Today · Wed, Sep 16
by Michael Potter on Twos
- Indoor lights and sleeping: For most of human history, the light available after sunset was fire from candles, oil lamps or hearths. All of it burned around 1800K, deep amber, infrared-rich, and dim. Our circadian systems evolved over time calibrated to that spectrum as a signal: the day is ending, wind down, prepare for sleep. Then in about a century, we replaced all of it with electric light running at 3000K to 4000K, closer to midday sun than candlelight.