What is Celestial mechanics?
{{no sources|date=March 2023}} '''Celestial mechanics''' is a part of [[astronomy]] that looks at the movement of the objects in the [[sky]], and tries to find [[Scientific model|models]] to describe and explain these movements. The objects described include [[stars]] and [[planets]], and also [[comets]], and other similar objects. The mathematics of celestial mechanics include [[spherical geometry]], [[trigonometry]] and [[Newton's laws of motion]]. == History == The first known examples of celestial mechanics are from [[Mesopotamia]], around 3000 [[BC]]. The [[Venus tablet of Ammisaduqa]] is a record of observations about the planet [[Venus]]. The tablet also describes the finding that [[Solar eclipse|solar]] and [[lunar eclipse]]s are periodic events. About the same time, ancient Egyptians found the length of the solar year to be 365.25 days. In Europe, this figure was in used until the [[Gregorian calendar]] was introduced in the 16th century. At the same time, [[Eratosthenes]] worked out that the [[Eratosthenes#Circumference of the Earth|radius of the Earth]] was 252.000 stadia, or 50 times the distance between [[Alexandria]] and [[Aswan]]. This value is {{Convert|41750|km}}. It is very close to the real value of {{Convert|40075|km}} at the [[equator]]. In the 2nd century BC, [[Hipparchus]] calculated the distance between the Earth and the Moon to be 30 times the [[diameter]] of the Earth. This value is also very close to the modern one. In the 17th century, [[Johannes Kepler]] observed the motion of planets in the sky. He created [[Kepler's laws|three laws of planetary motion]] that described their orbits. == Related pages == *[[Astrophysics]] [[Category:Celestial mechanics| ]]