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One problem I've always thought of with science fiction characters becoming invisible is that they should go blind, because their retina does not catch any light.

Obviously a lot of soft SF or fantasy would gloss over this. But I'm sure that hard SF authors have had a go at it. How can invisibility and sight be reconciled?

closed as too broad by Rogue Jedi, Jason Baker, Möoz, Adamant, Politank-Z Aug 25 '16 at 4:20

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    Excellent frackin question! I hadn't considered the implication. – user296 Feb 1 '11 at 14:30
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    It's not strictly Sci-fi, so I'm not giving it as an answer, but the Joel Rosenberg 'Guardians of the Flame' series addresses this at one point, with a wizard casting not just an invisibility spell (that would render the recipient blind while it was active), but an Advanced Invisibility spell, that basically restores one or both eyes. – K-H-W Oct 16 '11 at 17:07
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H.G. Wells' The Invisible Man (the original) dealt with it. The eponymous character tests his formula on a cat first, and the author notes 'there remained two little ghosts of her eyes'.

I seem to recall from somewhere that he injects his eyeballs with something to achieve the effect.

  • chosen to accept this answer (both are great) because this one mentions The Invisible Man which is the big story on this topic. – Reinstate Monica Jan 31 '11 at 7:59
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    Exactly... your retinas will have to capture light so be at least semi-opaque. Sometimes the older authors get it right! – Adam Jan 31 '11 at 15:29
  • In thinking about this, only the retina cells would be capturing light energy and not emitting them. So really, worst case is that you'll have a field of cell sized minor distortions... but at that size you'll probably not be able to see it at all. So, yes, you should be able to see as long as whatever you due to your retinas to absorb light works... on the other hand if you're warping the light around you... you're SOL unless your able to not warp the light at your sockets. – Adam Feb 2 '11 at 15:41
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    @Adam It's more than just the retinas. Your vision wouldn't work at all without the focusing power of the rest of the eyeball; the retinas themselves are just photodetectors. – Ryan Reich Jun 14 '14 at 15:59
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    In response to Ryan: The eyeball's focusing power (the lens) would still be functional. It's done through a physical effect, so invisibility wouldn't affect that aspect. The main concern would be all of the other light passing through the eyes without passing through the lens or being filtered by the iris. – user31178 Jan 15 '15 at 6:48
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In the Recluce universe, LE Modesitt Jr deals with this. his "Order Mages" can bend light to become invisible. When they do, they are also blinded because they can not see.

EDIT

I have also remembered the TV show Invisible Man (aka I-Man) dealt with this as well. the "I-Man", when invisible, could not see in the "normal" spectrum of light. In the show, they hypothesized that he "saw" in the infra-red spectrum. They often leveraged this "fact" in the show.

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In Warren Ellis's Planetary he specifically addresses this with his version of the Invisible Woman from the Fantastic Four. She needs special goggles to see -- otherwise she's blind while invisible.

A variant can be found in James Alan Gardner's books Expendable and Ascending. One of the characters, Oar, is translucent to humans. However, it's made clear that this was only applicable in the wavelengths of normal human eyesight, and she's not completely invisible.

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Well, there is one kind of invisibility that alleviates the problem. If you don't bend the light but absorb it and create it anew on the other side of the body you want to conceal, then you can do whatever you want inside, including displaying the outside world. This is nicely implemented in Ghost in the Shell.

Ghost in the Shell invisibility thingy initializing

You'd still need some way to record the light hitting you but that's plausible with something like distributed light field technology that could in principle use a large number of microscopic, lens-free sensors.

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    Thanks for this. Would such a person produce a shadow? – Reinstate Monica Mar 22 '14 at 18:57
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    @Wikis If you look at the video, then the answer at least for the Ghost in the Shell universe appears to be yes. However, if the hypothetical display technology covering such an invisibility cloak perfectly reproduced the intensity and direction of all light rays hitting it, then no, it wouldn't cast a shadow. In practice, every display has a maximum brightness of course and the surface of the sun is likely to be a little bit too bright for almost any display (let alone problems with overheating and being too visible in infrared). So good call, Ghost in the Shell. – Christian Mar 22 '14 at 23:49
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This is actually the punch line of a short story (I guess by Robert Sheckley, but may also be Arthur C. Clarke's 'Tales From The White Hart'). It evolves at a bar where a guest confesses to another that he once helped an alien of a race that is known for its generosity with a paperclip and is granted a wish. He asks for being invisible once a day for an hour and is persuaded by the other guest to stay on until it happens. He stays put at bar stool eventually becoming both invisible and blind.

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