was associated with rotation—his invariable plane. Louis Poinsot in 1803 began representing rotations as a line segment perpendicular to the rotation, and elaborated on the "conservation of moments". In 1852 Léon Foucault used a gyroscope in an experiment to display the Earth's rotation. William J. M. Rankine's 1858 Manual of Applied Mechanics defined angular momentum in the modern sense for the first time:...a line whose length is proportional to the magnitude of the angular momentum, and whose direction is perpendicular to the plane of motion of the body and of the fixed point, and such, that when the motion of the body is viewed from the extremity of the line, the radius-vector of the body seems to have right-handed rotation.In an 1872 edition of the same book, Rankine stated that "The term angular momentum was introduced by Mr. Hayward," probably referring to R.B. Hayward's article On a Direct Method of estimating Velocities, Accelerations, and all similar Quantities with respect to Axes moveable in any manner in Space with Applications, which was introduced in 1856, and published in 1864. Rankine was mistaken, as numerous publications feature the term starting in the late 18th to early 19th centuries. However, Hayward's article apparently was the first use of the term and the concept seen by much of the English-speaking world. Before this, angular momentum was typically referred to as "momentum of rotation" in English. See also Footnotes References Further reading . External links "What Do a Submarine, a Rocket and a Football Have in Common? Why the prolate spheroid is the shape for success" (Scientific American, November 8, 2010) Conservation of Angular Momentum – a chapter from an online textbook Angular Momentum in a Collision Process – derivation of the three-dimensional case Angular Momentum and Rolling Motion – more momentum theory Physical quantities Rotation Conservation laws Moment (physics) Angular momentum