THE SOUTHWORTH PLANETARIUM
207-780-4249       www.usm.maine.edu/planet
70 Falmouth Street  Portland, Maine 04103
43.6667° N,                    70.2667° W
Founded January 1970
          "In summer heat, the tree flourishes externally - a
luxuriance of leaves.  In autumn, its leaves perish and in so doing
decay into the soil that imparts its nutrients into the roots.  These
roots strengthen in winter and, in spring, through the conveyance of
ascending waters, rejuvenate the dormant buds.   From this we learn
that all healing-like health, itself-is internal.    The poignant
anguish, the profound regrets, the unredressed injuries, and  the
unfulfilled longings all possess healing properties.  In those moments
when sorrow prevails over joy, remember at that instant you are as a
tree in winter.  Allow all that has perished to settle.  Absorb it
slowly. Draw from it deeply. In so doing you are gathering the
nutrients that will enliven you to your natural exuberance.     As the
Greeks said, 'that which wounds you shall make you whole.'"





THE DAILY ASTRONOMER
Wednesday, January 20, 2016
The Dark Side


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QUIZ CORRECTION:
New Brunswick, not Quebec, is Canada's only
officially bilingual province.    Thanks to the
subscriber who brought this error to my attention.
My apologies for the mistake.
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The other morning, a news commentator reported about the Chinese Space
Program's plans to deploy an unmanned probe to the "dark side of the
Moon" in 2018.   Named Chang’e-4, after a Chinese mythological moon
goddess, this probe will be the first craft to explore this unseen
region.   Humans have imaged this "dark side" and found it to be
different in appearance from the region facing us.   The most
distinctive difference relates to craters, as the dark side is far
more pockmarked than the near side.

This report inspired us to write a brief article pertaining to the
moon's "dark side," merely to discuss a few matters.

First, the oft-used term "dark side" is a misnomer.    It relates to
the time when astronomers thought that the moon didn't rotate and
therefore one of its sides remained in perpetual darkness.   They
derived their notion of a non-spinning moon by their observation that
only one side of the moon faced Earth.     Astronomers know today that
the moon does rotate and that all of its regions receive equal amounts
of sunlight.      We only see one side of the moon because its
rotational and revolutionary periods are equal.  If these periods were
unequal, we would be able to see all regions of the moon.

Secondly, one might wonder why the far side is more cratered than the
near side.  The answer is pleasantly simple.     Impacting asteroids
gouge craters into the surfaces of large bodies.     The moon's far
side is more exposed to these asteroids because it always faces away
from Earth.  The near side is more protected because Earth behaves
like a shield.   Think of the situation this way.  You are outside in
winter speaking  face-to-face with a friend.  For whatever reason, you
are encircled by people who are pelting you both with snowballs.  Your
back is exposed and will be hit more often than front, which your
friend protects.

We are delighted that someday soon humans will land a probe on the
moon's hitherto unexplored far side.  Perhaps this mission will be a
precursor to the eventual return of humans, themselves, to Earth's
closest neighbor.