Aether (ether) = properties of space - has been replaced in modern physics by the theory of relativity and quantum theory . (future generations will refer to quantum theory as a source of faith, the religion of the enlightened [not a pun, a coincidence?] ...an opinion. 1920: To deny the ether is ultimately to assume that empty space has no physical qualities whatever. The fundamental facts of mechanics do not harmonize with this view. For the mechanical behaviour of a corporeal system hovering freely in empty space depends not only on relative positions (distances) and relative velocities, but also on its state of rotation, which physically may be taken as a characteristic not appertaining to the system in itself. In order to be able to look upon the rotation of the system, at least formally, as something real, Newton objectivises space. Since he classes his absolute space together with real things, for him rotation relative to an absolute space is also s...