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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).
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).
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.
The geographical mile is an international unit of length determined by 1 minute of arc ( 1 / 60 degree) along the Earth's equator. For the international ellipsoid 1924 this equalled 1855.4 metres. [1] The American Practical Navigator 2017 defines the geographical mile as 6,087.08 feet (1,855.342 m). [2]
The MERU, or Milli Earth Rate Unit, is an angular velocity equal to 1/1000 of Earth's rotation rate. It was introduced by MIT's Instrumentation Laboratories (now Draper Labs) to measure the performance of inertial navigation systems. [79] One MERU = 7.292 115 × 10 ^ −8 radians per second [80] or about 0.2625 milliradians/hour.
A nautical mile is a unit of length used in air, marine, and space navigation, and for the definition of territorial waters. [2] [3] [4] Historically, it was defined as the meridian arc length corresponding to one minute ( 1 / 60 of a degree) of latitude at the equator, so that Earth's polar circumference is very near to 21,600 nautical miles (that is 60 minutes × 360 degrees).
The angular velocity of the Earth is defined to be ω = 72.921 15 × 10 −6 rad/s. [11] This leads to several computed parameters such as the polar semi-minor axis b which equals a × (1 − f) = 6 356 752.3142 m, and the first eccentricity squared, e 2 = 6.694 379 990 14 × 10 −3. [11]
cubic centimetre of atmosphere; standard cubic centimetre: cc atm; scc ≡ 1 atm × 1 cm 3 = 0.101 325 J: cubic foot of atmosphere; standard cubic foot: cu ft atm; scf ≡ 1 atm × 1 ft 3 = 2.869 204 480 9344 × 10 3 J: cubic foot of natural gas: ≡ 1000 BTU IT = 1.055 055 852 62 × 10 6 J: cubic yard of atmosphere; standard cubic yard: cu yd ...