Egyptian constellations

The Egyptians developed their own constellation system based on important gods and animals in their mythology, although it was not as extensive as in other cultures. For example, historian and mathematician Hugh Thurston (1996) mentions an Egyptian catalog of the universe dating to about 1100 bc that lists only five constellations, two of which are similar to our Orion and Ursa Major. Of course, if one includes the decan star groups, then this number jumps by 36.

Southern Circumpolar Constellations

Figure 2.6. A pull-out plate of the plan of the temples at Karnak, from J. Norman Lockyer's (1894) The Dawn of Astronomy. 17.5 x 41.2 cm. Note the arrows indicating the orientations of the main buildings. For example, the text tells us that temple M at the upper center faces the direction where the star Gamma Draconis rises in the sky, and temple L faces where the star Canopus sets.

Figure 2.6. A pull-out plate of the plan of the temples at Karnak, from J. Norman Lockyer's (1894) The Dawn of Astronomy. 17.5 x 41.2 cm. Note the arrows indicating the orientations of the main buildings. For example, the text tells us that temple M at the upper center faces the direction where the star Gamma Draconis rises in the sky, and temple L faces where the star Canopus sets.

Like the Mesopotamians and Chinese, the circumpolar constellations were important to the Egyptians, not so much because they never set but because they never appeared before the rising Sun. Thus, they were often linked with the powers of darkness and with ferocious animals. For example, the circumpolar area around our Draco was often associated with a crocodile or hippopotamus, and the Plough (our Big Dipper) asterism of Ursa Major was viewed as the thigh or foreleg of an ox or bull (representing the evil god Seth). Thoth, a lunar deity, was usually shown with a Moon symbol above its head. It was also depicted as a baboon (an animal that shrieks before dawn), representing the transition from night to day. Both of these images could be combined, as is illustrated in Figure 2.5. And, as we have seen, Nut was associated with the Milky Way as it arched across the sky.

Lull and Belmonte (2006) have recently analyzed a number of Egyptian images located in tombs and on temple ceilings to find parallels between the traditional Egyptian constellations and the constellations that we visualize today. For example, they would view the female hippopotamus image in the lower left center of Figure 2.4 as representing the large area of the sky centering around the circumpolar constellation Draco, from Lyra to Bootes. The crocodile on her back would represent the area around the head of Serpens. The reclining lion and crocodile images in the lower right center represents Leo and Hydra, respectively. And, of course, the thigh/bull combination located in the upper center part of Figure 2.4 would be Ursa Major.

Following the death of Alexander the Great, one of his generals, Ptolemy, took over the administration of Egypt, thus initiating the Ptolemaic Period (323-30 bc). During this time, Greek ideas involving the cosmos and astrology began to gain influence in Egypt. In addition, Greek constellations were intermingled with those native to Egypt in images on temple ceilings and other monuments. A case in point is the famous image that dates from just after this period that was once located on the ceiling from the Temple of Hathor at Dendera. This so-called "Dendera zodiac" depicts the circle of the heavens held up by 12 figures representing the constellations of the zodiac (Figure 2.7). The outer ring of figures in the circle represents the 36 traditional decanal stars and constellations. The innermost figures are Egyptian constellations, and these are surrounded by the Greek constellations of the zodiac mixed in with images representing the planets, depicted as gods holding staffs.

2.3.5 Differences from China and Mesopotamia

Egyptian cosmology differed in two important ways from that of China and Mesopotamia. First, it was less interested in perceiving omens from celestial events. Portent-based interpretations were not central to the Egyptian mythology, and a system of astrology did not appear until it was imported from Mespotamia and Greece. Without the stimulus of omens, the Egyptians consequently did not produce the kinds of regular records of eclipses, planetary movements, or other celestial events that we have seen in other ancient cultures.

Second, the Egyptians eschewed mathematical approaches to astronomical events. Although some celestial patterns were noted and used qualitatively when they related to religious notions or agricultural needs (e.g., the heliacal rising of

Sirius), a numbering system amenable to algebraic calculations did not develop along the Nile. Instead of a place-value system, the Egyptians had symbols for different numbers (like 1, 10, 100), and they simply repeated them as was necessary. Thus, although many early Greek astronomers and philosophers, like Thales of Miletus, Democritus, and Plato, spent time with scholars in Egypt, it is likely that they were more influenced by Babylonian imports than native Egyptian traditions, since the direction of Greek astronomy seemed to follow Mesopotamian models more than anyone else. Two exceptions were the 365-day civil calendar and the division of the day and night into 12 hours, both of which were homegrown Egyptian products that were taken up by the Greeks.

