It is commonly believed that science is the most orderly of human endeavors. After all, the essence of science is the establishment of logical and systematic rules that explain the true order underlying the seeming chaos of nature. In each scientific discipline can be seen the gradual accumulation of knowledge over a period of generations—punctuated by scientific revolutions—and the carefulness with which each scientific advance is fitted into the blocks already laid. Despite this image, it is also commonly believed that scientific discovery is not an orderly process at all, but rather an art. This can be seen clearly in most histories of science: from Galileo Galilei on the Tower of Pisa to James Watson and Francis Crick in the double helix, discovery is described in terms of imaginative genius, and certainly is not to be reduced to a routine.
Thus, although academics and popular writers alike have been willing to forecast the economic and technological future, there is a marked reluctance to predict the course of science itself. Instead, science is regarded as a source of future miracles: the inexhaustible energy source, the interstellar spaceship, or the ultimate bomb.
Cosmic Discovery is a remarkable attempt to penetrate the mists of scientific advance. It first dissects the present course of astronomy, and then attempts to predict its future. It does not seek to forecast scientific advances themselves, but rather the type and scale of progress that can be expected. Martin Harwit is essentially trying to bring a comprehensive planning perspective to both professional astronomers and the governmental funding agencies that largely determine what sort of astronomical research will be done. Perhaps unintentionally, he gives the layman a fascinating glimpse into the stuff of which astronomy is really made.
Harwit spends a good part of his book describing the chief features of past astronomical discoveries, and it quickly becomes clear that in at least one central way, an astronomer’s work is fundamentally different from that of most other scientists. The classical scientific method is a sequence of observation, hypothesis, experimentation, and conclusion. The astronomer must work without perhaps the most important of these steps—experimentation—simply because he is completely removed from what he is studying. The biologist can inject his vaccine into a rat to observe its effect; the astronomer, however, cannot run tests on the stars. At least until space travel advances far beyond its current state, astronomers will essentially be limited to the deductions they can draw from their observations.
The difficulties this poses for astronomy are immense. Consider, for example, the difficulty of proving conclusively that Earth moves around the Sun. An astronomer with godlike powers could make this proof with a few simple experiments; he could, for example, remove the Sun and observe the resulting movements of Earth. Lacking such abilities, astronomers required nearly two centuries to produce direct evidence of Earth’s solar revolution after the theory was put forth by Nicholas Copernicus in 1543. One of the few devices conceived for producing such evidence was through the measurement of a star’s parallax. If Earth actually moved around the Sun (it was reasoned), then stars relatively close to the solar system should appear to move back and forth against the background of more distant stars as Earth moved back and forth around the Sun. (To picture this, a person can hold a finger a foot or so before his eyes, and sway his head back and forth. His eyes become analogous to an observer on Earth moving around the Sun; at the extreme ends of his orbit, or sway, his finger will appear to move against the background.) Unfortunately, no one could measure the parallax of a star—partly because no one had any way of knowing which stars were closest to the solar system (and would thus have the largest parallax), and partly because sufficiently powerful telescopes to measure the tiny variations involved were not built until the nineteenth century.
One of the unsuccessful searchers for parallax, James Bradley of England, found that all of the stars in a given part of the sky appeared to change position slightly when Earth, according to Copernican theory, was moving around the Sun at a right angle to the stars’ location. What Bradley had discovered, in Harwit’s words, was that “just as rain or snow always appear to be coming from the direction in which an...
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