# invisiblility eyes **URL:** \ **Category:** Factual Questions\ **Created:** [July 18, 2002, 2:13pm UTC](https://boards.straightdope.com/t/invisiblility-eyes/119617 "2002-07-18T14:13:50Z")\ **Posts on this page:** 20\ **Page:** 1
**Author:** ![paulberserker](https://avatars.discourse-cdn.com/v4/letter/p/c4cdca/32.png) [@paulberserker](https://boards.straightdope.com/u/paulberserker)\ **Post date:** [July 18, 2002, 2:13pm UTC](https://boards.straightdope.com/t/invisiblility-eyes/119617/1 "2002-07-18T14:13:50Z")
if you invented a formula or process for making yourself invisible, and going on the basis you were still there but refracting or allowing light to pass through you, surely you wouldnt be able to see due to light not hitting your brain through your (see through) eyes. surely they couldnt function in the same way they would when visible? i hope this makes sense as a question, cos i watched the sucky hollow man again the other night and it occurred to me. cheers, pauly t 😕 ---
**Author:** ![Mangetout](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/mangetout/32/19_2.png) [@Mangetout](https://boards.straightdope.com/u/Mangetout)\ **Post date:** [July 18, 2002, 2:31pm UTC](https://boards.straightdope.com/t/invisiblility-eyes/119617/2 "2002-07-18T14:31:39Z")
you’re right; in order for your retinas to register an image, they must absorb light - that absorbed light is not available for transmission and so anyone looking at you from behind would see two dark spots where the backs of your eyes were, furthermore, the lenses in your eyes wouldn’t work if they were invisible (rather than just transparent and refractive), so those would have to be there too. In fact you’d need your entire eyes to be normal to prevent stray light spilling in through the sides. ---
**Author:** ![ultrafilter](https://avatars.discourse-cdn.com/v4/letter/u/3d9bf3/32.png) [@ultrafilter](https://boards.straightdope.com/u/ultrafilter)\ **Post date:** [July 18, 2002, 2:52pm UTC](https://boards.straightdope.com/t/invisiblility-eyes/119617/3 "2002-07-18T14:52:14Z")
Actually, in a book called _The Flying Circus of Physics_, the author (whose name escapes me) discusses that you could see while invisible, if your eyes had a complex index of refraction. ---
**Author:** ![Achernar](https://avatars.discourse-cdn.com/v4/letter/a/e274bd/32.png) [@Achernar](https://boards.straightdope.com/u/Achernar)\ **Post date:** [July 18, 2002, 3:17pm UTC](https://boards.straightdope.com/t/invisiblility-eyes/119617/4 "2002-07-18T15:17:28Z")
Ugh, that’s messing with my head. Will a pure imaginary index work? ---
**Author:** ![Achernar](https://avatars.discourse-cdn.com/v4/letter/a/e274bd/32.png) [@Achernar](https://boards.straightdope.com/u/Achernar)\ **Post date:** [July 18, 2002, 3:24pm UTC](https://boards.straightdope.com/t/invisiblility-eyes/119617/5 "2002-07-18T15:24:20Z")
Ugh, that’s messing with my head. Will a pure imaginary index work? ---
**Author:** ![ultrafilter](https://avatars.discourse-cdn.com/v4/letter/u/3d9bf3/32.png) [@ultrafilter](https://boards.straightdope.com/u/ultrafilter)\ **Post date:** [July 18, 2002, 3:28pm UTC](https://boards.straightdope.com/t/invisiblility-eyes/119617/6 "2002-07-18T15:28:27Z")
I have no idea. ---
**Author:** ![Mangetout](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/mangetout/32/19_2.png) [@Mangetout](https://boards.straightdope.com/u/Mangetout)\ **Post date:** [July 18, 2002, 3:31pm UTC](https://boards.straightdope.com/t/invisiblility-eyes/119617/7 "2002-07-18T15:31:16Z")
How could the nerves be stimulated without extracting some of the energy from the light? ---
**Author:** ![ultrafilter](https://avatars.discourse-cdn.com/v4/letter/u/3d9bf3/32.png) [@ultrafilter](https://boards.straightdope.com/u/ultrafilter)\ **Post date:** [July 18, 2002, 3:33pm UTC](https://boards.straightdope.com/t/invisiblility-eyes/119617/8 "2002-07-18T15:33:58Z")
Once again, you got me. All of my knowledge on the subject is contained in my original post. Unfortunately, I don’t have a copy of the book I referenced, so I can’t check on it. ---
**Author:** ![scr4](https://avatars.discourse-cdn.com/v4/letter/s/59ef9b/32.png) [@scr4](https://boards.straightdope.com/u/scr4)\ **Post date:** [July 18, 2002, 3:35pm UTC](https://boards.straightdope.com/t/invisiblility-eyes/119617/9 "2002-07-18T15:35:39Z")
You can’t detect the position and/or direction of a particle (photon) without affecting its path. If you could, I think that will allow you to violate the uncertainty principle, which says you can’t know the position and momentum of a particle to an arbitrary precision. By trying to measure the position accurately you disrupt the momentum, and vice versa. ---
**Author:** ![Allen\_Parine](https://avatars.discourse-cdn.com/v4/letter/a/57b2e6/32.png) [@Allen\_Parine](https://boards.straightdope.com/u/Allen_Parine)\ **Post date:** [July 18, 2002, 4:09pm UTC](https://boards.straightdope.com/t/invisiblility-eyes/119617/10 "2002-07-18T16:09:56Z")
Strictly speaking, to be in_visible_, one’d just have to be transparent to light in a certain frequency range. Then “seeing” would be a matter of modifying the retina to respond to light at a frequency at which it’s opaque rather than in the visible spectrum. Sounds like a simple problem for someone who’s discovered human invisibility. The question of being able to see aside, is it even theoretically possible for there to be a macroscopic body that does not interact with photons of any frequency? ---
