i think what they mean is less literal than that -
i think they mean the image of everything that is around us ...
i mean for example if you stay completely still and look at your room it COULD be seen as 2d
it is only when you move around or something else moves that you can conclude it is...
doesn't it just follow the conservation of momentum ? so the body would travel in the opposite direction to the emitted photon at a speed which is dependant on its mass relative to the speed and mass of the emitted photon