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The average of the true solar day during the course of an entire year is the mean solar day, which contains 86,400 mean solar seconds. Currently, each of these seconds is slightly longer than an SI second because Earth's mean solar day is now slightly longer than it was during the 19th century due to tidal friction. The average length of the ...
Because Earth's solar day is now slightly longer than it was during the 19th century due to tidal deceleration, each day varies between 0 and 2 ms longer than the mean solar day. [157] [158] Earth's rotation period relative to the fixed stars, called its stellar day by the International Earth Rotation and Reference Systems Service (IERS), is ...
Geology (from Ancient Greek γῆ (gê) 'earth' and λoγία (-logía) 'study of, discourse') [ 1 ][ 2 ] is a branch of natural science concerned with the Earth and other astronomical objects, the rocks of which they are composed, and the processes by which they change over time. [ 3 ]
Earth Day is an annual event on April 22 to demonstrate support for environmental protection. First held on April 22, 1970, it now includes a wide range of events coordinated globally by EARTHDAY.ORG (formerly Earth Day Network) [ 1 ] including 1 billion people in more than 193 countries. [ 2 ][ 1 ][ 3 ] In 1969 at a UNESCO Conference in San ...
The history of Earth is divided into four great eons, starting 4,540 mya with the formation of the planet. Each eon saw the most significant changes in Earth's composition, climate and life. Each eon is subsequently divided into eras, which in turn are divided into periods, which are further divided into epochs. Eon.
The latitude of the circle is approximately the angle between the Equator and the circle, with the angle's vertex at Earth's centre. The Equator is at 0°, and the North Pole and South Pole are at 90° north and 90° south, respectively. The Equator is the longest circle of latitude and is the only circle of latitude which also is a great circle.
One complete orbit takes 365.256 days (1 sidereal year), during which time Earth has traveled 940 million km (584 million mi). [2] Ignoring the influence of other Solar System bodies, Earth's orbit, also called Earth's revolution, is an ellipse with the Earth–Sun barycenter as one focus with a current eccentricity of 0.0167. Since this value ...
The Earth phase, Terra phase, terrestrial phase, or phase of Earth, is the shape of the directly sunlit portion of Earth as viewed from the Moon (or elsewhere extraterrestrially). From the Moon, the Earth phases gradually and cyclically change over the period of a synodic month (about 29.53 days), as the orbital positions of the Moon around ...