The Earth-Moon system consists of the planet Earth and its only natural satellite, the Moon. The Moon orbits Earth at an average distance of about 238,855 miles (384,400 kilometers) and takes approximately 27.3 days to complete one orbit. This gravitational relationship affects various phenomena, including ocean tides on Earth. The Moon has a significant impact on Earth’s environment and has been a subject of human exploration. The first successful crewed mission to the Moon was Apollo 11 in 1969, when astronauts Neil Armstrong and Buzz Aldrin became the first humans to set foot on its surface.