International Business Times writes:
A new peer-reviewed paper (open, DOI: 10.1063/1.4953807) on the EmDrive from Finland states that the controversial electromagnetic space propulsion technology does work due to microwaves fed into the device converting into photons that leak out of the closed cavity, producing an exhaust.
So how could something come out that you can't detect? Well, the photons bounce back and forth inside the metal cavity, and some of them end up going together in the same direction with the same speed, but they are 180 degrees out of phase. Invariably, when travelling together in this out-of-phase configuration, they cancel each other's electromagnetic field out completely.
That's the same as water waves travelling together so that the crest of one wave is exactly at the trough of the other and cancelling each other out. The water does not go away, it's still there, in the same way the pairs of photons are still there and carrying momentum even though you can't see them as light.
If you don't have electromagnetic properties on the waves as they have cancelled each other out, then they don't reflect from the cavity walls anymore. Instead they leak out of the cavity. So we have an exhaust – the photons are leaking out pair-wise.
(Score: 3, Interesting) by Immerman on Friday June 17 2016, @04:15AM
That wouldn't change anything. Every erg of energy generates X photons with Y momentum. You can do all the fancy bouncing and resonating you want, but so long as conservation of momentum holds, when the photons finally exit the device they will depart with Y momentum, and the device will gain Y momentum in the opposite direction.
(Score: 0) by Anonymous Coward on Friday June 17 2016, @07:59AM
Immerman, you are blowing everyone's "liberal arts" paradigm with your physics and logic and sciency stuff. Please stop.
(Score: 2) by Immerman on Friday June 17 2016, @03:03PM
Hey, if you can't take the math, get out of the science discussion :-D