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Celestial mechanics Reference Libraries

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Earth Day
2012-04-23 12:12:49

Earth Day is a day early each year on which events are held to increase awareness and appreciation of the Earth’s natural environment. It is now coordinated worldwide through the Earth Day Network, founded by Dennis Hayes, and is celebrated in more than 175 countries every year. The United Nations designated April 22 as International Mother Earth Day in 2009, and will continue to be held each...

Summer Solstice Midsummer
2011-06-20 11:32:36

The Summer Solstice, or "Midsummer," derived from the Latin sol (sun) and sistere (to stand still), occurs exactly when the Earth's axial tilt is most inclined towards the sun at its maximum of 23° 26'. This is the time when the Sun is at its highest, or most northerly, point in the sky in the Northern Hemisphere. Except in the polar regions, where daylight is continuous for many months...

Astronomy
2014-01-12 00:00:00

Sample Entry: Astronomy is the scientific study of stars, planets, comets, galaxies, and other phenomena that occur outside Earth's atmosphere (e.g. cosmic radiation). Astronomy deals with the evolution, physics, chemical makeup, meteorology, and motion of celestial objects, and also the formation of the universe. The word Astronomy comes from the Greek words astron (meaning "star") and...

Autumnal Equinox
2004-10-19 04:45:44

Autumnal Equinox -- In astronomy, is the equinox at the beginning of autumn in the northern hemisphere: the moment when the sun appears to cross the celestial equator, heading southward. The equinox occurs around September 22-24, varying slightly each year according to the 400 year cycle of leap years in the Gregorian Calendar. In the southern hemisphere, the equinox occurs at the same...

Satellite
2004-10-19 04:45:44

Satellite -- A satellite is an object that orbits another object. With sufficient tangential velocity, the object does not collide with the primary object it orbits, but maintains a distance from that object as the rate at which it falls towards that object is similar to the rate that it travels away, thus the object orbits the primary object and becomes a satellite. In other words:...

Retrograde Motion
2004-10-19 04:45:44

Retrograde Motion -- Retrograde motion is the orbital motion of a body in a direction opposite that which is normal to spatial bodies within a given system. 'Retrograde' derives from the Latin words retro, backwards, and gradus, step. In the Solar system, mostly everything rotates in the same sense: all major planets orbit the Sun counterclockwise as seen from the pole star (Polaris). Most...

Lagrangian Point
2004-10-19 04:45:44

Lagrangian Point -- In Lagrangian mechanics, a Lagrangian point (or L-point) is one of five positions in space where the gravitational fields of two bodies of substantial but differing mass combine to form a point at which a third body of negligible mass would be stationary relative to the two bodies. Bodies at the L-point will not move relative to the parent bodies if they are not...

Keplers Laws of Planetary Motion
2004-10-19 04:45:44

Kepler's Laws of Planetary Motion -- The astronomer Johannes Kepler's main contribution to astronomy was his three laws of planetary motion. Kepler found these laws empirically by studying extensive observations recorded by Tycho Brahe. He found the first two laws in 1609 and the third one in 1618. Isaac Newton was later able to derive the laws from his laws of motion and gravity, thereby...

Planetary Ring
2004-10-19 04:45:42

Planetary Ring -- A planetary ring is a ring of dust and other small particles orbiting around a planet in a flat disc-shaped region. The most spectacular and famous planetary rings are those around Saturn, but all four of the solar system's gas giant planets (Jupiter, Saturn, Uranus, Neptune) possess ring systems of their own. The origin of planetary rings is not precisely known, but...

Orbit
2004-10-19 04:45:42

Orbit -- An orbit is the path that an object makes around another object under the influence of some force. The classical example is that of the solar system, where the Earth, other planets, asteroids, comets, and smaller pieces of rubble are in orbit around the Sun; and moons are in orbit around planets. These days, many artificial satellites are in orbit around the Earth....

Word of the Day
tessitura
  • The prevailing range of a vocal or instrumental part, within which most of the tones lie.
This word is Italian in origin and comes from the Latin 'textura,' web, structure.