Portability of Stonehenge

[Mark Brader]

Whatever we think of the content, we must all agree on the charm
of this simile posted by Munach Rvi'i in net.lang.c:

> "C" is as portable as Stonehenge!!

Thank you, Munach.

This article is just to point out that Stonehenge is actually even
less portable than all you net.lang.c readers probably think.  Big stones
can be moved -- they had to be moved to build it -- but it turns out that
the DESIGN of Stonehenge is not portable!

See, one of the several stoneworks at Stonehenge -- possibly the oldest
-- consisted of 4 stones called the "station stones", marking the
corners of a rectangle.  (2 of the 4 station stones survive now.)
The great stone circle that you think of when you think of Stonehenge
sits inside the rectangle, just clearing its sides by a few feet.

Now, from a given place on Earth, the directions where the sun will rise
and set depend only on the day of the year.  The directions where the
moon will rise and set, however, depend on a composition of three things:
the day of the year, the phase of the moon, and a further cycle of 18.61
years "caused by the combined effects of tilt and precession of the
orbit ... [which] even an astronomer has trouble visualizing".

The interesting thing is this:  if you stand at a certain one of
the station stones, on the summer solstice, at sunrise, you will
see the sun rise over another of the station stones.  Now, if it
also happens that the moon is full [so that two of the three cycles
affecting the moon are at their extreme points], AND if you wait
the 1/2 day until moonrise, THEN the range of positions along which
the moon might rise [according to the 18.61-year cycle] is precisely
delimited by the OTHER TWO station stones as seen from where you are.

But the station stones are set in a rectangle!  So this means that
at Stonehenge, the angle between sunrise and moonrise can get as large
as 90 degrees but no larger.  This is true ONLY at the particular latitude
of Stonehenge (north or south).  (Whether the builders realized that the
maximum angle varies with latitude is, of course, a matter of conjecture.)

There are many other astronomical alignments in Stonehenge, mostly with
the rising or setting sun or moon at the solstices.  The station stone
rectangle can be used in reverse at the winter solstice -- I'm simplifying
a bit here -- and the great stone circle and trilithons (arches) have
their own alignments.  Most of these are specific to the latitude also,
though the unusual 90-degree angle is featured only in the station stones.

There are also traces of some circles of pits, and from the numbers of pits
in the circles and the other information known to have been provided by the
alignments, it is conjectured that the circles (plus movable markers)
acted as registers in a computer for predicting eclipses.

"There is a replica of Stonehenge at Maryhill, Klickitat County, WA,
where the Stonehenge sarsens and trilithons have been duplicated real-
istically in tons of concrete.  But Maryhill is at the wrong latitude
(5 degrees too far south), so alas, the alignments of the American
version of Stonehenge do not work."

Hmm, maybe Canada should build one at Banff, where the latitude is right. :-)


REFERENCE: "Stonehenge Decoded", by Gerald S. Hawkins in collaboration
with John B. White; Doubleday, 1965.  Specifically pages 107 and 154-5
for the station stone alignments, and Maryhill, and the quotations above;
and the footnote on page 144 for the signature quote below, attributed
to "a Boston University research student."


Anyway, I hope you all enjoyed this insight into the difficulties of porting
with Stone Age architecture.  It seems unlikely that followups will be
of interest to ALL of net.astro, net.travel, and net.lang.c, so I'm
directing followups to net.astro alone, and you can edit the Newsgroups
line if that's not what you want.

Mark Brader
"Okay -- so it was a computer -- but it was only a single-purpose machine."