@soothfast said
I've been thinking. Always perilous.
Commence with the logic of noise-cancelling headphones: an unwanted ambient sound of a certain frequency, such as the drone of a jet engine, can be cancelled out by emitting in equal measure a new sound of the same frequency yet 180 degrees out of phase with the unwanted sound. Each crest of the unwanted sound wave overlaps a troug ...[text shortened]... ficance itself.
What is there then? What is reality? Just change and contrast. Yin and yang...
A wave propagates and carries energy, unless it's a standing wave, so if there's two standing waves on a guitar string, say, and they're out of phase with each other by 180° then that will cancel out, but in the case of waves propagating from a source it's not so clear to me. If one imagines a couple of sources at some point and if one emits a wave then it propagates through whatever medium we've got and transmits energy by displacing the medium. Suppose the other source emits sound (or whatever) 180° out of phase with it, then if they both start emitting at once at the same frequency and amplitude
no energy will propagate from the combined non-source. There's no displacement of the medium and so I think we can safely say that we can distinguish between something and nothing in this case.
Of course, in practice we cannot have two sources at one point, the closest we can manage is either to have two small loudspeakers near each other, in which case what we'll actually see is some sort of interference pattern, or a single loudspeaker with two signals being fed into it in which case the two signals will cancel out and the material the loudspeaker is made of won't vibrate.
So, I don't think your physics introduction really works, although I don't mind the conclusion. In the modern picture of physics the vacuum is just the lowest energy state. So, in Dirac's picture, there's a dense sea of negative energy electrons, when one interacts with a gamma ray with more energy than the mass gap it's knocked into a positive energy state and the resulting hole in the negative energy sea is seen as a positron. This seems similar to the picture you're presenting in the second half of your OP.