TOKYO Tokyo spreads outward from Tokyo Bay. The city is dotted with intense
white light set on a background of bluish-green. White lights come from a variety
of sources, whereas the bluish-green color comes from mercury-vapor lamps,
which were once common in the U.S. It’s now illegal to buy these lamps in the
U.S. and they will soon be banned in the European Union. Traditionally, they have
been used in unshielded fi xtures. Their old, unshielded design, along with their
bluish cast, make them ineffi cient sources that contribute greatly to light pollu-
tion. LEDs are the wave of the future for Tokyo and most cities as they replace
older lighting sources. LEDs save energy and are highly directional, keeping
their light pointed downward. The best LED streetlight conversions use only the
proper amount of illumination, have light that is low in color temperature (3100K,
around 5100ºF or 2800ºC), and incorporate after-hours dimming.
EL PASO & CIUDAD JUÁREZ The differences in lighting between the
city of El Paso, Texas (right) and the Mexican city of Ciudad Juárez (left) are strik-
ing from space. El Paso uses mostly full-cutoff lighting whereas Ciudad Juárez
does not. Historically, the two cities have been divided by the Rio Grande. Now,
the international border is illuminated and easily visible from space. El Paso has a
population of about 700,000 and Ciudad Juárez has about twice as many people.
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