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Comment by Silverback_VII | Hacker News Reader

I always thought that it's because that they are descendants of a bacterium that was forced to use the less profitable part of the light spectrum(blue & red) because the main part was already occupied by other bacteria. By reflecting green from the sun, they reflect the strongest wavelength.

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This is the hypothesis I remember being taught 20 years ago. Rhodopsin, used by phototrophic archea, evolved first and has a broad absorption peak in the green (giving it a purple colour). Chlorophyll evolved to absorb light either side of this peak, in the red and blue.

So, are there multiple competing explanations being offered for this in general, and none of them have ever become entirely settled?

Welcome to true science

That's fine, but there seems to be explanations spread around that are not really established. Or said otherwise, chains of people who forgot how to say "we don't know".

I know. The thing you’re objecting to is fundamental to our process of coming to know.

But that would only make sense if the bacteria were stacked on top of each other.

Otherwise there is plenty of space under the sun, even in water.

The peak of the solar spectrum seems to be in the blueish zone, though.

Yeah ... this line is misleading: "most of the energy that the sun radiates is in the green part of the spectrum."

After filtering by the atmosphere, at the Earth's surface, blue and green energies are comparable. See e.g. the figure shown at [https://en.wikipedia.org/wiki/Sunlight#Spectral_composition_...

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