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A New Age for Telescopes
| Article
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18969 |
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Section : |
NATURAL SCIENCE
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| Issue
Date : |
2 / 1991 |
2,786 Words |
| Author
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Seth Shostak
Seth Shostak, who currently resides in Mountain View,
California, has spent most of his career as a research radio
astronomer. |
A telescope is a simple device, with a construction so obvious that its would-be inventor, the seventeenth-century Dutchman, Hans Lippershey, was refused a patent. But of the many instruments fashioned by man, probably none has more radically altered science and philosophy. Applied to astronomy, the telescope has precipitated many of the most important advances in physics.
In the 400 years since Galileo Galilei first turned a telescope on the heavens, astronomers have continually refined the tool of their livelihood. The Hubble Space Telescope, launched last year, was seen as an advance in astronomical instrumentation as important as the completion of the 200-inch glass giant on Mount Palomar, in 1948 (all sizes in this article refer to lens or mirror diameters). Alas, Hubble's mirror system is flawed and the reality may not equal the promise.
During the 1980s, however, while the space telescope was being built and readied for launch, an unexpected revolution in thinking about ground-based optical telescopes took place. Flawed or not, Hubble was destined to find that its mountain-hugging competition back on earth, rather than being left in the dust, would soon be able to equal, and even surpass, it for many observations.
New technology, primarily the computer, has suddenly made it possible to contemplate telescopes that will make Palomar look positively Lilliputian. Many of the most profound secrets of the universe, now just beyond our reach, will be grasped in the next decade as these mammoth instruments open their eyes to the heavens. The way to build telescopes has changed, and changed radically.
It is a truism unchanged in four centuries: To make a significantly better telescope, you need to make it bigger. In this context, size refers to the lens or mirror that the telescope uses to focus the faint light that comes to us from some distant star or galaxy. But why is bigger better?
To begin with, a larger telescope collects more light. This trivial fact is important. If, for example, we wish to examine the early history of the universe, we have to look at galaxies that are far away. Light from these galaxies has been traveling to us for billions of years, so we view them as they were when the universe was young. Paradoxically, these same galaxies can reveal to us the long-term future of the universal either indefinite expansion or ultimate collapse and
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