[Ahmaditani]

My question is only that I need an example on trasnforming energy into mass

[Perito]

Hmmm. Mass into energy is easy. Energy into mass -- that's more difficult.

You could try the transporter on the Startship Enterprise ;-)

A photon has "zero rest mass", but it has mass when it's moving. It can be emitted from atoms with vibrational energy or electrons in high energy states. This might be one example of mass to energy (or maybe not).

Actually, when molecules absorb energy, energy is converted into mass -- but it's so small that it's essentially impossible to measure.

[Perito]

I'm not sure that qualifies as a "disagreement". In fact, I know it doesn't. Just because you don't understand is no reason for that.

You're familiar with the atom bomb and fusion reactions in the sun. That's conversion of matter to energy.

A photon is a particle that has zero rest mass. That's part of its definition, plain and simple. A photon can also be thought of as a particle traveling at light speed. Of course, that's also the definition of light. A photon is essentially pure energy, but it's also a particle. When you create a photon, you create a particle out of energy. It might sound like science fiction, but it's not.

Similarly, when a photon is absorbed by an atom, the atom actually becomes heavier. The increase in mass is virtually impossible to measure, but it does increase in mass -- at least that's the theory.