The Great North Road

Jupsat Pro Astronomy Software

Secrets of the Deep Sky

Get Instant Access

Perhaps some of the above-mentioned astronomical correlations are just casual. However, there is overwhelming evidence that the sacred landscape of Chaco was deeply connected with the celestial cycles, and that these connections were established across great distances (Sofaer 1997, Sofaer and Sinclair 1986b). Clearly, it is extremely difficult to be accurate when working on such distances, but accuracy of alignments certainly presented no problem to the Chacoans.

To be further convinced, one only needs to look at the roads. Indeed, the careful observation of solar and lunar cycles was only one of two hobbies at Chaco Canyon. The other was building roads. Between circa 1050 and 1125 AD, the Chacoans were engaged in a frenetic program of road construction. The Anasazi roads were built by digging up the surface of the ground and, when necessary, integrating the roadways with masonry work or slicing through rocks.

It is easy to spot Anasazi roads from aerial photographs because the roads are straight. The Anasazi did not like bends or curves. What is today called the Great North Road, for instance, begins at the northern rim of Chaco. From here it runs (in a straight line) in a direction 13 degrees east of north for 3 kilometers. It then proceeds (straight) in the direction of true north for 16 kilometers as far as a site known as Pierre's Complex, which is made up of a collection of small buildings. It then heads (straight) in the direction two degrees north of east for 31 kilometers as far as the peak of Kutz Canyon (most of the road consists of two—on some stretches, even four—lanes, with a breadth that exceeds modern two-lane highways). There are no forks, no bends, no intersection, and no intervening villages—nothing. The closest Anasazi complexes, apart from Chaco where the road starts, are Salmon Ruin and Aztec Ruin, which are scores of kilometers away. The importance of the road, however, is evident in Chaco itself, as numerous secondary roads

Figure 7.4: A map of the Chaco National Park, showing ancient buildings and the network of ancient roads. The Great North Road is easily recognizable.

and stairways carved into the rocks converge onto it from Pueblo Bonito and from other buildings up to the beginning of the road at Pueblo Alto.

The building of the road was no mean feat and entailed the shifting of great masses of earth and vegetation. When the road had to pass through rocky outcrops, the rocks were duly hewn and modeled so that a straight path might be hewn through them. Everything is grossly out of scale for any mere utilitarian purposes. Archaeological study has found no signs of wear on the road due to traffic, and a considerable amount of pottery has been found, perhaps deliberately broken, both along the way and at its end, as well as on the flights of stairs carved into the rocks on the peak of Kutz Canyon. Thus, even though many in the past argued that the Anasazi roads were trade or communication routes, it is clear today that they had no commercial purpose (Sofaer et al. 1989, Stein and Levine 1983). We can only conclude that the Great North Road, for example, was built for the simple reason that the builders wanted it to be built—however unsatisfactory and frustrating such an explanation might appear (the same might be said of various other stretches of road built by the Chacoans).

From the technical point of view, the question raised by the Anasazi roads is, How did the builders manage to mark out such straight paths? Imagine yourself in a desolate canyon, having to solve the problem that the Anasazi faced when they created the stretch of the Great Road leading to Pierre's Complex: moving 16 kilometers in the direction of true north with maximum error of a quarter of a degree. Today such good precision can be easily obtained with a theodolite or a GPS system (not a compass, however, since even the best magnetic compass, after having corrected its reading by taking into account magnetic declination and possible anomalies, is unlikely to give you an accuracy better than a half of a degree). For the Anasazi, the only possibility was to use the sun during the day or the stars at night.

The sun may be used to find the cardinal directions by employing a method sometimes called Indian circle. A post (gnomon) is placed in the center of a circle and then, during the day, the two points where the shadow of the post passes over the circumference, in the morning and in the afternoon, are marked: the east-west line can then be found connecting the two points. Yet it is impossible (at least in the view of many, myself included) to obtain an accuracy greater than half a degree or so in this way, since there are too many geometric operations to be carried out with ropes and poles.

The stars can be used to determine north in a very precise way by two methods. The first method makes use of the stars which rise and set. The astronomer constructs an "artificial horizon,'' that is, a circular wall whose top is perfectly smooth and leveled, and then stands immobile at the center of the circle, signaling to his assistant—who marks them on the wall—the rising and setting point of the chosen star. Bisecting the angle formed by the two ideal lines joining the two points on the horizon with the position of the astronomer indicates north. The other possibility is to identify, using a reference instrument able to measure angles (for example a cross-staff), the upper and lower culmination, that is, the maximum and minimum heights reached, or the maximum east-west elongation, of a circumpolar star, and then looking for the mean point. It is important to remember that the method of finding the celestial north pole with the pole star is only approximate, and it can be used only in the periods in which precession brings the pole close to a sufficiently bright star; the celestial south pole always lies in a zone in which bright stars are not present.

In using one of these two stellar methods, very good accuracy (say 10' or even less) is undoubtedly attainable (as we shall see during the age of the pyramids in Egypt, accuracy of a few arc minutes was also attained with a method based on two circumpolar stars). The mystery, if any, lies in the depth and seriousness of the commitment that drove the astronomers to operate at such a high level of accuracy. Indeed, we have to imagine the Anasazi astronomers determining north by night, and then their engineers building the road, bit by bit, on the basis of their observations, sending ahead runners armed with fire signals and marking for them the position on the horizon until they were in alignment with the meridian, kilometer after kilometer, night after night.

Even more difficult is to align long straight roads that are skewed with respect to true north, as for example the path leading to Kutz Canyon. It is difficult to avoid making curves, but this avoidance seems to have been of vital (life-giving, literally) importance for the Anasazi. Possibly the directions to follow were associated with astronomical phenomena (rising or setting points of stars), so that the builders could "recalibrate" on the stars each night. The Polynesians navigated far out in the ocean this way, as we shall see in Chapter 12, and maybe the same procedure was adopted by Hopewell when they marked out the Great Road linking Newark and Chillicothe, as we saw in Chapter 6.

Was this article helpful?

0 0
Telescopes Mastery

Telescopes Mastery

Through this ebook, you are going to learn what you will need to know all about the telescopes that can provide a fun and rewarding hobby for you and your family!

Get My Free Ebook

Post a comment