IEEE Spectrum October, 2016 - 46
bulbs in my home office. But months later, returning from
a week's vacation in rural Maine, I was shocked to find my
neighborhood lit by a stark bluish blaze that washed out
almost all of the stars in the night sky.
Lately, lighting companies have introduced LED streetlights with a warmer-hued output, and municipalities have
begun to adopt them. Some communities, too, are using
smart lighting controls to minimize light pollution. They
are welcome changes, but they're happening none too soon:
An estimated 10 percent of all outdoor lighting in the United
States was switched over to an earlier generation of LEDs,
which included those problematic blue-rich varieties, at a
potential cost of billions of dollars.
The episode invites a few questions: How did an energysaving technology that looked so promising wind up irritating so many people? Why has it taken so long for the impacts
of blue-rich lighting to become widely known? And why did
blue-rich LEDs so captivate municipal lighting engineers
long before better options reached the market?
46
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arly innovations in street lighting were
largely driven by brightness and convenience. The ancient Greeks and Romans lit
terra-cotta oil lamps to illuminate their
streets. Candles and oil lanterns brightened
preindustrial cities, with some 3,000 streetlamps said to
be used in Paris in 1669. In the early 1800s, whale-oil lamps
and lanterns began to give way to relatively inexpensive
gas streetlights, which were first installed throughout
London, Paris, and St. Petersburg, Russia.
Not until the 20th century did engineers start worrying
about efficiency. Brilliant arc lamps were the original electric
streetlights in the late 1800s, but it took more practical incandescent bulbs to persuade most cities to replace gas streetlights with electric ones. These were gradually phased out
for even higher-efficiency successors: mercury-vapor lamps
starting in 1948, and then high-pressure sodium in 1970.
The bluish LEDs were a stark counterpart to the orangish
high-pressure sodium lights that came before them. Switch-
E
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Table of Contents for the Digital Edition of IEEE Spectrum October, 2016
IEEE Spectrum October, 2016 - Cover1
IEEE Spectrum October, 2016 - Cover2
IEEE Spectrum October, 2016 - 1
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IEEE Spectrum October, 2016 - Cover3
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