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
Unconverted long-term prisoners in North Korea, and Revised Romanisation for places now in South Korea. Unconverted long-term prisoners Unconverted long-term prisoners is the North Korean term for northern loyalists imprisoned in South Korea who never renounced "Juche". The North Korean government considers them to be "pro-reunification patriotic fighters", while South Korean scholars have described them as "pro-communist spies". In March 1998, South Korean president Kim Dae-jung declared an amnesty for long-term prisoners over the age of 70, as well as some suffering from disease. In February 1999, President Kim declared another amnesty for 17 unconverted long-term prisoners. In 2000, as part of the