RT @NASAhistory: #OTD in 1957, the International Geophysical Year, which saw the launch of Sputnik and Explorer 1 (pictured), began https://t.co/nj2kNrJezu
RT @NASAhistory: #OTD in 1957, the International Geophysical Year, which saw the launch of Sputnik and Explorer 1 (pictured), began https://t.co/nj2kNrJezu