But my point was that like Tesla, others can and do make assumptions to move forward. Gravity helps to explain or describe how things function in reality.

So yes, that would be ignorance if it was something that could be known, but it isn't, is it? There is an idea of aether, but is it demonstrable? Gravity decreases in it's effect when we get closer to outer-space. At least that word and what it purports has measurable effects.

Can you know that aether exists? "God"? I see the argument against the idea of aether as an argument against the idea of "God". You can't prove the non-existence of something usually, so the default position is that it doesn't exist until it can be proven to exist. If a model of aether serves to move people forward in their application of things in reality, it could be a model that is true, or just a model invented to try to make of how other things work.