What is Space exploration?
[[File:Laika mockup.gif|thumb|Laika the space dog.]] [[File:ALSEP AS11-40-5951.jpg|thumb|Scientific work on the Moon.]] '''Space exploration''' is a term which describes searching [[outer space]]. There are many reasons for space exploration. The most important reasons are for scientific [[research]] and the interest of humans to learn more about outer space. For centuries, [[human]]s had dreamt of reaching outer space. [[Rocket]]s made it possible in the later [[20th century]]. On October 4, 1957, the former [[Soviet Union]] launched the [[Sputnik 1]], which was the first [[artificial satellite]]. This started the [[Space Race]] and people later went into [[orbit]] and Americans visited the [[Moon]] in [[Project Apollo]]. Many [[space probe]]s have gone to various [[planet]]s and other places in the [[Solar System]] to send back information. When people first went to space they didn't know what the effects of microgravity would have on humans so they sent animals instead. But in 1961 the Soviets launched the first human into space, [[Yuri Gagarin]]. The journey to planets is hazardous enough so that humans will probably not be used, and machines can pick up samples. Some people think that Mars can be mined for minerals which are rare and valuable. There are no plans at present to send humans to Mars. == Astronomy == {{Main|Astronomy}} The first [[telescope]] was probably invented in 1608 by [[Hans Lippershey]]. The [[Orbiting Astronomical Observatory 2]] was the first [[space telescope]] launched on December 7, 1968.<ref name=joseph>{{cite book|author=Joseph A. Angelo |title=Spacecraft for Astronomy |url=https://books.google.com/books?id=y8BMepjeciEC&pg=PA20 |year=2014|publisher=Infobase Publishing |isbn=978-1-4381-0896-4|page=20}}</ref> As of February 2, 2019, about 3,891 [[exoplanet]]s have been discovered. The [[Milky Way]] galaxy has more than 100–400 [[billion]] [[star]]s<ref>{{cite web|url=http://asd.gsfc.nasa.gov/blueshift/index.php/2015/07/22/how-many-stars-in-the-milky-way/ |title=How Many Stars