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
Summer term Summer term Summer term is the summer academic term at many British schools and universities and elsewhere in the world. In the UK, 'Summer term' runs from the Easter holiday until the end of the academic year in June or July, and thus corresponds to the Easter term at Cambridge University, and Trinity term at Oxford, Dublin and some other places. 'Summer term' is defined in some UK statutory instruments, such as the Education (Assessment Regulations) (Foundation to Key Stage 3) Order (Northern Ireland) 2007, which says: "summer term" means the period commencing immediately after the Easter holiday and ending