Daoism has made a tremendous contribution to the development of ancient astronomy and has deepened man's understanding and mastery of the outside world. Daoism holds that the universe is created from emptiness. For example, The Book of the Supreme Venerable Sovereign's Opening of the Heavens ( 太上老君開天經 Taishang Laojun Kaitian Jing ) says that the evolutionary process of the universe is made up of many phases, such as "great origin", "chaotic origin", "supreme beginning", "supreme start", "supreme simplicity", "chaos", "nine palaces", and "original sovereign" (see p. 618, Vol. 34, ''The Daoist Canon'' ( 道藏 Daozang )). Although such a theory is still within the religious intellectual system, it initiates man's understanding of the universe and gestates the sprout of science of the universe. Daoists came to know gradually that the universe has gone through an evolutionary process of growing from small to large. Ge Hong adopts the view that "Pangu created the world" mentioned in Three-Five Calendar ( 三五曆記 Sanwu Liji ) by Xu Zheng of The Three Kingdoms, holding that "before the formation of heaven, earth, the sun and the moon, the universe was in the shape of an egg; chaotic, black and yellow," and that the heaven and earth were not created until Perfect Man Pangu roamed in the universe and created the sun and the moon (see Records of Immortals of the Original Beginning and the Highest Perfection ( 元始上真衆仙記 Yuanshi Shangzhen Zhongxian Ji ), p. 23, vol. 3, in The Daoist Canon). Daoist Theories of the universe developed continuously afterwards. Daoism explains the structure of the universe with the theory of integral heaven, holding that heaven is a ball-shaped shell wrapping the earth, which floats in the ball of heaven in the shape of a board, while the sun, the moon, and stars are attached to the ball of heaven, and that the buoyant force of the "tie of the vital breath" enables heaven and earth not to fall. The famous Daoist Hao Datong of the Complete Perfection Tradition ( 全真道 Quanzhen Dao ) was an expert at calendrics and arithmetic, while Zhao Youqin conducted large-scale research in astronomical physics. The latter studied solar and lunar eclipses and did optical experiments. Some of his experiments and discoveries recorded in his New Book on the Changing Astronomical Phenomena ( 革象新書 Gexiang Xinshu ) were revolutionary in the history of world astronomy.
Daoism holds that constellations in heaven are the abodes of spirits. Also due to the Daoist belief in the theory of correspondence between heaven and man, ancient Daoists devoted a great deal of energy to observing the stars and drawing star charts. The 28 constellations in heaven that signify energy nodes and orientations have caught people's attention ever since the emergence of Daoism. Daoism holds that worship of the Big Dipper could eliminate disasters and get rid of diseases, prolong the life span and achieve longevity. Therefore, in The Daoist Canon, there are a number of Daoist scriptures about prayer to the Big Dipper or concerning the Dipper constellation, and numerous scriptures are illustrated with the star chart of the Big Dipper. Many of the ancient Chinese astronomers and astrologists were Daoists or persons influenced by Daoism, such as Li Chunfeng, Yuan Tiangang, and so on.
Based on the observation and research of the laws of heaven, earth, and the universe, Daoism establishes "calendar of 24 energy nodes" which bears important influence on subsequent Chinese calendars (For details, see p. 438, vol. 28, The Daoist Canon). In The Daoist Canon, there is also a Daoist calendar named "calendar of 28 constellations", a "solar calendar" which is different from that of the government. It prescribes that one year has 12 months and each month has 30 days, and divided a year in half, the first half starting with the Kui constellation and the second with the Jiao constellation. This calendar has major influence on the "calendar of 12 vital breaths" formulated by Shen Kuo.
The characteristics of Daoist cultivation methods determine that Daoists need exact timing when cultivating inner alchemy and outer alchemy. As a result, many Daoists delve into timing techniques so that they make much valuable contribution in this field. One of the early Daoist devotees' major suggestions accepted during the reign of Emperor Aidi of the Han dynasty is that the 100 degree-gradation, which is the gradation standard of the timing instrument "louke", is changed into 120 degree-graduation (see "Biography of Li Xun" in History of the Han). The Daoist Li Lan of the Northern Wei dynasty invented "chenglou" (steelyard timer). After being improved in the Song dynasty, it had been used by the government till the Northern Song dynasty. Tao Hongjing, a famous Daoist of the Southern Dynasties, once designed "natural louke". His reason was, "flowing water can be made into natural louke. Then the twelve hours circulate, and people do not have to wait and watch." (p. 735, vol. 22, The Daoist Canon .) Daoists of the Complete Perfection Tradition even invented some handy timing instruments that are "ingenious, delicate, and simple"(see p.137, vol. 32. The Daoist Canon).