Earth's orbit

its orbitorbitEarth orbitsEarth-Sun distancemotion of the Earthorbit of the Earth Orbit of Earth distanceEarth revolvesEarth's elliptic motion
All astronomical objects in the Solar System, including the planets like Earth, orbit around the Solar System's centre of mass.wikipedia
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All astronomical objects in the Solar System, including the planets like Earth, orbit around the Solar System's centre of mass.
Earth revolves around the Sun in 365.26 days, a period known as an Earth year.

Astronomical unit

AUastronomical unitsAUs
The average distance between Earth and the Sun is 149.60 million km (92.96 million mi), and one complete orbit takes days (1 sidereal year), during which time Earth has traveled 940 million km (584 million mi).
Earth's orbit around the Sun is an ellipse.


heliocentricheliocentric modelheliocentric theory
Heliocentrism is the scientific model that first placed the Sun at the center of the Solar System and put the planets, including Earth, in its orbit.
While the sphericity of the Earth was widely recognized in Greco-Roman astronomy from at least the 3rd century BC, the Earth's daily rotation and yearly orbit around the Sun was never universally accepted until the Copernican Revolution.


seasonsseasonalfour seasons
This variation in the weather (because of the direction of the Earth's axial tilt) results in the seasons.
On Earth, seasons result from Earth's orbit around the Sun and Earth's axial tilt relative to the ecliptic plane.


ecliptical orbitsecliptic planeplane of the ecliptic
Because of Earth's axial tilt (often known as the obliquity of the ecliptic), the inclination of the Sun's trajectory in the sky (as seen by an observer on Earth's surface) varies over the course of the year.
This plane of reference is coplanar with Earth's orbit around the Sun (and hence the Sun's apparent path around Earth).


autumnal equinoxautumn equinoxequinoxes
By astronomical convention, the four seasons are determined by the solstices (the two points in the Earth's orbit of the maximum tilt of the Earth's axis, toward the Sun or away from the Sun) and the equinoxes (the two points in the Earth's orbit where the Earth's tilted axis and an imaginary line drawn from the Earth to the Sun are exactly perpendicular to one another).
However, because the Moon (and to a lesser extent the other planets) cause the motion of the Earth to vary from a perfect ellipse, the equinox is now officially defined by the Sun's more regular ecliptic longitude rather than by its declination.

Solar time

mean solar timesolar dayapparent solar time
As seen from Earth, the planet's orbital prograde motion makes the Sun appear to move with respect to other stars at a rate of about 1° (or a Sun or Moon diameter every 12 hours) eastward per solar day.
First, Earth's orbit is an ellipse, not a circle, so the Earth moves faster when it is nearest the Sun (perihelion) and slower when it is farthest from the Sun (aphelion) (see Kepler's laws of planetary motion).

Milankovitch cycles

Milankovitch theoryMilankovitchMilankovitch cycle
In modern times, Earth's perihelion occurs around January 3, and the aphelion around July 4 (for other eras, see precession and Milankovitch cycles).
In the 1920s, he hypothesized that variations in eccentricity, axial tilt, and precession of the Earth's orbit resulted in cyclical variation in the solar radiation reaching the Earth, and that this orbital forcing strongly influenced climatic patterns on Earth.

Geocentric orbit

GeocentricEarth orbitorbital
Geocentric orbit – the orbit of any object orbiting the Earth, such as the Moon or an artificial satellite
Earth's orbit

Earth's rotation

rotationrotation of the EarthEarth rotates
Earth's rotation
Earth's orbit


myaMamillion years ago
A year is the orbital period of the Earth moving in its orbit around the Sun.

Stellar parallax

parallax shiftparallaxparallax method
Created by the different orbital positions of Earth, the extremely small observed shift is largest at time intervals of about six months, when Earth arrives at exactly opposite sides of the Sun in its orbit, giving a baseline distance of about two astronomical units between observations.


Morning Starevening starCytherocentric
Orbiting within Earth's orbit, Venus is an inferior planet and never appears to venture far from the Sun; its maximum angular distance from the Sun (elongation) is 47.8°.

Position of the Sun

Sun's positionpositionapparent position
As Earth orbits the Sun over the course of a year, the Sun appears to move with respect to the fixed stars on the celestial sphere, along a circular path called the ecliptic.

Little Ice Age

mini Ice Age1596climate deterioration
Several causes have been proposed: cyclical lows in solar radiation, heightened volcanic activity, changes in the ocean circulation, variations in Earth's orbit and axial tilt (orbital forcing), inherent variability in global climate, and decreases in the human population (for example from the Black Death and the colonization of the Americas).

Stability of the Solar System

Digital Orrerychaotic behavior
The Solar System is stable in human terms, and far beyond, given that it is unlikely any of the planets will collide with each other or be ejected from the system in the next few billion years, and the Earth's orbit will be relatively stable.

Greenhouse and icehouse Earth

greenhousegreenhouse Earthicehouse period
There are five known great glaciations in Earth's climate history; the main factors involved in changes of the paleoclimate are believed to be the concentration of atmospheric carbon dioxide, changes in the Earth's orbit, long-term changes in the solar constant, and oceanic and orogenic changes due to tectonic plate dynamics.

Lunar mansion

30 segmentstwenty-eight subdivisions
Since the Moon's position at given stage will vary according to Earth's position in its own orbit, the lunar mansions are an effective system for keeping track of the passage of seasons.

Tropical year

solar yearmean tropical yearsolar
Because of the precession of the equinoxes, the seasonal cycle does not remain exactly synchronized with the position of the Earth in its orbit around the Sun.

1754 in science

* Immanuel Kant, German philosopher, postulates retardation of Earth's orbit.

2010 TK7

2010 TK 7
is a sub-kilometer near-Earth asteroid and the first Earth trojan discovered; it precedes Earth in its orbit around the Sun.

Sun path

apparent pathsun-pathcomplex path of the Sun
Sun path, sometimes also called day arc, refers to the daily and seasonal arc-like path that the Sun appears to follow across the sky as the Earth rotates and orbits the Sun.

Rømer's determination of the speed of light

speed of lightdemonstrated in 1676light has a finite speed
By timing the eclipses of the Jupiter moon Io, Rømer estimated that light would take about 22 minutes to travel a distance equal to the diameter of Earth's orbit around the Sun.

United States Space Surveillance Network

GEODSSUS Space Surveillance NetworkSpace Surveillance
Correctly map objects travelling in the Earth's orbit;

Campo Imperatore Near-Earth Object Survey

CINEOSCampo ImperatoreCampo Imperatore Observatory
The CINEOS program (Campo Imperatore Near-Earth Object Survey), started in 2001, is dedicated to the discovery and follow-up of near-Earth objects (NEOs), namely asteroids and comets which periodically approach or intersect the Earth's orbit.