Photons

[ollyoxenfree]

It appears photons have almost unlimited energy, yet they have no mass, unless I am mistaken isn't this against E=mc2? Since obviously there is not a very big chance that one person is going to tear down relativity, I will assume that there is an answer that I am missing and it is fortunate that the title includes "no question to easy" I guess .

[Chris Peterson]

It appears photons have almost unlimited energy, yet they have no mass, unless I am mistaken isn't this against E=mc2? Since obviously there is not a very big chance that one person is going to tear down relativity, I will assume that there is an answer that I am missing and it is fortunate that the title includes "no question to easy" I guess :).

Photons don't have unlimited (or even "almost unlimited") energy. They have a very specific, and individually small energy, E = h*c/lambda, where h is Planck's constant and lambda is the wavelength of the photon.

Furthermore, photons don't have zero mass. They are members of a class of particles that have zero rest mass. However, such particles are never at rest, and have a momentum, which means they also have an equivalent mass- which works out to be exactly what you'd expect from E=mc^2.