a substance (aether) once thought to fill all space
1973 — Somewhere, through exhaustion, redirection, gusts of white noise out in the aether, this arrangement has begun now to dissolve. — Thomas Pynchon, Gravity’s Rainbow
in ancient philosophy
2002, Philip Ball, The Elements: A Very Short Introduction, Oxford 2004, p. 10
There is thus a fifth classical element, which Aristotle called the aether. But it is inaccessible to earthly beings, and so plays no part in the constitution of mundane matter.
