Sputnik 1

"On Oct. 4, 1957, Sputnik 1 successfully launched and entered Earth's orbit. Thus, began the space age. The successful launch shocked the world, giving the former Soviet Union the distinction of putting the first human-made object into space. The word 'Sputnik' originally meant 'fellow traveler,' but has become synonymous with 'satellite' in modern Russian.

This historic image shows a technician putting the finishing touches on Sputnik 1, humanity's first artificial satellite. The pressurized sphere made of aluminum alloy had five primary scientific objectives: Test the method of placing an artificial satellite into Earth orbit; provide information on the density of the atmosphere by calculating its lifetime in orbit; test radio and optical methods of orbital tracking; determine the effects of radio wave propagation though the atmosphere; and, check principles of pressurization used on the satellites."