Sputnik 1 was the first artificial satellite launched into space by the Soviet Union on October 4, 1957. This small, spherical satellite measured about 58 centimeters in diameter and weighed approximately 83.6 kilograms. It emitted radio signals that could be received on Earth, marking a significant milestone in the Space Race between the United States and the Soviet Union. The launch of Sputnik 1 shocked the world and demonstrated the Soviet Union's advanced technology. It paved the way for future space exploration and led to the development of more complex satellites and missions, including the eventual landing of humans on the Moon during the Apollo program.