I would point out that cars have gears, but then someone would say that in the US they do not, and I would have to explain that that is not the case, actually, and it would all get very tiring very quickly.
> Who are the experts on emDrive tech, and what principle does the emDrive violate?
A physicist would point out that momentum is conserved, so nothing can start moving without something else moving in the opposite direction, but then someone would point out that cars seem to be able to do just that, and then I would point out this big round thing underneath a car, and it would all get very tiring very quickly.
How does that relate to airflow?
It is purported to generate thrust by reflecting microwaves internally in the device, in violation of the law of conservation of momentum and other laws of physics.
https://en.wikipedia.org/wiki/EmDrive
Extraordinary evidence is required for extraordinary claims. Any hint of evidence at all is required for idiot claims before waisting people's time.
Not sure a mechanic is better than anyone with understanding of car dynamics, but the "air flow" argument is the key to this.
Who are the experts on emDrive tech, and what principle does the emDrive violate? If you can't say, then you are indeed a pessimist.