Also, why would you evolve eyes tuned to wavelengths that don't penetrate water well? That seems maladaptive in an aquatic environment.

https://en.m.wikipedia.org/wiki/Electromagnetic_absorption_b...

Why would you evolve eyes that could see wavelengths that don't penetrate your environment?

Yeah, why would you?

I'm not sure if this exchange means that there is no good reason to do that, or if it means that the reason why one would want to do that is blindingly obvious to everyone except me. :)

The reason you want to see wavelengths that don't penetrate your environment is so that you can see your environment.

None of that light would ever reach your eyes for you to see it, though, right? Or am I missing something really obvious?

Maybe I should have elaborated a bit more. My original point was that it makes sense that the visible spectrum was colocated with the frequencies not readily absorbed by water.

Which is to say, eyes were made for seeing the light that was bouncing around in the sea (and not the frequencies that had already been absorbed).

So yes, the simplest answer you can imagine.

Also to the same point: eyes evolved to see the wavelengths where the Sun outputs the majority of its energy, which is a significant factor in its ability to penetrate water to any depth.

Right, that makes perfect sense. I'm mostly unsure of what tempestn said.

Yeah, if the water is the surroundings.

I was answering the broader question of not wanting light to penetrate "your surroundings" - ie the desk in front of me or walls around me. Would make life difficult if everything was transparent. Normally when one talks about "surroundings" it means that stuff, not the air (analogous to the water for marine life) both of which obviously need to be at least somewhat transparent for vision to be useful.

In that case, how well will this new lidar work in the rain?

Rain is actually very little water at any one path. A drop is falling at 10 meters per second and heavy rain is ~1 cm per hour. So to ballpark it's around 1 part in 3.5 million water on average and assuming 1mm drop size you will see ~3.6km on average before you encounter a drop.

Note this is instantaneous, human vision deals with after images which adds blur.

That's a good calculation. http://hypertextbook.com/facts/2007/EvanKaplan.shtml backs up your facts and claims that a raindrop is actually more like 6 mm, which makes the straight line view much longer.

However in the rain, on a highway, we have water falling, water splashed up from the ground, a mist formed by cars, high humidity, and a wet layer on the outside of the car. These factors reasonably could impact this device if the laser is emitting at water's absorption frequency.

I currently work on a self-driving lorry, we get around this issue by installing over a dozen lidars.