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# Earth's orbit

Earth's orbit is the trajectory along which Earth travels around the Sun. [1]

72 relations: Andrey Kolmogorov, Antarctic Circle, Apparent retrograde motion, Apsis, Arctic Circle, Argument of periapsis, Aristarchus of Samos, Astronomical unit, Axial tilt, Barycenter, Carl Friedrich Gauss, Clockwise, Copernican heliocentrism, Copernican Revolution, De revolutionibus orbium coelestium, Diurnal motion, Earth, Earth's rotation, Ecliptic, Epoch (astronomy), Equator, Equinox, Fixed stars, Frequency, Geocentric model, Geocentric orbit, Gravity, Heliocentrism, Henri Poincaré, Hill sphere, Invariable plane, IOP Publishing, Jacques Laskar, Jürgen Moser, Jean Meeus, Joan Blaeu, Joseph-Louis Lagrange, Kilometre, Longitude of the ascending node, Longitude of the periapsis, Lunar distance (astronomy), Milankovitch cycles, Moon, N-body problem, NASA, Nicolaus Copernicus, Orbit, Orbital eccentricity, Orbital inclination, Orbital period, ... Expand index (22 more) »

## Andrey Kolmogorov

Andrey Nikolaevich Kolmogorov (a, 25 April 1903 – 20 October 1987) was a 20th-century Soviet mathematician who made significant contributions to the mathematics of probability theory, topology, intuitionistic logic, turbulence, classical mechanics, algorithmic information theory and computational complexity.

## Antarctic Circle

The Antarctic Circle is the most southerly of the five major circles of latitude that mark maps of the Earth.

Apparent retrograde motion is the apparent motion of a planet in a direction opposite to that of other bodies within its system, as observed from a particular vantage point.

## Apsis

An apsis (ἁψίς; plural apsides, Greek: ἁψῖδες) is an extreme point in the orbit of an object.

## Arctic Circle

The Arctic Circle is the most northerly of the five major circles of latitude as shown on maps of Earth.

## Argument of periapsis

The argument of periapsis (also called argument of perifocus or argument of pericenter), symbolized as ω, is one of the orbital elements of an orbiting body.

## Aristarchus of Samos

Aristarchus of Samos (Ἀρίσταρχος ὁ Σάμιος, Aristarkhos ho Samios; c. 310 – c. 230 BC) was an ancient Greek astronomer and mathematician who presented the first known model that placed the Sun at the center of the known universe with the Earth revolving around it (see Solar system).

## Astronomical unit

The astronomical unit (symbol: au, ua, or AU) is a unit of length, roughly the distance from Earth to the Sun.

## Axial tilt

In astronomy, axial tilt, also known as obliquity, is the angle between an object's rotational axis and its orbital axis, or, equivalently, the angle between its equatorial plane and orbital plane.

## Barycenter

The barycenter (or barycentre; from the Ancient Greek βαρύς heavy + κέντρον centre) is the center of mass of two or more bodies that are orbiting each other, which is the point around which they both orbit.

## Carl Friedrich Gauss

Johann Carl Friedrich Gauss (Gauß; Carolus Fridericus Gauss; 30 April 177723 February 1855) was a German mathematician and physicist who made significant contributions to many fields, including algebra, analysis, astronomy, differential geometry, electrostatics, geodesy, geophysics, magnetic fields, matrix theory, mechanics, number theory, optics and statistics.

## Clockwise

Two-dimensional rotation can occur in two possible directions.

## Copernican heliocentrism

Copernican heliocentrism is the name given to the astronomical model developed by Nicolaus Copernicus and published in 1543.

## Copernican Revolution

The Copernican Revolution was the paradigm shift from the Ptolemaic model of the heavens, which described the cosmos as having Earth stationary at the center of the universe, to the heliocentric model with the Sun at the center of the Solar System.

## De revolutionibus orbium coelestium

De revolutionibus orbium coelestium (On the Revolutions of the Heavenly Spheres) is the seminal work on the heliocentric theory of the Renaissance astronomer Nicolaus Copernicus (1473–1543).

## Diurnal motion

Diurnal motion (lit, from dies, lit. "day") is an astronomical term referring to the apparent daily motion of stars around Earth, or more precisely around the two celestial poles.

## Earth

Earth is the third planet from the Sun and the only astronomical object known to harbor life.

