When the sun goes down, colour temperature is determined by the alternative light source. For most of the past 100,000 years, life on our rotating planet has re

When the sun goes down, colour temperature is determined by the alternative light source. For most of the past 100,000 years, life on our rotating planet has relied on moonlight (cold) or firelight (warm) to see at night. Incandescent lights (Edison light bulbs) are a bit cooler than the candles and (most of the) oil lamps they replaced. Bright cold (high Kelvin rating) lighting at night is a very modern invention: Temperature (K) Source 1,700 Match flame 1,850 Candle flame, sunset/sunrise 2,700–3,300 Incandescent lamps 3,000 Soft White compact fluorescent lamps 4,100–4,150 Moonlight,[2] xenon arc lamp 5,000 Horizon daylight 5,000 tubular fluorescent lamps or Cool White/Daylight compact fluorescent lamps (CFL) 5,500–6,000 Vertical daylight, electronic flash 6,500 Daylight, overcast 6,500–9,300 LCD or CRT screen 15,000–27,000 Clear blue northern sky