Moon the correct values of about 60 and 0.273 respectively. Archimedes (287–212 BC) designed a planetarium that could calculate the motions of the Moon and other objects in the Solar System. During the Middle Ages, before the invention of the telescope, the Moon was increasingly recognised as a sphere, though many believed that it was "perfectly smooth". In 1609, Galileo Galilei drew one of the first telescopic drawings of the Moon in his book and noted that it was not smooth but had mountains and craters. Telescopic mapping of the Moon followed: later in the 17th century, the efforts of Giovanni
Craters of the Moon (geothermal site) of the Moon are the result of hydrothermal eruptions. The pressure of the steam beneath the surface exceeds the pressure exerted by the weight of the overlying ground. This results in an explosion. A mixture of hot water, steam, hot mud and pumice is ejected into the air. Material may be blown up to 100 m, leaving behind holes or craters as deep as 20 m. Hydrothermal eruptions occur about once a year. The openings in the earth surface, where geothermal steam and gases are emitted, are called fumaroles. These vary in size from one centimetre to half a meter