I think this thread is a bit outdated but it does touch some interesting concepts, that were starring mostly in BO1.
"The ancients found a way to breach the void ; Follow in their footsteps." - Samantha, Origins.
Aether in the story is supposed to be the space in between matter (similarly to physics theories floating around, they even got support from Einstain).
What keeps the universe in tact is Element 115, in the proper amounts.
115 flows all around creation, in the space at the void, i.e the Aether. Opening rifts and jumping between dimensions is super dangerous because it messes with the flow.
This ties into another concept which is "energy fields". You can read more about fields in here: https://en.wikipedia.org/wiki/Vector_field
irl the term "energy fields" is meaningless because energy does not have a direction. However, it could very easily make sense with the zombies story,
as the Aether is not limited to our 3D world, and so technically the energy can be directed "in and out of reality itself". A field directly implies a flow when you have interactable matter.
This is also tied to Agartha as well.
The Casmir affect is directly tied into Aether, as it speaks about Vaccum, which is technically a space without matter, but as we know such places are occupied by the Aether.
From wikipedia, you can once again this concept is connected to wormholes (i.e rifts):