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In contrast, the Lunar distance (LD or ), or Earth–Moon characteristic distance, is a unit of measure in astronomy. More technically, it is the semi-major axis of the geocentric lunar orbit . The lunar distance is on average approximately 385,000 km (239,000 mi), or 1.28 light-seconds ; this is roughly 30 times Earth's diameter or 9.5 times ...
The Moon is Earth's only natural satellite.It orbits at an average distance of 384,400 km (238,900 mi), about 30 times the diameter of Earth. Tidal forces between Earth and the Moon have synchronized the Moon's orbital period (lunar month) with its rotation period at 29.5 Earth days, causing the same side of the Moon to always face Earth.
[20] [21] The distance continually changes for a number of reasons, but averages 385,000.6 km (239,228.3 mi) between the center of the Earth and the center of the Moon. [22] The orbits of the Moon and planets are integrated numerically along with the orientation of the Moon called physical libration. [23]
Orion took the snapshot around its maximum distance from Earth of 268,563 miles. That's the farthest any human-oriented spacecraft has traveled, beating even Apollo 13's record of 248,655 miles ...
With a mean orbital velocity around the barycentre between the Earth and the Moon, of 1.022 km/s (0.635 miles/s, 2,286 miles/h), [6] the Moon covers a distance approximately its diameter, or about half a degree on the celestial sphere, each hour.
It calculates the Earth's diameter to be 8,000 miles (modern: 7,928 miles), [6] the diameter of the Moon as 2,400 miles (actual ~2,160) [6] and the distance between the Moon and the Earth to be 258,000 miles [6] (now known to vary: 221,500–252,700 miles (356,500–406,700 kilometres). [12]
It is usually quoted as "light-time for unit distance" in tables of astronomical constants, and its currently accepted value is 499.004 786 385(20) s. [3] [4] The mean diameter of Earth is about 0.0425 light-seconds. The average distance between Earth and the Moon (the lunar distance) is about 1.282 light-seconds.
Eratosthenes (c. 276 – c. 194/195 BC), a Greek mathematician who calculated the circumference of the Earth and also the distance from the Earth to the Sun. Hipparchus (c. 190 – c. 120 BC), a Greek mathematician who measured the radii of the Sun and the Moon as well as their distances from the Earth. On the Sizes and Distances