If we had to do merely with the ether that fills the interplanetary space and conveys energy through it, we could confine our attention to the mass and neglect the chemical nature of the ether.

Consider ethanol and ether. Both molecules have the same molecular formula (C 2 H 6 O) yet there is a large difference in boiling points. Ethanol (CH 3 CH 2 OH) is a liquid at room temperature ...