
Experiment reveals evidence for a previously unseen behaviour of light - raattgift
https://www.theguardian.com/science/life-and-physics/2017/sep/03/experiment-reveals-evidence-for-a-previously-unseen-behaviour-of-light
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raattgift
In this article Joe Butterworth (of the University College London's High
Energy Physics Group) writes an excellent example of what science journalism
should be.

I think he does a very good job in explaining the distinction between
inelastic and elastic photon-photon scattering.

(Unfortunately he also refers to photon-proton work he's done in the past, so
maybe he's right to revert to light-light scattering later in the article, and
perhaps should have done that almost from the beginning as an aid for the
casual reader.)

(A précis might be: when looking at a point fixed in space relative to you, a
pair of high-momentum photons with well-defined trajectories through that
point can interact at or very close to that point with the result that the two
photons will have new trajectories but unchanged momenta.)

