Precession of the equinoxes (from David Ulansey, The Origins of the Mithraic Mysteries ). 

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... astronomers emphasized positional stellar astronomy in reference to the pole star and in India the motions of the sun, moon and planets had greater importance. This is most probably because the majority of China is north of the Tropic of Cancer, which runs central to India. In India, the position of the sun and its motion are much more critical in constructing the built world due to the environmental impact of the sun and resulting hot temperatures. In the northern latitudes of China, the motion of the stars about the pole star are much more visually appreciable, whereas the environmental concerns due to the position of the sun are less critical to their constructed world. In ancient times both of these systems relied on the gnomon to determine their astronomical calculations. It should be mentioned that the earth’s axis is tilted with respect to the sun, which is why the celestial equator (the projection of the earth’s equator onto the cosmic sphere) and the ecliptic (the zodiacal constellations and the apparent path of the sun around the earth) do not align. In the northern hemisphere, because the earth’s axis is tilted, the days are longer during the summer when the sun is high in the sky, the longest day and the sun’s highest point is at the summer solstice; the days are shorter in the winter when the sun is lower in the sky, the shortest day and the sun’s lowest point is at the winter solstice. The fall equinox and the spring equinox occur when the celestial equator and the ecliptic cross, and are when the lengths of the day and the night are equal (figure 2). The celestial pole was fundamental to ancient Chinese astronomy and formed the basis of their cosmological thinking regarding relationships between the microcosmic and the macrocosmic. According to myth, atop the celestial pole was the Imperial Star above the heavenly Central Palace where the sky emperor lived, central to his kingdom of eight surrounding “sky palaces.” This location mirrored the position of the emperor on earth, around whom feudal land-holding practices were modeled as squares within squares based on a nine-square grid. Chinese maps were drawn with the north arrow pointing down. More than likely this was so that the map would be co-ördinated with the emperor’s view looking down on his kingdom. The Imperial Star was the pole star of the Great Bear constellation and is fixed, around which all the other stars revolve. According to Confucian authority, the ruler on earth should govern by the sky emperor’s example: “He who exercises government by means of his virtue may be compared to the pole star, which keeps it place while all the stars turn around it.” 5 The fundamental basis of Chinese cosmology was the relationship between the pole star and the terrestrial horizon, which is divided by the cardinal directions into the four directions of space (figure 3). Each direction of space corresponds to a seasonal palace: the Blue Dragon in the east (spring), the Vermilion Bird in the south (summer), the White Tiger in the west (fall), and the Black Tortoise in the north (winter). This designation dates to an antiquity of at least -14 th century. There are seven hsiu grouped in each of these four equatorial palaces, for a total of twenty- eight houses. The twenty-eight divisions radiate from the pole star like the spokes of an umbrella that intersect the horizon line. 6 The constancy of the Great Bear and the pole star was fundamental to ancient Chinese cosmology. However, when considered over the span of many millennia, the referent pole star the Chinese actually used changed over time due to the “wobble” of the earth’s rotation on its axis. This is known as the precession of the equinoxes and makes one full cycle every 25,920 years. In short, the plane of the celestial equator is always perpendicular to the earth’s axis. The ecliptic, the location of the zodiacal constellations and the apparent path of the sun, always remains the same due to the earth’s orbit around the sun. However, because of the earth’s “wobble” on its axis, the two equinoctial points along the ecliptic, which is where the celestial equator and the ecliptic cross, precess through the constellations of the zodiac. 7 Although the constellation of the Great Bear always appears to circle in the general vicinity above the North Pole, the earth’s axis or celestial pole does not always point to the same star. The effect of the precession on the position of the celestial pole is considerable: in effect, the celestial pole inscribes a large circle that has the pole of the ecliptic at its origin. This astronomical fact was fully recognized by the ancient Chinese as early as the +4 th century. 8 The gnomon was the instrument that the Chinese used to calculate the precession of the equinoxes, to determine latitude in fixing provincial and other territorial boundaries, to construct their calendars, and to determine auspicious times. 