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The claim here is that 1 a match between these two frequency ranges is needed for eyes to evolve; and 2 eyes are needed for intelligent life to evolve; hence we could only have evolved on a planet where these two frequency ranges match closely. However, neither 1 nor 2 is convincing.
Red and blue stars give out plenty of light in the visible spectrum else you wouldn't be able to see them in the night sky , so there's no reason to think eyes couldn't exist on a planet orbiting such a star, and that's without even considering that they might be made of some other substance that is transparent at the star's peak frequency range. Even if eyes were impossible on such a planet, it's hardly difficult to imagine an intelligent species that relies on other senses instead.
The only other way these two facts could be related is if the temperature of the Sun and the transmission spectrum of water share a common cause. But there are in fact other stars at different temperatures, so we can immediately rule that out. Having eliminated all the ways in which these two facts could be causally related, we have to conclude that they aren't related at all; it's just a coincidence. I believe this is just an coincidence, but might also have been an important factor in the evolution of life on Earth, since improves the effectiveness of photosynthesis.
I think it's a kind of survivorship bias. The majority of stars have spectra that don't coincide in this way, and perhaps nobody intelligent evolved on planets orbiting those stars to ask questions similar to yours :. The spectrum of the Sun's solar radiation is close to that of a black body with a temperature of about 5, K. There are spectral classifications of stars, and sun type stars in temperature seem to be 7. That is an appreciable probability to allow for a random coincidence with the water absorption curve even without considering the type of planets around them.
There are some good articles on this, which of course I can't track down right now. In all likelihood, the "water gap" is only part of the story behind the evolution of our eyes' spectral sensitivity. Now, it happens that there are lots and lots of photons in the near-infrared range of solar irradiance, but these photons are relatively low energy, and there just aren't any organic compounds with a small enough bandgap to be excited by infrared photons. This is not to say that the utility of sensing particular wavelengths e.
A red dwarf would have a very different emissions spectrum. Compare the action spectrum for chlorophyll as such no other chromophore helpers to a red dwarf's optical emission. Photosynthesis likes a red sun.
The radiance of the sun – Barriere Star Journal
And our sun's evolution is expected to wander in temperature as simulated here :. And during its aging there has been times when water and the radiation have not lined up.
Perhaps we are here now partly because the characteristics of our environment now wet planet, peak sun power are favorable to make use of all this water and light energy. Evolution tries to find the peaks for any system.
Whether it is availability of food or energy light, sound, etc. While it seems surprising that water and our sun's black body temperature line up, that is probably not a coincidence, but rather something that evolution took advantage of. This made the fluid water ideal for transmission of the peak amount of light in our atmosphere.
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So our eyes are mostly filled with water and optimized for green light. There is nothing to say that on a dryer planet or different atmosphere or a system with a different temperature star that some other solution wouldn't be more optimal yet look like a coincidence. If we evolved without the ability of sight, perhaps on a dark planet, we wouldn't even notice that water and a K star radiance spectrum line up at the peak.
There are probably many other things that might peak around other temperature stars too that no one has bothered to notice because it isn't relevant to us or our environment. EDIT: Just to clarify I'm saying it's a coincidence that K sun and water are closely aligned. And I'm saying the fact that our eyes take advantage of that fact is not a coincidence at all. Home Questions Tags Users Unanswered. Calculations of both the constant background sun glitter radiance and the sun glitter radiance modulation show that these parameters are very sensitive to wind speed, to view angle with respect to acquisition time, and to observation geometry as a whole.
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