Brugh na Boinne

The remarkable complex at Brugh na Boinne (Figure 6.7) provides the best evidence of a contextual (rather than a statistical) nature for extensive and precise interest in astronomy. The three great mounds of Newgrange, Knowth, and Dowth and associated monuments are for the most part intervisible, and together, they form a kind of massive record, which we may only now be starting to understand. Eogan's (1986) work at Knowth has revealed two massive passage graves, one aligned to the east (and so to the rising equinox Sun), in which the sunlight directly penetrates the main burial chamber, the other aligned to the west (and the equinox setting Sun), with sunlight penetrating far down the passage but prevented from actually entering the burial chamber by a bend. The bent shaft is a feature reminiscent

5 Tradition implies a common background. A convergent tradition involves groups becoming more alike, usually because of common external factors. A parallel tradition merely preserves common, older features, but that may not have been originally explicit.

Figure 6.7. The funerary complex

Figure 6.7. The funerary complex

of the second passage grave at Gavr'inis. The kerbstones around the monument and many interior decorated stones provide the most extensive collection of megalithic art yet known, thanks to Eogan's work. At Newgrange, Michael O'Kelly (1982/1989) meticulously reset stones and cleaned and reconstructed the mound, while carefully recording information on the building sequence, construction techniques, and chronology of the mound, which stands more than 45 ft high and 300 ft across. Its quartz crystal facing glistens again in the Sun, making Newgrange one of the most visually impressive of all the megalithic monuments (Figure 6.8). He discovered a "roof box," a 62-ft long window shaft over the top of the entrance passage that still lets the rays of the rising winter solstice Sun illuminate the great corbel-vaulted chamber almost6 as it did 5000 years ago. The discovery has helped to convince archeologists of the deliberate and accurate nature of the astronomical alignment of this passage, which was first demonstrated by Patrick

6 We say "almost" because the obliquity of the ecliptic has decreased by about 0.5° over that interval, decreasing the azimuth of rise of the midwinter Sun by about 1°.

Figure 6.8. A photographic mosaic of the front of the quartz crystal facing of the passage grave monument at Newgrange, one of the most visually impressive of all the megalithic monuments. Photos by E.F. Milone.
Figure 6.9. Views and close-ups of the spirals on kerbstone 1 and on the opposite side kerbstone of the Newgrange passage grave. Photos by E.F. Milone.

(1974a,b) and refined by Rea (1988), who showed that in neolithic times, the sunrise rays could have penetrated far into the interior, illuminating a three-leafed spiral on the back wall.

Although the carbon-fourteen data from Newgrange suggest a date about 3100 b.c. for the construction of the mound (O'Kelly 1989, p. 351), a similar date from Knowth antedates the construction of the main mound there, suggesting that Knowth may be slightly later than Newgrange (O'Kelly 1989, pp. 109-110). Interpretations by Brennan (1983), whose activities and lack of meticulous surveying and incomplete documentation of his work have led to strong personal differences with archaeologists who have worked in this area, nevertheless provide some important insights. Three passage graves show alignments related to the winter solstice: the sunrise of Newgrange, the sunset at Dowth, and a possible noon alignment at Mound K—a badly damaged structure that nonetheless still indicates that the passage must have had a very low roof, which would have allowed sunlight to enter the chamber only at midday, when the Sun crosses the celestial meridian. At such a time, it will be remembered from earlier chapters, see, especially, Figure 3.17, the Sun is due South, and at the highest point of its diurnal arc, at an altitude given approximately by h = (90 - f) + 5. (6.5)

At midwinter, the solar declination is equal to the negative of the obliquity of the ecliptic, 5 = -e ~ -24°; the latitude at Dowth is f = 53°41', so we find h ~ ~12°. At the main mound of Knowth, a cruciform chamber is lighted by the rising equinox Sun and an angled passage grave is illuminated by the equinox setting Sun, to the point of the bend. The unique property of these passage graves is the unambiguous direc tion of the alignments. The shaft subtends a small solid angle on the horizon, and that angle is small due to the lengths of the shafts providing the alignments. Slight changes in the direction of the Sun cause different portions of the passageways and the burial chambers to be illuminated, giving high precision to the astronomical alignment. These passage graves provide strong evidence that precision in alignment direction was of direct concern to the people who built these structures, and so make at least plausible some of the arguments by Thom that distant foresights were used to accomplish similar precise alignments of other structures.

