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Spherical Earth or Earth's curvature refers to the approximation of the figure of the Earth as a sphere . The earliest documented mention of the concept dates from around the 5th century BC, when it appears in the writings of Greek philosophers. [ 1][ 2] In the 3rd century BC, Hellenistic astronomy established the roughly spherical shape of ...
t. e. In geodesy, the figure of the Earth is the size and shape used to model planet Earth. The kind of figure depends on application, including the precision needed for the model. A spherical Earth is a well-known historical approximation that is satisfactory for geography, astronomy and many other purposes.
It is called planetary geodesy when studying other astronomical bodies, such as planets or circumplanetary systems. [2] Geodesy is an earth science and many consider the study of Earth's shape and gravity to be central to that science. [3] [4] It is also a discipline of applied mathematics. [5] [6]
Globe. Topography globe featuring physical features of the Earth. A globe is a spherical model of Earth, of some other celestial body, or of the celestial sphere. Globes serve purposes similar to maps, but, unlike maps, they do not distort the surface that they portray except to scale it down. A model globe of Earth is called a terrestrial globe.
The geographical centre of Earth is the geometric centre of all land surfaces on Earth. Geometrically defined it is the centroid of all land surfaces within the two dimensions of the Geoid surface which approximates the Earth's outer shape. The term centre of minimum distance [1] specifies the concept more precisely as the domain is the sphere ...
The actual Hill radius for the Earth-Moon pair is on the order of 60,000 km (i.e., extending less than one-sixth the distance of the 378,000 km between the Moon and the Earth). [9] In the Earth-Sun example, the Earth (5.97 × 10 24 kg) orbits the Sun (1.99 × 10 30 kg) at a distance of 149.6 million km, or one astronomical unit (AU). The Hill ...
Earth's inner core is the innermost geologic layer of the planet Earth. It is primarily a solid ball with a radius of about 1,220 km (760 mi), which is about 19% of Earth's radius [0.7% of volume] or 70% of the Moon 's radius. [ 32][ 33] The inner core was discovered in 1936 by Inge Lehmann and is generally composed primarily of iron and some ...
World map. A world map is a map of most or all of the surface of Earth. World maps, because of their scale, must deal with the problem of projection. Maps rendered in two dimensions by necessity distort the display of the three-dimensional surface of the Earth. While this is true of any map, these distortions reach extremes in a world map.