Reaching for the Stars
The life and work of Copernicus, Tycho, Galileo and Kepler
In previous articles of this series we talked about the geocentric universe, one that had the Earth at its centre, and how this concept dominated scientific thinking for seventeen centuries. It would take the brilliant mind of Nicolaus Copernicus to upset Aristotle’s and Ptolemy’s geocentric universe.
Born into a prosperous family, Copernicus lived most of his life in Warmia, Prussia, now part of Poland. He learned several languages and wrote most of his works in Latin, the language of science in his time. Copernicus was a true polymath. He obtained degrees in Church Law and worked as physician, classics scholar, governor, diplomat and economist. In economics he developed the quantity theory of money which became the philosophical basis of Milton Friedman’s work on monetarism in the twentieth century. At the age of eighteen Copernicus enrolled in the University of Krakow where he became a pupil of Polish mathematician, astronomer and Aristotelian scholar Albert Brudzewski. The publication in 1543 of Copernicus’ work Revolutions of the Heavenly Spheres is the beginning of two centuries of profound transformations in mathematics, astronomy, physics, biology and chemistry. The work of Copernicus marks the beginning of the scientific revolution.
Copernicus’ starting point was just an intuition that it does not seem natural for thousands of stars to be spinning rapidly around the earth every 24 hours. The far away stars would have to be moving at impossible speeds. It is far more likely that the stars are actually stationary and the earth itself is spinning. Copernicus then developed the concept that the earth and all the other planets orbit around the sun. The sun is the center of the universe and what appears as motion of the sun is actually due to the orbital motion of the earth around the sun. The other planets have a similar orbital motion around the sun. Copernicus developed his theory of the heliocentric universe in 1514 but did not publish it until 1543, the year of his death, fearing condemnation of the Church. When he did publish it, he dedicated the book to the Pope, in an obvious effort to escape condemnation. Though revolutionary for Copernicus’ time, when Church doctrine and scientific beliefs in academia were dominated by Aristotelian ideas, the new concept was not very different from what Aristarchus of Samos had proposed eighteen centuries earlier.
The great English mathematician and philosopher Bertrand Russell wrote in 1945 that Copernicus does not seem to have known of Aristarchus’s heliocentric theory. There is evidence however that Russell is incorrect. The name of Aristarchus does not appear in Copernicus’s published work but it appears several times in the original manuscript which was discovered 300 years after his death. Apparently Copernicus removed two pages before sending the manuscript for publication. The two pages contained references and credits to the heliocentric system of Aristarchus. There is quite some debate about this among scholars but the reason for the removal of the credits by Copernicus is still a mystery. What is important in the work of Copernicus is that man and the earth are dethroned from their cosmological supremacy. Equally important is the fact that the new cosmological paradigm is deeply rooted in ancient Greek astronomy. The contradictions in Ptolemy’s version of the Aristotelian universe are resolved with the restoration and refinement of the Aristarchean universe.
From a scientific point of view this is a smooth evolution of the cosmological paradigm. An evolution that almost follows in textbook fashion the Hegelian dialectic, thesis (Aristarchus), antithesis (Aristotle), synthesis (Copernicus). From a political point of view however, it is a bold revolution against a cosmological concept espoused by Christian theology, where man was created by God and placed on the earth, the centre of the universe.
The new cosmology of Copernicus did not receive immediate recognition. The fear of religious persecution was partly responsible, especially in Catholic countries, where the Inquisition had virtually ended all scientific discovery. But even in Lutheran countries, acceptance of heliocentrism was met with obstacles. Both Luther and Calvin attacked the new theory as being in disagreement with the Scriptures.
Tycho Brahe was a Danish nobleman with a passion for astronomy. Born in 1546, just three years after Copernicus’ death, Tycho was raised by his wealthy and childless uncle and began his university studies at the very young age of 13, studying law, philosophy and various other subjects at the University of Copenhagen. In 1560 Tycho was quite impressed by the fact that a partial solar eclipse had been predicted and happened right on schedule. The predictability of a celestial event against Tycho’s own uncertain life had an impact on young Tycho and inspired him to dedicate his life in the study of astronomy.