2.4 INDIA 2.4.1 Cosmology

Cosmology in India goes back some 6,000 years to Vedic times. Historian and engineer Subhash Kak has categorized early Indian astronomy into several periods. The first was Rgvedic astronomy (ca. 4000 bc-2000 bc), which focused on the motions of the Sun and Moon, the observations of planetary periods, and the division of the sky into naksatras (which will be described in Section 2.4.3). Historian John North has cited creation myths from this period that included ideas that the universe was a building of wood made by the gods, with the heavens and the Earth supported by posts, or that it was created from the body of a primeval giant and inhabited by a world-soul. The Sun was sometimes seen as an astral god drawn in a chariot by seven horses.

The second period related to the texts of the Brahmanas (2000 bc-1000 bc), which described the non-uniform motions of the Sun and Moon in non-circular orbits, calculated the cycles of time that were related to the relative positions of the heavenly bodies, formalized the luni-solar calendar with its intercalations, presented cosmological ideas related to the "strings of wind" joining the Sun with the planets, and suggested that the Earth rotated on its axis (an idea later popularized by Aryabhata around 500 ad). This is known to us from later Indian texts and from the writings of Lagadha (ca. 1350 bc), whose Vedanga Jyotisa is the only extant astronomical text from the Vedic period, according to Kak. During this period, there was much symbolism in the field, with certain numbers having special meanings and altars being constructed to represent the geometry of the heavens. Kak relates this to the connection or equivalence between astronomical, terrestrial, physiological, and psychological realms that characterizes Indian thought and is often represented by similar numbers—for example, the 360 bones of the infant being related to the 360 days of the year.

The third period consisted of early Puranic and early Siddhantic writings (1000 bc-500 bc). Kak views the Siddhantas as being more mathematical and the Puranas as being more encyclopedic and empirical but also more cryptic and

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Figure 2.7. Copper schematic engraving of the famous "Dendera zodiac" planisphere at the Temple of Hathor at Dendera, from Denon's (1808) Viaggio nel Basso e Alto Egitto. 29.1 x 28.8 cm. Note the traditional Egyptian constellations in the center: hippopotamus (area around Draco) and thigh of an ox (Big Dipper). These are surrounded by figures representing the Greek zodiac and the planets (depicted as gods holding staffs). On the rim of the circle are figures representing the 36 decans.

speculative. These sources provided information on the relative sizes and distances of the Sun, Moon, and planets; introduced the concept of kalpa (i.e., a day of Brahma, the creator of time, equaling 4.32 billion years); and described and further developed the great cycles of time that were of interest to early Indian astronomers. Some of these implied that the planets revolved around the Sun, which in turn went around the Earth. There were also hints of a primitive epicycle theory.

In addition, Kak cites later Indian sources as giving a figure for the speed of light that is much like our own and supposedly reflected an earlier Puranic tradition; however, he believes that the accuracy of this value was probably a lucky guess. Some early Indian sources described an atomic theory that consisted of four atoms (earth, water, fire, and air) that combined to form matter. Light rays were a stream of high-velocity fire atoms.

After 500 bc, there were additional Puranic and Siddhantic writings. Kak describes two models of the universe mentioned in the Puranas. One conceived of it as consisting of seven underground worlds below the orbital plane of the planets and seven regions that encircled the Earth. In the center of the flat, circular Earth is a large mountain, Meru, which represents the axis of the universe. In another model, there is a central Earth that is orbited by the Sun, beyond which are the orbits of the Moon, asterisms, planets (in order: Mercury to Saturn), and then Ursa Major followed by the pole star. Beyond this are four additional spheres. Surrounding our universe is the limitless space with countless other universes. This cosmology envisions cycles of creation and destruction of 8.64 billion years, or a day and night of Brahma. The universe itself was said to last for 100 Brahma years (each of which has 360 Brahma days and nights).

