I figure matter-energy is the ultimate complementarity (e.g., Lorenz transformable quanties) in the physical universe. That is neither a strictly cosmological, nor a philosophical observation. I gather it's simply the meaning of E = mc2....
Although I also recognize that not all particles have mass.... Can you suggest a cosmological reason for this? Seriously, I'm just wondering whether you have a view on this.
Thanks for writing, RW!
It's very, very complicated. We haven't yet spotted the carrier particle for mass--the Higgs boson. Not all matter is mass, in fact, any manifestation of anything would not be matter but would be material. Not all particles have mass, but momentum is a different thing. Photons have no mass, but carry momentum. Momentum is not inertia. Matter is what all that is made of. That is to include everything, electrons, gravity fields, string fields, fermions, bosons, whatever. Yes, a thought is material, something made of matter. You know matter, matrix, and mother are all the same word in different dialects.