Questions. Why 360 Degrees? Why Base 60?
We know that the Egyptians had a concept for slope which they called "seked" (equivalent to our cotangent), but beyond this there are no surviving documents explaining how (or even whether) they measured angular separations.
However, if the length of a side of the Great Pyramid was intentionally designed to equal 1/8th of a minute of latitude, then the supposition must be that the Egyptian architect was employing a circular measurement system of 360 with further subdivisions of 60 minutes per degree.
Is it conceivable that such a system was in use over 2,000 years prior to its recorded emergence?
The idea of a circle being divided into 360 parts (degrees) first appears in the currently known written historical record as an innovation of the Babylonian culture a few hundred years prior to the birth of Christ.
The division of each degree into 60 'minutes', and each minute into 60 'seconds', etc., is of Babylonian (via Sumerian) provenance as well.
Although there is no currently known surviving written evidence that the ancient Egyptians had previously developed these methods, it is not beyond the realm of possibility that they had. The association of the number 360 during the Old Kingdom with a complete cycle, or circular context, could have come about in a variety of different ways.
As previously mentioned, the Egyptians introduced a 365 day calendar shortly after the unification of Upper and Lower Egypt in about 3,000 B.C. With this change, the year was divided into three seasons, each containing four '30 day' months.
Each of these months was next further divided into three ten-day weeks. As a result, a year contained 36 ten-day weeks for a total of 360 days, with the calendar year's five remaining days being added somewhat ceremoniously to the end of this 360 day period.
It is interesting to note that these five added days were not always considered (perhaps for religious reasons) to be a legitimate part of the more preferable 360 day per year cycle.
In addition to this correlation, the number 360 has a direct connection with the sun itself. The sun has an apparent diameter of just over 1/2 of a degree, or about 1/720th of a full circular rotation of the sky.
River fog conditions will often allow the sun's disk to be clearly viewed for brief periods with the naked eye, thus making the task of measuring of the sun's relative apparent diameter a fairly simple undertaking along a river such as the Nile. (The apparent diameter of the full moon, though somewhat variable, is also almost exactly 1/2 of a degree.)
On a daily basis, due to the Earth's progress in its orbit, the sun appears to move the equivalence of two of its own diameters (i.e., about 1/360th of a full rotation) eastward through the heavens relative to the fixed stars.
The Egyptians were very concerned with recording the first visibility immediately before sunrise of various stars, and so would certainly have been well aware of the sun's daily eastward displacement relative to these stars.
None of the above observations are difficult to make, and each would have again brought up numbers related both to circular contexts and to the number 360. It may have been understood, however, that numbers as measured in the exterior world should not be expected to be exactly the same as a particular "ideal" number, but only to represent, or point the way to, this ideal. It is perhaps this approach that Plato had in mind when he has Socrates say:
These sparks that paint the sky.....we must recognize that they fall far short of the truth, the movements namely, of real speed and real slowness in true number and in all true figures both in relation to one another and as vehicles of the things they carry and contain. These can be apprehended only by reason and thought, but not by sight.
Corroboration for the choice of 360 could have been taken from the fact that it is wholly divisible by all of the first 12 numbers except for 7 and 11, an attribute that greatly facilitates the further partitioning of the circle into whole number sections. It is also the smallest number that is divisible by 10, 20, 30, 40, 90 and 60.
The concept of dividing a whole unit into 60 parts, and then dividing each of these parts into 60ths, and so on, originated in the Mesopotamian region.
There is evidence (drawn from clay tablets excavated at a site known as Jemdet Nasr, located in present day Iraq) that the workings of a "base sixty" system was already in use by about 3,000 B.C.
There is also evidence of substantial Mesopotamian influence taking place in Egypt at precisely this same point in time. In fact, some of the evidence of such contact is based on findings unearthed at this same Jemdet Nasr site. With the Mesopotamian impact of this period having affected Egyptian architectural and artistic designs choices, it would seem reasonable to suppose that there was coincident Egyptian exposure to base sixty counting methods as well.
If, as can be construed by the length of the perimeter of the Great Pyramid, Egyptian architects were aware of a base sixty system, and chose to divide a circle into 360 degrees, then why is there no demonstration of either usage in the surviving written historical record of ancient Egypt?
The answer may be due to a combination of factors. It may have been thought that since the use of this knowledge allowed access to such intrinsically powerful results (i.e., trigonometry), then perhaps this knowledge should be closely held by only a select few.
It may also have been found that the use of a base sixty, and a 360 system, ran counter to methods that were already well entrenched and in daily use. Cultural inertia, then, may have prevented their widespread adoption. (This would be similar to the present day resistance in the United States to the adoption of the metric system).
And lastly, it may be due to the very limited amount of material that has endured through the ages until the present time. It has been wisely noted in regard to ancient Egyptian capabilities, that "it would be rash to assume that no advance was made beyond what can be found in the scanty and mostly fragmentary surviving texts".
In addition to the length of each side of the Great Pyramid, there is one other Old Kingdom design choice that may possibly offer confirmation not only of the issues discussed in the preceding paragraphs, but also of the initial assumptions stated at the beginning of this essay. I refer to the Old Kingdom choice for the length of the ancient Egyptian standard unit of measure, the Royal Cubit.