My father was an environmental expert, so I have some interest in environmental issues too. So yesterday, I tried Lights Down. Lights Down is a movement encouraging people to use as little lighting as possible in the days leading up to the summer solstice. As part of this movement, the illumination of Tokyo Tower and other landmarks was also turned off for 19 days. At home, we had dinner and took a bath by candlelight. It makes one feel very calm.
While taking a bath with my daughter, who is learning haiku at school, we came up with a verse together.
On the bathwater’s surface, the candle flame sways on a summer solstice night.
I gave my older daughter a problem.
“Suppose you can read a book comfortably with a reading light positioned 40 cm above it. The desk is 80 cm high, and the ceiling is 240 cm high. How many times as bright does the ceiling light need to be as the reading light?”
Since brightness is inversely proportional to the square of the distance,
((240-80)/40)2 = 16, so it requires 16 times the electrical power.
If every company in Japan introduced task lights, office electricity use could probably be reduced considerably. Why do they not do it…?
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