axis of precession
81Year — A year (from Old English gēar) is the orbital period of the Earth moving around the Sun. For an observer on Earth, this corresponds to the period it takes the Sun to complete one course throughout the zodiac along the ecliptic. In astronomy, the… …
82Frame-dragging — Albert Einstein s theory of general relativity predicts that rotating bodies drag spacetime around themselves in a phenomenon referred to as frame dragging. The rotational frame dragging effect was first derived from the theory of general… …
83Pole shift hypothesis — Polar Shift redirects here. For the Clive Cussler novel, see Polar Shift (novel). For the Antarctica benefit compilation, see Polar Shift (album). This article is about the hypothesis of pole shift in its historical context. For a description of… …
84geoid — geoidal, adj. /jee oyd/, n. 1. an imaginary surface that coincides with mean sea level in the ocean and its extension through the continents. 2. the geometric figure formed by this surface, an ellipsoid flattened at the poles. [1880 85; < Gk… …
85Rotation (mathematics) — Rotation of an object in two dimensions around a point O. In geometry and linear algebra, a rotation is a transformation in a plane or in space that describes the motion of a rigid body around a fixed point. A rotation is different from a… …
86Longitude — For Dava Sobel s book about John Harrison, see Longitude (book). For the adaptation of Sobel s book, see Longitude (TV series). Map of Earth Longitude (λ) Lines of longitude appear vertical with varying curvature in this projection, but are… …
87Hindu calendar — The Hindu calendar used in ancient times has undergone many changes in the process of regionalization, and today there are several regional Indian calendars, as well as an Indian national calendar. Most of these calendars are inherited from a… …
88True polar wander — is a phenomenon in which a planet or moon changes its orientation so that different points become the North and South Poles. This can happen when the two larger moments of inertia are near equal.The Earth is not a true sphere, and therefore has… …
89nutation — nutational, adj. /nooh tay sheuhn, nyooh /, n. 1. an act or instance of nodding one s head, esp. involuntarily or spasmodically. 2. Bot. spontaneous movements of plant parts during growth. 3. Astron. the periodic oscillation observed in the… …
90Foucault pendulum — The Foucault pendulum (pronEng|fuːˈkoʊ foo KOH ), or Foucault s pendulum, named after the French physicist Léon Foucault, was conceived as an experiment to demonstrate the rotation of the Earth.The experimentThe experimental apparatus consists of …
