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Comment by marvindanig | Hacker News Reader

Have you ever noticed that B(lue) and G(reen) are the center most frequencies of the visible spectrum—VIBGYOR? If the human eye is naturally adapted for blue skies and green forests, how could the blue wavelength ever be harmful to our eyes? Those are the healthiest frequencies our eyes “consume!”

So much bullshit is marketed these days that it is impossible to sleep well.

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Circadian rhythms are primary drivers for various hormones in your body (e.g. melatonin, body temps, cortisol levels). These rhythms are tightly tied to external/evolutionary triggers. Yours body resets its internal clock* based on external cues, the strongest of which are eating and exposure to daylight. Since we don't have little clocks saying it's 6:05 in our heads, the body uses blue light hitting the retinas as a proxy. It's the knock-on-effects of having misaligned cortisol levels (which further induce lack of sleep / stress) that are the problem, not the blue light.

*The natural rhythm of each individual differs, hence the cave/space experiments where some people naturally fall into a ~25h cycle [due to lack of external cues]).

Well the theory behind it doesn’t say „blue is unhealthy or harmful“ but „blue is daytime“.

Hence the idea to filter out blue at times when there is no blue sky in nature (aka at night).

Moonlight and starlight are blue-biased. There is very little red or green light at night...

I'm just regurgitating the theory, I'm not saying I'm buying into it... ;)

In my personal experience (anectdata), the effects are very neglibable (to the degree they might be placebo)

Where did you go to school? It's ROYGBIV you monster!

Endianness strikes again.

During most of the evolution of our genus bright blue or green light meant it was daytime and hence time to be awake. But the red light from fires would often be present when our ancestors were sleeping. It isn't that you should avoid bright blue or green light in general, it's that you should avoid it for maybe an hour or so before you go to bed until when you want to wake up.

> But the red light from fires would often be present when our ancestors were sleeping.

I don't believe this is related. I believe it's simply that blue is the best/easiest/earliest color. The circadian rhythm is ancient, used by bacteria, plants, and mammals [1], long before humans had fire. Blue is most energetic, and is all that can be seen in the depths of the ocean, where life mostly likely originated.

[1] https://schaechter.asmblog.org/schaechter/2023/04/sensing-bl...

We have way better receptors for dark and bright, so for that color reception isn't necessary.

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