Sundial, calendar and Khmer temples
Astro-archaeology = Astroarchaeology
Determining celestial north
A method for
determining cardinal directions - proposed by Dr. Kate Spence
Dr. Kate Spence, an
Egyptologist at Cambridge University, UK, proposed in an article
in Nature, 16 November 2000, that the ancient Egyptians might have used
the circumpolar stars Kochab and Mirza for aligning the Great Pyramid at
Giza in Egypt straight true north-south in the middle of the 3rd
Nowadays Polaris is located
close to celestial north, but due to the precession of the equinoxes it
was not so 4500 years ago. Kate Spence's theory is that the master
planners before digging out the foundation of the pyramid at night time
waited until Kochab and Mirza were located vertically above one another
because they knew that e vertical line connecting the two stars would
pass celestial north.
measurement of alignment taken with a plumb line toward the stars at
this time would be oriented exactly to true north.''
''The simultaneous transit method involves making an alignment toward
two stars when they are vertically aligned. The alignment can be taken
when either of the stars is in the upper position. Because the upper
culminations of the two stars fall approximately twelve hours apart,
with the time of culmination of each star moving slowly through 24 hours
in the course of a year, for about half the year the vertical alignment
that falls within the hours of darkness will have one of the stars
always above, and for the other half of the year the second star will be
in the position of upper culmination when the two stars are vertically
aligned during the course of the night.
When the chord between these two stars passes precisely through the
celestial pole, an alignment taken toward the stars when they are in
simultaneous transit will be exact with either star at its upper
Ancient Egyptian chronology and the astronomical orientation of pyramids
|Above: The stars around celestial north in
August 2467 BC.
The magnitude of Polaris, the Northern Star,
is 1.90, which is a little brighter than Kochab and Mirza (2.08
Since Spence's article in
Nature her theory has been launched by popular TV-programs as the
HISTORY Channel and Discovery as if it was a generally accepted method.
Also scholars working in the field of Khmer archaeology have been
considering whether the method was implemented by the ancient Khmers as
well. The latter is the reason why this web-page is made.
The author see no reason why the ancient Khmer master
builders should have used a method as proposed by Spence. First of all
because the Khmer constructions are of a much later date. Secondarily
because they most likely used the
Indian Vedic Circle method.
A third reason (which might
also exclude the ancient Egyptians) is that the method is appealing on
paper or in a astronomical animation program on a desk top, but
difficult to implement in real life.
One obstacle is that the alignment has to be done at night
time aligning two dim stars with a plumb line on a night with absolutely no wind.
A second obstacle is that there must be two plumb lines (not
only one as mentioned by Spence) in order to obtain a foresight and a back sight (two points
are needed in order to construct a line). As the altitude of Kochab was
app. 40.5° the distance between the plumb
lines must be relatively short or the back sight plumb line rather long
(app. equivalent to the distance between the plumbs): 1. A long plumb
line demands an environment with no wind. 2. Long distance between
foresight and back sight gives more accurate readings.
Proposal (experimental archaeology): Chose two stars of similar
magnitude and similar altitude and test the theory in real time in
showing the proportions of sight lines (plumb lines) needed for
constructing a true N-S line when using the two stars Kochab and
The moon at an altitude of 8 degrees.
Egyptian chronology and the astronomical orientation of pyramids
The American Scientist:
Astronomy and the Great Pyramid
Robert G. Bauval:
Brief Evaluation of Kate Spence's Article in NATURE
On the astronomical orientation of the IV dynasty Egyptian pyramids
Shaltout and Belmonte:
On the orientation of ancient Egyptian Temples I: upper Egypt and lower
12 January 2007
© Asger Mollerup