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I'm considering what consequences would come from the development of hypothetical devices that could convert photons to axions at cost and power requirements accessible to governments, large businesses, and wealthier individuals. Three things come to mind:

  1. Stealth capabilities and observability, at the cost of not being able to communicate or see very well
  2. Heat management: radiant photons are now axions that hardly interact with anything at all
  3. Discreet communication, assuming one has a partner that can convert axions to photons

I'm curious if I'm overlooking or not understanding unintended consequences of such a technology, and also wondering what "knobs to turn" there are to make this more easily balanced. For instance, what if there was a floor or ceiling for wavelength that could be converted? If only gammas or long wavelengths could escape the device's field, for instance, that does allow some, albeit flawed, detection. This would certainly help anyone inside of such a field see out of it if they had the right instruments!

Finally, besides very intense magnetic fields, does any other process or mechanism come to mind, such as exotic metamaterials?

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  • $\begingroup$ What's their mass? Could be used to supplement the thrust of light propulsion. $\endgroup$
    – Escaped dental patient.
    Jul 8 at 22:57
  • $\begingroup$ Probably the same as the photons going in, so it wouldn't give you anything over a photon rocket in the first place except lower observability. $\endgroup$
    – cthon
    Jul 8 at 23:02
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    $\begingroup$ @cthon I think maybe what EDP is getting at is that if axions have mass>0 and speed<c then an axion rocket has lower exhaust velocity and higher thrust. Photon rockets could switch to a less efficient mode where more energy is spent to achieve much higher thrust. $\endgroup$
    – BMF
    Jul 8 at 23:38
  • $\begingroup$ I don't think that would really help much since the momentum would have to be conserved. You're not losing more mass and thus having a lower isp and higher thrust by doing this, you're just converting photons to axions within a field after they've already imparted momentum to the ship, unless you have some way to push on the axions as they leave your conversion field, which I believe is practically impossible. $\endgroup$
    – cthon
    Jul 8 at 23:53
  • $\begingroup$ @cthon if it's a process like neutrinos flipping, then intrinsic energy stays the same, no new momentum to steal. (Although photon energy is frame-dependent, so one wonders how the new axions decide how much intrinsic energy they now have.) If the process is like photon+??? -> axion, where ??? is energy stolen from the field (from a particle or other form), then there's higher energy in the axion, some of which is locked up intrinsically in mass which is better at trading momentum. $\endgroup$
    – BMF
    Jul 9 at 0:14

2 Answers 2

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I've contemplated a similar idea, although mine was a field that turned all baryons to dark matter too, not just photons. Here's a couple ideas:

  1. If "shields" using the photon-axion principle could be made, and if the photon energy interaction range is narrow, then that'd give some meaning to the popular sci-fi phrase "tuning the shields to the enemy's laser frequency". Free electron lasers can cycle through a wide range of frequencies, plus the use of non-linear crystals to do sudden frequency shifting, i.e., halving, doubling, tripling.

  2. One of the greatest challenges with torchship engines like fusion or antimatter is the massive flux of hard radiation, which adds a lot of mass and complexity, shielding engine components and the rest of the ship. In a gamma ray photon rocket, the only radiation is gamma. Such a device could maybe neutralize most of the errant radiation in the places that matter most, cutting down on redundant shielding and boosting efficiency.
    Hypothetically, if the device works well enough to neutralize photon rocket exhaust (and this is an idea taken from my own universe), you could put the engine inside the ship, tucked away from enemy fire behind an armored hull, while giving the outside impression of a reactionless drive system.

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  • $\begingroup$ "Lasers will do jack squat" is a great point! $\endgroup$
    – cthon
    Jul 9 at 5:31
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I don't really see how you justify any of these. Axions are hypothetical particles which might resolve the strong CP Symmetry problem.

The Axion, by definition, does not interact with the electromagnetic field. So like, were does the Stealth come from ? Being able to make Axions out of Photons will do nothing to reduce your visibility.

Heat management as well is sus. Heat is a field as well and we have no real concept of how Axions would interact with that one. All we know that, as a dark matter candidate, it is not radiating any heat.

Communication I can see, but why should it be any better than Photons ? If anything it would be worse. In your world, Axions would presumably be dark matter. In which case, there are a lot of Axions out there considering their mass is so low.

Maybe i am missing something here but i dont see how any of the points you listed are actually improved / done with Axions.

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    $\begingroup$ Regarding your first point, OP appears to be using a model of axions that interact via the Primakoff effect. In regards to heat management, I think maybe what OP had in mind was using the axion conversion field device to "discard" radiated waste heat (thermal photons). $\endgroup$
    – BMF
    Jul 9 at 9:58
  • $\begingroup$ Regarding the Primakoff thing, fair enough. The issue with Heat management is that OP suggests converting Photons to Axions, which will happen in accordance with E = mc² because photons are massless, while Axions are not. Mass to Energy conversion is not efficient. Even black holes just manage ~80% if some people are to be belived. $\endgroup$
    – ErikHall
    Jul 9 at 10:59
  • $\begingroup$ Photons have momentum. You don't need to have a rest mass for photons to convert to anything else. I'm also not asking for permission for go what if in a sci-fi, I'm asking "what if it did, then what?" $\endgroup$
    – cthon
    Jul 9 at 17:39
  • $\begingroup$ @cthon yeah they do, not a lot though. And nobody is talking about permission other than you. My point is that it does not seem like the usage of Axions is motivated beyond the name. $\endgroup$
    – ErikHall
    Jul 9 at 18:13
  • $\begingroup$ In order: Yes, hypothetical, in a what-if scenario for a scifi. The point is to convert photons which we can detect into axions which we really can't detect well at all. Thermal photons being turned into something that does not interact would be a way to dump radiant heat. The point was postulating a reverse process to turn axions back into photons for detection and thus communication. $\endgroup$
    – cthon
    Jul 9 at 19:57

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