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: 0) by Anonymous Coward on Friday June 17 2016, @07:50AM
(Score: 2) by HiThere on Friday June 17 2016, @07:04PM
Not clear. IIUC, some models say that photons are absorbed rather than destroyed by energy absorption, and thus when they are emitted, they are actually being re-emitted from a previously absorption.
So creation and destruction may not happen. This probably depends on exactly what photons are. If they are just packets of energy, then it works fine, but photons also have spin, so I'm not sure that it does (or doesn't) work.
*IF* photons are just packets of energy, or even essentially packets of energy, then they can neither be created nor destroyed, only absorbed or emitted. But polarization makes this messier, so perhaps you can disassemble a photon into energy (absorbed into one process) and spin (absorbed into another). If so, I've never heard of this being done, but I'm not a specialist in this area...or even in physics.
Still, my first guess is that photons are neither created nor destroyed.