Which was the first artificial satellite launched into space?

The first artificial satellite launched into space was Sputnik I. This historic event occurred on October 4, 1957, when the Soviet Union successfully placed Sputnik I into orbit around the Earth. This satellite marked the beginning of the space age and initiated the space race between the United States and the Soviet Union. Sputnik I was a simple, spherical satellite that transmitted radio signals back to Earth, demonstrating the feasibility of sending objects beyond our planet's atmosphere. Its launch had significant implications for science, technology, and geopolitics, leading to advancements in satellite technology and human space exploration.

The other options also represent significant milestones in space exploration but came after Sputnik I. Skylab, for instance, was the United States' first space station launched in 1973. Explorer I was the first satellite launched by the United States in 1958, and Friendship 7 was the spacecraft that carried John Glenn in orbit around Earth in 1962. However, none of these events occurred before the launch of Sputnik I.