When we look at the immensity of the universe, we see suns and planets and other forms of matter. We see intense energy being expended and having its effects. We see incredible motion as the universe expands, galaxies rotate and move through the universe, collide, and deflect one another; we see stars born, grow and eventually die and collapse into black holes. All of this tremendous activity takes place within an immensity of space, and for those who enter into a spiritual consciousness, there is a perception of a silent, eternal, immutable reality which acts as the substrate and the origin of substance while neither being bound by, nor contained within the physical universe and its actions. This substrate some have called ether, but that is the subtle essence of Matter, and too physical a description for what is essentially beyond all physicality.
“All this surface of cosmic movement is a diverse becoming of natural existences in the one eternal Being, all is extended, manifested, rolled out by the universal Energy from the seeds of her Idea deep in his existence; but the spirit even though it takes up and enjoys her workings in this body of ours, is not affected by its mortality because it is eternal beyond birth and death, is not limited by the personalities which it multiply assumes in her because it is the one supreme self of all these personalities, is not changed by the mutations of quality because it is itself undetermined by quality, does not act even in action…, because it supports natural action in a perfect spiritual freedom from its effects, is the originator indeed of all activities, but in no way changed or affected by the play of its Nature.”
“As the all-pervading ether is not affected or changed by the multiple forms it assumes, but remains always the same pure subtle original substance, even so this spirit when it has done and become all possible things, remains through it all the same pure immutable subtle infinite essence. That is the supreme status of the soul…, that is the divine being and nature…, and whoever arrives at spiritual knowledge, rises to that supreme immortality of the Eternal.”
Sri Aurobindo, Essays on the Gita, Second Series, Part II, Chapter 13, The Field and Its Knower, pp. 404-405