A New Aether

In honour of Graham D's quantum vacuum aether, and his diligence in rereading Newton, let us recall the long history and mutation of the meaning of the aether, which even Einstein revived in a new form for General Relativity. In Newton's time, modern materialism was as yet unknown and various forms of Aether media were discussed. His original Aether proposal was intended to support a Particle theory for light, and he strongly objected to the wave proposal, which was more absolutist in its separation of light and background. Newton says:

And so if any one should suppose that Aether (like our Air) may contain Particles which endeavour to recede from one another (for I do not know what this Aether is) and that its Particles are exceedingly smaller than those of Air, or even than those of Light: The exceeding smallness of its Particles may contribute to the greatness of the force by which those Particles may recede from one another ... and exceedingly more able to press upon gross Bodies, by endeavoring to expand itself.

We see that Newton was not necessarily committed to a Particle nature for the Aether itself, but to the necessity of complexity in the mechanism of separation between Particle bodies. It was not Newton's Aether that was rejected in 1905, but rather a $19$th century descendant, after the success of Maxwell's theory for light. Ironically, the reintroduction of a Particle theory for light occurred so near to the abandonment of the Aether of the time that the distinct ideas of Newton were largely forgotten.

The great anti-materialist Mach criticised Newton for his absolutist views, but in the sea of $19$th century classical thought it must have been difficult to appreciate the true intention of Newton's words. From a more quantum perspective, the absolutism still appears to muddy Newton's world, but now it swells up from his views on the divine, while the local mechanics of the Aether retains its wonder.