Seahenge, and the 27-day sidereal cycle of our Moon: of course people
living long ago in the British Isles would have figured out to how keep
track of natural cycles in the Earth’s sky of our Moon, Sun and stars,
while using “Sun-Moon calendars” built simply from from stones, chalk
pits or wooden posts!
A new crop
picture at Oliver’s Castle shows a “ring” of 27 “small circles”, which
might be interpreted as the “large ring” of a 27-hole, megalithic
“Sun-Moon calendar”. Each “hole” in such a “calendar” could be occupied
by either (or both) of two movable markers (say tall sticks) which would
represent our “Sun” or “Moon”.
any full Moon, the “Moon marker” from this “calendar” could be moved
forward by one hole per day. After 27 days, it will turn by one
revolution of the “large ring”, and lie close to 27.32 days for the
known (and easily visible) orbital motion of our Moon, relative to
background stars. Once every three lunar phase cycles, we can “skip” 1
day of moving the “Moon marker” forward. Then (3 x 27) + 1 = 82 days by
our simple calendar will match (3 x 27.32) = 81.96 days as the true and
exact length of time, for three star-centred or “sidereal” lunar months.
Can we use
these same “27 holes”, arranged in the shape of a “large ring”, to
represent the combined motions of our Moon and Earth, as they move in
two different orbits around the Sun? A full solar year equals 365.24
days, while 1/27 of a solar year equals 13.5 days. If we move our “Sun
marker” ahead by one hole every 13.5 days (as 13 days alternating with
14 days), that will match the much faster motion of one hole ahead per
day for our “Moon marker”.
days, our “Moon marker” will have gone around the “large ring” by one
full turn of 27 holes, while our “Sun marker” will have gone ahead by
just two holes. After 29 days, our “Moon marker” will have gone around
the ring by one full turn of 27 holes, plus another two holes, while our
“Sun marker” will have gone ahead by just two holes, and a little bit
more as (2 / 13.5) = 0.15 of its distance to the third hole.
days, our “Moon marker” should intersect with our “Sun marker”
precisely, in order to match 29.53 days for the known monthly phase
cycle or “synodic” period of our Moon, relative to the Sun rather than
to background stars. This alignment in our simplest 27-hole calendar
would take place after 29.16 days. So our simplest 27-hole calendar
shows an error of about 0.37 days per lunar month, for
predicting when the next new Moon or full Moon will take place. After
three lunar months, this error would be (3 x 29.53) = 88.59 days for a
true date, versus (3 x 29.16) = 87.48 days for a calculated date, while
using our simplest “calendar”.
Yet if we
skip moving the “Moon marker” forward by 1 day in every
three lunar months, as suggested above, then our 27-hole
calendar will require a slighter longer (87.48 + 1) = 88.48 days to
predict three lunar phase cycles. The remaining error will be only 88.59
true days. versus 88.48 calculated days, or 0.11 day in three lunar
months, amounting to a tolerable 0.5 day per solar year. Once every two
solar years, we could skip moving the “Moon marker” again by one day.
Also by adding another movable “node marker”, as suggested by astronomer
Fred Hoyle, early man could also have used this simple calendar to
accurately predict solar or lunar eclipses.
“Seahenge” wooden circles were built in England around 2000 BC, with 55
wooden posts arranged in the shape of a large ring. Here 55 = 2 x 27.5,
which nearly matches the 27.32 days required for a “sidereal” monthly
cycle of our Moon (see
At Stonehenge around the same time, someone built a large ring from 56
“Aubrey holes”. Here 56 = 2 x 28, which might suggest a related 28-hole
“Sun-Moon calendar” (see
archaeologists seem, for the most part, to be totally oblivious
to what would have been a pressing need in early human societies on
Earth to track cycles of the Moon, Sun, stars and eclipses, and thereby
keep an accurate track of long periods of time through many centuries.
The people who lived then were no less intelligent, in a genetic sense,
than the professional astronomers who work for NASA or other
institutions today. Of course they could have figured it out!
up with their bare hands, what we still can’t do today.”
(Dr. Horace R. Drew)