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Let's say we have perfected a meta-material that is invisible to the complete range of electromagnetic radiation. I reckon that since light (ionizing or not) entering the material is simply being bend/redirected instead of passing through without being absorbed too much power can still hurt.

Using known science, would the perfect invisibility cloak truly be invincible to energy based weapon? If not, how to build one that would be invincible to energy based weapons?

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  • $\begingroup$ Please define how your "known science" permits a perfect invisibility cloak. Please define "energy based weapons" - as far as I can tell, all melee and ranged weapons are energy based; be it kinetic energy, thermal energy, or nuclear energy. $\endgroup$ – Aify Aug 22 '17 at 5:13
  • $\begingroup$ @Aify: our known universe is consist of matter and energy, dark or not. Energy is simply a property of matter and it has the ability to do work and in this case I refer it as all spectrum of the electromagnetic waves... currently researchers had already develop metamaterial to bend microwave so that there is no reflection only refraction. I need something that works for all of the em ranges... hope that helps! $\endgroup$ – user6760 Aug 22 '17 at 5:53
  • $\begingroup$ I'm too tired to do a write up, but the webcomic Schlock Mercenary has a model you should look at. If matter/energy conversion and gravity manipulation are available, you can dump power into maintaining a gravitic deflection bubble that would also be invisible in visual spectra. It would also be really obvious to anyone who could detect and manipulate gravity, but hey, there you have it. $\endgroup$ – Sean Boddy Aug 22 '17 at 6:37
  • $\begingroup$ @SeanBoddy: you mean like artificial gravitational lensing? since light and I mean all photon regardless of wavelength travels in a geodesic path it could work... however I need something that isn't too far-fetch ;) $\endgroup$ – user6760 Aug 22 '17 at 7:30
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    $\begingroup$ @user6760, I would rather say that matter is a form of energy... you know, E=mc^2 and along... $\endgroup$ – L.Dutch Aug 22 '17 at 7:54
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Kinetic energy weapons will not care at all about meta-materials, they will simply transfer kinetic energy to it, like they would do on any other target. I presume you mean EM energy weapon.

Meta-materials work thanks to a carefully arranged geometry. Though they are chosen to be as much transparent as possible (there is no perfect transparency) for the light they are supposed to work with, EM weapons have such an high power that even a small absorbance yields noticeable effects. (absorbing 0.1% of a 100 kW beam is still 100 W, not peanuts...)

Such effects can be:

  • Increased temperature. Easy to understand, as a material absorb light, it converts it to heat and warms up. This will disturb the geometry and damage the invisibiliy effect.
  • Photons carry momentum. Enough photons can deliver enough momentum to actually physically damage the geometry, hampering again the invisibility.
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  • $\begingroup$ Yes you're right I'm not making a black-hole or another Capt America's shield, as for temperature is there any way for the electron to vibrate in a specific manner so that it only gives off non-lethal infrared and visible light? Your last point amuse me as I kept thinking of ION drive... the invisible user would fly around in a cape while constantly being bombarded by laser beams :> $\endgroup$ – user6760 Aug 22 '17 at 8:26
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If you're taking the technology to perfection then any detectable energy has to apparently pass through volume covered by the cloak entirely unchanged from any angle.

If that's not the case, then the technology isn't perfect.

An energy weapon, being detectable energy, would hence have to apparently pass through without being affected. I fire from one side, the person standing beyond gets fried, volume within cloak doesn't even get warm.

Using known science? No chance. But then known science barely provides energy weapons so I wouldn't worry that much.

It would also be very dark inside the cloak and, if fully concealed by it, you wouldn't be able to see what was going on outside. After all, all detectable energy passes you by.

If you want to be able to see from the inside then the cloak is no longer "perfect", it's now a point along the scale and L.Dutch's calculations for how much energy from weapons penetrates apply along with visible light.

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  • $\begingroup$ To clarify I'm not making a "perfect glass" and there is a difference, mine scatter lights in a more controlled manner. By controlled I meant some visible light can be redirected to the user's eye... ;> $\endgroup$ – user6760 Aug 22 '17 at 7:52
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    $\begingroup$ @user6760, in that case it's no longer a perfect invisibility cloak, there's now both a detectable edge and partial absorption of energy weapons. Perfect is perfect, or it's not perfect. $\endgroup$ – Separatrix Aug 22 '17 at 7:57
  • $\begingroup$ Let's agree to disagree... perfect in this context I'm referring to the technique of bending all freq of light while allowing visible light to reach the user, invisibility is simply stealth and cloak is just something light-weight that a person can don. I hope it'll make at least a little sense now :> $\endgroup$ – user6760 Aug 22 '17 at 8:06
  • $\begingroup$ @user6760, in that case you need to consider "how perfect" it is, if 1% of light penetrates then so does 1% of energy weapons and someone sensitive enough would be able to spot it. $\endgroup$ – Separatrix Aug 22 '17 at 8:10
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The problem is (AFAIK) that metamaterials are capable of bending/redirecting specific wavelengths to a specific degree. So a metamaterial that could (for a simplified example) bend green light perfectly around a human-sized bubble would have trouble with red light, and so on. Even if you would manage to get one that bends all visible light around it (a rather impressive range of wavelengths), there's still a lot of range below (infrared...) and above (ultraviolet) that.

Overall, a metamaterial-based invisibility is - using current tech - highly unlikely, and even if you somehow (through VERY creative use of geometry to make a suit out of several metamaterials, each redirecting a range of wavelenghts along specific paths around the body?) got it to work I really doubt you could get it to work on all wavelengths. Especially since - as L.Dutch mentioned - even a small percentage of imperfection would already lead to heating and damaging of the complex, and likely fragile, arrangement of metamaterials.

As for the second part, "how to build one that do"(sic)... if you want to stick with current science, "not". Invulnerability to energy weapons is a thing for handwavium force fields, handwavium sci-fi materials, magic, thick bunker walls or "not being where they shoot".

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If you are physically present, then you are physically vulnerable.

The main advantage of an invisibility cloak is that you cannot be seen and are therefore unlikely to be directly attacked. However your invisibility cloak works, bending or otherwise manipulating normal incident light cannot be the same as handling an energy blast, whatever form that energy blast might take - even if it is simply light energy, it is unlikely to be simply 'visible' light.

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I can think of one energy-based weapon that does not rely on radiation: an electrical arc. If the attacker can generate enough positive potential on one side of the target, and enough negative potential on the other, a discharge will follow the path of least resistance between them in traveling to ground. Even an advanced metamaterial likely has better conductivity than air.

This may be very difficult to achieve under most circumstances, and of course invisibility would hinder targeting. But with the right setup--an armed trap within a security system, for instance--the electrical arc would not only be able to "seek" the user of the cloak, but presumably deliver a great deal of energy that would not be affected by refraction.

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