Geocentric model explanation in terms of the Earth's revolution about the sun. In 1838, astronomer Friedrich Wilhelm Bessel measured the parallax of the star 61 Cygni successfully, and disproved Ptolemy's claim that parallax motion did not exist. This finally confirmed the assumptions made by Copernicus, providing accurate, dependable scientific observations, and conclusively displaying how distant stars are from Earth. A geocentric frame is useful for many everyday activities and most laboratory experiments, but is a less appropriate choice for solar system mechanics and space travel. While a heliocentric frame is most useful in those cases, galactic and extragalactic astronomy is easier if
Central bank may incorporate the word "Central" (for example, European Central Bank, Central Bank of Ireland, Central Bank of Brazil). In some countries, particularly in formerly Communist ones, the term national bank may be used to indicate both the monetary authority and the leading banking entity, such as the Soviet Union's Gosbank (state bank). In rare cases, central banks are styled "state" banks such as the State Bank of Pakistan and State Bank of Vietnam. Many countries have state-owned banks or other quasi-government entities that have entirely separate functions, such as financing imports and exports. In other countries, the term national bank