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Essays for amateurs and professionals interested in  Science


    the foundation for community access to science Henry Mulder
[1939-2009]
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Henry Mulder
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Rebuilding the Universe - Copernicus Galileo Kepler and Newton
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Image courtesy of NASA


Image courtesy of NASA


Image courtesy of NASA


Image courtesy of NASA


Feature Article
Rebuilding the Universe(ESS16)

Copernicus, Galileo, Kepler and Newton


Written by...

"For, behold, I create new heavens and a new earth: and the former shall not be remembered, nor come into mind."

Isaiah 65:17 KJV


Nicolaus Copernicus
As we have seen, one result of the new spirit of discovery of the 15th century was a new way of looking at the sky. This began with a Polish astronomer Mikolaj Kopernik (better known as Nicolaus Copernicus). He came up with a system, perhaps borrowed from Aristarchus of Samos, that the Sun and not the earth was at the heart of the solar system

Until that time, the prevailing wisdom was based on the system devised by Claudius Ptolemy and the physical structures suggested by Aristotle. This involved the use of as many as fifty-five concentric transparent or crystal spheres all rotating around the earth at varying speeds, carrying along the various heavenly bodies.

Because these explanations had become a part of Scholastic science, the Church of Rome, the only authority that mattered, tended to favor this view of the universe as the only acceptable one. This was no doubt in part because it placed man at the center of a perfect (round) universe permeated by the presence of God.

Copernicus was born on February 19, 1473, in Torun, Poland. He was educated at various universities, including several in Italy among which the University of Bologna. In 1518 he began his seminal work, On the Revolutions of the Celestial Spheres, which was finished by 1530 although not published until 1543, just before his death.

In it he suggested that the earth rotates daily on its axis and revolves yearly around the sun. He also argued that the other planets circle the sun, and that the earth wobbles on its axis like a top as it rotates. Understandably he didn't completely throw out the old system. His theory retained some features including the solid, planet-bearing spheres, and the finite outermost sphere bearing the fixed stars.

But he threw out enough. At a stroke, he took man out of the center of the universe and made him part of the heavenly realm. If you were a god-fearing catholic in the 16th century you can see the problem. First of all it would tamper with the notion that man was the crowning achievement at the center of God's creation and secondly it would place him squarely in the domain reserved for the Almighty himself. Sacrilege!

Galileo Galilei
Now it was all well and good to speculate about how the universe worked but could you prove it? That was a task undertaken by the next suspect in our tale. Galileo was born in Pisa, Italy on February 15, 1564. After a life spent on various ventures including several teaching posts, work on a pendulum and the study of falling bodies, he begins working with a new device, a telescope.

First he studied the moon and discovered that in God's perfect universe the surface of this body was not divinely smooth and even1 but rough and textured. Next he discovers what he decides are four little satellites or moons orbiting Jupiter. Then he spots what would later prove to be the rings around Saturn. All these observations make the idea of a perfect universe with smooth perfect bodies more and more difficult to defend.

Next he discovers the most damning evidence yet when he notices that the planet Venus goes through phases just like the moon. For this to occur, Venus could not possibly be attached to a "crystal" sphere circling the earth. The only logical explanation had to be that the earth and Venus both circled the Sun. In 1611 he begins to study sun spots which had already been observed by others. (Blemishes on the Sun?)

After Copernicus' theories and the observations of Galileo and others have been common knowledge for some time, in February of 1616 the Inquisition in Rome finally takes formal notice of the fact "that the proposition that the Sun is the center of the universe is absurd in philosophy and formally heretical and that the proposition that the Earth has an annual motion is absurd in philosophy and at least erroneous in theology."

Even now very little happens officially and Galileo pretty much carries on as before. A friend and patron of Galileo is elected Pope Urban VIII. The latter even bestows a small pension on Galileo's son. Finally in June 1633, after what can only be described as a tragic comedy of errors, Galileo is formally charged by the Inquisition and forced to recant his views and is condemned to house arrest for the rest of his life.

