The theoretical foundation for artificial Earth-orbiting satellites dates back over three hundred years, to Isaac Newton's work in developing the theory of gravitation. However, it was not until the early 20th century that Robert Goddard in America and Konstantin Tsiolkovsky in Russia demonstrated the technological foundations that, in the future, would make use of rockets to carry satellites into orbit.
During World War Two, rocket technology advanced dramatically, with systems such as the German V2 commanding great public attention. Yet even the best rocket technology of the 1940's was inadequate to achieve Earth orbit. Even so, in 1945 author Arthur C. Clarke envisioned a network of communications satellites in geosynchronous orbit 22,300 miles above the earth. (Today, satellites in geosynchronous orbit are said to reside in the "Clarke Belt".)
Theory became reality on the evening of October 4, 1957, when the Soviets launched Sputnik 1 into orbit atop an ICBM. Radio listeners around the world monitored signals from Sputnik's one-watt transmitter until its battery became exhausted 18 days later.
The U.S. followed with its own launch of Explorer 1 on January 31, 1958. A succession of Soviet and American launches resulted in larger and more sophisticated satellites reaching orbit. Then, on April 12, 1961 Yuri Gegarin became the first man in orbit aboard the USSR's Vostok 1.
The Space Race accelerated with Russian and American launches into orbit becoming almost routine. And these two countries did not have space to themselves for long. An ever-growing list of nations has added to the traffic in Earth orbit. Today, tens of thousands of man-made objects circle the Earth. Most of these can be categorized as junk, dead satellites, spent rocket boosters, and a variety of fragments, bits, and debris. A typical evening of gazing at the sky will confirm the space around our planet has become surprisingly crowded in a very short time.