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Because humans are mostly confined to the surface of the Earth, historical astronomers were forced to estimate and calculate astronomical data based only on surface observations. The rotation of the Earth, its direction, and its speed were originally calculated by using the North Star, Polaris, which is very close to matching the imaginary line of the Earth's Celestial North Pole. Since Polaris generally remained in the same relative spot in the sky while all the other stars moved around it, astronomers could assume that either the cosmos or the planet was in motion; scientific evidence later proved that the Earth itself was rotating in a counter-clockwise direction. This is shown by the various constellations that surround Polaris; since they move around the sky in a counter-clockwise direction, the Earth itself is seen as rotating counter-clockwise "when viewed looking down on the North Pole" (University of Oklahoma).
These attributes made Polaris a vital part of pre-technological navigation, as True North could almost always be estimated by locating Polaris. By locating the "bucket" of the Big Dipper and following the two pointer stars (Merak and Dubhe), one can easily find Polaris, which is the last star in the "handle" of the Little Dipper. This only works in the Northern Hemisphere of Earth; sailors in the Southern Hemisphere had to use other stars for navigation.
Polaris or North Star is a part of the Little dipper and aligned with the the two stars of the Big Dipper, Merak and Dubhe. Both Little Dipper and Big Dipper appear to move around Polaris a circle if observed at daily at a rate of about one degree per day. This apparent change in position is due to the change of position of the earth in the space. The direction of rotation of earth around the sun is opposite to the apparent direction of rotation of the Little Dipper and Big Dipper around polaris.
The Greek astronomers observed this phenomenon and concluded that the earth is moving. This observation can be made with the naked eye without using any optical aid in a clear sky in the country side where the atmosphere is not illuminated with the artificial lighting. In populated area like cities and big towns, the sky is illuminated so much due to lights that the stars are not generally visible.
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