Universo come oggetto fisico
Philosophers and scientists of antiquity used to speak of material things or bodies, by taking for granted that world was naturally divided into separate objects. Probably that notion is due to the fact that we are living in a comparatively cold sur-rounding (the surface of the Earth), where most bodies are in a solid state. Modern physics has profoundly modified our way of conceiving physical bodies. General relativity led us to think of the universe as of a unique body, governed by a non euclidean geometry and being today in a rapid expansion. So far we do not know whether that expansion will one day stop and be replaced by a contraction, or will instead go on forever. Moreover, recent studies in quantum mechanics have shown that, strictly speaking, the universe cannot be split into separate and independent particles. This is still quite a puzzle.