Notes on an Outmoded World View |
by Mordecai Plaut|
I think that no one looks at the sky anymore. Astronomers watch the skies, of course, and an occasional poet may still experience the sublime aspect of the heavens, but no one else regards the sky as anything more than a crude predictor of the weather. Simple observation of the heavens, more than a glance yet less than rigorous contemplation, is an archai pursuit these days. Those who can, may watch the earthly limits of their gardens, but precious few attend their heavenly extremes. How many, even among the educated, can discuss the attitude of the skies through the seasons or the changes in the rising and setting of the sun, and how few, even among those who are aware of the phenomena, have attended to the events themselves? Once people notice the daily procession of the sun, the yearly procession of the stars, and the relationship between these two. No more.|
We might speculate on the reasons for this decline. We might list as factors the shift in the focus of life in the past century or so from a rural, agrarian orientation with its heavy dependence on events of skyward origin to our urban society with its concomitant preoccupation with the effects of our own actions, or the grand achievements of science which have mitigated, somewhat, the mystery which formerly attached to the workings of the celestial spheres. We might note, however, that our modern view of the sky provides as more forbidding reason for ignoring the skies. How can we watch the apparent diurnal of the sun across the heavens and its meanderings across the zodiac when we firmly believe that things do not happen that way? How can we bring ourselves to engage in an activity which continually provides apparent evidence against the picture that we have of the solar system?
The Copernican cosmology, which is responsible for the general way in which we view the universe, has proven to be of considerable value. With a clear, fairly simple model it has been able to account for all observations of the relative motions of the planets. Historically, the assumption of the sun as stationary relative to the earth allowed the replacement of the ponderous Ptolemaic system of epicyclical motions with the familial ellipsoidal motion in a structure that is childishly simple in comparison.
The story is usually told as a classic tale of scientific progress. The earth had been accepted as the center of the universe from the time of the Greeks. Working in the fourth century, Ptolemy had given a complete, detailed account of all that was known of planetary motion in his time, using the earth as the primary center of all celestial motion. His Almagest was accepted for over a thousand years as the definitive work on astronomy, although subsequent refinements in observational techniques required some compensating changes in the system that Ptolemy originally elaborated. It is maintained that these changes eventually resulted in a system which became uncomfortably ad hoc until Copernicus' proposal allowed the assimilation of all that was known in one sweepingly elegant structure. This account has recently been exposed as something of a fairy tale by writers on the subject, notably Professor Thomas Kuhn. They note that Copernicus' own system was hardly more accurate than other contemporary systems and, although such things are difficult to measure, that there is no obvious scale upon which his own system could be found simpler than its rivals. Our own modern representation owes much to the refinements of Kepler who was born about a generation after Copernicus' death. Although Kepler owed much to observational data, his works abound in religious symbolism and mystical proofs of a decidedly unscientific character. We mention this only in passing, for our concern is not so much with the causes of the acceptance of Copernicus' ideas as with their effects; not so much with the past as with the future.
The gains which have resulted from the simplification that heliocentrism ultimately allowed have been vast and fundamental. As a leading astronomer of his time, Copernicus had been consulted on the topic of calendar reform, the need for which had been becoming increasingly obvious, but he advised that such changes be postponed, as the calculations could not be done with sufficient accuracy for a permanent calendar. The Gregorian calendar that was adopted about forty years after the publication of Copernicus' monumental work was based on his innovations. To take a modern extreme, travel and research in space were, to some extent, simplified and perhaps in some degree suggested by the use of our heliocentric system. As vicarious participants in that adventure, we may all be said to have gained from that four-hundred-year-old innovation of Copernicus.
Man's flights of fact into space are possibly the greatest and certainly the most dramatic technical achievements that may be credited in part to the Copernican system. The Copernican system's effects in science are equally important, though the drama has dissipated in the course of time. Before Copernicus, and for a considerable period after him, the objects visible in the heavens were thought to be completely different from the everyday things we encounter, and subject to laws of their own. Some of the properties they were said to have were attributed to them for reasons having little to do with their observed behavior, but there was -- in those times -- definite empirical evidence that the laws which governed the activity of the stars and the planets were radically different from those which bind earthbound objects. One had only to make a crude log of their motions to see that their regular paths implied a movement unlike any that can be observed in natural bodies on earth. From the perspective of the time, with the earth as the stationary center of the universe (as it does actually appear), the "fixed" stars trace regular circular paths, while the sun and planets move in daily circles with some gross irregularities against the background of the fixed stars. From the reference frame afforded by those fixed stars, the sun, in addition to its daily progression across the sky, changes its relationship to those stars in a constant direction in its yearly circuit within that portion of the stars known as the zodiac. The planets (wandering stars), in addition to their individual versions of this motion through the zodiac in one general direction, periodically move in an opposite (retrograde) direction vis-a-vis the other stars. The complicated system of epicycles which was used by astronomers to account for the retrograde motion of the planets was intended to display the universal order of the heavens, in that all bodies were shown to move on paths based on the ideal geometrical figure, the circle. This ideal circular motion, even such as it was in the heavens, is not common on the earthly sphere and was, in fact, thought to be largely limited to the heavenly bodies because of their greater perfection. It is still clear that if the motions of the objects in the heavens are described in terms of epicycles, then they are governed by laws which are substantially different from those which determine the behavior of the more immediately familiar terrestrial bodies. In contrast, within the later scheme with the sun as center and the planets describing more or less regular elliptical orbits around it, the way was clear for Newton's astouding (at the time) unification of terrestrial and celestial mechanics. In that system, especially with the laws Kepler was able to formulate within it on planetary motion, there was no longer any obvious reason for supposing that heavenly bodies were at all different in any essential way from those we encounter on earth. Their behavior was no longer described from the ideal circular basis, with the ironic result that it could be represented as a simpler and more regular motion. Subsequently, Newton was able to demonstrate that the characteristics of all motion, in the heavens and on earth, were deducible from a few simple laws. If the earlier system is used to describe planetary motion, the planets' paths are grossly incompatible with what would be expected under Newtonian laws -- although those laws retain their full utility for terrestrial objects. This is an important source of value for the Copernican system to science: that it allows the laws of motion of all observable bodies to be subsumed under one set of laws, a synthesis which remained unchallenged in the Einsteinian critique of Newtonian physics. Before leaving this topic we might point out that the Copernican cosmology removed the obvious distinction between terrestrial and celestial at the price of a nonobvious description of the motion of the latter. The laws which govern familiar objects can be extended to cover heavenly bodies only by supposing that we should observe them differently. We have little choice with earthbound objects since they are given fully to us in situations which we are able to control, but we can (and do) claim that the perspective from which we view the heavens is not the best one and does not show us planetary motions the way they really "are." We will return to this point later. For now we will merely note the contrast between the Ptolemaic and the Copernican systems. The latter allows an obvious explanation of celestial motion though it is forced to use a distinctly unobvious description of that motion, while the former describes motion in the heavens in the obvious way though it provides no obvious explanation of that phenomenon.
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