On 27/06/2012 10:11 AM, Warp wrote:

> How is the invisible man able to see anything?

> Even if the retinas did catch light (which they don't because they would
> by definition become visible if they did), it would still not help him see
> anything because his eyes are not focusing the light properly (if they did,
> they would also become visible as a distortion.

Many very small sea creatures are nearly completely invisible because 
they are transparent and they match seawater's salinity. Often the only 
really visible part is... the eyes.

> (The only pseudoplausible way out of this conundrum is if the invisibility
> were only on the visible light spectrum, but his eyes could still catch eg.
> infrared ok. However, that would require a physical modification of the
> retinas to be able to see infrared light, which would be a problem all in
> itself.

Well, if we postulate not an invisible "man", but an invisibility suit, 
there's no particular problem with the suit having infrared goggles.

> Also, I think it would probably also break some law of physics if
> his body were to let visible light through unhindered but react to infrared
> light normally. This is probably something physically impossible.)

I don't know. People have built things like antenna arrays with have a 
negative index of refraction at radio wavelengths, but (obviously) 
behave perfectly normally at visible wavelengths. Whether you could make 
something that does not affect radiation /at all/ over one specific band 
is another matter, I'll admit...

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