What is “The Far Side of the Moon”?

25 September 2014

The Short Answer (TSA)

            Maybe one of the strangest facts about our moon is its rotation.  For example, the Earth orbits around the Sun about every 365 days – a year.  On the other hand, the Earth rotates on its axis every 24 hours – a day.  But our Moon takes about 27 days to orbit once around the earth.  How long does it take to Moon to rotate on its axis?  Again, about 27 days.  The Moon’s “year” and the Moon’s “day” are exactly the same.  A remarkable coincidence.

            But this remarkable coincidence produces a remarkable effect.  If you were on the Moon, you’d experience one slow day and one slow night every 27 earth-days.  But if you watch the Moon from the Earth, the Moon doesn't seem to rotate at all.  Since it’s always been that way, most of us don’t notice that, when you watch from the Earth, you always see the same side of the Moon.  Only one side.  Viewed from the Earth, you never see “the far side of the Moon.” 

The Far Side of the Moon

            Over the centuries, the far side of the Moon developed quite an air of mystery.  You could imagine anything to be there. 

            In the early 1950’s, George Adamski, the owner of a café near California's Mt. Palomar Observatory, reported receiving visits from outer space aliens.  Looking and dressing like us, the aliens would stop by his café to chat.  Adamski also reported taking several trips into outer space with his alien friends in their flying saucer.  He closely observed the far side of the Moon and reported that it supported a large civilization and population.  He even brought back “moon potatoes,” which reportedly looked like rocks.

            But, Adamski’s claims came into question, in 1959, when the Soviet Luna 3 space probe circled the Moon taking photographs.  The resulting atlas, published in 1960, included precise details of the topography of the (no longer) mysterious far side of the Moon.  In 1968, the Apollo 8 astronauts became the first humans to view the far side of the Moon directly.  (No signs of life, civilization, or potato farms were to be seen.) 

            The far side of the Moon used to be called “The Dark Side of the Moon.”  This phrase was accurate enough if the speaker meant to refer to the side of the Moon that was “dark” in the sense of being unknown to viewers on Earth.  But the problem with the name was that the “dark” side of the Moon wasn't always dark.  During half of the 27 earth-days it takes the Moon to complete one of its own days, the so-called dark side is, in some part, sunlit.

            So, the side of the Moon we can never see from the Earth is, now, called “the far side of the Moon.”  But, the phrase “dark side of the Moon” is, now, used to mean the half of the Moon that is actually dark at any particular moment. 

            So, for example, at the “New Moon” phase, the Moon can’t be seen from the Earth because the side facing the Earth isn't sunlit.  At that time, the side of the Moon facing the earth would be “the dark side of the moon.” At the Full Moon phase, the entire visible face of the Moon is sunlit.  So, with the Full Moon,“the dark side of the moon” would also be the far side of the Moon.   

M Grossmann of Hazelwood, Missouri
(& Belleville, Illinois)
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