What is space-time "made out of"? A thread in another forum about the definition of "nothing" got me thinking. I know matter is composed of molecules, which are composed of atoms, which are composed of electrons, neutrons and protons, which are composed of quarks, etc ... But what about space-time itself? Since in General Relativity space-time is said to be curved, it must exist as a thing in some way. If mass or matter is thought of as "clumps" in space time, and matter is composed of clumps of atoms and so forth, does "empty" space, i.e. space with no rocks, gas or dust clouds, etc .. just a vacuum, contain sub-atomic particles as well, just perhaps not as bunched together? And I also understand that in our universe matter is neither created nor destroyed, only rearranged. Was all the matter in the universe created in the Big Bang, or was it already there, and the Big Bang merely changed its form?