In 1980, U.S. spacecraft Voyager I sent back the first close-up pictures of Saturn. Voyager 1 found that about seven percent of the volume of Saturn’s upper atmosphere is helium while almost all the rest is hydrogen. Learn more at http://voyager.jpl.nasa.gov/science/saturn.html.

In 1981, for the first time, a spacecraft was launched twice. The second Space Shuttle mission was STS-2. Its mission objectives included safe re-launch and return of the crew as well as verification of the performance of the Space Shuttle vehicle. Learn more at http://www.nasa.gov/mission_pages/shuttle/shuttlemissions/archives/sts-2.html.

In 1851, the telescope was patented by Alvan Clark of Cambridge, Massachusetts. Alvan Clark and his two sons had almost no formal training but learned how to build the finest refracting telescopes in the world at that time. Learn more at http://www.oneminuteastronomer.com/66/alvan-clark-master-telescope-maker/.

In 1951, the first long distance telephone call without operator assistance was made. The mayor of Englewood, New Jersey, M. Leslie Downing dialed 10 digits and, eighteen seconds later, reached the mayor of Alameda, California, Frank Osborne. Learn more at http://www.corp.att.com/attlabs/reputation/timeline/51trans.html.

In 1934, astronomer Carl Sagan was born. Carl Sagan was a consultant and adviser to NASA since the 1950s. He briefed the Apollo astronauts before their flights to the Moon, and was an experimenter on the numerous expeditions to the planets.   He hosted the

In 1895, Wilhelm Röntgen discovered x-rays. A week after his discovery, Rontgen took an X-ray photograph of his wife’s hand which clearly revealed her wedding ring and her bones. Learn more at http://inventors.about.com/od/xyzstartinventions/a/x-ray.htm. Photo credit: NASA