I have been asking myself of late whether or not the energy of a fundamental (point-like) particle has a component attributable to its spin. My understanding has been that a point-like particle has no energy of spin because its moment of inertia is zero. This article appears to both agree and to imply the opposite (see words in bold below): Competition between spin and orbital photon angular momentum transfer in liquid crystals Abstract: We present a theoretical and experimental study on the transfer of angular momentum from a light beam to a nematic liquid crystal film. In the angular momentum transfer process photons are not destroyed, but scattered in a different angular momentum state: a process known as self-induced stimulated light scattering (Santamato E, Daino B, Romagnoli M, Settembre M and Shen Y R 1988 Phys. Rev. Lett. 61 113-16). Each photon in the incident beam transfers to the material only the change of its angular momentum, producing a torque on the body. Under the action of this torque, the body starts to rotate, changing, in turn, the amount of angular momentum extracted from the light beam. The process is intrinsically nonlinear and, as proved by the experiments reported in this paper, it can be initiated by a light beam carrying no angular momentum at all. -- Piccirillo et al 2002, Journal of Optics B: Quantum and Semiclassical Optics, Vol. 4 No. 2 And yet this implies we can compute an amount of rotational energy contributed by each photon, i.e. the rotational kinectic energy of the body divided by the number of photons "scattered" by the body. A way out of this paradox may be in the words "spin" and "orbital", which appear in the title but not the abstract. I have not read the article itself, as I am uncertain the access fee will purchase enlightenment or just regret about the $24. Thanks in advance!