If we understand that the term ethereal substance in modern terms refers to the quantum field then we do know from quantum electrodynamics that light does arise from vibrations in the ethereal substance. One of the most beautiful things of QED is how you can derive electro-magnetism (light) by just imposing sysmetries on in the quantum field. So light or quanta is in fact a vibration of the quantum field, yet this vibration as all things quantum mechanical are explicitly non-physical. They only become ‘physical’ when a ‘measurement’ or ‘observation’ is made. In my opinion there is where the mystery lies and the act of measurement could represent some sort of bridge between the idealized world and physical matter. Towards the end of another article I wrote a while back I try and explain my thinking on this in the context of this fascinating passage from Baha’u’llah’s writings :https://medium.com/@vahidhoustonranjbar/emergence-a-possible-bridge-between-the-material-and-spirit-c8bda12974bd