Mirror Telescopes

For thousands of years, people have been looking up and wondering about the twinkling lights they see in the night sky, seeing shapes in their configurations, and making up names and stories about them. While the records so far back are sketchy at best, it's believed that the first mirror telescope was invented by Niccola Zucchi in 1616. It was crudely manufactured and imperfectly shaped, and it was another 50 years before Sir Isaac Newton made a practical telescope mirror.

Telescope mirrors are shaped as parabolas to collect the parallel incoming light rays that are emitted by all stars and reflected from planetary bodies and focus them into a single point. The larger the mirror, the more light rays it can collect, and the further can be seen into the universe. Until the mid-twentieth century, astronomers were frustrated in their efforts to increase the power of their telescope mirrors because after a certain point, they would sag and warp under their own weight. Today most large telescope mirrors are made with Pyrex sheet glass for its strength and coated with a reflective material such as aluminum or silver. The solution was to use multiple mirrors to gather the light. Just as this technique was coming into use, scientists began to use molten glass in molds to form larger mirrors.

With advances in computer technology and a technique for combating atmospheric turbulence developed by the US military known as adaptive optics, even clearer images were possible. The next step anticipated in improving images that collect light nearly as far back as the Big Bang are liquid parabolas utilizing mercury.