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Earth radius (denoted as R 🜨 or R E) is the distance from the center of Earth to a point on or near its surface. Approximating the figure of Earth by an Earth spheroid (an oblate ellipsoid), the radius ranges from a maximum (equatorial radius, denoted a) of nearly 6,378 km (3,963 mi) to a minimum (polar radius, denoted b) of nearly 6,357 km (3,950 mi).
Principles. The geologic time scale is a way of representing deep time based on events that have occurred throughout Earth's history, a time span of about 4.54 ± 0.05 Ga (4.54 billion years). [5] It chronologically organises strata, and subsequently time, by observing fundamental changes in stratigraphy that correspond to major geological or ...
The timeline of wars has been split up in the following periods: List of wars: before 1000. List of wars: 1000–1499. List of wars: 1500–1799. List of wars: 1800–1899. List of wars: 1900–1944. List of wars: 1945–1989. List of wars: 1990–2002.
History of the metre. An early definition of the metre was one ten-millionth of the Earth quadrant, the distance from the North Pole to the Equator, measured along a meridian through Paris. The history of the metre starts with the Scientific Revolution that is considered to have begun with Nicolaus Copernicus 's publication of De revolutionibus ...
The geological time scale (GTS), as defined by international convention, [3] depicts the large spans of time from the beginning of the Earth to the present, and its divisions chronicle some definitive events of Earth history. Earth formed around 4.54 billion years ago, approximately one-third the age of the universe, by accretion from the solar ...
Timeline for the day of the September 11 attacks. The hijacked United Airlines Flight 175 approaching the South Tower (left) as the North Tower (right) burns next to it. The September 11 attacks of 2001, in addition to being a unique act of terrorism, constituted a media event on a scale not seen since the advent of civilian global satellite links.
On 7 October 2008, an approximately 4 meter asteroid labeled 2008 TC 3 was tracked for 20 hours as it approached Earth and as it fell through the atmosphere and impacted in Sudan. This was the first time an object was detected before it reached the atmosphere and hundreds of pieces of the meteorite were recovered from the Nubian Desert. [94]
The geological history of the Earth follows the major geological events in Earth's past based on the geological time scale, a system of chronological measurement based on the study of the planet's rock layers (stratigraphy). Earth formed about 4.54 billion years ago by accretion from the solar nebula, a disk-shaped mass of dust and gas left ...