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
National Register of Historic Places listings in Central Chicago Chicago architecture. Architect Louis Sullivan's work is represented by the Carson, Pirie, Scott and Company Building, and Auditorium Building. Though Frank Lloyd Wright worked downtown early in his career as an assistant to Sullivan - including work on the James Charnley House - his own work in the central city is represented only by a renovation of the lobby of Daniel Burnham's and John Wellborn Root's Rookery Building. At least three sites relate to the city's role in nationwide retailing. Included also are several religious buildings, six hotels, and four theaters. National Register of Historic Places listings in Central Chicago