i recall einstein idicating that there was no longer a reason to posit an aether after special relativity was published, but later wrote a short paper indicating that there was, in effect, an aether after all. ref - http://www.aetherometry.com/Electronic_Publications/Science/einstein_aether_and_relativity.php so, is he indicating that there is an electromagnetic field which permeates spacetime, and that photons are simply excitations of that EM field? is that the erstwhile "aether" now? do all fields likewise permeate spacetime, such as the gravitational field, and is the graviton an excitation of the gravitational field? how many fields are there according to the standard model, and do they all permeate spacetime? is there anything other than fields, considering that all particles are merely illusionary manifestations of underlying fields? are all particle interactions the result of interacting fields? thanks.