9 The sundial was also used to align the earthly with the divine. Sundials were related to the magnetic compass and the diviner’s board ( shih ): the compass for preliminary orientation with the pole star and the diviner’s board to determine auspices (figure 4). Magnetic north changes often with atmospheric conditions, is not exactly in the direction of the celestial pole and can vary from solar north by as much as 33o; however, its use was to preliminarily determine orientation until it could be verified using a gnomon. The Great Bear of this shih is on a rotating round plate that signifies the heavens of the celestial pole, which is on a square plate representing the earth. The square plate of the earth is marked with the eight trigrams of Wen Wang located at the cardinal and inter-cardinal directions, which are said to be in the “world of the senses” arrangement and relate to the real, phenomenal world in which we live; the world perceptible to the senses (figure 6). 10 Divining with the shih , then, relates the cosmological to the real world of persons, sense- perception and occurrences of daily living such as could discerned by the fortunes of the I Ching ( Yih King ). The shih predates the Chinese lo-pan , or Feng Shui geomancer’s compass. The lo-pan is used to determine the orientation of a site and auspicious times for construction. Although the Great Bear center is replaced by a mariner’s compass in the lo-pan , it generally will have all of the divinatory aspects of the shih plus more. The mariner’s compass represents the t’ai chih , or “great origin.” The eight trigrams of the lo-pan are in the arrangement of Fuh-Hi , which are considered to be the more ancient mathematical arrangement as opposed to the later occult arrangement of Wen Wang (figure 6). 11 The trigrams of Fuh-Hi are also known as the “world of thought” arrangement, which is said to show the idealized interchange of yang and yin as cosmic principles and the balance of opposites. 12 The lo-pan uses the Fuh-Hi arrangement of trigrams because the geomantic art of Feng Shui determines auspicious conditions for constructing the earthly world, the architectural operations of which are the product of the imaginative mind. The lo-pan also contains the numbers of the Lo Shu or magic square of three, which is a heavenly diagram that is based on the mathematical operations of the higher intellect and represents the divine condition of the balance of opposites around a central axis. The art of divining is to align the earthly with the cosmic and the lo-pan is the geomancer’s instrument in China. Feng Shui calculations regarding orientation begin with Chinese cosmology and the seasonal palaces at the edge of the terrestrial horizon: the dragon to the east, the phoenix to the south, the tiger to the west and the tortoise to the north. The geomancer’s art of Feng Shui and the lo-pan are related to the heavens and divining with the shih is related to the earth. Both divinational systems describe the earth as a flattened square bowl. The notion of the earth being “square with the world” is an iconology common to most ancient cultures, unique to China is an emphasis on the corner. The Chiu-kung ching (the Classic of the Nine Halls), from the Han Dynasty (202 BC to 220 AD), gives a mythological description of the Chinese landscape with respect to the Five Sacred Mountains of China, which provides a cosmological view of the constructed world that is unique to the Chinese. The Five Sacred Mountains are located at the cardinal directions and the center, while the rivers run diagonally from the corners toward the center at the inter-cardinal directions. The mountains and the rivers that were mentioned in the Chiu-kung ching are actually located in northern China near the capital cities of the Han dynasty. 13 The central mountain acts as a cosmic axis relating the land to the heavens above. The corners of the square would suggest gateways to this cosmic center. In addition to ordering their world as squares within squares based on the nine- square grid, this would suggest an overlying landscape organizing principle based on the inter- cardinal directions. The emphasis on gateways at the inter- cardinal directions is a system of organization that was not manifested in the actual layout of the ancient Chinese city. The diagonal is a cosmological relationship that has to do with the division of space into four quadrants with respect to the cardinal directions: by dividing the square along the diagonal, all within one of each of the four cardinal directions would be within one of the four seasonal palaces. This is a cosmological relationship only—it does not apply to the physical layout of the ancient Chinese city. The ancient Chinese city was based on a nine-square grid oriented along a north-south celestial pole-pointing processional axis with its important official buildings at the north facing south. The country as a whole was conceived as a nine-square grid of squares within ...