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10.16 cm = 1.016 dm – 1 hand used in measuring height of horses (4 inches) 12 cm = 1.2 dm – diameter of a compact disc (CD) (= 120 mm) 15 cm = 1.5 dm – length of a Bic pen with cap on; 22 cm = 2.2 dm – diameter of a typical association football (soccer ball) 30 cm = 3 dm – typical school-use ruler length (= 300 mm)
≡ 4π sr [16] – The solid angle subtended by a sphere at its centre. ≈ 12.566 37 sr: square degree: deg 2; sq.deg.; (°) 2: ≡ (π ⁄ 180) 2 sr: ≈ 0.304 62 × 10 −3 sr: steradian (SI unit) sr The solid angle subtended at the center of a sphere of radius r by a portion of the sphere having an area r 2. A sphere subtends 4π sr. [16 ...
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]
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 planet Earth has a rather slight equatorial bulge; its equatorial diameter is about 43 km (27 mi) greater than its polar diameter, with a difference of about 1 ⁄ 298 of the equatorial diameter. If Earth were scaled down to a globe with an equatorial diameter of 1 metre (3.3 ft), that difference would be only 3 mm (0.12 in).
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 second is readily determined from the Earth's rotation period. Unlike other units, time multiples are not decimal. A second is 1 / 60 of a minute, which is 1 / 60 of an hour, which is 1 / 24 of a day, so a second is 1 / 86 400 of a day.
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).