The ground-based optical telescope is arguably one of the most important scientiœc inventions as it was the œrst to extend the range of our natural senses in exploring the Universe, thereby heralding a new era in scientiœc method aided by technological advances. A modern-day large telescope is also an excellent example of what our civilization does well. In the 400 years since its invention, the collecting area of the optical telescope has increased 100,000 times, and we are now poised to witness a further increase of a factor of 10 (Figure 14.1). Progressively larger and more powerful telescopes have led to numerous discoveries that have shaped our view of the Universe.