Which spacecraft is acknowledged as marking the true beginnings of the space age in October 1957?

Sputnik I is recognized as marking the true beginnings of the space age because it was the first artificial satellite launched into Earth orbit on October 4, 1957, by the Soviet Union. This event represented a significant milestone in space exploration and sparked a new era of technological competition and interest in space among nations, particularly between the United States and the USSR, which is often referred to as the Space Race. The launch of Sputnik I also had profound effects on science, technology, and education, influencing policies and programs in various countries. Its successful deployment not only demonstrated the feasibility of placing a satellite in orbit but also contributed to advancements in space science and engineering that continue to impact society today.