Astronomical Measurement

Modern archaeoastronomy began with a discovery by F.C. Penrose, that some of the public buildings in the region showed possibly significant astronomical alignments. These data were used by Lockyer (1894/1973, pp. 416ff) to demonstrate building dates for these structures, which did not adequately consider archeological evidence, and thus lost credibility with a large segment of the scientific community of his time. Lockyer (1894/1973, p. 416) claimed that Penrose's (1892/1893) observations supported a claim that the Parthenon was oriented to the rising of the Pleiades at a date of 1150 b.c.; Penrose surveyed 28 temples and found orientations between 21° N of east to 18°25' S of east. He considered the bright stars that could rise within the limits established by the range of azimuths and suggested 17 stars that might have been used, and that the purpose was to use the heliacal rise of a particular star as a warning of the arrival of a feast day. Penrose, whose comments are reproduced in Lockyer (1894/1973, 417ff), asserted that seven temples were (equinoctially) aligned to a Arietis, whereas no Egyptian temple had been, but many Egyptian and "early" Greek temples were (solticially) aligned to Spica. This he attributed to precession, as the vernal equinox moved westward from Taurus into Aries. Because, he claimed, the solsticial "year was thoroughly established" in Egypt, there was no need to erect "temples to the new warning star a Arietis."

Orientations of cities, buildings, and temples from before ~2200 b.c. to Roman times are shown in Pedley's (1993) attractive compilation of Greek art and archeology. Among temples having E-W orientations are the temples of

(1) Artemis at Corcyra,23 dating to ~580 b.c. (Pedley 1993, Fig. 6.7)

(2) Apollo at Syracuse in Sicily, from ~560 b.c. (Pedley 1993, Fig. 6.22)

(3) Hera, ~550 b.c., and a second ~470-460 b.c. (Pedley 1993, Figs. 6.26, 7.15), at Poseidonia

(4) Athena (~500 b.c.) at Poseidonia (Pedley 1993, Fig. 6.26)

(5) Zeus at Olympia, ~460 b.c. (Pedley 1993, Fig. 7.1)

(6) Zeus at Akragas (modern Agrigento in Sicily), ~480-406 b.c. (Pedley 1993, Fig. 6.25) (see Figure 7.11)

(7) Athena Polias at Priene, ~340 b.c. (Pedley 1993, Fig. 9.17)

(8) Artemis at Magnesia, ~175 b.c. (Pedley 1993, Fig. 10.5)

23 The west pediment (triangular relief sculpting at the top) of this temple has as its central figure the Medusa (Pedley, Fig. 6.8). The head of the Medusa has been associated with the variable star Algol;among the Greek constellations, the head was held aloft by the hero Perseus, and Algol is one of four or five stars shown on it.

All of these temples face east. Many others face somewhat north (as the Parthenon on the Athenian Acropolis (447-432 b.c.), the temples of Apollo at Corinth, ~560 b.c., and Didyma, ~550 and ~330 b.c., and those of Hera, earliest of which may be 8th century b.c.). Some earlier temples and important buildings, on the other hand, appear to open to the southeast. One interesting example is a 13th-century (b.c.) palace at Pylos (Blegen and Rawson 1966) on an acropolis that trends northeast-southwest. In this wellpresented complex, there is a large hall with a central, circular hearth. Four surrounding columns were placed at the cardinal points.

Whatever one thinks of the Penrose/Lockyer conjectures, the alignments of structures do not require notions about the celestial sphere. As discussions in §6.2 indicate, solar alignments can be established relatively easily, with simple tools. The early Greeks probably used gnomons to establish dates of solstices and equinoxes and directions to the rising and setting Sun. Anaximandros of Miletos (~610 to ~545 b.c.), a younger contemporary of Thales (also of Miletos, ~624 to ~545 b.c.) is reported to have done so (Sarton 1952/1970, I, p. 1740). Dicks (1970, p. 88; cf. also pp. 45, 174), however, writes: "Now, recognition of the equinoxes and of the inequality of the seasons implies a comparatively sophisticated stage in astronomical thought, and presupposes at least some knowledge of the concept of the celestial sphere and a spherical earth." We disagree. On the contrary, any use of a gnomon should lead easily to the identification of the equinoxes (when the morning shadow is in line with the evening shadow) and simple counting of days should lead to recognition of what modern astronomers call the "inequality of the seasons" (see below). Dicks (1970) moreover asserts that it is easiest to determine the summer solstice. Solsticial observations were certainly attributed to Aristarchos and Hipparchos, but given the slow movement of the Sun along the horizon at that time, they were not favored by ancient astronomers. Ptolemy says that since observations of solstices are, in general, hard to determine accurately, and since, furthermore, the observations handed down [from the schools of Meton, Euktemon, and Aristarchos] were conducted rather crudely (as Hipparchos too seems to think), we abandoned those, and have used instead . .. equinox observations. . .. (Almagest, III 1, H203; in Toomer 1984, p. 137)

