Archaeoastronomy in the British Isles - The Stones and the Stars: Building Scotland's Newest Megalith - page 48

it was obvious that the relationships were far from coincidental.
The recurring intermediate solar positions led him to postulate a
pre-Celtic calendar dividing the year into 16 parts [ 2 ].
Euan MacKie makes the important point that Thom's
histogram was drawn up before the scale of radiocarbon dating was
revised, when it was believed that the peak of Neolithic culture
fell between 2000 and 1500 b.c. Although that Neolithic period
now spans 4000-1800 b.c., MacKie's own research on brochs, the
circular stone towers of the Iron Age, has convinced him that the
same astronomical principles continued to be applied after the
Stone and Bronze ages ended [ 3 ].
Still more importantly, the obliquity of Earth's axis was
decreasing, so the positions of the solar and lunar alignments in
the key to Fig. 4.1 have to be moved to the right to allow for the
greater ages of the sites - and the matches for summer and winter
solstice, the equinoxes, Martinmas/Candlemas and the other solar
calendar dates are improved as a result. So, too, are those for the
Moon's four limiting declinations (the major and minor standstills).
Extending the inclined lines showing the changing declinations of
the stars, due to precession of the equinoxes, gives improved fits
for Rigel, Sirius, Antares, Betelgeuse, Procyon, Altair, Spica, Pol-
lux, Castor, Vega and Arcturus, and earlier ones for Pollux, Castor
and Capella. The high peak for Capella in 2000-1600 b.c. remains,
but there is an explanation for that. Between those dates Capella
was becoming circumpolar in the British Isles for the first time,
clearing the northern horizon instead of setting, and Thom sug-
gested that the Hill o' Many Stanes at Mid Clyth recorded the
observations made as it did so. The revision of the radiocarbon
dating scale makes the histogram still more convincing.
One foolish argument, raised all too often in reply, is that because
there's no other record of the events, we can't say that the stone
alignments point to solstice sunsets, etc., because we don't know
where those events took place. For all we know, some unknown
cause may have altered them, perhaps an undetected shift in Earth's
polar axis, or a major variation in its rate of change. It's an argument
that might need to be considered if we were talking about just one
alignment - midsummer sunrise at Stonehenge, say. But when we're
calculating hundreds of them, and they all fit, that could only mean
that none of them fitted before and the effect of the supposed change