ABERRATION OF LIGHT
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Discovery - Aberration of light
In 1725, James Bradley, then a professor Saviliano of Astronomy at the University of Oxford, tried to measure the distance to a star by observing its orientation in two different seasons. The position of the Earth change as they orbit the Sun and, therefore, provides a baseline for the triangulation of the star. To his surprise, found that the fixed stars showed apparent systematic movement, related to the direction of motion of the Earth in its orbit and was not dependent, as anticipated, the position of Earth in space.Concept - Aberration of light
Bradley's discovery, called stellar aberration, is analogous to the situation that occurs when raindrops fall. A drop of rain, though falling vertically with respect to an observer standing on Earth, it falls at an angle to a moving observer. Thus, a particle model of light could explain the stellar aberration easily. Moreover, the wave theory also provides a satisfactory explanation, provided that the ether remains perfectly still when the Earth passing through.The maximum difference between the observed position and the actual position of a star reaches a maximum of 20.47 arcseconds denominating aberration constant. The trigonometric tangent of the constant of aberration is very close to the ratio of Earth's orbital speed to the speed of light (this simple formula is a formula approach to relativistic exact). The phenomenon of aberration of light is used to measure by trigonometry the distance at which there is a star nearby, then called parallax annual basis and defining the unit of interstellar distance, the parsec, defined as the distance is a star which has an annual parallax arc second, equal to 3'2616 light years.