MARGINALIA
Astronomy and the Great Pyramid
J. Donald Fernie
Pointing at the Heavens
The first modern European astronomer on the scene was probably John
Greaves, a professor of geometry at Gresham College. In 1637,
Greaves suddenly abandoned the academy in order to undertake
measurements of the Great Pyramid. His work was thorough and
extensive, and Newton and others scrutinized the published results
for data to develop their theories. Upon his return to England in
1640, Greaves's reputation won him the Savilian Professorship of
Astronomy at Oxford. Unfortunately, he fell from this lofty position
after being fired for misappropriation of funds!
Some two centuries later, a much more famous astronomer named
Charles Piazzi Smyth, Astronomer Royal for Scotland, turned his
attention to the Pyramid. A curious figure, Smyth produced some
first–rate science in other fields, but he lost almost all
rationality when it came to this subject. For example, he attributed
great significance to the fact that the slope of the Pyramid is near
the ratio 10:9, and that its height of 484.9 feet (or 0.09184 mile)
multiplied by 109 equaled 91,840,000 miles.
Coincidentally, that number is close to the actual distance between
the Earth and the Sun. Smyth believed that the coincidence meant
that the Pyramid builders must have also known this distance. There
was much more along these lines, with liberal doses of religious and
prophetic conclusions. He published a three–volume,
1,600–page opus about his findings, which, needless to say,
was a great hit among the like–minded, but which was dismissed
by one reviewer as containing "more extraordinary
hallucinations than has appeared in any other three volumes of the
past century." Nevertheless, Smyth was not entirely without
redemption. Like a previous investigator, he was intrigued by the
extraordinary straightness of the Descending Passage and took care
to measure carefully its angle of descent, noting that a person
within the passage looking out through the surface opening would see
a patch of sky close to the celestial north pole. However, Polaris,
the current pole star, would not have been visible to the builders
because precession (the slow wobble of the earth's axis of spin)
would have placed the pole much farther from Polaris than it is now.
A possible (though not very likely) pole star for people of that era
is the magnitude 3.7 star Thuban (Alpha Draconis), which, Smyth
calculated, would have been visible in the opening at lower
culmination (the time of its lowest point in the sky) around the
years 2123 and 3440 B.C. He suggested that the Pyramid might have
been built near either of those dates, which despite the flimsiness
of his argument is not entirely ridiculous when compared to the
modern estimate at about 2500 B.C.
A long–standing problem relating not only to the Great
Pyramid but also its smaller cousins is the question of how the
builders managed to orient such colossal structures to the cardinal
points with surprisingly high accuracy. The eastern side of the
Great Pyramid, for example, points only three arcminutes away from a
true north–south line, and other pyramids in the group are not
much worse. This makes it virtually certain that some astronomical
method was used to establish the local meridian. At first thought
this does not seem too difficult a problem, even without a bright
star close to the north celestial pole during the millennia of
interest. (Even today, Polaris is some 43 arcminutes from the pole,
and during this time it was about 25 degrees away.)
Still, other possibilities spring to mind. An obvious method would
be to note the directions of sunrise and sunset on a given day and
bisect the angle between the two—the result marks the
meridian. But this, and other seemingly straightforward methods,
while fine in principle, turn out to be unsatisfactory in practice,
at least when accuracies of a small fraction of a degree are called
for. For instance, in this case the rising and setting sun must be
seen over an absolutely flat horizon, which Giza lacks. Then there
is refraction in the earth's atmosphere: When one sees the lower
edge of the setting sun just touching the horizon it has in fact
already set. The light rays are bent to produce an image above the
horizon, thereby shifting the direction in which the sun appears to
set. And since the amount of refraction depends on air temperature,
pressure and other factors, all of which can differ between morning
and evening, the effect may not be consistent between rising and
setting. Furthermore, the sun's celestial coordinates will change
during the course of the day, spoiling the symmetry of the method.
All in all, these practical hurdles have stymied modern astronomers
who tried to figure out just how the early Egyptians managed to
orient their pyramids as precisely as they did.
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