personification of the sky or upper air breathed by the Olympians; son of Erebus and night or of Chaos and darkness

ether: a medium that was once supposed to fill all space and to support the propagation of electromagnetic waves
wordnetweb.princeton.edu/perl/webwn

According to ancient and medieval science, aether (Greek αἰθήρ aithēr), also spelled ¾ther or ether, is the material that fills the region of the Universe above the terrestrial sphere.
en.wikipedia.org/wiki/Aether_(classical_element)

Aether (also ®there, Αἰθήρ), in Greek mythology, is one of the Protogenoi, the first-born elemental gods. He is the personification of the upper sky, space, and heaven, and is the elemental god of the "Bright, Glowing, Upper Air. ...
en.wikipedia.org/wiki/Aether_(mythology)

It is pretty clear that both spellings are acceptable.


A