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> Sunlight has significant blue light. (This makes sense, considering that our sensitivity to blue light evolved in order to sync to the day/night cycle). Your

> Sunlight has significant blue light. (This makes sense, considering that our sensitivity to blue light evolved in order to sync to the day/night cycle). Your thesis about the evolution of our sensitivity to blue light comes from the fact that sunlight has blue light, but now you're using (a) to prove (b).

tzs 9y ago
Most general discussion on the net about the adverse effects of blue light is in the context of artificial light, such as from screens. People sometimes get the mistaken impression from this that natural light does not have significant blue content, and the bad effects of blue light in artificial sources comes from blue light being something that we did not evolve to deal with it all. The point of the parenthetical comment was that our sensitivity to blue light is not because it is something we did not naturally encounter and so it is some kind of irritant we have not developed a tolerance for, but rather because we evolved sensitivity to it as a way to sense the day/night cycle, so of course there is significant blue light in sunlight. If there wasn't we would not have developed sensitivity to it. We would have developed sensitivity to some other color that is significant in sunlight. It probably could have been phrased better.
- SketchySeaBeast 9y ago
  It absolutely is a natural evolution - the pineal gland in our brain, which regulates the sleep cycle via hormones, responds to blue light as a signal to wake up. We see blue light - it's a sign the sun is up and the sky is lit and it's time to go hunting. According to wikipedia, the moon full moon provides about 0.05–0.1 lux. The sun, even on an overcast sunrise provides 40 lux, and can provide up to 120,000 lux. Even assuming a logarithmic response (as in hearing), that's still a huge difference, so I doubt that it provides enough stimulation to get us to regulate the hormones poorly (though I'm sure the moon did affect our sleep regardless).

tzs 9y ago

Most general discussion on the net about the adverse effects of blue light is in the context of artificial light, such as from screens. People sometimes get the mistaken impression from this that natural light does not have significant blue content, and the bad effects of blue light in artificial sources comes from blue light being something that we did not evolve to deal with it all. The point of the parenthetical comment was that our sensitivity to blue light is not because it is something we did not naturally encounter and so it is some kind of irritant we have not developed a tolerance for, but rather because we evolved sensitivity to it as a way to sense the day/night cycle, so of course there is significant blue light in sunlight. If there wasn't we would not have developed sensitivity to it. We would have developed sensitivity to some other color that is significant in sunlight. It probably could have been phrased better.

SketchySeaBeast 9y ago
It absolutely is a natural evolution - the pineal gland in our brain, which regulates the sleep cycle via hormones, responds to blue light as a signal to wake up. We see blue light - it's a sign the sun is up and the sky is lit and it's time to go hunting. According to wikipedia, the moon full moon provides about 0.05–0.1 lux. The sun, even on an overcast sunrise provides 40 lux, and can provide up to 120,000 lux. Even assuming a logarithmic response (as in hearing), that's still a huge difference, so I doubt that it provides enough stimulation to get us to regulate the hormones poorly (though I'm sure the moon did affect our sleep regardless).