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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).
Paleomagnetic data has been used to calculate that the radius of Earth 400 million years ago was 102 ± 2.8 percent of the present radius. [32] [6] Examinations of data from the Paleozoic and Earth's moment of inertia suggest that there has not been any significant change of Earth's radius during the last 620 million years. [3]
The tangential speed of Earth's rotation at a point on Earth can be approximated by multiplying the speed at the equator by the cosine of the latitude. [42] For example, the Kennedy Space Center is located at latitude 28.59° N, which yields a speed of: cos(28.59°) × 1,674.4 km/h = 1,470.2 km/h.
The inclination of exoplanets or members of multi-star star systems is the angle of the plane of the orbit relative to the plane perpendicular to the line of sight from Earth to the object. [5] An inclination of 0° is a face-on orbit, meaning the plane of the exoplanet's orbit is perpendicular to the line of sight with Earth.
The Hill sphere (gravitational sphere of influence) of the Earth is about 1,500,000 kilometers (0.01 AU) in radius, or approximately four times the average distance to the Moon. [12] [nb 2] This is the maximal distance at which the Earth's gravitational influence is stronger than the more distant Sun and planets. Objects orbiting the Earth must ...
The Earth's rotational rate around its own axis is 15 minutes of arc per minute of time (360 degrees / 24 hours in day); the Earth's rotational rate around the Sun (not entirely constant) is roughly 24 minutes of time per minute of arc (from 24 hours in day), which tracks the annual progression of the Zodiac.
The polar Earth's circumference is simply four times quarter meridian: = The perimeter of a meridian ellipse can also be rewritten in the form of a rectifying circle perimeter, C p = 2πM r. Therefore, the rectifying Earth radius is: = (+) / It can be evaluated as 6 367 449.146 m.
The angles for Earth, Uranus, and Venus are approximately 23°, 97°, and 177° respectively. In astronomy , axial tilt , also known as obliquity , is the angle between an object's rotational axis and its orbital axis, which is the line perpendicular to its orbital plane ; equivalently, it is the angle between its equatorial plane and orbital ...