If energy equals mass times the squared velocity....?

Question

....of light centimeters per second.

Then is a photon really massless.

Is the reason it is said to have no mass because the constant speed Lorentz contracts a photon (assuming sum over paths vs wavefunction) to the point of non-spatial existence thus for all intents and purposes it is said to be without mass?

Answer 1

why centimeters per second? what units are you estimating mass in  if you are using centimetres per second?? are you maybe contending that if it's massless then the speed doesn't matter so why bother with units anyway?  did I type too many question marks at the end of the second question?

Answer 2

Good thinking, but you really know that if a photon had mass it could not move at the speed of light.

Answer 3

mass and energy are actually synonyms generally speaking! A photon has no Mass of Rest – this is what they mean for ‘massless photon’. You are right when speaking of Lorentz stuff!

Look more: photon is not a mass-less particle actually! A star visible at the edge of the Sun disk in the sky (EG when eclipse) can be theoretically in the “shade” of the Sun if a beam from that star would be a straight line; it is visible however coz the beam is attracted by Sun’s gravitation, so that the beam is bent and can reach our eye! This behaviour of photons is similar to that of a fast moving asteroid and proves presence of gravitational mass of photon, that is m=E/c^2;

Answer 4

Technically speaking, the m in E=mc^2 is an object's rest mass or mass in a rest frame.  A photon has no rest mass.  Of course this is all very confusing since we know that when something emits a photon, it actually loses a bit of mass/energy.  Well when a particle has been accelerated, you use the function:

E = (relativistic mass) * c^2   -or-

E^2 = (pc)^2 + m^2 * c^4 where p is the momentum

In the case of a photon:

E = pc, which is what we observe.  The next particle to absorb the photon will gain that much mass/energy.