Another early accomplishment may have been at least a limited ability to predict eclipses (see §5.2.2 for a discussion of Thales's possible prediction of ~585 b.c.), although this knowledge does not seem to have been generally shared, if it existed.

The notion of the celestial sphere seems to arise with the Greeks. According to Dicks (1970, pp. 169, 175), the Babylonians had no concept of the celestial sphere or of longitude and latitude, or of circular motion, which he states was the principal mathematical tool of Greek astronomy, just as arithmetic progression was for the Babylonians (p. 176). Anaximenes of Miletos (d. in 63rd Olympiad, 528-525 b.c.) is said to be the first Greek to conceive of a rotating sphere of fixed stars (Sarton 1952/1970, I, p. 178).24 The 5th-century

24 An Etruscan depiction of Atlas holding a celestial sphere may be of similar date.

Figure 7.11. Ruins of the temple of Olympian Zeus at Akragas (modern Agrigento), Sicily, one of the largest Greek temples ever constructed: Built by Carthaginian captives in 480 b.c., it was destroyed in the Carthaginian sack of Akragas in 406 b.c. (a) View from the south along main axis. (b) A now prone Telemon pillar. (c) A capital of the massive pillars. Marie Milone provides scale. Photos by E.F. Milone.

(b.c.) Pythagorean astronomers Parmenides of Elea and Philolaos of (Croton/Tarentum) may have been the earliest Greeks to conceive of a series of concentric celestial spheres and to envisage a rotating Earth, respectively (Sarton 1952/1970, pp. 288-289). The first major cosmological scheme that seems to have been solidly based on extensive observational data joined to spherical concepts was that of Eudoxos. Eudoxos of Cnidus (~408-355 b.c.) came from Asia Minor (Cnidus was in Caria, South of Miletus, in what is now southwestern Turkey), but his ideas were shaped and tempered by study in Athens, Alexandria, and elsewhere. He was taught by the Pythagorean mathematician Archytas, and he heard Plato and other philosophers in Athens. A detailed account of his life is given by Dicks (1970, 151ff). Eudoxos wrote an account of the constellations that was later used by Aratos in his lengthy poem, Phainomena or Phaenomena, according to the later Greek astronomer Hipparchos (see §7.3). The poem was a major source of knowledge about the relationship of the Greek myths to the constellations,25 throughout the medieval period and even into the 19th century. The constellations as described by Aratos show positional discrepancies with respect to the sky of his time, and it has been maintained that these are evidence of pre-cessional changes from as early as 2200 b.c. Most scholars (beginning with Hipparchos) have regarded them as errors (Dicks 1970, pp. 153-157).

There is some evidence that Babylonian observations were widely used by Greeks. Ptolemy claimed that some observations were available from as far back in time as the reign of Nabonassar, and that planetary observations were made by Egyptians and Syrians. Aristotle emphasized that many occultation observations were available from these sources and that they provided much knowledge of the planets, and Aristotle's nephew, Callisthenes brought back from Babylonia a great number of records, a gift of Aristotle's famous pupil, Alexander the Great. However, there is no direct evidence that Eudoxos was trained by Babylonian astronomers, that he had access to the tablets containing the Babylonian planetary data, or that he knew cuneiform. He did use Babylonian planetary periods (Dicks 1970, p. 167), but later sources (e.g., Ptolemy) also reported that he made many observations himself. Dicks (1970, pp. 257-258, Fn 355) cites the Roman architect Vitruvius (2nd century b.c.), who says in connection with sundials, that Eudoxos invented the arachne, "spider." Dicks notes that "Later, the movable disc (representing the ecliptic) of the planispheric astrolabe was called the 'spider'... but Eudoxos certainly did not know this instrument."

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