At Newgrange, 31 of the 97 kerbstones are known to be decorated, but only about 1/3 of the stones have been completely exposed (M.J. O'Kelly 1982, p. 15; C. O'Kelly 1973/1978/1982/1984, p. 152). Some are decorated not only on the exterior, but also on the side facing the mound, which would have been invisible at any time since the mound was constructed. The alignment of the passage grave is marked by kerbstone 1 (K1) at the entrance and by kerbstone 52 directly opposite. Both of these are bilaterally divided down the middle. K1 has a group of clockwise spirals on the left of the dividing line and a group of counterclockwise spirals on the right (see Figure 6.9).

Brennan suggests that the spiral marks the passage of the rising Sun on successive days northward along the horizon. The horizon movement, as we have described extensively (§2.3.1), continues northward from winter solstice until summer solstice, when the movement comes to a stop (the "solstice") and then reverses. We will return to this spiral motif again and again; it is a motif shared by many cultures.7 Brennan suggests that the CCW spiral describes

7 In her book on Polynesia, Makemson (1941, p. 22) refers to "the spi-raling path of the Sun."

the northward movement, and the CW spiral describes the southern. Other stones, some not in alignment with extreme or equinox positions, are also marked with spirals, making the interpretation less convincing.

Surrounding the mound is another interesting feature, a ring of standing stones. Figure 6.10 shows the stones in a counterclockwise pacing around the northeast arc of these stones.

MacKie (1977a, pp. 72-73) regards the ring of stones as half ellipse and half circular arcs, with "the arcs of circles centered on the corners of two opposed right-angled Pythagorean triangles." However that may be, in ~2015 b.c. [Sweetman's (1984) date for the stone ring], Stone 1 of the ring cast a shadow onto the three-leafed spiral on the kerbstone in front of the entrance, K1, at the winter solstice. Prendergast (1991a,b) confirmed this circumstance (with the standing stone most directly in front of the entrance, GC1 in his designation,8 casting a shadow, for a 20-minute interval after dawn, to K1's three-leafed spiral only for -23°56' < 8 < -23°22', and found solar declination ranges for the shadows of other stones on the spiral as well: that of GC-2 for -01°14' < 8 < +01°26', and that of GC-1 for -12°53' < 8 < -09°51', corresponding to equinox and midseason declinations. Other determinations were: CG11 to GC7 aligned to 8 = -23°49'; GC5 to GC3 to a midseason 8 = +11°33'; and GC1 to GC-2 aligned to +23°15', a possible summer solstice alignment). Figure 6.11, from Prendergast (1991, Fig. 5), shows the shadow play on K1.

Claire O'Kelly (1982/1984, p. 149) argues that K1 and K52 were in position before the neighboring stones were placed—possibly before the bulk of the monument was constructed. This raises the possibility that the ring predates the mound, and that stones of the ring bearing known alignments were used in laying out the passage grave. In fact, the size of the mound would have precluded any use of the ring in terms of alignments. If some of the kerbstones were used in conjunction with shadows of the ring stones in laying out the passage grave, the symbols on the interior faces of the kerbstones may become explicable. K13, possibly used in summer solstice sunrise-winter solstice sunset alignments, is extensively decorated on both faces, so that it is possible that it was intended to be used in connection with the construction of the mound and the correct placement of its reciprocal, K67. Later stratigraphic work by Sweetman (1984) suggested that the standing stones were erected a millennium after the positioning of K1. Even if true, and the alignments with K1 are somehow fortuitous, the internal alignments among the standing stones remain. Prendergast (1991) also estimates the probability that the apparent solar alignments are due to chance placements of the standing stones and K1. He uses the uncertainty in azimuth, oA, to produce a probablility of a random alignment in the sector of interest of p = S 2oA/180°, that is, the

Figure 6.10. Portions of the ring of standing stones around the passage grave monument at Newgrange: Three successive views proceeding CCW around the entrance. Photos by E.F. Milone.

8 The designations of the standing stones are those of M.J. O'Kelly: proceeding clockwise from the tomb entrance, but allowing for gaps, as GC1, GC3, and so on; and the stones proceeding in a counterclockwise direction just to the northeast of GC1 are labeled GC-1, GC-2, and so on.

Figure 6.11. Simulation of shadow effects on kerbstone 1 by standing stones in the ring at Newgrange (Prendergast 1991, Fig. 5, modified by Sharon Hanna): (a) Shadows cast by standing stone GC1 at winter solstice over a 20-minute interval starting at sunrise with a solar declination -23°56', appropriate for 2015 b.c. (b) Shadows cast by stone GC-1 when the Sun had a mid-declination of -11°53'. (c) Shadows cast by stone GC-2 at equinoxes (declination 00°31').

