<p> The Golden Age of Discovery in Astronomy</p><p>1st revolution (1610-1650) in astronomy: During this short interval, our picture of the universe changed dramatically.  Adoption of the heliocentric model of the Universe  An understanding that the planets were worlds of their own, and might be visited.  The universe contained countless stars and was much vaster and complex than previously imagined. 2nd revolution (1910-1930) in astronomy: During the early years of the 20th century, our view of the Universe changed again.  The theory of relativity was developed, explaining motion and gravity in a profound new way.  Proof that the Milky Way was an “island universe”, one of billions of galaxies in the Universe  The Sun was located well away from the center of the Milky Way Galaxy; implying the solar system was not a preferred location.</p><p> Discovery of the universal expansion, implying that the Universe had an origin in time. In the last 30 years of the 20th century we have experienced a “golden” age of discovery in astronomy. In many ways this period can be considered the 3rd revolution in our view of the Universe. Why ?  Two interrelated reasons, rooted in technological advances prior to and during this era. 1. Access to Space  Allows on-site exploration of the worlds within the solar system.  Permits astronomical observations to be conducted free of the effects of Earth’s atmosphere The first earth-orbiting satellite was launched in 1957, the first successful planetary probe in 1962. 2. The ability to explore the entire electromagnetic spectrum  Technological advances in our ability to collect and detect radiation from high-energy gamma rays to low-energy radio waves has opened up an entire new universe to our investigation. The first celestial radio waves were detected in 1932; radio astronomy became a separate experimental discipline in the 1950s. </p>