The late interpreter of the Quran and the Bible: Mohammed Ali Hassan Al-Hilly, said in his book (The Universe and the Quran) since 1947 [although he did not graduate at any primary school even]:
The ether fills every space, and goes through or permeates the intermolecular spaces of all material objects.
All celestial objects swim in the ether.
This ether is very transparent like the air; its particles are far more smaller and finer than those of the air; and for this reason, it cannot be seen by material creatures; moreover, it cannot be touched or perceived.
But it is possible only for spiritual creatures (: angels, genies or demons and human souls) to see, touch and perceive the ether.
(But each [of the sun, moon and earth] is swimming along into a [specific] orbit.)
This is the explanation of the Quran 36: 39
وَكُلٌّ فِي فَلَكٍ يَسْبَحُونَ
The ether