[rrmm]

Neat-o. A little bit more info at https://en.wikipedia.org/wiki/Two-photon_physics . Basically two photons with enough energy to interact via virtual pairs created.

It will be interesting to see the cross-section rates and maybe hopefully some new physics (as the wikipedia page weakly hints).

[ajross]

Yeah. The article is a little confused with terminology. Photon/photon interaction is "illegal" in QED in the same way and for the same reasons that wave solutions to classical electromagnetism don't interact (well, except to propagate). What's happening here are interactions between the two photons and the vacuum.

So the new science here isn't unexpected confirmation of new physics, it's our ability to probe our existing understanding of the vacuum with new interactions.

[rrmm]

Right, the new physics the wikipedia article is alluding to is that in previous experiments indirectly measuring two photon interaction cross-sections, the cross-section was higher than what the standard model would predict (but those experiments didn't have tight enough error bounds to say anything definitive).

[phkahler]

>> Basically two photons with enough energy to interact via virtual pairs created.

Or could it be that a photon bends space-time as though it had mass, and they simply follow the local curvature and it looks like scattering? Just speculating, because for some purposes photons act like a solid particle with their energy equivalent mass traveling at speed c.

[jessriedel]

It is not gravitational. That effect would be far, far too weak.

[Florin_Andrei]

For that to happen, the energy-equivalent of the photons would have to be close to the Planck mass. That's an unbelievably high value for photons. We're not going to see that reproduced experimentally any time soon.