Gravitational constant

The Newtonian constant G of gravitation was first measured by Henry Cavendish (Philosophical Transactions 1798). 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. Their faint attraction to other balls placed alongside the beam was detectable by the deflection it caused.

In terms of metric units, the constant of gravitation is:

G = 6.673 x 10^-11 meter³second^-2kilogram^-1.

G plays a fundamental role in General Relativity, appearing in the Einstein equation.

This entry might eventually use a like to Johannes Kepler.