One of the most profound human undertakings of modern times, space exploration has carried instruments and people beyond Earth’s atmosphere into a realm that was largely unknown or understood until recently. The results have been amazing and awe-inspiring: the mountains of the Moon, the phases of Venus, the rings of Saturn, many comets, and more planetary bodies; and in the 21st century the Voyager 1 and 2 probes have gone far enough to leave our Solar System’s heliosphere, making them among the most distant objects still actively studied.
Countries vary in their definitions of what is considered space, from the 50 miles or so above ground acknowledged by most to over 600 miles where the International Space Station orbits. Humans have explored space by living and working for extended periods in orbiting space stations, and uncrewed space probes have landed on the Moon, the planets Venus and Mars, and on several asteroids and a comet.
In addition to the scientific work performed by astronauts and cosmonauts—who are generally salaried employees of NASA or other nations’ space agencies—there is also artistic and cultural activity in outer space. Its manifestations range from signals and other visual representations like Yuri Gagarin’s selfie in space and the image The Blue Marble to drawings and songs (like Chris Hadfield’s cover of Space Oddity on board the ISS) to more permanent installations.