Mercury,
November/December 2004 Table of Contents
by
Arthur Upgren
Moonlight
varies over a greater range than the light from any other bright
celestial object—planet, satellite, or star—in the entire
sky. We all know how bright it seems in our minds, but it is not
so commonly known that even at the phase we call full, the variations
are extensive.
In
our modern world, where gasoline stations raise the light level
above their pumps ever higher and street lights blanch the eyes
of motorists with direct glare, it is useful to know just how bright
is our only luminous natural nocturnal light source, the Moon. Nothing
quite like it can be found anywhere in the sky; the Sun, at some
400,000 times its brightness, changes night into day—no basis
for comparison there. And no planet or star, not even the dazzling
Venus, can light up the whole night sky.
Today
the reasons for a full understanding of the brightness of the Moon,
particularly the full Moon, have taken on a new level of importance.
Recent research on the influence of night brightness upon the human
pineal gland near the brain, reveals a marked effect on its secretion
of melatonin and its regulation of biorhythms, possibly affecting
the incidence of cancer. Like most other creatures, the human being
is affected by the diurnal circadian rhythm of light and dark more
than was previously recognized, although anyone exposed to jet lag
gets the idea that these rhythms are not disrupted without side
effects. The level of light that disturbs this gland and its secretions
is not yet accurately known, but indications are that this level
is not much brighter than the full Moon.
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