personification of this sky or top air breathed because of the Olympians; boy of Erebus and evening or of Chaos and darkness
- a medium which was as soon as likely to fill all space and also to support the propagation of electromagnetic waves
- See Ether.
According to Huygens's principle (see Diffraction) each aether particle, set vibrating by an incident wave, can itself act as a new centre of excitement, emitting a spherical wave; and similarly each particle on this wave itself produces wave systems. All systems which are emitted from a single source can by a suitable optical device be directed that they simultaneously influence one and the same aether particle.