Since the times of the ancient Greeks, scientists and philosophers have generally agreed that everything that takes up space, or matter, is made up of tiny bits of material that have come to be known as elementary particles. The only thing that has...

Alchemy, natural philosophy, and early modern physics proposed the existence of a medium of the æther (also spelled ether, from the Greek word (αἰθήρ) aether, meaning "upper air" or "pure, fresh air" [1]), a space-filling substance or field,...