The Short Answer (TSA)
Today, the “dark side of the moon”
refers to the side of the moon that happens to be dark at any particular
moment.
As the
earth rotates, we experience night and day. At any one moment, the part of the earth that
is in darkness could be called the “dark side of the earth.” Of course, the side of the earth that’s dark
changes minute to minute and second to second repeating the whole cycle of
light and dark every 24 hours.
The moon
has its own “day and night.” Watching
from earth, a lunar day lasts a bit over 29 days. And, like earth, at any one moment, half of
the moon is in darkness. That dark half
is the “dark side of the moon.”
So, at the
full moon, you can see the whole light side of the moon. And, at the new moon, when it seems that
there’s no moon visible in sky, you are looking at the whole dark side of the
moon.
But there’s
a twist to the history of the phrase “dark side of the moon.” Until 1959, the
term “dark side of the moon” referred a side of the moon that no one had ever
seen.
The Side of the Moon We Can't See From Earth
Because
it’s always been that way, most of us don’t notice one of the most remarkable
coincidences about the moon in relation to the earth. The moon’s “day” is exactly the same period
of time it takes for the moon to cycle once around the earth.
The amazing
effect of that coincidence is that, instead of seeing the front and back of the
moon as it slowly rotates, we see only one side, one face, of the moon. Viewed from earth, the side facing us never
changes and never seems to rotate.
Until 1959,
when the Soviet Union's Luna 3 space probe circled the moon and took pictures
of the other side of the moon – the side not facing the earth -- no one had any
idea what the other side of the moon looked like.
Luna 3's First Photo of the, then, "Dark," now, "Far Side of the Moon"
We
understood that the moon rotated and had days.
But we used the term “dark side of the moon,” not to mean the side
that’s actually in darkness at any one moment. Instead, the "dark side of the moon" was used to mean the side of the moon that was “dark”
to us. That is, the side of the moon we
could never see.
So, the phrase
“dark side of the moon” was a bit of a poetic phrase meaning that there was a
whole side of the moon that we couldn’t see – so its nature remained “dark” to
us. Well, when everyone had seen the
1959 pictures, the “dark” side of the moon wasn’t “dark” or unknown to us anymore.
So, meaning of the term “dark side of the moon” changed. Now, the phrase refers to the side of the moon that happens to be in actual
darkness at the moment. What about the
other side of the moon? The side we can
never see from earth? Now, it’s called
the “far side of the moon” because its always a bit farther away from us than side
we can see.
By the way,
the term “dark side of the moon” is still used poetically to describe any
quality or place or thing about which we don’t have, and may not be able to get, any information.
M Grossmann of Hazelwood,
Missouri
& Belleville, Illinois
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