Since 1963 the Arecibo Observatory, largest radio/radar telescope on Earth, has been an internationally acclaimed facility for astronomers and other scientists to learn more about the universe around us. During this time many exciting discoveries have taken place. One of the largest structures in the universe - a clustering of galaxies - was mapped at Arecibo. In observations closer to home, scientists determined the true rotation of the planet Mercury, refuting earlier claims that one side of the planet always faced the sun. During a search for pulsars (rotating neutron stars), the first planets outside the solar system were found. From other pulsar observations came the first evidence of the existence of gravitational waves and an eventual Nobel prize in physics for scientist Joe Taylor and Russell Hulse.