V t = (9.399511 x 10 11) / (3.155693 x 10 7)Ī rough, general figure for the Earth's mean orbital speed is 30 kilometers per second (km/s), or 18½ miles per second (mi/s).Īlso see the Table of Physical Units and Constants. Let v t be the Earth's mean orbital speed as defined based on the tropical year. Let v s be the Earth's mean orbital speed as defined based on the sidereal year. This can result in either of two figures. The Earth's mean orbital speed, in meters per second (m/s), is obtained by dividing this number by the length of the year in seconds. Therefore, the circumference is about 9.399511 x 10 11 m. To get to the sun, we need 0 km/s net velocity, so moving 29.78 km/s relative to Earth To get out of the solar system, we need 42.1 km/s in the direction of Earths motion, so 42.1-29.78 12. This radius is also known as the astronomical unit ( AU), and is about 1.4959787 x 10 11 meters (m). Although sunlight falling on Earth will be slightly more intense today than it is in July, winter will continue unabated. The circumference of the Earth's orbit is approximately 2 pi (6.283185) times the mean radius of its orbit. January 4, 2001- This morning at 5 oclock Eastern Standard time (0900 UT) Earth made its annual closest approach to the Sun - an event astronomers call perihelion.Northerners shouldnt expect any relief from the cold, however. The tropical year is the time it takes for the Earth to revolve once around the sun, as measured between two consecutive March equinoxes. This is approximately 365.2564 mean solar days, or 3.155815 x 10 7 seconds (s). The sidereal year is the time it takes for the Earth to revolve once around the sun with respect to the distant stars.
You can see that the orbit is elliptical, as described earlier, and that the Earth exhibits a tilt (inclination) relative to the plane of its orbit around the sun (plane of the ecliptic).
This is defined in two different ways, based on the sidereal year and the tropical year. Figure 5 below shows the position of the Earth relative to the sun at four times of the year. Earth's mean orbital speed is the average speed at which the Earth revolves around the sun.
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