According to ancient and medieval science, aether is the material that fills the region of the universe above the terrestrial, or sublunary, sphere. This sphere was the realm of changing nature. Beginning with the Moon, up to the limits of the universe, everything was permanent, regular and unchanging – the region of aether where the planets and stars are located. Only in the sublunary sphere did the powers of physics hold sway. To go "beyond the aether" is a metaphor for transcending the very limits of the all that is known and unknown.