Inspired by Isaac Newton’s theory of gravity, Henry Cavendish first discussed the possibility to establish the weight of earth in a letter to his friend John Michell in 1783. Michell proposed using a torsion balance to measure the tiny gravitational pull between metal spheres, an experiment also carried out by French physicist Charles Augustin de Coulomb.
In 1797, Cavendish used Michell’s apparatus to “weigh the earth,” publishing his first results the next year.
And Earth is picking up weight too, packing an extra 100,000 pounds every year from dust and meteoric material, residue of burning fuel, and from salt from ocean spray. Perhaps no wonder Earth is slowing down.