history of astronomy

Around 270 BC, Aristarchus of Samos used lunar eclipses and the half-moon angle to calculate the Sun's distance and size — and concluded the Earth orbits the Sun, not the reverse.

Space exploration began on October 4, 1957, when the Soviet Union launched Sputnik 1. In the decades since, humans have walked on the Moon, robots have visited every planet, a space station has been continuously crewed since 2000, and Artemis II sent four astronauts around the Moon in April 2026.