pass through two slits at the same time and interfere with itself. Wrap your head around that.
https://www.youtube.com/watch?v=TT-_uCLwKhQ
>>7977925
Photons are not massless, they have relativistic mass equal to mc^2
>springs store energy when you compress them
>electric and magnetic fields have energy
>heat is the transfer of energy by radiation
All perfectly fine
>the massless photon has energy
whawhawhaaat?
What's the problem?
photons have mass but do not have energy.
thats why you go blind if you look at the sun too long, it's like being pelted with sand
>>7980504
>>7977925
photons have no mass but have momentum.therefore they can interact with matter, like radiation pressure.
>>7977925
Photons have no rest mass.
>>7979817
Yo, m is the mass in that equation
so if you were gonna fuck shit up wouldn't it be at least m = E/(C^2)
>>7977945
>relativistic mass
Please, for the love of Einstein, let this concept die already. Mass is a Lorentz invariant. It doesn't transform; velocity does.