A flamboyant and hot-tempered young man, Tycho lost a good chunk of his nose during a duel with a fellow student over who was the best mathematician. For the rest of his life Tycho used a metal nose to cover the disfigurement. His prosthetic nose was made of copper but he had silver and gold noses to wear on special occasions.
Tycho’s uncle died of pneumonia after saving the King of Denmark from drowning. The King showed his gratitude by giving Tycho an entire island and all the resources needed to build an observatory. Tycho married a peasant’s daughter in 1573 and the marriage between a nobleman and a commoner scandalized many of his contemporaries.
Tycho lived an excessive and colorful life and died during a banquet under mysterious circumstances in 1601, at the age of 54. There was a theory that he was poisoned because he had an illicit affair with the Queen of Denmark, an affair that may have inspired Hamlet, the Shakespearean masterpiece of intrigue, infidelity and murder in the court of the Kingdom of Denmark. Another theory said that Kepler murdered Tycho in order to get the extensive records of Tycho’s astronomical observations. These theories of Tycho’s murder have since been discredited but they are characteristic of Tycho’s larger-than-life persona.
Tycho was a master of precision who was never satisfied with the accuracy of astronomical tables available at the time. He built his own instruments for his painstaking observations and measurements and these instruments became the best devices available before the invention of the telescope. Tycho was able to measure celestial distances to a precision of one arcminute, which is one sixtieth of one degree. It is believed that Kepler’s construction of his model of the solar system could not have been possible without Tycho’s astronomical records.
In 1572 Tycho observed a bright star that appeared suddenly in the constellation of Cassiopeia, the familiar star pattern that resembles a sitting woman, the Queen of the night sky. Some observers believed that the new star was a certain unexplained phenomenon in the area between the moon and the earth, as the world of the stars was considered unchangeable, both in the Aristotelian and in the Copernican universe. Tycho had a different opinion, as he noticed that the position of the new star in the sky was not changing as it had to if it were a part of the solar system. Observations over several months convinced Tycho that this was a new star far in the sky, way beyond our planetary system.
Tycho published a book on the new star which we know now that it was an exploding star, or supernova. In the preface of his book Tycho wrote “Oh thick wits. Oh blind watchers of the sky”, referring to those who doubted the significance of his discovery for astronomy. Tycho was quite right, this discovery was very significant in the evolution of our knowledge of the universe, as it shattered the dichotomy between the fixed and immutable heavens and the ever-changing planetary system.
Tycho’s concept of the universe was different from the Copernican system. In Tycho’s system the sun and moon orbited the earth, while the planets orbited the sun. Tycho believed that the idea of a moving Earth would be in violation of physics as well as the Scriptures. It is evident that Tycho’s system retains features from both Aristotle’s geocentric system and the heliocentric system of Copernicus.
For many of Tycho’s contemporaries, his system became a viable compromise of keeping attractive features from both the geocentric and the heliocentric systems. Some scholars argue that Tycho’s system is mathematically equivalent to Copernicus’ system, that is, one can be transformed to the other with a mathematical transformation. Tycho’s geocentrism became the leading theory of his day but its popularity did not last very long. However, the value of his astronomical observations is immense and his contribution to the scientific revolution of his day is undisputed.
One of the most fervent supporters of the Copernican system was the Italian physicist and astronomer Galileo Galilei. Born twenty years after the death of Copernicus, Galileo was destined to start a new scientific revolution and elevate science to a prominent discipline with concepts and methods of a whole philosophical system. Albert Einstein has said that Galileo is the father of modern science. Galileo attended medical school at the University of Pisa but quickly turned into the study of mathematics. While at the university he experimented with pendulums, falling objects and became interested in astronomy. Galileo challenged Aristotle’s assertion that heavy objects fall faster than light ones by dropping balls of various weights from the top of the Leaning Tower of Pisa.
Galileo invented the telescope and used it to make astronomical observations. His observations of the moon revealed that it is not the smooth and perfect sphere believed by Aristotle but has a rugged surface with mountains and craters. Galileo used his telescope to observe the planet Jupiter. He saw three small bright points near Jupiter and initially thought they were distant stars but with subsequent observations he noticed that they had moved to the other side of Jupiter. He concluded that these were moons orbiting Jupiter. The universe was not geocentric after all. There were celestial bodies orbiting other bodies, not the earth.
