Further down on this page you can locate the different categories on our site. You can also find the latest additions the links further down on this page.
|David Cameron launches anti-terror task force to tackle extremism|
|Can Crystal Palace rise again?|
|Metropolitan Police commissioner keeps his distance from the press|
|Leaving Leveson up to the courts? That will make things even slower|
|After the McAlpine libel case, maybe we need a time limit on damages|
|The Woolwich footage was grotesque. Our reaction need not be|
|Woolwich murder: three more arrested over killing of Lee Rigby|
|Men charged with endangering plane|
|Woolwich attack: 'Muslims are free of guilt. We had to condemn this killing'|
|What goes on when lightning strikes?|
|Woolwich killing: what made two gang members turn to jihad?|
|Twitter at its worst is not Bercow, but the braying mob | Barbara Ellen|
|Woolwich: this brutal act defies an over-simplistic response | Observer editorial|
|Mass surveillance wouldn't have saved the life of Drummer Rigby | Henry Porter|
|Stop playing a crude numbers game with immigration. We must be open | Will Hutton|
|Terrorism: life-denying ideologies have no place in this country | Nick Cohen|
|The rules | The essential etiquette guide to modern life|
|If there's any justice, prisoners must get the vote | Kevin McKenna|
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.