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Comment by peterisza | Hacker News Reader

A bit unrelated but I found this interesting: water is transparent only within a very narrow band of the electromagnetic spectrum, so living organisms evolved sensitivity to that band, and that's what we now call "visible light".

http://hyperphysics.phy-astr.gsu.edu/hbase/Chemical/imgche/w...

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I like to joke that while nitrogen gas is the most common thing around us, we are blind to it. Of course, that's a feature, since it allows us to perceive everything else further away, instead of stumbling through a perpetual fog.

This location-dependent tradeoff is something to think about when it comes to "false color" images in astronomy. If some aliens described Earth as "a boring uniform nitrogen-colored ball", we'd probably be a little offended at their ophthalmo-centrism, and tell them that the fault lies in their eyes, not in our planet.

Is there a camera that would show me what our world looks like through the eyes of these hypothetical aliens? Would love to see it.

It would probably be some application of spectral imaging [0], highly dependent on what data you choose to capture based on your assumptions about how the aliens see.

Even if you have a mathematical "photo of a planet of nitrogen gas clouds", that leaves the problem of how to present it to humans, since we have no concept of what "nitrogen gas color" is supposed to be.

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

As OP said, most astronomical pictures, even in the visible, target specific wavelengths and are thus "converted" for human vision. It's also obviously the case of any picture in wavelength beyond visible light. Keep in mind that there is also massive processing to clean the pictures, not just a translation of the wavelengths

Given the fluid inside your eyeball is mostly water, this is probably very related.

It’s interesting (kinda optimal) that different cones explore near both edges.

visible light is also the last octave before you hit ionizing radiation. it’s very energetic. good for harnessing in chemical processes. not so energetic that the electrons leave the party.

Interesting, given that most life is water based, most life will respond the most to this spectrum.

A guy copied&pasted this comment to X and got 42k likes lol: https://x.com/sridatta/status/1947180254684237851

At least he gave credit to HN, so the diaspora could find the source. The article is interesting. I think more needs to be said about how our eyes perceive color w.r.t. led lighting.

I thought it was mostly that those are the wavelengths output out by the sun.

But I guess it could be both.

The sun is very close to a black body radiator, so all wavelength. The atmosphere and water filters a lot.

It is actually quite strange that plants are green -- that's the wavelength the atmosphere lets through particularly well, so would be particular good to be absorbed instead of reflected, for energy production. It seems nature hasn't come up with a good, cheap way to move the absorption into that wavelength.

Or it could have another reason: https://www.quantamagazine.org/why-are-plants-green-to-reduc....

Well, black-body radiation is still peaked around a certain range of wavelengths depending on the temperature, it's not just equal power at all wavelengths.

Light visible to humans is at the peakiest bit of the sun's black body spectrum, see here image here: https://i.sstatic.net/kRUju.png

Green isn't just the wavelength the atmosphere lets through the best, or the wavelength humans are most sensitive to, it's also the peak of the sun's black body spectrum.

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