#ELI5 Why is water see through?
I'd never thought about it like this. Wow.
@Jdreben hm... Why then vision evolved for this particular (narrow) range, while water is transparent to a lot more? I can guess why big wavelength were less advantageous, as you want to see small things with good resolution, not blurry blobs saying "your speck of food is vaguely in this cubic meter of space". But why we don't see in UV or X-ray ranges?
@isagalaev @Jdreben Speculating: As the screencap notes, x-rays pass through flesh and only reflect off bones. If a jellyfish or octopus was transparent to you, you'd risk becoming their next meal.
@zeborah @Jdreben indeed! I missed that implication.
Also, thinking further, UV (and up) becomes irrelevant, as at smaller wavelength it should scatter fast due to all the micro-stuff in the body of the water. On the other hand, scattering doesn't mean it's invisible. There should be plenty UV in the first 10 meters…
Anyway, don't mind me, I'm just thinking aloud :-)
@isagalaev
Adding to that: For evolution, "good enough" is all that is required. There was no task "conceive a maximum-range detector with ideal resolution" or the like. Just about a little better then that of the competition would do.
@zeborah @Jdreben
@lothar @zeborah @Jdreben oh, I'm well aware of that one :-) But if UV vision was giving advantage, life would likely adopt that. I'm just trying to figure out why it doesn't (apparently) give any advantage.
P.S. As for X-Ray and generally higher-than-UV energy radiation, the answer, I think, is pretty simple: it didn't exist on Earth in appreciable quantities until humans started producing those.
@isagalaev @lothar @zeborah @Jdreben it can sometimes! Bees can see in UV, which lets them see nectar better