The discoveries of the moons of Jupiter were initially met with enthusiasm by the top echelons of the Catholic Church but Galileo’s subsequent adoption of the Copernican heliocentric universe took him to a trial before the Inquisition in Rome. Galileo was sentenced to house arrest and was later allowed to retire in his villa near Florence. After 359 years, in 1992, Galileo was finally cleared of heresy and pardoned by Pope John Paul II with a statement expressing the regret of the Church for the way Galileo had been treated. Galileo became a martyr of objectivity and is probably the only scientist in history who has achieved the status of a popular hero.
With the invention of the telescope Galileo revolutionized astronomy. His experiments on motion, falling bodies and trajectories prepared the ground for the development of classical mechanics by Isaac Newton. Apart from his discoveries and his championing of Copernican cosmology, Galileo’s importance is in the revival of science and the scientific method. Galileo’s method has its roots in Aristotle’s scientific work but Galileo laid the foundations of the modern scientific method with his innovative combinations of mathematics and experiment.
The life of Galileo set the stage for a new cultural movement of intellectuals. A movement that emphasized reason and individualism rather than dogma and tradition. The new movement swept Europe like a huge tidal wave and marked the beginning of the scientific revolution and the beginning of the Age of Enlightenment.
Galileo had many successors and the most prominent one, Johannes Kepler, was to play an important role in the refinement and widespread acceptance of the Copernican universe. Kepler was born in 1571 in Weil der Stadt, a small town near Stuttgart. He was born prematurely and was weak and sickly as a child but impressed everyone around him with his phenomenal mathematical abilities. His parents struggled to make ends meet but they managed to foster young Kepler’s intellectual interests and to provide him with a good education.
Kepler attended the University of Tubingen where he studied theology, philosophy, languages and science. It was at Tubingen where Kepler was introduced to Copernican cosmology. Kepler achieved an immortal position in the history of astronomy with his three laws of planetary motion. The first two were published in 1609 and the third ten years later. The first law states: The orbit of a planet is an ellipse and the sun occupies one focus of the ellipse. The second law states: The line joining the planet to the sun sweeps out equal areas in equal times. The third law states: The square of the orbital period of the planet is proportional to the cube of its average distance from the sun.
Let us now make a mental detour and think about what many people say today about the relativity theory and quantum physics: that they are not intuitive. I will have much more to say about this in another article. If we think about elliptical orbits of planets we must admit that in Kepler’s time they were counter-intuitive as well. This is probably why circular orbits, both in the Aristarchean-Copernican and in the Aristotelian-Ptolemaic universe, stood the test of time for so long. The circle is a perfect shape and circular orbits satisfied common sense and aesthetic values. We have here an important epistemological issue about the nature of intuition: is intuition an inherent ability of the mind or is it empirical, shaped over time by new sensations and new experiences? How does intuition affect our ability to acquire new knowledge?
The counter-intuitiveness of Kepler’s first law would be an impediment to its wide acceptance but this is a problem with all bold discoveries in science. The second law is equally shocking: the planet does not orbit the sun with a constant velocity. This is not elegant at all, all notions of balance and aesthetic symmetry are shattered. The planet moves faster at the perihelion, the closest distance from the sun on the elliptical orbit and moves slower at the aphelion, the farthest from the sun on the orbit. At all other points on the orbit the planet’s speed is somewhere between these two extremes. While the first two laws deal with each planet separately, the third law affords a basis of comparison of the movements of all planets. It says that the length of a planet’s year and its average distance from the sun have the same mathematical relationship for all planets.
The movements of the planets could now be described in mathematical equations. The value of this accomplishment cannot be overestimated. Mathematicians, physicists and astronomers could now use the equations to discover new relationships and explain phenomena that could not be explained before. One such person was Isaac Newton, who developed his theories of motion and gravitation and then used these theories to derive Kepler’s laws. This was an astonishing confirmation of Kepler’s heliocentric cosmology, as well as Newton’s own theory. Newton went further and used his theory and Kepler’s laws to explain the trajectories of comets, the tides, the precession of equinoxes and other planetary phenomena.