## Earth's rotation

Earth's rotation is the rotation of Planet Earth around its own axis.

## Ecliptic

The ecliptic is the circular path on the celestial sphere that the Sun follows over the course of a year; it is the basis of the ecliptic coordinate system.

## Epoch (astronomy)

In astronomy, an epoch is a moment in time used as a reference point for some time-varying astronomical quantity, such as the celestial coordinates or elliptical orbital elements of a celestial body, because these are subject to perturbations and vary with time.

## Equator

An equator of a rotating spheroid (such as a planet) is its zeroth circle of latitude (parallel).

## Equinox

An equinox is commonly regarded as the moment the plane (extended indefinitely in all directions) of Earth's equator passes through the center of the Sun, which occurs twice each year, around 20 March and 22-23 September.

## Fixed stars

The fixed stars (stellae fixae) comprise the background of astronomical objects that appear to not move relative to each other in the night sky compared to the foreground of Solar System objects that do.

## Frequency

Frequency is the number of occurrences of a repeating event per unit of time.

## Geocentric model

In astronomy, the geocentric model (also known as geocentrism, or the Ptolemaic system) is a superseded description of the universe with Earth at the center.

## Geocentric orbit

A geocentric orbit or Earth orbit involves any object orbiting Planet Earth, such as the Moon or artificial satellites.

## Gravity

Gravity, or gravitation, is a natural phenomenon by which all things with mass or energy—including planets, stars, galaxies, and even light—are brought toward (or gravitate toward) one another.

## Heliocentrism

Heliocentrism is the astronomical model in which the Earth and planets revolve around the Sun at the center of the Solar System.

## Henri Poincaré

Jules Henri Poincaré (29 April 1854 – 17 July 1912) was a French mathematician, theoretical physicist, engineer, and philosopher of science.

## Hill sphere

An astronomical body's Hill sphere is the region in which it dominates the attraction of satellites.

## Invariable plane

The invariable plane of a planetary system, also called Laplace's invariable plane, is the plane passing through its barycenter (center of mass) perpendicular to its angular momentum vector.

## IOP Publishing

IOP Publishing (previously named Institute of Physics Publishing) is the publishing company of the Institute of Physics.

Jacques Laskar (born 28 April 1955 in Paris) is a French astronomer.

## Jürgen Moser

Jürgen Kurt Moser (July 4, 1928 – December 17, 1999) was an award-winning, German-American mathematician, honored for work spanning over 4 decades, including Hamiltonian dynamical systems and partial differential equations.

## Jean Meeus

Jean Meeus (born 12 December 1928) is a Belgian meteorologist and amateur astronomer specializing in celestial mechanics, spherical and mathematical astronomy.

## Joan Blaeu

Joan Blaeu (23 September 1596 – 21 December 1673) was a Dutch cartographer born in Alkmaar, the son of cartographer Willem Blaeu.

## Joseph-Louis Lagrange

Joseph-Louis Lagrange (or;; born Giuseppe Lodovico Lagrangia, Encyclopædia Britannica or Giuseppe Ludovico De la Grange Tournier, Turin, 25 January 1736 – Paris, 10 April 1813; also reported as Giuseppe Luigi Lagrange or Lagrangia) was an Italian Enlightenment Era mathematician and astronomer.

## Kilometre

The kilometre (International spelling as used by the International Bureau of Weights and Measures; SI symbol: km; or) or kilometer (American spelling) is a unit of length in the metric system, equal to one thousand metres (kilo- being the SI prefix for). It is now the measurement unit used officially for expressing distances between geographical places on land in most of the world; notable exceptions are the United States and the road network of the United Kingdom where the statute mile is the official unit used.

## Longitude of the ascending node

The longitude of the ascending node (☊ or Ω) is one of the orbital elements used to specify the orbit of an object in space.

## Longitude of the periapsis

In celestial mechanics, the longitude of the periapsis, also called longitude of the pericenter, of an orbiting body is the longitude (measured from the point of the vernal equinox) at which the periapsis (closest approach to the central body) would occur if the body's orbit inclination were zero.

## Lunar distance (astronomy)

Lunar distance (LD or \Delta_), also called Earth&ndash;Moon distance, Earth–Moon characteristic distance, or distance to the Moon, is a unit of measure in astronomy.

## Milankovitch cycles

Milankovitch cycles describe the collective effects of changes in the Earth's movements on its climate over thousands of years.

