Ben (narrator/author of the LessWrong post)

Repeat for liquids of different refractive indices.

Do the experiment, see that the force on the mirror increases with refractive index as predicted by Minkowski.

Simple, and without the measurement uncertainties of the fiber experiment.

No, too simple.

While the measurement uncertainties are very low in these experiments, there is a sub-controversy about how they are to be interpreted.

Mirrors are characterized not just by the fraction of the optical energy that reflects back from them, but also by the phase shift imposed on the reflected light wave.

For a metal mirror it's usually A. Here's a formula.

Phase shift, but any phase shift it possible with the right mirror.

The contention is that the phase shift imposed by the mirror will affect the radiation pressure observed, and that all the studies to date saw the Minkowski result only because they all used mirrors with the phase shift pi.

This paper claims that to get the real momentum you need to average over mirrors with different phase shifts.

My own, possibly erroneous, read on this position is that we can imagine the photon is more like a swimmer or rowing boat than a runner and that momentum is periodically exchanged between the medium and the boat at the optical frequency.

The phase on reflection from the mirror, somehow, picks out at which point in the stroke cycle we interrupt and reflect the photon, and that at different points in the cycle different amounts of momentum are in the photon itself or the medium.

The claim that one should average over different mirrors leads to the claim that the correct momentum is in fact the direct average of Abraham and Minkowski.

Other pro-Minkowski experiments exist.

For example by photons being absorbed by atoms in fluid.

Consensus.

Consensus is a poor substitute for truth.

But if you are interested in the more sociological aspects of science you may well be wondering which theory is mainstream and which is the one beloved by cranks and crackpots.

My own impression is that engaging with a discussion at all to advocate any position is considered slightly cranky.

I can't offer evidence for this claim, it's all vibes.