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A googol is the large number 10100. In decimal notation, it is written as the digit 1 followed by one hundred 0s: :. The term was coined in 1920 by 9-year-old Milton Sirotta (1911–1981), nephew of American mathematician Edward Kasner.〔 (retrieved March 17, 2015)〕 Kasner popularized the concept in his 1940 book ''Mathematics and the Imagination''.〔 The relevant passage about the googol and googolplex, attributing both of these names to Kasner's nine-year-old nephew, is available in 〕 Other names for googol include ten duotrigintillion on the short scale, ten thousand sexdecillion on the long scale, or ten sexdecilliard on the Peletier long scale. __NOTOC__ == Size == A googol has no special significance in mathematics. However, it is useful when comparing with other very large quantities such as the number of subatomic particles in the visible universe or the number of hypothetical possibilities in a chess game. Kasner used it to illustrate the difference between an unimaginably large number and infinity, and in this role it is sometimes used in teaching mathematics. To give a sense of how big a googol really is, the mass of an electron, just under , can be compared to the mass of the visible universe, estimated at between and .〔(【引用サイトリンク】title=Mass of the Universe )〕 It is a ratio in the order of about 1080 to 1090, still much smaller than the value of a googol. Carl Sagan points out that the total number of elementary particles in the universe is around 1080 (the Eddington number) and that if the whole universe were packed with neutrons so that there would be no empty space anywhere, there would be around 10128. He also notes the similarity of the first calculation to that of Archimedes in The Sand Reckoner. The decay time for a supermassive black hole of roughly 1 galaxy-mass (1011 solar masses) due to Hawking radiation is on the order of 10100 years,.〔Particle emission rates from a black hole: Massless particles from an uncharged, nonrotating hole, Don N. Page, ''Physical Review D'' 13 (1976), pp. 198–206. . See in particular equation (27).〕 Therefore, the heat death of the universe is lower-bounded to occur a googol years in the future. 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Googol」の詳細全文を読む スポンサード リンク
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