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[1] [7] By comparing the corrected lunar distance with the tabulated values, the navigator finds the Greenwich time for that observation. Knowing Greenwich time and local time, the navigator can work out longitude. [1] Local time can be determined from a sextant observation of the altitude of the Sun or a star.
The average lunar distance is approximately 385,000 km (239,000 mi), or 1.28 light-seconds; this is roughly 30 times Earth's diameter. Around 389 lunar distances make up an astronomical unit (roughly the distance from Earth to the Sun). Lunar distance is commonly used to express the distance to near-Earth object encounters. [1]
Its mass is 1.2% that of the Earth, and its diameter is 3,474 km (2,159 mi), roughly one-quarter of Earth's (about as wide as the contiguous United States). Within the Solar System , it is the largest and most massive satellite in relation to its parent planet , the fifth-largest and fifth-most massive moon overall, and larger and more massive ...
A light-year, alternatively spelled light year (ly or lyr [3]), is a unit of length used to express astronomical distances and is equal to exactly 9 460 730 472 580.8 km, which is approximately 9.46 trillion km or 5.88 trillion mi.
A degree (in full, a degree of arc, arc degree, or arcdegree), usually denoted by ° (the degree symbol), is a measurement of a plane angle in which one full rotation is 360 degrees.
The appropriate decimal places are used, [1] negative values are given using a hyphen-minus character. [2] The designation of a location as, for example [54.1855,-2.9857] means that it is potentially computer searchable and that it can be located by a generally (open) referencing system such as Google Earth or OpenStreetMap .
On March 1, 2009, Chang'e 1 was intentionally impacted on the lunar surface completing the 16-month mission. On October 1, 2010, China launched the Chang'e 2 lunar orbiter. China landed the rover Yutu and the Chang'e 3 lander on the Moon on December 14, 2013, became the third country to have done so. [ 40 ]
Posidonius calculated the Earth's circumference by reference to the position of the star Canopus.As explained by Cleomedes, Posidonius observed Canopus on but never above the horizon at Rhodes, while at Alexandria he saw it ascend as far as 7 + 1 ⁄ 2 degrees above the horizon (the meridian arc between the latitude of the two locales is actually 5 degrees 14 minutes).