Pendulum experiments still continued to be performed, by Robert von Sterneck (1883, results between 5.0 and 6.3 g/cm 3) and Thomas Corwin Mendenhall (1880, 5.77 g/cm 3). Ĭavendish's experiment proved to result in more reliable measurements than pendulum experiments of the "Schiehallion" (deflection) type or "Peruvian" (period as a function of altitude) type. cm −3, which is actually worse than Cavendish's result, differing from the modern value by 1.5%.Ĭavendish's experiment was first repeated by Ferdinand Reich (1838, 1842, 1853), who found a value of 5.5832(149) g Measurements with pendulums were made by Francesco Carlini (1821, 4.39 g/cm 3), Edward Sabine (1827, 4.77 g/cm 3), Carlo Ignazio Giulio (1841, 4.95 g/cm 3) and George Biddell Airy (1854, 6.6 g/cm 3).
G is quite difficult to measure because gravity is much weaker than other fundamental forces, and an experimental apparatus cannot be separated from the gravitational influence of other bodies. The accuracy of the measured value of G has increased only modestly since the original Cavendish experiment. It is surprisingly accurate, about 1% above the modern value (comparable to the claimed standard uncertainty of 0.6%). In spite of the experimental design being due to Michell, the experiment is now known as the Cavendish experiment for its first successful execution by Cavendish.Ĭavendish's stated aim was the "weighing of Earth", that is, determining the average density of Earth and the Earth's mass. Their faint attraction to other balls placed alongside the beam was detectable by the deflection it caused. He used a horizontal torsion beam with lead balls whose inertia (in relation to the torsion constant) he could tell by timing the beam's oscillation. He determined a value for G implicitly, using a torsion balance invented by the geologist Rev.
The first direct measurement of gravitational attraction between two bodies in the laboratory was performed in 1798, seventy-one years after Newton's death, by Henry Cavendish. L 3 M − 1 T − 2 īased on this, Hutton's 1778 result is equivalent to G ≈ 8 ×10 −11 m 3⋅kg −1⋅s −2.ĭiagram of torsion balance used in the Cavendish experiment performed by Henry Cavendish in 1798, to measure G, with the help of a pulley, large balls hung from a frame were rotated into position next to the small balls.
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