“…axions are potentially detectable through their weak coupling to electromagnetism…” -Aaron Chou
We know, from hundreds of years of experience with the laws of physics, that momentum is strictly conserved, and therefore a reactionless drive is impossible. What’s not impossible is an engine that has a reaction that’s simply invisible, or otherwise undetectable to us. This has been seen in experiments involving neutrinos, but NASA’s impossible space engine, the EMdrive, offers another possibility: a dark matter reaction.
Image credit: ESO/L. Calçada, of the illustration of the dark matter halo surrounding the luminous disk of our galaxy.
You see, one of the leading candidates for dark matter is the axion, an ultra-light, massive, abundant particle that would couple to microwave photons under the right conditions. While ADMX, the axion dark matter experiment, looks for this coupling in a microwave cavity, it’s come up empty so far. Could the tinkerer who invented the EMdrive have accidentally stumbled upon dark matter instead?
The surface magnetic field of an active EMdrive, during the NASA test. Image credit: NASA Spaceflight forums, via Chris Bergin.