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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).
The poles of the dipole are located close to Earth's geographic poles. At the equator of the magnetic field, the magnetic-field strength at the surface is 3.05 × 10 −5 T , with a magnetic dipole moment of 7.79 × 10 22 Am 2 at epoch 2000, decreasing nearly 6% per century (although it still remains stronger than its long time average). [ 145 ]
The North Pole is by definition the northernmost point on the Earth, lying antipodally to the South Pole. It defines geodetic latitude 90° North, as well as the direction of true north. At the North Pole all directions point south; all lines of longitude converge there, so its longitude can be defined as any degree value. No time zone has been ...
Visualization of the ice and snow covering Earth's northern and southern polar regions Northern Hemisphere permafrost (permanently frozen ground) in purple. The polar regions, also called the frigid zones or polar zones, of Earth are Earth's polar ice caps, the regions of the planet that surround its geographical poles (the North and South Poles), lying within the polar circles.
For comparison, Earth's Moon is even less elliptical, with a flattening of less than 1/825, while Jupiter is visibly oblate at about 1/15 and one of Saturn's triaxial moons, Telesto, is highly flattened, with f between 1/3 and 1/2 (meaning that the polar diameter is between 50% and 67% of the equatorial.
The equator is the circle that is equidistant from the North Pole and South Pole. It divides the Earth into the Northern Hemisphere and the Southern Hemisphere. Of the parallels or circles of latitude, it is the longest, and the only 'great circle' (a circle on the surface of the Earth, centered on Earth's center). All the other parallels are ...
Earth bulges slightly at the Equator; its average diameter is 12,742 km (7,918 mi), but the diameter at the equator is about 43 km (27 mi) greater than at the poles. [ 1 ] Sites near the Equator, such as the Guiana Space Centre in Kourou , French Guiana , are good locations for spaceports as they have the fastest rotational speed of any ...
The 45th parallel north is often called the halfway point between the equator and the North Pole, but the true halfway point is 16.0 km (9.9 mi) north of it (approximately between 45°08'36" and 45°08'37") because Earth is an oblate spheroid; that is, it bulges at the equator and is flattened at the poles. [1]