Astronomical calendar

Astronomy is the foundation of the calendar. In the pre-Qin period, people thought that the sky was round and supported by four pillars, east, west, north and south. The sky covered the earth like a hemispherical cover. This is why there are descriptions such as "four poles are abandoned" and "the sky does not overlap" in "Goddess Mending the Sky", while "Chilechuan" says that "the sky is like a vault, and the cage covers four fields". The ancients often used astronomical phenomena to predict personnel, and linked astronomical phenomena with good or bad luck on earth. For example, a comet is a celestial body orbiting the sun with a long tail, and its appearance was considered by the ancients as an omen of military disaster. It is said in "Tang Drama Live Up to its Mission" that "Zhuan Xu's sting also caused a comet to attack the moon", because the moon is the symbol of the vassal, so this astronomical phenomenon is ominous for the vassal. Liao is a military ruler (the king of Wu), and he will be stabbed, so there is such a celestial phenomenon in the world. Through the observation of the moon, people associate the profit and loss of the moon with the gathering and dispersion of people. Countless literati look at the moon to express their feelings and borrow it to send their feelings. Please see "Poor man wandering upstairs on the moon, looking away from the mirror" and "He knows that the dew will frost tonight, and the moonlight at home will be bright! "and" the moon, now at sea, Tianya * * * at this time ". How many human joys and sorrows are contained in these poems.

In order to predict the good or ill fortune of the world with the change of astronomical phenomena, ancient astrologers also called the starry sky area and the state on the ground corresponding to each other, called the "dividing line". In this way, heaven and earth are integrated, and some changes in the sky in a certain area directly indicate the good or ill luck of the corresponding area on the ground. Su Jing is the dividing line of Yongzhou (now most of Gansu and Shaanxi), and Shu Road spans Yizhou and Yongzheng. "Crossing the well" means that the Shu Road is on the extremely high mountains of Yi and Yong countries. People have to look up and touch the stars in the sky before they can cross it.