Fifty years ago this evening,...

...America's first satellite, Explorer I was launched. Alan Boyle reviews the event here and Jack Kennedy provides links to a couple of videos here.

Explorer 1 gave America a chance to recover some of its confidence and prestige after the Sputnik shock, but there was a scientific payoff as well: The data returned by the satellite showed that Earth was not surrounded by a swarm of killer pebbles, as some scientists had feared. However, the cosmic-ray readings hinted at the existence of bands of radiation surrounding the planet - an unexpected result that led to the discovery of the Van Allen Belts.