Gravity and Gravitation - The History Of Gravity, Newtonian Gravity, General Relativity
mass object pair proportional
Gravity is a force of attraction that exists between every pair of objects in the Universe. This force is proportional to the mass of each object in each pair, and inversely proportional to the square of the distance between the two; thus,
where m1 is the mass of the first object, m2 is the mass of the second object, r is the distance between their centers, and G is a fixed number termed the gravitational constant. (If m1 and m2 are given in kilograms and r in meters, then G = 6.673 × 10-11N m2/kg2.)
Additional Topics
Aristotle's model of the Universe also included the Moon, Sun, the visible planets, and the fixed stars. Aristotle assumed that these were outside the layer of fire and were made of a fifth element, the ether or quintessence (the term is derived from the Latin expression quinta essentia, or fifth essence, used by Aristotle's medieval translators). The celestial bodies circled the Ear…
Newton's universal law of gravitation states that all objects in the Universe attract all other objects. Thus the Sun attracts Earth, Earth attracts the Sun, Earth attracts a book, a book attracts Earth, the book attracts the desk, and so on. The gravitational pull between small objects, such as molecules and books, is generally negligible; the gravitational pull exerted by larger objects, …
German physicist Albert Einstein (1879–1955) realized that Newton's theory of gravity had problems. He knew, for example, that Mercury's orbit showed unexplained deviations from that predicted by Newton's laws. However, he was worried about a much more serious problem. As the force between two objects depends on the distance between them, if one object moves closer, the…
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