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The gravitational constant, approximately and denoted by letter , is an empirical physical constant involved in the calculation(s) of gravitational force between two bodies. It usually appears in Sir Isaac Newton's law of universal gravitation, and in Albert Einstein's general theory of relativity. It is also known as the universal gravitational constant, Newton's constant, and colloquially as Big G. It should not be confused with "small g" (''g''), which is the local gravitational field of the Earth (equivalent to the free-fall acceleration〔Fundamentals of Physics 8ed, Halliday/Resnick/Walker, ISBN 978-0-470-04618-0 p336〕). ==Laws and constants== According to the law of universal gravitation, the attractive force (''F'') between two bodies is directly proportional to the product of their masses (''m''1 and ''m''2), and inversely proportional to the square of the distance, ''r'', (inverse-square law) between them: : The constant of proportionality, ''G'', is the gravitational constant. The gravitational constant is a physical constant that is difficult to measure with high accuracy.〔. A lengthy, detailed review. See Figure 1 and Table 2 in particular.〕 In SI units, the 2014 CODATA-recommended value of the gravitational constant (with standard uncertainty in parentheses) is: : with relative standard uncertainty . 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「gravitational constant」の詳細全文を読む スポンサード リンク
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