Chapter 55 Chapter 15 The Naive Cosmic Theory

Gaitian theory is the oldest cosmological theory in China.The "Zhou Bi Suan Jing", written in the Han Dynasty, records two stages in the development of Gaitian theory. The old theory of Gaitian holds that the sky is round, like a canopy.The ground is square, like a chessboard.The sky is tilted, and its center is on the north side of people.The sky rotates to the left with this center as the axis, and the sun and the moon are like ants on the lid of a pot. Although they are constantly moving to the right, they still have to move to the left with the sky.The space is full of yin and yang, and the yin is turbid, which cannot be penetrated by human eyes, so the sun enters the yang in the morning and retreats into the yin at night.And there is more yang in summer than in winter, so the days in summer are longer than in winter.

With the continuous expansion of the scope of activities of the ancients, it is difficult to believe that the "square" of the earth is unbelievable, and it is impossible to bridge the circle of the sky and the place.Of course, these are the most untenable places that Old Gaitian said. The new theory of Gaitian believes that both the sky and the earth are round, with the middle high and the surroundings low, the earth is like an inverted plate, and the sky is like a bamboo hat.The top of the hat represents the North Pole, and the sky revolves around the North Pole.While the sun rotates with the sky, it also changes its orbit. It changes six times to the south and six times to the north in a year, so the sun has seven orbits in total.As shown in Figure 19, the sun moves along the internal balance circle at the time of the summer solstice.On the winter solstice, move along the outer balance circle.In terms of correspondence with the twenty-four solar terms, all Zhong Qi moves on the scales from the first scale to the seventh scale, and the sun moves between scales and scales during other solar terms.

Gaitian said that according to the results of the standard shadow measurement, he used the Pythagorean theorem to calculate that the distance between the sky and the earth is 80,000 miles.At the summer solstice, the place where there is no shadow is 119,000 miles away from the geographical North Pole.On the winter solstice, the place where there is no shadow is 238,000 miles away from the geographical North Pole.China is 103,000 miles away from the geographic North Pole.Fig. 20 is a sectional view of the Gaitian structure, which is convenient for readers to understand.

Gaitian also believes that the range of sunlight is limited, and its radius is only 167,000 miles.At the same time, the distance that humans can see is also 167,000 miles, which means that celestial bodies outside this range will not cause visual reactions.Based on this reasoning, the sun should be less than 167,000 miles away from us during the day, and beyond this distance at night. Gaitian said that using this model and data can indeed explain some astronomical phenomena.As shown in Figure 21, the place O (that is, China) where people live is within the inner balance circle. With O as the center, draw a circle with a radius of 167,000 miles, and connect the inner balance, middle balance, and outer balance to A, B, C, and D , E, F points.On the summer solstice day, the sun walks around the inner balance. When the sun reaches point A, it can be seen by people, which is equivalent to sunrise. A is the direction of sunrise for O. The process of the sun moving from A to B is daytime.When the sun passes point B, it is invisible to people, which is equivalent to the sunset. B is the direction of sunset for O, and the process of the sun walking back from B to A is night.The theory of Gaitian successfully explains why the sun appears in the northeast and disappears in the northwest on the summer solstice.And because the distance from A to B is longer than the distance from B to A, the summer solstice has the longest day and the highest temperature.The same explanation applies to the winter solstice.

However, Gaitian said that there are also many unexplainable problems.For example, at the vernal equinox and the autumnal equinox, the sun should be in the due east (ie point C) and not in the due west (ie point D), which is generally good from the picture.But day and night should be equally divided into one day, and the distance from C to D on the picture is almost only 1/3 of the distance from D to C.Furthermore, according to the regulations of Gaitian, the path of the winter solstice (i.e. external balance) is 238,000 miles, which is exactly twice the path of 119,000 miles on the summer solstice (i.e. internal balance), so the sun will travel more on the winter solstice day than on the summer solstice day. Twice the distance, that is to say, the speed of the sun on the winter solstice is twice as fast as that on the summer solstice, which is obviously inconsistent with the astronomical phenomenon.Gaitian said that in fact, he couldn't stand careful scrutiny.