This paper proposes a physical explanation for the cause of gravity. The proposal is built upon two fundamental postulates: (1) the existence of aether as a sub-atomic substance;and (2) the absorption of aether by atoms. The explanation which the paper offers for the cause of gravity is that the absorption of aether by atoms causes a flow of aether towards the atoms (e.g., the Earth) and the flowing aether exerts momentum upon any matter in its path. The result is gravity. In addition, this paper suggests that the above concept provides an explanation for dark matter, dark energy and other phenomena.
Keywords: gravity, ether, dark matter