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
Umbrella term Umbrella term An umbrella term is a popular metaphorical phrase that covers a wide range of concepts belonging to a common category. For example, "cryptology" is an umbrella term that encompasses cryptography and cryptanalysis, among other fields. Similarly, an umbrella organization is a central and coordinating body representing a number of smaller, separate bodies. A blanket term is a closely related word or phrase that is used to describe multiple groups of related things. The degree of relation may vary or have a minimal relationship, but blanket terms often trade specificity for ease of use. In other words, a blanket