<Tr> <Th> Period </Th> <Td> 96.2 minutes </Td> </Tr> <Tr> <Th> Epoch </Th> <Td> 4 October 1957, 15: 12: 00 UTC </Td> </Tr> <P> Sputnik 1 (/ ˈspʌtnɪk /; "Satellite - 1", or "PS - 1", Prosteyshiy Sputnik - 1, "Elementary Satellite 1") was the first artificial Earth satellite . The Soviet Union launched it into an elliptical low Earth orbit on 4 October 1957 . It was a 58 cm (23 in) diameter polished metal sphere, with four external radio antennas to broadcast radio pulses . It was visible all around the Earth and its radio pulses were detectable . This surprise success precipitated the American Sputnik crisis and triggered the Space Race, a part of the Cold War . The launch ushered in new political, military, technological, and scientific developments . </P> <P> Tracking and studying Sputnik 1 from Earth provided scientists with valuable information, even though the satellite itself wasn't equipped with sensors . The density of the upper atmosphere could be deduced from its drag on the orbit, and the propagation of its radio signals gave information about the ionosphere . </P>

When did the u.s.s.r launch the first satellite to orbit the world