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|Football spot-fixing claims: three held by police|
|UK flights return to normal after air traffic control glitch|
|India's Congress party suffers local election 'meltdown'|
|Nelson Mandela: national day of prayer for country's 'guiding light'|
|Ukip councillor Victoria Ayling defends immigration video remarks|
|German president boycotts Sochi Winter Olympics|
|Thailand opposition to quit parliament|
|Police launch new investigation into football match-fixing claims|
|Susan Boyle: 'I have Asperger's'|
|Most seal pups feared dead in storm surge found to have survived|
|Ofsted chief says England's schools failing white working-class children|
|MPs' 9% pay rise set to embarrass party leaders|
|South Korea extends its air defence zone to overlap with China's|
|Prince Harry's race to the South Pole abandoned for safety reasons|
|Greek parliament approves budget projecting sliver of growth|
|Boat race protester Trenton Oldfield's wife asks UK not to punish their child|
|William Hague letter brings hope to Shaker Aamer in Guantánamo|
|The Observer's faces of 2013|
Astronomy is one of the oldest sciences. Prehistoric cultures left behind astronomical artifacts such as the Egyptian monuments, Nubian monuments and Stonehenge, and early civilizations such as the Babylonians, Greeks, Chinese, Indians, Iranians and Maya performed methodical observations of the night sky.
However, the invention of the telescope was required before astronomy was able to develop into a modern science. Historically, astronomy has included disciplines as diverse as astrometry, celestial navigation, observational astronomy, the making of calendars, and astrology, but professional astronomy is nowadays often considered to be synonymous with astrophysics. During the 20th century, the field of professional astronomy split into observational and theoretical branches.
Observational astronomy is focused on acquiring data from observations of celestial objects, which is then analyzed using basic principles of physics. Theoretical astronomy is oriented towards the development of computer or analytical models to describe astronomical objects and phenomena. The two fields complement each other, with theoretical astronomy seeking to explain the observational results, and observations being used to confirm theoretical results.