**Author:** ![paulberserker](https://avatars.discourse-cdn.com/v4/letter/p/c4cdca/32.png) [@paulberserker](https://boards.straightdope.com/u/paulberserker)\ **Post date:** [July 20, 2002, 1:44pm UTC](https://boards.straightdope.com/t/invisiblility-eyes/119617/11 "2002-07-20T13:44:57Z")
hellfire! who’d of thought being invisible and seeing could be so complex? to be invisible and see properly then, would the best way be to slightly shift out of the normal frequency we see at (if thats the right term) and adjust your eyes accordingly? pauly t ---
**Author:** ![Chronos](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/chronos/32/134_2.png) [@Chronos](https://boards.straightdope.com/u/Chronos)\ **Post date:** [July 20, 2002, 10:03pm UTC](https://boards.straightdope.com/t/invisiblility-eyes/119617/12 "2002-07-20T22:03:21Z")
One could also have some sort of device to first measure light at the eyes, and then re-create light behind the eyes to make things look normal to an observer. This couldn’t be done perfectly at the photon level, due to quantum mechanics, but again, due to QM, it wouldn’t be detectable that it wasn’t perfect. ---
**Author:** ![Bryan\_Ekers](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/bryan_ekers/32/183_2.png) [@Bryan\_Ekers](https://boards.straightdope.com/u/Bryan_Ekers)\ **Post date:** [July 20, 2002, 11:32pm UTC](https://boards.straightdope.com/t/invisiblility-eyes/119617/13 "2002-07-20T23:32:59Z")
Easier to just hypnotize everybody into _thinking_ you’re invisible, as The Shadow did. ---
**Author:** ![Rhythmdvl](https://avatars.discourse-cdn.com/v4/letter/r/85f322/32.png) [@Rhythmdvl](https://boards.straightdope.com/u/Rhythmdvl)\ **Post date:** [July 20, 2002, 11:57pm UTC](https://boards.straightdope.com/t/invisiblility-eyes/119617/14 "2002-07-20T23:57:01Z")
Or sign up for one of those “How Not to be Seen” courses the Pythons offer. ---
**Author:** ![Quasimodem](https://avatars.discourse-cdn.com/v4/letter/q/e274bd/32.png) [@Quasimodem](https://boards.straightdope.com/u/Quasimodem)\ **Post date:** [July 21, 2002, 12:13am UTC](https://boards.straightdope.com/t/invisiblility-eyes/119617/15 "2002-07-21T00:13:53Z")
Plus, how would you ever close your eyes and sleep? You’d be **seeing** all the time, right? Q ---
**Author:** ![Quasimodem](https://avatars.discourse-cdn.com/v4/letter/q/e274bd/32.png) [@Quasimodem](https://boards.straightdope.com/u/Quasimodem)\ **Post date:** [July 21, 2002, 12:19am UTC](https://boards.straightdope.com/t/invisiblility-eyes/119617/16 "2002-07-21T00:19:17Z")
I got caught up in the science fiction of the whole question, and forgot the original point was that it’s completely impossible based on the information already given. Going back to my **H. G. Wells**.:smack: Quasi ---
**Author:** ![AskNott](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/asknott/32/5790_2.png) [@AskNott](https://boards.straightdope.com/u/AskNott)\ **Post date:** [July 21, 2002, 3:31am UTC](https://boards.straightdope.com/t/invisiblility-eyes/119617/17 "2002-07-21T03:31:37Z")
> [@](#): > > \*Originally posted by Achernar \* > \*\*Ugh, that’s messing with my head. Will a pure imaginary index work? \*\* I imagine that it would, yes. –Nott ---
**Author:** ![DougC](https://avatars.discourse-cdn.com/v4/letter/d/7feea3/32.png) [@DougC](https://boards.straightdope.com/u/DougC)\ **Post date:** [July 21, 2002, 5:02pm UTC](https://boards.straightdope.com/t/invisiblility-eyes/119617/18 "2002-07-21T17:02:44Z")
- - - You don’t need light to pass through you to be invisible: it just has to strike one side of you, and be transmitted out the other. - DougC ---
**Author:** ![Wearia](https://avatars.discourse-cdn.com/v4/letter/w/13edae/32.png) [@Wearia](https://boards.straightdope.com/u/Wearia)\ **Post date:** [July 21, 2002, 5:14pm UTC](https://boards.straightdope.com/t/invisiblility-eyes/119617/19 "2002-07-21T17:14:03Z")
Are we talking light going through you, or around you? If its going through you, then your blind. If it going around you then I’m really not sure… ---
**Author:** ![Mangetout](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/mangetout/32/19_2.png) [@Mangetout](https://boards.straightdope.com/u/Mangetout)\ **Post date:** [July 21, 2002, 10:05pm UTC](https://boards.straightdope.com/t/invisiblility-eyes/119617/20 "2002-07-21T22:05:11Z")
Transparency isn’t the same as invisibility; prawns are pretty much transparent and pretty much invisible in water, but take them out of water and they are very easy to see; not particularly because of pigmentation but because light passing through them is refracted and you don’t see the backdrop perfectly. To render a human invisible, you’d have to make him transparent to visible wavelengths and alter his refactive index to match that of the medium in which he is immersed (which, if it was air would be quite tricky, I imagine), so that there is no effective interface. [Next page](https://boards.straightdope.com/t/invisiblility-eyes/119617.md?page=2)