Question: Which mountain range separates Kinnaur and Spiti from the country that had many contacts during the Yuan dynasty with the country of the philosopher who accurately described evaporation?

Han-era astronomers adopted a geocentric model of the universe, theorizing that it was shaped like a sphere surrounding the earth in the center. They assumed that the Sun, Moon, and planets were spherical and not disc-shaped. Although others disagreed with his model, Wang Chong accurately described the water cycle of the evaporation of water into clouds. They also thought that the illumination of the Moon and planets was caused by sunlight, that lunar eclipses occurred when the Earth obstructed sunlight falling onto the Moon, and that a solar eclipse occurred when the Moon obstructed sunlight from reaching the Earth. <SEP> Wang Chong (; 27 – c. 100 AD), courtesy name Zhongren (仲任), was a Chinese meteorologist, astronomer, and philosopher active during the Han Dynasty. This book contained many theories involving early sciences of astronomy and meteorology, and Wang Chong was even the first in Chinese history to mention the use of the square-pallet chain pump, which became common in irrigation and public works in China thereafter. He developed a rational, secular, naturalistic and mechanistic account of the world and of human beings and gave a materialistic explanation of the origin of the universe. His main work was the "Lunheng" (論衡, "Critical Essays"). Wang also accurately described the process of the water cycle. <SEP> Other historians also assert that these Ming titles were nominal and did not actually confer the authority that the earlier Yuan titles had. Van Praag writes that the "numerous economically motivated Tibetan missions to the Ming Court are referred to as 'tributary missions' in the Ming Shih." Van Praag writes that these "tributary missions" were simply prompted by China's need for horses from Tibet, since a viable horse market in Mongol lands was closed as a result of incessant conflict. Morris Rossabi also writes that "Tibet, which had extensive contacts with China during the Yuan, scarcely had diplomatic relations with the Ming." The late Turrell V. Wylie, a former professor of the University of Washington, and Li Tieh-tseng argue that the reliability of the heavily censored History of Ming as a credible source on Sino-Tibetan relations is questionable, in the light of modern scholarship. <SEP> the yuan undertook extensive public works. among kublai khan's top engineers and scientists was the astronomer guo shoujing, who was tasked with many public works projects and helped the yuan reform the lunisolar calendar to provide an accuracy of 365.2425 days of the year, which was only 26 seconds off the modern gregorian calendar's measurement. road and water communications were reorganized and improved. to provide against possible famines, granaries were ordered built throughout the empire. the city of beijing was rebuilt with new palace grounds that included artificial lakes, hills and mountains, and parks. during the yuan period, beijing became the terminus of the grand canal of china, which was completely renovated. these commercially oriented improvements encouraged overland and maritime commerce throughout asia and facilitated direct chinese contacts with europe. chinese travelers to the west were able to provide assistance in such areas as hydraulic engineering. contacts with the west also brought the introduction to china of a major food crop, sorghum, along with other foreign food products and methods of preparation. <SEP> the final years of the yuan dynasty were marked by struggle, famine, and bitterness among the populace. in time, kublai khan's successors lost all influence on other mongol lands across asia, while the mongols beyond the middle kingdom saw them as too chinese. gradually, they lost influence in china as well. the reigns of the later yuan emperors were short and marked by intrigues and rivalries. uninterested in administration, they were separated from both the army and the populace, and china was torn by dissension and unrest. outlaws ravaged the country without interference from the weakening yuan armies. <SEP> The name ``Spiti ''means`` The Middle Land'', i.e. the land between Tibet and India. The Spiti Valley is a cold desert mountain valley located high in the Himalaya mountains in the north - eastern part of the Indian state of Himachal Pradesh.