Motie "Light Sail"

I wonder how the Space Environmental Effects Team at Nasa feel knowing
their measurements of photon pressure on reflective materials are
measurements of a force that can't exist or that their stationary
sample would only have pressure exerted on it if it was moved by the
photons and so cause the photons to Red-Shift ( that being where the
transfer of energy supposedly takes place)! Although the mechanisms
are beyond my scope there seems no doubt that light does exert
pressure on reflective materials and that light sails are a feasible
form of propulsion for space vehicles.
Ken