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The orbital speed of Earth averages about 29.78 km/s (107,200 km/h; 66,600 mph), which is fast enough to travel a distance equal to Earth's diameter, about 12,742 km (7,918 mi), in seven minutes, and the distance from Earth to the Moon, 384,400 km (238,900 mi), in about 3.5 hours.
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).
The Earth's radius is the distance from Earth's center to its surface, about 6,371 km (3,959 mi). While "radius" normally is a characteristic of perfect spheres, the Earth deviates from spherical by only a third of a percent, sufficiently close to treat it as a sphere in many contexts and justifying the term "the radius of the Earth".
Earth's circumference is the distance around Earth. Measured around the equator, it is 40,075.017 km (24,901.461 mi). Measured passing through the poles, the circumference is 40,007.863 km (24,859.734 mi). [1] Treating the Earth as a sphere, its circumference would be its single most important measurement. [2]
Diameter Notes Sources (most suitable unit) (km, with scientific notation) (km, as a power of 10, Logarithmic scale) Earth: 12,756.2 km (equatorial) 1.28×10 4: 4.11: Measurement comprises just the solid part of the Earth; there is no agreed upper boundary for Earth's atmosphere. The geocorona, a layer of UV-luminescent hydrogen atoms, lies at ...
Asteroids with a 1 km (0.62 mi) diameter strike Earth every 500,000 years on average. [17] [18] Large collisions – with 5 km (3 mi) objects – happen approximately once every twenty million years. [19] The last known impact of an object of 10 km (6 mi) or more in diameter was at the Cretaceous–Paleogene extinction event 66 million years ago.
On the basis of the seismic data, the inner core is estimated to be about 1221 km in radius (2442 km in diameter), [5] which is about 19% of the radius of the Earth and 70% of the radius of the Moon. Its volume is about 7.6 billion cubic km (7.6 × 10 18 m 3), which is about 1 ⁄ 146 (0.69%) of the volume of the whole Earth.
For planet Earth, which can be approximated as an oblate spheroid with radii 6 378.1 km and 6 356.8 km, the mean radius is = (( ) ) / = .The equatorial and polar radii of a planet are often denoted and , respectively.