Aether is the medium in which electromagnetic waves travel. Conventional physics denies the presents of Aether, for the most part because it cannot be detected. There have also been experiments performed, such as the Michelson-Morly experimentMichelson-Morely Experiment which supposedly disproved the existence of aether. Since the time of the experiment, however, there have been many arguments regarding the way in which the experiment is done, as well as explanations as to why the particular experiment fails to detect the aether.
According to the AAM, the aether is composed of particles much smaller than the atomic scale, or, using terms from the material scale, MS-2 and lower particles. These are the atomic particles or our own atomic particles, and atomic particles of those particles, and so on, to infinity. It is very hard for our current technology to detect and understand particles of the atomic scale, it would be next to impossible for us to detect particles that are billions of times smaller than atomic particles within our material scale level. We can only see their side effects, which are revealed in certain physical phenomenon like electromagnetic waves and gravity.