[quote=@thewizardguy]
[@AtomicNut]

E=MC^2 declares that mass can be measured in energy, but also that the opposite applies. Effectively any particle that possesses energy must also possess mass. Energy in fact can be defined as mass measured in a different unit.

Photons are bent by gravity, but the effect of gravity on a particle is measured based on their mass. If photons truly possessed 0 mass then they would not be affected by gravity. However we know that light is bent by gravity ever since the effect of the sun's gravity well on the light of the stars was measured by Edward Eddington in 1919.

Invariant mass is measured as m = sqrt{E2/c4 - p2/c2} which returns that photons have no mass, and therefore light has no mass. However relativistic mass is defined by velocity.

[/quote]

It doesn't apply to photons. Relativistic mass was essentially defined as an artifact to assimilate the changes in properties as objects drew closer to the speed of light by relating it to the rest mass. You have no reason to to apply it to photons, since all their phenomena can be expressed as massless.

And the effect of gravity on light can be summed as the distortion of the 4-space, rather than an intrinsic property of the photon. You're looking it the wrong way. Photons are NOT affected by gravity. The Space-Time IS.

Also, here's what good ol' Albert thought on the subject.

[quote="Albert Einstein in letter to Lincoln Barnett, 19 June 1948 (quote from L. B. Okun (1989), p. 42)]
It is not good to introduce the concept of the mass [img]https://wikimedia.org/api/rest_v1/media/math/render/svg/8dccf40d5ea0e15d8b97019f8f49ce9e56bcf8a0[/img] of a moving body for which no clear definition can be given. It is better to introduce no other mass concept than the ’rest mass’ m. Instead of introducing M it is better to mention the expression for the momentum and energy of a body in motion.[/quote]

(Taken from the wiki)

Now for the love of, stop vandalizing my beloved Physics in such a way. I do have a degree in that and these things hurt.