What is the gravitational constant?
Quick Answer
The gravitational constant, usually written as G, is the number used in Newton’s law of gravitation to calculate the strength of gravity. Its value is about 6.674 × 10^-11 in SI units.
The Full Story
The gravitational constant is a universal constant that sets the scale of gravitational attraction in Newton’s law of universal gravitation and in Einstein’s theory of general relativity. Its accepted value is approximately 6.67430 × 10^-11 m^3 kg^-1 s^-2. Because G is so small, gravity is extremely weak between ordinary objects unless one or both are very massive, like planets or stars. It was first introduced in Isaac Newton’s 1687 work Philosophiae Naturalis Principia Mathematica and later measured experimentally by Henry Cavendish in 1798.
Key Facts
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