- The Moon is Earth’s only natural satellite. Its diameter is about one-quarter of Earth’s (comparable to the width of Australia), making it the fifth largest satellite in the Solar System and the largest and most massive relative to its parent planet. It is larger than all known dwarf planets in the Solar System. The Moon is a planetary-mass object with a differentiated rocky body, making it a satellite planet under the geophysical definitions of the term. It lacks any significant atmosphere, hydrosphere, or magnetic field. Its surface gravity is about one-sixth of Earth’s at 0.1654 g—Jupiter’s moon Io is the only satellite in the Solar System known to have a higher surface gravity and density.
- Geography (Wikipedia)
Geography (from Ancient Greek γεωγραφία geōgraphía; combining gê ‘Earth’ and gráphō ‘write’) is the study of the lands, features, inhabitants, and phenomena of Earth. Geography is an all-encompassing discipline that seeks an understanding of Earth and its human and natural complexities—not merely where objects are, but also how they have changed and come to be. While geography is specific to Earth, many concepts can be applied more broadly to other celestial bodies in the field of planetary science. Geography has been called “a bridge between natural science and social science disciplines.”