Johannes Kepler (1571-1630)
One can only speculate about all the political maneuvering that must have taken place around this whole sorry chapter of man's journey into the light. In the rest of Europe, both Copernicus' and Galileo's writings had not gone unnoticed. A number of people had begun to do their own research. One of these was a German by name of Johannes Kepler.

By about 1592 Kepler accepted the Copernican system having learned about it from his instructor, Michael Maestlin. Then a rather fortuitous event ocurred. In 1600 he was invited by Tycho Brahe, the famous eccentric Danish astronomer, to Prague to become his assistant and calculate new orbits for the planets from Tycho's observations. I say fortuitous because Brahe had amassed the largest collection of astronomical observation data ever assembled.

When Brahe died in 1601 Kepler inherited the lot. In 1610 Kepler heard and read about Galileo's discoveries with the telescope. He quickly composed a long letter of support and fired it off to Galileo which by all accounts was greatly appreciated. Then, later that year, he obtained the use of a suitable telescope and set out to confirm all the observations that Galileo had reported. Then in 1619 he published the work for which he is best known.

In it, he describes his ideas about the true elliptical shape of the orbits of the planets. Up till then, Copernicus' belief in circular orbits was still accepted at least by those who agreed with the Copernican system to begin with. Having at his disposal, all of Brahe's highly accurate charts of the movement of the stars and planets, Kepler was able to show that elliptical orbits most closely fit the facts.

Meanwhile all was not well for anyone not completely in tune with the prevailing theological mood in Rome and even in Austria and Germany, Protestants were having their problems with expulsions or worse. Because of these and other difficulties Kepler died, somewhat impoverished, in 1630, 12 years before Galileo's death. Astronomy meanwhile, had made some gigantic strides. For the next and final player in this little drama we turn to England.

Isaac Newton
What had been achieved so far was a clean break from the rather fanciful "crystal" spheres that had been official scientific theory, to a universe which was beginning to look more and more like a giant machine. What was missing was any kind of theory that could successfully explain how this newly minted solar system could actually function. It fell to Isaac Newton to fill in that part of the puzzle.

Newton, a mathematician and physicist and arguably one of the foremost scientific intellects of all time was born into a poor farming family at Woolsthorpe in Lincolnshire, England on December 25, 1642. He was not a good farmer and so was sent to Cambridge to study to become a preacher instead. Most people know that he became something else entirely.

During his life Newton studied and was responsible for an unbelievable amount scientific and mathematical insights. These ranged from the study of optics, motionóleading to his famous three laws, developed the differential calculus (some say along with Gottfried Leibniz) and more importantly for our discussion, universal gravitation.

To understand how that could solve the puzzle, we have to sidetrack a little. In order to explain planetary motion, two forces were needed. One was continued motion in a straight line and the other was some force constantly tugging at the planet which would cause it to curve inward into the elliptical path Kepler had discovered. The straight-line bit was explained by Newton's first law of motion.

A body at rest remains at rest and a body in motion continues to move at a constant velocity unless acted upon by an external force.
The rest could be explained with exquisite elegance by the law of universal gravitation.

Much has been written about how Newton came to discover the idea that all bodies in the universe appeared to ultimately obey the law of gravity. Indeed, this little piece can hardly do justice to the astonishing contribution in many fields that he made to our understanding of how our universe works. It's easy enough to find more information on his many accomplishments including here for example.

For our purposes, we have now completed in a simplified way, a reprise of man's journey out of the dark ages of superstition and magic into the light of rational discovery relating to one of the key elements of our understanding of our world. It was in many ways a perilous journey hampered in no small way, by people who present themselves as custodians of our more noble aspirations.

Will we ever learn?


1 It was an article of faith that anything outside the imperfect earthly realm with its nasty bits would be round, smooth and perfect as was to be expected in the realm of heaven. Imagine the chagrin when one of the first heavenly bodies they looked at was full of crags and craters looking for all the world like another kind of earth.

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