SPACE EXPLORATION

                SPACE EXPLORATION

MILESTONES IN SPACE EXPLORATION 1957 First Soviet satellite, Sputnik I
1958 First U.S. satellite, Explorer I
1961 First men in space
1963 woman in space
1969 First people on moon
 1969 First Soyuz space station
 1972 Apollo 17, last moon mission


centuries of scientific breakthroughs-from Chinese rockets to Newtonian physicslaid the groundwork for 20th-century spaceflight. Serious impetus took hold in mid-century and played out actively amid Cold War politics, as the Soviet Union and the United States staged a game of orbital one-upmanship, sending satellites and humans into space.Since the end of the Cold War, in- ternational cooperation has largely replaced competition. It has become common for countries to pool re- sources and share technology. Even the most advanced methods of spaceflight cuminue to conform to the basic principles that Newton laic out nearly 400 years ago, however

Every voyage into space, whether manned or unmanned, obeys the law of gravity. Rocketry forms the back- bone of space exploration, and New- ton's third law of motion governs the the L principle behind the rocket: The ac- tion is the high-speed escape of gas through the rocket's nozzle, and the the reaction is the forward movement of
the rocket. In 1957 a Soviet rocket launched the first artificial satellite, om Sputnik I, into space. The United States responded with Explorer the in following year. Once satellites were successful, mid it was only a short wait until the first manned flight into space took place. dogs were enlisted for prelimi- ted ding Various animals, from mice to chimp, to a nary tests. ther Cosmonaut Yuri Gagarin edged e law out Americas onauts with his mack pathbreaking i 1361 Inaugu- dew rating the Apolie program in 1961, the United States took the lead in the s the e ac- moon race in 1969, landing Apollo Il there on July 20. The US remains the sole nation to have accomplished manned extraterrestrial landings.