I'm am new to this board, and except for some light reading, I haven't studied physics in a few years, but a book on Quantum physics got me thinking about something and I was wondering if anyone has done research along the same lines. It seems that the further we delve into the nature of matter, the less and less we seem to find. Atoms, the original indivisible unit of matter, are made up of protons, neutrons and electrons. These in turn are made up of even smaller fundamental particles which may or may not have their own substructure. Since Einstein showed that mass and energy are related, I was thinking what if what we call matter was just a characteristic of concentrated energy? String theory and its successor, M theory, talk about space-time having multiple dimensions wrapped up so small that we cannot see them. What if the features we ascribe to matter, specifically its mass, were the result of the energy bound up in these microscopic dimensions? Another subject that drove me into this line of thinking is the relationship of dark matter to normal matter. Cosmologists suspect that dark matter comprises 90 percent of the known universe. If a mass could be ascribed to the energy contained in the cosmic background radiation, would that be enough to account for this “missing” mass? I would appreciate any suggestions for further reading anyone might have. Keep in mind that my understanding of current physics is limited so please, no dissertations or research papers.