Hello all, newbie here. No acadamic background in physics, but greatly interesting in relativity and theoretical physics nonetheless.

I have a question regarding mass-energy equivalence. I roughly understand the equation and its implications and all, but can any of you give me any "real world" examples either here on earth or in outer space where energy is being converted into mass? For example, is there a stream of powerful X-rays in some galaxy somewhere generating electrons or something? And furthermore, if large amounts of energy create mass, how do you create a proton?

Thanks! Look forward to your reponses.:)

Pair production turns gamma radiation into electron and positron.

Changes in the binding energy which holds atoms together can be measured as mass increases and decreases. So in atomic reactions, the reactants and products can have different masses because of differences in these energies, as well as kinetic energies before and after the collisions which cause the reactions.

Also, even as far back as the late 1800's, the charge/mass ratio of electrons was known to decrease as the velocity of the electrons approached the speed of light, suggesting that electrons gain mass as their velocities increase. Scientists didn't know how to explain it until Einstein came along.

Im surprised no one has mentioned electron-positron annihilation.

Um, they have. That's what the reverse of pair production is.

God bless hoo, i must have missed his post :)