The Copernican Revolution

The story of Copernican Revolution is the classic example of a major shift in worldview. So, before exploring what is happening in the present day and where it may be leading us, let us first go back and briefly recap the salient features of this earlier revolution. The parallels between what happened then and what may be about to happen now will begin a journey that will take us far beyond the current worldview to a startling new vision of reality that has far-reaching repercussions for both science and religion. We may be standing on the threshold of changes even more fundamental and far-reaching than those initiated by Copernicus.

The Geocentric Universe

Five hundred years ago, as the Middle Ages began to give way to the Renaissance, the reality within which most people lived and conducted their affairs was one in which human beings played a pre-eminent role; everything revolved around man, both physically and in God's eyes. The Old Testament story of Genesis was taken as historical fact. God had created the Earth and the Heavens around. Man (and to a lesser extent woman) was the focus of God's attention.

The model of the cosmos was still that formulated by the Greek philosopher Ptolemy around 140 AD. The sun, moon, planets and stars all revolved around the earth in circular orbits. Back then, everyone “knew” that the earth stood still at the center of the universe. But there were problems with this model. Although the stars move smoothly through the heavens along fixed circular orbits, the planets do not. They wander among the other stars (which is where the term “planet” came from; it means “wanderer” in Greek). Their speed varies, their orbits wobble, and they occasionally reverse their direction of travel -- what is known as "retrograde" motion. At that time it was believed that planetary motion must be based on circles. Plato had argued that heavenly bodies were governed by different laws than those that governed the motion of objects on earth. Heavenly bodies being perfect, displayed perfect motion, and the perfect motion, according to Plato, was circular motion. So how could the planets’ wandering movements be explained in terms of circles?

The best solution astronomers could come up with was to propose a system of epicycles. An epicycle is the path traced out by a point on circle that is itself rolling around another circle. Imagine a wheel rolling along the ground. A point on the rim of the wheel is almost still relative to the ground when it is at the bottom of the wheel, but moving twice the speed of the wheel when it has reached the top. And a point beyond the rim of the wheel would actually be moving backwards when it is at the bottom. So if the planets moved around small circles that themselves rolled along the larger circular orbits then this could explain some of the strange planetary motions.

As more accurate data was collected, it became apparent that simple epicycles could not account for all the irregularities in the planetary motions. So medieval astronomers proposed more complex epicycles -- circles moving along circles moving along circles. And when these failed, added various other oscillations, until the system became very complex indeed.

The Copernican Revolution

This view of the universe, cumbersome as it was, survived, virtually unchallenged, for thirteen hundred years, until the early sixteenth century when the Polish astronomer, Nicolaus Copernicus, put forward a radically different model. The reason the stars appeared to orbit the earth was, he suggested, because the earth itself was moving, rotating on its own axis once every twenty-four hours. The apparent movement of the heavens was an illusion, caused by the movement of the observer.

Suggesting that the earth moved was heresy enough. But Copernicus went on to argue that the wandering motion of the planets could be explained if they were orbiting the sun rather than the earth. This led to the theory that the earth was itself just another planet also in orbit around the sun. (This was not a totally new theory. A little know Greek philosopher, Aristarchus, had advanced the idea that the earth and the other planets moved around the sun in 270 BC. If his views, rather than those of Plato and Ptolemy, had held sway, history might have taken a very different course.)

Being a distinguished churchman, Copernicus knew the views of the Vatican on the earth's all important position at the center of the universe, and how tenaciously it held to that view. In proposing his theory, he was not just challenging orthodox science; he was challenging the established religious view of reality -- which in those days held even greater sway than the scientific view. So, fearing the wrath of the church, he kept his ideas to himself for thirty years. Only as he was nearing death, and feeling that he did not want to take this important knowledge with him to the grave, did he finally decide to publish his little book On the Revolutions of the Celestial Spheres. When it was eventually published, in 1543, (Copernicus first saw a copy on the day he died) it was immediately placed on the papal index of forbidden books.

So it remained, ignored and forgotten, for nearly eighty years, until the Italian scientist Galileo Galilei took up an interest in planetary motions. Utilizing the newly invented telescope, he found convincing evidence in favor of the Copernican model. He saw that Venus had phases, just like the moon, when only half, or just a crescent, of it would be lit -- which is what would happen if Venus orbited the sun. He also found that Jupiter had its own moons in orbit around it, dispelling the idea that everything went around the earth.

After publishing his findings, Galileo was contacted by Pope Paul V, who demanded he retract his heretical ideas. Fearing for his life, he did so. But a few years later, unhappy that so important a truth should remain suppressed, he published a brilliantly composed dialogue in which he defended and supported the Copernican theory. Again, under threat of torture, he was forced to "abjure, curse, and detest" the absurd view that the earth moves around the sun. He was then put under house-arrest so that he could be watched and prevented from causing any further trouble -- and remained there till his death.

At the same time as Galileo was making his critical observations of the planets, a German mathematician, Johannes Kepler, was putting into place another key piece of the puzzle. Copernicus had argued that the sun, not the earth, lay at the center of things, but he still adhered to the Platonic ideal of circular motion, and although his model explained planetary movements much better than the old geocentric model, there were still unexplained irregularities, which Copernicus tried to account for with various epicycles. Kepler had the good fortune to be a student of the Danish astronomer Tycho Brahe, who had accumulated volumes of accurate astronomical observations. Brahe set Kepler to work on the motion of Mars, the planet with the most troublesome orbit. Kepler’s breakthrough was the discovery that the movements of Mars, and all the other planets, could be accounted for, without any need for epicycles, if their orbits were ellipses rather than circles. But as to why the orbits should be circles rather than ellipses, he had no idea.

The final piece of the puzzle was put in place some 50 years later by the English mathematician, Sir Isaac Newton. He realized that heavenly bodies were governed by exactly the same laws as earthly objects; the force that causes an apple to fall is the same force that holds the moon in its orbit around the earth. Working out the resulting equations of motion he established that any orbiting body would indeed move in an ellipse -- just as Kepler had discovered.

The revolution was now complete. The journey had been started by Copernicus, but putting it all together had involved other equally significant breakthroughs in thinking, and had taken nearly 150 years to complete. (Although it was not until 1992 that the Vatican finally admitted Galileo been right.)


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