How is Aether conceptually distinguished from the four terrestrial elements in alchemical philosophy?

Answer

It is often described as the celestial element, the stuff of the heavens

Aether is often described as celestial, distinct from the terrestrial elements confined to the sublunary sphere, representing the spiritual or life-force aspect.

How is Aether conceptually distinguished from the four terrestrial elements in alchemical philosophy?
HistorysciencephilosophyElementsalchemy