## Moon

The Moon is an astronomical body that orbits planet Earth and is Earth's only permanent natural satellite.

## N-body problem

In physics, the -body problem is the problem of predicting the individual motions of a group of celestial objects interacting with each other gravitationally.

## NASA

The National Aeronautics and Space Administration (NASA) is an independent agency of the executive branch of the United States federal government responsible for the civilian space program, as well as aeronautics and aerospace research.

## Nicolaus Copernicus

Nicolaus Copernicus (Mikołaj Kopernik; Nikolaus Kopernikus; Niklas Koppernigk; 19 February 1473 – 24 May 1543) was a Renaissance-era mathematician and astronomer who formulated a model of the universe that placed the Sun rather than the Earth at the center of the universe, likely independently of Aristarchus of Samos, who had formulated such a model some eighteen centuries earlier.

## Orbit

In physics, an orbit is the gravitationally curved trajectory of an object, such as the trajectory of a planet around a star or a natural satellite around a planet.

## Orbital eccentricity

The orbital eccentricity of an astronomical object is a parameter that determines the amount by which its orbit around another body deviates from a perfect circle.

## Orbital inclination

Orbital inclination measures the tilt of an object's orbit around a celestial body.

## Orbital period

The orbital period is the time a given astronomical object takes to complete one orbit around another object, and applies in astronomy usually to planets or asteroids orbiting the Sun, moons orbiting planets, exoplanets orbiting other stars, or binary stars.

## Orbital speed

In gravitationally bound systems, the orbital speed of an astronomical body or object (e.g. planet, moon, artificial satellite, spacecraft, or star) is the speed at which it orbits around either the barycenter or, if the object is much less massive than the largest body in the system, its speed relative to that largest body.

## Perihelion and aphelion

The perihelion of any orbit of a celestial body about the Sun is the point where the body comes nearest to the Sun.

## Pierre-Simon Laplace

Pierre-Simon, marquis de Laplace (23 March 1749 – 5 March 1827) was a French scholar whose work was important to the development of mathematics, statistics, physics and astronomy.

## Polar night

The polar night occurs in the northernmost and southernmost regions of the Earth when the night lasts for more than 24 hours.

## Precession

Precession is a change in the orientation of the rotational axis of a rotating body.

## Ptolemy

Claudius Ptolemy (Κλαύδιος Πτολεμαῖος, Klaúdios Ptolemaîos; Claudius Ptolemaeus) was a Greco-Roman mathematician, astronomer, geographer, astrologer, and poet of a single epigram in the Greek Anthology.

## Random House

Random House is an American book publisher and the largest general-interest paperback publisher in the world.

Retrograde motion in astronomy is, in general, orbital or rotational motion of an object in the direction opposite the rotation of its primary, that is the central object (right figure).

## Satellite

In the context of spaceflight, a satellite is an artificial object which has been intentionally placed into orbit.

## Season

A season is a division of the year marked by changes in weather, ecology, and amount of daylight.

## Secular variation

The secular variation of a time series is its long-term non-periodic variation (see Decomposition of time series).

## Semi-major and semi-minor axes

In geometry, the major axis of an ellipse is its longest diameter: a line segment that runs through the center and both foci, with ends at the widest points of the perimeter.

## Sidereal year

A sidereal year (from Latin sidus "asterism, star") is the time taken by the Earth to orbit the Sun once with respect to the fixed stars.

## Solar System

The Solar SystemCapitalization of the name varies.

## Solar time

Solar time is a calculation of the passage of time based on the position of the Sun in the sky.

## Solstice

A solstice is an event occurring when the Sun appears to reach its most northerly or southerly excursion relative to the celestial equator on the celestial sphere.

## Space station

A space station, also known as an orbital station or an orbital space station, is a spacecraft capable of supporting crewmembers, which is designed to remain in space (most commonly as an artificial satellite in low Earth orbit) for an extended period of time and for other spacecraft to dock.

## Sun

The Sun is the star at the center of the Solar System.

## Tropic of Cancer

The Tropic of Cancer, also referred to as the Northern Tropic, is the most northerly circle of latitude on Earth at which the Sun can be directly overhead.

## Tropic of Capricorn

The Tropic of Capricorn (or the Southern Tropic) is the circle of latitude that contains the subsolar point on the December (or southern) solstice.