So I have heard that to much exposure to specifically blue light can make it harder to sleep but how?I mean it’s light and blue is seen as a calming color so how can exposure to to much blue light make it harder to sleep?
In: Biology
We have special cells in our eyes that aren’t related to vision called intrinsically photosensitive retinal ganglion cells or ipRGC’s, which detect a very narrow band of colors of light. These cells are in lots of different animals, including insects, so they evolved first hundreds of millions of years ago, when all life was in the ocean. When you get deep enough in the ocean, the only light that can penetrate is blue, specifically light around 475nm in wavelength, which is like a sky-blue or cyan color. White light is a mix of colors, but you can’t tell whether a white light source contains a lot or a little of any specific color just by looking at the light.
Our internal clocks are largely set by the signals that these cells produce. During the day and especially in the morning, getting light in that color range tells your body that it’s daytime. At night, if those wavelengths are absent, your body can produce melatonin and help you sleep.
Since when these cells evolved, blue was the only color of light available to tell day from night, that was what they evolved to detect. Before artificial light, there was never an issue because fire doesn’t have a lot of blue in the light it produces. With the electric light, we started to move indoors during the day more and more, meaning we usually don’t get *enough* blue light to tell our clocks it’s daytime. With the switch to LED, there’s more blue light in the typical white lights we use, which has made it harder to avoid blue light at night.
What you can do about this for yourself is make sure to get outside as early as possible in the day to get good light for a half hour or so to set your circadian clock, and starting from about 3 hours before bed, dim your lights as much as possible.
Here’s a quick explainer video that might help: [https://youtu.be/5wAr0KYoOxc](https://youtu.be/5wAr0KYoOxc)
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