#### Kerala PSC General Science Book Study Materials Page 653

Book's First PageCarl Sagan (1934-1996, American) could be called "the astronomer of the people". He championed the search for extraterrestrial intelligence, which continues today with a number of missions to Mars to search for signs of life on that planet. Kip Thorne (1940-, American) contributed to the understanding of black holes. Stephen Hawking (1942-, British) is another brilliant mind of the twentieth century. He combined the theory of general relativity and quantum theory in order to prove that black holes emit radiation and eventually evaporate. Despite being completely immobile as a result of Lou Gehrig"s disease, he has written numerous books to bring astronomy, physics, math, and cosmology to the general public. Alan Guth (1940-, American) developed a new theory called the inflationary universe as an addition to the Big Bang Model. Inflation theory predicts that the universe is flat and infinite. INDIAN ASTRONOMERS Aryabhata (476 CE - 550 CE) was the first in the line of great mathematician-astronomers from the classical age of Indian mathematics and Indian astronomy. His works include the Aryabhaṭiya and the Arya-siddhanta. He also worked on the approximation for pi. Varahamihira (505 - 587 CE), was an astronomer, mathematician, and astrologer who lived in Ujjain. In the 6th Century, Indian astronomers proposed that the same force holding objects to the Earth also held the celestial bodies in place. This was an advance upon Anaximander’s idea of equilibrium and recognition of a proto-gravitational theory, long before Newton. Varahamihira proposed that there must be some type of attractive force keeping objects stationary. Brahmagupta (597 - 668 CE) was a mathematician and astronomer who wrote two important works on mathematics and astronomy: the Brahmasphuṭasiddhanta, a theoretical treatise, and the Khaṇḍakhadyaka, a more practical text. Brahmagupta was the first to give rules to compute with zero. In the 7th Century CE, he arrived at a figure of 36000 kilometers for the circumference of the earth, very close to the actual figure. Bhaskara I (600 – 680 CE) was a 7th-century Indian mathematician, who was apparently the first to write numbers in the Hindu decimal system with a circle for the zero, and who gave a unique and remarkable rational approximation of the sine function in his commentary on Aryabhata"s work. Bhaskara II (1114–1185), was an Indian mathematician and astronomer. Using an astronomical model developed by Brahmagupta in the 7th century, he accurately defined many astronomical quantities, including, for example, the length of the sidereal year, the time that is required for the Earth to orbit the Sun, as 365.2588 days which is the same as in Suryasiddhanta. The modern accepted measurement is 365.2563 days, a difference of just 3.5 minutes. UNIVERSE 652

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