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Earth radius is the distance from Earth's center to its surface, about 6,371 km (3,959 mi). This length is also used as a unit of distance, especially in astronomy and geology, where it is usually denoted by R⊕.
The ångström or angstrom (IPA: /ˈɔːŋstrəm/); Swedish: [ˈɔŋstrøm]) is a unit of length equal to 10−10 m (one ten-billionth of a metre) or 0.1 nanometre. Its symbol is Å, a letter in theSwedish alphabet.