In October of 1957 the Soviet Union launched Sputnik, the first man-made object ever to leave the Earth's atmosphere. At the time, Soviet news agency Tass reported that the Soviet Union had won the space race. But in reality the space race was just beginning. Sputnik attained an altitude of 560 miles (900 kilometers) above the earth and a speed of 17,000 miles per hour, circling the earth every hour and a half.
The Soviet Union and the USA had both committed to launching satellites for research as part of the International Geophysical Year(IGY). Delegations of both countries' IGY committees were at a reception at the Soviet Embassy in Washington, D.C. when the news of the launch was received. Dr. Joseph Kaplan, the chairman of the American IGY committee congratulated the Russians on what he called "a remarkable achievement".
Given Sputnik's weight (180 pounds)some American experts at the time speculated that perhaps the rocket which launched Sputnik might also be capable of carrying a nuclear weapon thousands of miles. The fact that Sputnik also overflew the United States seven times a day also raised some concern in Washington. At the time there were calls for an immediate review of US defenses, given the implications of the technological leap ahead by their cold war enemy.
Sputnik transmitted information via radio signals to Soviet scientists for three weeks. The radio signals fascinated both radio enthusiasts and Western scientists.

President Eisenhower was informed of the Soviets success but said that the United States would not rush it's own satellite programs as a result of the Sputnik launch.
In November 1957 Sputnik II was launched with a passenger aboard - a dog called Laika. The flight allowed Soviet scientists to learn much about the prospects for human space travel. At the time, Soviet scientists had reported that Laika had died painlessly after a week in space. In 2002 new evidence revealed however that the dog died from over-heating and panic just a few hours after take-off.
The U.S. program suffered a setback in December 1957 when a rocket carrying a test satellite into space exploded. In February of 1958, the U.S. did finally successfully launch its first satellite into space, 'Explorer'. With both super powers having successfully launched satellites into outer space the space race was now truly on.