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 Europe do not clearly define the region, but Encarta places the same countries into Central Europe in its individual articles on countries, adding Slovenia in "south central Europe". The German Encyclopaedia "Meyers Grosses Taschenlexikon" ("Meyers Big Pocket Encyclopedia"), 1999, defines Central Europe as the central part of Europe with no precise borders to the East and West. The term is mostly used to denominate the territory between the Schelde to Vistula and from the Danube to the Moravian Gate. Usually the countries considered to be Central European are Austria, Croatia, the Czech Republic, Germany, Hungary, Poland, Slovakia, Slovenia, Switzerland; in the