Telescopes and astronomy: A 400-year retrospect and future prospects

The year 2009 has been declared the International Year of Astronomy by the United Nations, to mark the 400th anniversary of the first observation of celestial bodies by means of a telescope, conducted by Galileo Galilei. In this paper the author identifies four milestones in the development of telescopes and relevant technologies during the past 400 years, then discusses each milestone and its subsequent developments. The paper proceeds to describe the telescopes that have been completed in China as well as those that are being developed. The author supports the development of three new telescope projects in China in the next decade. The author offers a summary of the achievements in astronomy over the past 400 years in terms of their close relationship to fundamental theories of astronomy and physics. For the future, the author believes that dark matter and dark energy, especially dark energy, should be the most important field of research.