Figure 6.11. Simulation of shadow effects on kerbstone 1 by standing stones in the ring at Newgrange (Prendergast 1991, Fig. 5, modified by Sharon Hanna): (a) Shadows cast by standing stone GC1 at winter solstice over a 20-minute interval starting at sunrise with a solar declination -23°56', appropriate for 2015 b.c. (b) Shadows cast by stone GC-1 when the Sun had a mid-declination of -11°53'. (c) Shadows cast by stone GC-2 at equinoxes (declination 00°31').

sum of all ranges of angle ±oA centered on particular azimuths. He follows Schaefer (1986) to obtain an overall probablility that the apparent astronomical alignments are significant.9 If M represents the number of such apparent astronomical alignments, and N is the total number of lines between the stones at the site, then the probability that the alignments are due solely to chance is

He concludes that the probability that the Newgrange alignments among the stones are due to chance is ~0.01. Note, however, that this approach is hardly foolproof in general; as the errors in the alignments, oA, become very large, so does p, and as p approaches 1, P(M) approaches 0. Here, however, o can be assumed to be at most tens of arc-minutes.

9 Generally, the chance probability in achieving X successes out of N trials in any situation in which the probability of a "success" is p can be written: NCX pX(1 - p)N-X, where NCX is the number of ways (combinations) to achieve these successes: NCM = N!/[X! x (N- X)!] = [N x (N-1) x (N - 2) x .. . (N- X + 1)]/[1 x 2 x ... x X].

The second of the great funerary centers in the Boinne complex is Knowth. At Knowth, 90 of the surviving 123 kerbstones are decorated externally and 11 are decorated on the interior side (Eogan 1986, p. 150). The structure of the principal mound, the placement of its kerbstone elements, and their ornamentation can be seen in Figure 6.12.

Calendrical concerns are suggested in the spirals and perhaps temporal concerns in what appears to be the face of a vertical sundial at the top of the fifth kerbstone to the south from the eastern entrance (Figure 6.13).

The radiating lines and the two depressions (albeit very shallow depressions) resemble those seen on a flat Egyptian sundial found at Luxor and now in the Ägyptische Museum, Berlin (Clagett 1995, Fig. III.56; see Figure 4.5). The Luxor sundial supported a weighted string that indicated the vertical and presumably a horizontal stylus to provide a shadow. If the Knowth kerbstone is indeed a sundial, it may be the earliest known example. A gnomon for such a device could have been horizontal with solid footing on the ground and two fingers to steady it in the two depressions. Because the length of a gnomon's shadow at any measured instant can give seasonal information, such a sundial might have been useful in the placements of some of the other kerbstones. The markings on the northern half of the Knowth dial include eight major points and eight minor points. This is exactly the sort of division one would expect if the 16 calendar divisions postulated by Thom (1967/1972, pp. 109ff) have validity, but if this were a sundial, it would antedate by more than a thousand years the alignments that led Thom to postulate such a calendar.

It is noteworthy that the kerbstones at the entrances to the two passage graves are also divided down the middle, like those at Newgrange. A bisecting shadow is cast onto the exterior face of the kerbstone at the west entrance at the equinoxes. Brennan has written at length about the possible interpretations of many of these kerbstones, but other than calling attention to the markers, he has not made any explicit attempt to determine the relationship between the "decorations" (or possibly notations) and associated alignments. The concept of a notational system, intermediate between icono-graphic symbolism and true writing is not one that most megalithic scholars have had occasion to consider prior to Brennan's work, and Brennan does not phrase his studies in these terms. The nature and implications of such a system are treated most fully, to our knowledge, in a work by Langley (1986) relating to repeated symbols in similar contexts in the art of Teotihuacan. Many of his general remarks are probably applicable here.

Of all Brennan's interpretations other than for the previously mentioned spiral, DHK finds that K52 (in Eogan's numbering; SW22 in Brennan) is the most convincing (Figure 6.14).

It displays a series of 22 crescents and 7 circles, features that could be stylized representations of the Moon over a synodic month. A spiral (representing the moving Sun?) cuts through three crescents and appears ten times on the right and nine on the left. Brennan also discusses possible

Figure 6.12. The grave monument at Knowth: (a) Diagram of the structure shows the kerbstone placements. Drawing by Rea Postolowski and Sharon Hanna. (b) Examples of ornamentation on the kerbstones related to their orientation at Knowth. The frequent use of spirals in funerary monuments probably implies a profound and widespread association between the human life cycle and the cyclical movements of the Sun and Moon. Drawing by Sharon Hanna.

Figure 6.12. The grave monument at Knowth: (a) Diagram of the structure shows the kerbstone placements. Drawing by Rea Postolowski and Sharon Hanna. (b) Examples of ornamentation on the kerbstones related to their orientation at Knowth. The frequent use of spirals in funerary monuments probably implies a profound and widespread association between the human life cycle and the cyclical movements of the Sun and Moon. Drawing by Sharon Hanna.

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