I believe that baro-san has weight on his side, excusing the pun, as referring to photons as being weightless, or rather, "messless", which spelled correctly reads, massless. In particle physics, a massless particle is an elementary particle whose invariant mass is zero. The two known massless particles are both gauge bosons: the photon (carrier of electromagnetism) and the gluon (carrier of the strong force). However, gluons are never observed as free particles, since they are confined within hadrons. Neutrinos were originally thought to be massless. However, because neutrinos change flavor as they travel, at least two of the types of neutrinos must have mass. The discovery of this phenomenon, known as neutrino oscillation, led to Canadian scientist Arthur B. McDonald and Japanese scientist Takaaki Kajita sharing the 2015 Nobel prize in physics. If consciousness had weight, or technically termed mass, we souls would never be all the same 21 grams, as the bigger brains, like Einstein, must contain more consciousness and weigh more, if consciousness=knowledge. But does knowledge have mass? After all, no one here will dare to argue that knowledge is not part of consciousness, would they? Because than we are back to the same old ground, no brain, no knowledge.