There is a way for something very light to mimic something very dense.

Measured individually air is very light. At sea level the pressure it exerts is very significant 14.7 pounds per square inch. The main stumbling block that occurs is where the pressure of something essentially very light is applied so the effect of an aether is present but not the restriction of a rigid medium.

The problem is always going to be how do you detect something that is part of and underpinning the nature of the known elements. The early Greeks knew about wind and assumed birds flew on the winds. That presented problems when birds would fly on calm days unless one assumes the wind comes from the wings or could be blown. It influenced their thinking and art.

This utube is part two of the pre Socratic philosophers Demokritos the series from part one shows the development of thought.