Your Body Is Your Eye

[Roger E. Moore]

Life might evolve an eye that covers a creatures whole body.

From the thread on astrobiological arXiv papers comes this thread:

Could an alien have the equivalent of a human eye that covers its entire body?

Well, you have heat sensors all over your body as a human, which isn't quite the same but can start the issue. I'm trying not to think of a creature like the mythological giant Argus, covered with real eyes. An undersea creature could have pressure sensors all over, so it picks up indications of nearby creatures.

(art, not mine, shows Hera ordering Argus to guard a white heifer)

[KaiYeves]

Oh hey, that’s from the D'aulaires' book!

[Noclevername]

Growing eyes is biologically expensive. That's why cave fish lose them. To cover the entire body with complex optics would require a strong evolutionary motive.

[CJSF]

Growing eyes is biologically expensive. That's why cave fish lose them. To cover the entire body with complex optics would require a strong evolutionary motive.

Yes, but he specifically stated he was trying NOT to think that route, but rather a distributed array of light sensors (maybe just on or under the skin?) that operates somewhat analogous to pressure sensors on some fish or touch sensation.

CJSF

[cjameshuff]

https://www.livescience.com/5970-bod...n-big-eye.html

[Trebuchet]

My body senses light all over! When it gets enough, I grow another cancer! Dermatology tomorrow.

[Delvo]

You could make an optical sensor out of a single cell or an assembly of just a few cells, and distribute as many of those as you want wherever you want, but it wouldn't work very well. It could detect how light or dark the environment is and what direction the light is coming from, but it wouldn't form images like what we usually think of as "vision". And, for that limited set of tasks, a much smaller set of sensors in just a few places would work just as well.

[Noclevername]

Yes, but he specifically stated he was trying NOT to think that route, but rather a distributed array of light sensors (maybe just on or under the skin?) that operates somewhat analogous to pressure sensors on some fish or touch sensation.

CJSF

But Roger also said sensors "equivalent to the human eye". That's what I was addressing.

[DaveC426913]

The key distinction is in whether such sensation can be focused and collimated.

One can certainly have a body covered in senses that detect some intecepted property, such as light or heat. But, other than intensity and general direction, it can't be used to focus.

Such sensors can be used to tell only what is directly impinging upon the body - they can't (easily) be used to tell what's out there. That's what makes an eye so powerful.

Insect eyes strike a good balance. Their compound eyes are really just individual sensors at the bottom of tubes. They don't need complelx lenses. Quite simple, but good enough to get a degree of resolution. These dozen sensors pick up lots of light, while those dozen sensors, immediately adjacent, pick up less light. With sufficient processing, you can sort of form an image.

This isn't what insects actually see, but it makes the point:

[Jens]

I guess you could say that plants do, sort of. They have photoreceptors throughout their leaves at least, that respond to photons, though I don’t know if would want to call them eyes.


Sent from my iPhone using Tapatalk

[CJSF]

This sea urchin's body is one big eye, this says.

https://www.livescience.com/5970-bod...n-big-eye.html

CJSF