Now You See It, Now You Don’t - The Stones and the Stars: Building Scotland's Newest Megalith - page 18

all, tried to fit their lunar calendar into the year. The cause is a lost
one. The lunar and solar cycles are not commensurate; i.e., they do
not fit together in any straightforward numerical relationship - and
different cultures made different compromises to divide the year into
approximate “months” of convenient length, while keeping religious
ritual and agricultural practice in step with the solar year.
Aubrey Burl says of the Neolithic era, when stone-age farming
still coexisted with coastal hunter-gathering and nomadic herding,
“It was a time when there were no months or weeks [ 4 ].” A clearer
example of modern humanity's divorce from the sky would be hard
to find; and yet that divorce is extremely recent, for many people
still within living memory. An 1869 star atlas in the author's col-
lection shows the full panoply of stars, month by month, from due
south of St. Paul's in London, and another book shows the brighter
stars from Westminster Bridge, month by month, above the 1930
gas lamps. In 1926 H.V. Morton wrote of “the Plough flinging its
clear symbol over a powdered sky” above the Embankment [ 5 ];
and in one old Encyclopedia you can find a plate of the stars from
Blackpool beach, without the Illuminations, with the Tower sil-
houetted against the natural background glow of the sky. Even in
this era, being able to navigate by the stars has gotten this author
out of trouble three times, including one memorable occasion in
downtown Los Angeles.
To review the events discussed above from a ground-based
viewpoint, Fig. 2.1 shows the celestial sphere as viewed by an
observer in the northern hemisphere. The altitude of the pole
above the northern horizon is equal to the observer's latitude, and
the heavenly bodies circle around it, parallel to the equator, with
the daily rotation of Earth.
The altitude of a body above the horizon, and its azimuth
measured along the horizon from the north point, change con-
stantly as Earth turns. Apart from the circumpolar stars, which are
too near the pole to rise and set, everything else rises in the east
and sets in the west at a position that is determined by the decli-
nation of the object, measured from the equator (Fig. 2.2 ) . Where
the declination equals the observer's latitude, the star passes over-
head once a day.
Without metals or metal tools to make the mural quadrants and
other sophisticated instruments of pre-telescopic astronomy,