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posted by martyb on Friday June 17 2016, @12:39AM   Printer-friendly
from the invisible-light dept.

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.


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  • (Score: 2) by Immerman on Friday June 17 2016, @01:54AM

    by Immerman (3985) on Friday June 17 2016, @01:54AM (#361361)

    Why do an EVA? If it's real it should generate the same thrust if you just bolt it to an inside wall.

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  • (Score: 3, Insightful) by deimtee on Friday June 17 2016, @02:00AM

    by deimtee (3272) on Friday June 17 2016, @02:00AM (#361365) Journal

    Just in case it really is emitting kilowatts of microwaves maybe? If I was on the station, I think I would prefer it to be outside.

    --
    If you cough while drinking cheap red wine it really cleans out your sinuses.
    • (Score: 2) by tangomargarine on Friday June 17 2016, @02:42PM

      by tangomargarine (667) on Friday June 17 2016, @02:42PM (#361571)

      Are the walls of the ISS thick enough to protect from that anyway?

      --
      "Is that really true?" "I just spent the last hour telling you to think for yourself! Didn't you hear anything I said?"
      • (Score: 2) by Immerman on Friday June 17 2016, @03:11PM

        by Immerman (3985) on Friday June 17 2016, @03:11PM (#361589)

        Should be - microwaves are normally reflected by even a thin sheet of metal (like the mesh on the front of your microwave oven). The only real question is how question would be just how perfectly canceled any emitted photon pairs are. If they're perfectly aligned, then for most practical purposes they cease to exist and it's not a problem. If however they're only *almost* perfect you'll get interference patterns around the device. Not really sure how shielding would effect that... I think all the normal formulas assume that you're dealing with each photon individually, when pairs start effectively popping in and out of existence.... I wouldn't know where to start.