Updated June 01, 2013

The Earth-Sun distance, which is 149 million km, on average, varies throughout the year. The Earth passes each semester, alternately, at perihelion, i.e. it is at this point closer to the sun at aphelion, i.e. it is at this point than away from the sun. The difference between these two distances is determined by the **eccentricity**. It is a parameter or **Milanković** or Milanković cycles corresponding to three astronomical phenomena affecting the Earth's **eccentricity**, **obliquity** and **precession**.

These parameters are used in the context of the astronomical theory of paleoclimate. They are partly responsible for natural climate change, whose main consequence, the glacial and interglacial periods. Describes the Earth in space, not a circle but an ellipse, which the Sun occupies one focus, but this ellipse is deformed up to a maximum eccentricity of 0.06. it is currently at 0.016 and the Earth - Sun distance varies from 3%, about 5 million km.

In the solar system, planets have orbits that are all roughly in the same plane, called the **ecliptic**.

The solar energy captured by the Earth is on average during the year of **1367 W/m2**.

This energy varies from 6% between the point closest to the Sun and the furthest point, it varies between 1408 and 1326 W/m2 W/m2. Over time, the eccentricity varies substantially, so that the Earth-Sun distance varies between 129 and 187 million km.

This eccentricity is due to the Sun and the gravitational attraction exerted by other planets. It characterizes the degree of flattening of the ellipse from a circle. It is currently very low, thereby stabilizing the climate. The attraction of the Sun imposes an elliptical motion but the gravitational pull of other planets tends to distort the ellipse slowly.

This eccentricity evolves over time with a period of **412,800 years** and a set of periods of about 100 000 years. There are 128 000 years during the last interglacial period, the eccentricity was close to 0.04 and the energy received by the Earth between the **perihelion** and **aphelion** ranged from approximately 16%.

NB: A high eccentricity decreases the smaller axis (perihelion) and increases the largest axis (aphelion), but does not alter the long axis.

Features of the Earth | Characteristics |

Average orbital radius (1 ua) | 149 597 887,5 km |

Aphelion | 152 097 701 km |

Perihelion | 147 098 074 km |

Orbital Circumference | 9,4×10^{8} km,or 6,283 au |

Orbital eccentricity | 0,016 710 22 |

Sidereal period of revolution | 365,256 96 days |

Mean orbital speed | 29,783 km/s or 107 218,8 km/h |

Orbital inclination | 0° |

Sidereal rotation period (sidereal day) | 0,997 258 days or 23,93419 h |

Speed of rotation (the equator) | 1 674,38 km/h |

Axis inclination | 23,45° |

The eccentricity of the orbit of the planet would have an effect on the fluctuations of the inclination and intensity of the geomagnetic field. This was stated Toshitsugu Yamazaki and Oda Hirokuni, scientists from the Geological Survey of Japan.

The Earth's magnetic field is generated by the motion of liquid metal core, the deep layers of the Earth.

By studying the long-term variations of the magnetic field, the two researchers have examined the magnetic properties of a column of marine sediments, 42 meters long, made over a period of 2.25 million years.

This enabled them to establish the intensity and direction of the magnetic field change with a cycle lasting 100,000 years.

Eccentricity measures the deviation of the Earth's orbit from a circular orbit.

It ranges from 0 for a circular orbit at 1 in a highly elliptical orbit. But the eccentricity of Earth's orbit varies between 0 and 0.06 for every 100 000 years.

They are partly responsible for natural climate changes that have major consequence, the glacial and interglacial periods.

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