Of the later Siddhantic writings, those of the great Indian astronomer Aryabhata (born 476 ad) were influential in southern India and dealt with the size of the universe and distances to the Sun and Moon, as well as making refinements to Puranic ideas concerning the relative diameters of the Earth, Sun, and Moon (although the angular sizes of the planets were too large by a factor of four). He also presented epicyclic models of the orbits of the planets that were different from those presented by Greek astronomers. For example, to account for two anomalies in location of a planet in the sky using a geocentric framework (due to the ellipticity of its real orbit around the Sun and to the fact that it is observed from a moving Earth), he employed two concentric epicycles rather than using an equant like Ptolemy (see Section 3.1.12). His writings also included some spherical trigonometry, a procedure for calculating the duration of an eclipse, and a mathematics section that allowed one to calculate an accurate value for pi. Finally, although his cosmology included Mount Meru as the center of the Earth, he also made statements supporting the rotation of the Earth and the revolution of the planets around the Sun.

A competing Siddhantic system was put forth by Brahmagupta (born 598 ad) that made improvements to some of Aryabhata's ideas and calculations and was influential in northern and western India, as well as in the Islamic world through its Arabic translations. Later, Bhaskara II (ca. 1150 ad) produced a comprehensive Siddhanta that was based on Brahmagupta's work and further developed the epicyclic theories involving the motions of the planets. He also developed notions of trigonometry that probably reflected Islamic influences, as did later Indian astronomy as well.

Mention should be made of the great stone observatories created by Jai Singh in the early 1700s, which were modeled after that built by Ulugh Beg at Samarkand. Although out of date when they were built, this effort nevertheless demonstrated a valiant attempt at observational astronomy, which had generally been neglected in India in favor of mathematical astronomy until the late 14th Century. Their remains can still be seen at Delhi, Jaipur, and Ujjain.

2.4.2 Time and the calendar

Traditionally, the Indian calendar was based on lunar months, each of which began with the full Moon. In time, this was integrated with the solar year. According to Kak, the lunar and solar calendars were brought into harmony in a variety of ways depending on local traditions: adding 11 days each year to the 354-day lunar year (i.e., 12 months of 29.5 days each); adding five days to a year made up of 30-day months; adding an intercalary 13th month twice in every five years; etc.

Attention was paid to both equinoxes and solstices, with the ritual year starting with the winter solstice and the civil year starting with the spring equinox. The ritual year was divided into two halves: when the Sun moved north in the sky, and when it moved south. The summer solstice was the midpoint, and it was recognized as far back as the Brahmanas that the number of days in each half were not equal due to the varying speed of the Sun in the sky (a fact not noted by the Greeks until the 5th Century bc). Ceremonies and festivals marked the time, such as the closing rite at the end of the year to celebrate the first ploughing. There were also sacrificial rituals every four months, ceremonies for the full and new Moons, and rites to mark the passage of the day.

2.4.3 Indian constellations

In keeping with the lunar calendar system, Indians astronomers during the Rgvedic period divided the sky along the Moon's path into 27 equal parts called naksatras (Figure 2.8). Specific stars or constellations associated with these areas were also called naksatras. In later literature the number of both the regions and associated stars was increased to 28, which better matched the Moon's progress in the sky. Other constellations were recognized that were similar to our own, such as the Bears (Ursa Major and Minor), the two divine Dogs (Canis Major and Minor), the Boat (Argo Navis), and the Pleiades in Taurus. According to Kak, in the Brahmanas period, Orion and the bright star Sirius were singled out, as well as possibly stars in our Gemini, Capricornus, and Cassiopeia.

The naked eye planets also were known and named since the Rgvedic period. In Vedic mythology, they were traditionally the offspring of other heavenly beings and were themselves equated with the gods: Mercury (Visnu), Venus (Indra), Mars

(Skanda, the son of Siva), Jupiter (Brahman), and Saturn (Yama). Venus was sometimes associated with the twins Asvins, reflecting its appearance as both a morning and evening planet. The Sun was linked to Siva, and the Moon to Uma, Siva's wife. The planets were also associated with colors (e.g., Mercury and Jupiter, yellow; Venus, white; Mars, red; Saturn, black). They were also part of references that alluded to the 34 lights in the sky, which were the 27 naksatras, the Sun, the Moon, and the five planets.

2.4.4 Outside influences

There is evidence for contact between Indian and Mesopotamian cultures during the Assyrian period. For example, North (1995) cites similarities with some of the statements found in the Mul Apin clay tables, which were produced early in the

Vedic Statements

Figure 2.8. The 27 naskatra constellations from Vedic mythology, from G.R. Kaye's Memoirs of the Archaeolgical Survey of India, No. 18: Hindu Astronomy, published in Calcutta in 1924. 22.7 x 27.4 cm. Note that they include both constellations and individual stars, some of which are familiar (e.g., Krittika, the Pleiades; Svati, the star Arcturus). See also Color Section 1.

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