On: Signatures of gravitational atoms from black hole ...

[cyberax]

> No, EM waves do not have mass. They are massless. They carry momentum and energy, yes, but not mass.

OK, EM waves can get _transformed_ into mass.

[pdonis → cyberax]

> EM waves can get _transformed_ into mass.

In the sense that they can be absorbed by matter and (possibly) increase the invariant mass of the matter, yes.