Nicolaus Copernicus Heliocentricity

Man has long since sought to explain the world and the heavens above. In a society in which more and more people live by farming, astronomical knowledge became increasingly important. This is borne out in impressive fashion by the so-called Sky Disk found in Nebra in central Germany, which dates back 3,600 years. But throughout most of history, man has seen himself and his planet as the centre of the universe. It would be a very long time before any other notion could take hold, but when it did, it was revolutionary. The first picture of the world of which we have any knowledge is that of the Babylonians. 5,000 years ago, they described the earth as a disk floating on the universal ocean. From its midst there arose the world mountain. The Babylonians explained the alternation of day and night by postulating that the sun and moon went round this mountain. The earth disk was crisscrossed by the rivers Euphrates, Tigris, Ganges and Nile, and above it all there floated the vault of heaven where the gods moved the stars. The ancient Egyptians placed the Nile in the centre of all things. The world for them had been created when the gods separated heaven and earth. In ancient Greece too, astronomical phenomena were explained at first with the help of mythology. Anaximander of Miletus was the first to draw a map of the world and to construct a celestial globe. He represented the earth as a cylinder in whose depths the underworld was located. Behind the vault of heaven, a huge fire was smouldering. The flames were visible through ventilation holes which appeared to us as the stars. It was not until Aristotle that things took a more scientific turn based on exact observation and logical deduction. For him, the world was a sphere composed of fire, earth, air and water. It was firmly anchored in the midst of the cosmos, but there were many different opinions on how this basic image was to be interpreted in detail. The Greek astronomer Hipparchus assumed that the earth was in the centre of the universe and orbited by the Sun. His picture of the world is thus termed geocentric. The Greek scholar Ptolemy is the best-known representative of the geocentric worldview. His work Almagest sets out the astronomical knowledge of his day. Centuries later, this book was one of those that got into the hands of Nicolaus Copernicus. In his work, Ptolemy states the opinion that the earth is uniquely stationary in the midst of the universe. All the planets, he said, orbit the earth on so-called spheres. These spheres can move independently of each other. The Sun is attached to one of the spheres, the planets each have one of their own, while the outermost sphere is that of the fixed stars. But Ptolemy was unable to produce a tidy explanation for apparent irregularities in the planetary movements. More than a thousand years later and 15th century Europe was in a state of intellectual upheaval. Two decisive events were driving developments. The invention of printing with movable type by Johannes Gutenberg made it possible to disseminate scientific works very quickly. The second important event was the European discovery of America by Christopher Columbus in 1492. This removed any lingering doubts about whether the earth was round or not. It was during this time of scientific upheaval that Copernicus was born on the 19th of February 1473 in what is now the Polish city of Turin. He attended the parish school and was later awarded the title of civicus academicus, academic and citizen. After the death of his father, his uncle Lucas von Watzenroder, a bishop, made sure the boy got an all-round education at the best universities. In 1491 Copernicus went to study at the University of Krakow which had been founded in 1364 and was known as a major center of scientific study, in particular astronomy. It still houses the oldest existing globe on which America is depicted. In 1496 Copernicus went to Bologna in northern Italy to study jurisprudence, but it was geography and astronomy which really fired his interest. In 1500 he was invited to Rome to give lectures on mathematics and astronomy at the La Sapienza University. Copernicus continued his studies in Italy. He studied medicine at Padua and it was as a doctor that he was best known among his contemporaries. In 1503 Copernicus took his doctorate in canon law at the University of Ferrara. Three years later he returned home to work as personal physician and secretary to his uncle, the Bishop of Ermoland. In 1512 Copernicus became a cathedral canon in the north German city of Frauenburg, now Frombork in Poland. This appointment assured him a financial security for life. It was no sinecure though, he had administrative duties to perform. Even so he found time for astronomy. He set up an observatory in a small turret on one corner of the cathedral. By 1514 his astronomical reputation had become so considerable that he was called upon by the Fifth Lateran Council to help with the planned reform of the calendar. During this period he wrote his first astronomical work entitled Commentariolus or Little Commentary. It already contains a sketch of his new system which placed the Sun in the centre of the universe, but he hesitated to publish it. Copernicus had the idea for his heliocentric or Sun-centred worldview from his reading of classical texts which first introduced him to what was in his eyes a revolutionary concept. All astronomers knew that at certain points in their orbits the planets appear to move backwards. The ancient Greek scholar Aristarchus of Samos had investigated this retrogression, as it's known, and come up with an explanation. If the Earth is also in motion and is moving around the Sun faster than the planets in more distant orbits, then at certain points it would overtake them. Viewed from the Earth it would look as if the other planet was going backwards. Aristarchus' idea was not followed up. It simply demanded too great a leap of the imagination. How could birds find their nest, people asked, if the Earth had meanwhile moved beneath them? Copernicus, however, was fascinated by this idea and drew up three theses of his own. Number one, the Earth rotates on its own axis once every 24 hours so that the daily motion of the stars is only apparent. Number two, the Sun is at the centre of the universe and the Earth revolves around it. And number three, the Earth is just one planet among others and does not occupy a special position in the universe. Copernicus showed by calculation that the movements of the planets could also be explained by the heliocentric hypothesis, in other words, that they too revolve around the Sun. But the new Copernican system was still pretty complicated. As he could not prove his theories, he could only achieve success in an intellectual climate that was open to new ideas, one that was prepared to question the opinions that had been handed down from antiquity. Copernicus decided to play a waiting game. After all, the geocentric system was defended by the Church on the basis of the scriptural text in which Joshua was said to have commanded the Sun to stand still. But in order to do that, it would have had to have been moving. In other words, this text was not compatible with the heliocentric view propounded by Copernicus. He was well aware of the explosive nature of his theory. That was why he hesitated to publish his views. But he did not stop his researchers. Between 1516 and 1521, Copernicus was an official at the castle in Allenstein, now Olstein in Poland. During the war between Poland and the Teutonic Knights, he organized the defense of the castle against the Knights so well that it withstood a siege in January 1521. Soon afterwards, a ceasefire was agreed and Copernicus took part in the peace talks. But even in Olstein, he found time for astronomy. He took measurements of the Sun's altitude in order to determine the date of the equinoxes. But Copernicus was now hooked on his heliocentric worldview. In 1542, he finally allowed his thesis to be published in Nuremberg. He was on his deathbed before he saw the publication of his major work under the title De revolutionibus orium coelestium, on the revolutions of the celestial spheres. He was no longer sure he could take it all in when a copy was pressed into his hands. Although the work was dedicated personally to the Pope, it was placed by the Catholic Church on the index of banned books in 1616. But that did not lessen its pioneering and fundamental importance in modern astronomy. The Middle Ages were dominated by a self-centered view of the world. Copernicus took a broader view and thereby opened the way to our modern image of the world. There were no great practical benefits to start with. Copernicus still assumed that the planetary orbits were circular and so there was no improvement in the prediction of their positions. It was not until 1594 that another astronomer, Johannes Kepler, calculated the planetary orbits more precisely by assuming them to be elliptical. Kepler adopted the basic idea of the Copernican system and, in 1609, expanded it into a practical theory in his Astronomia Nova or New Astronomy. An Italian helped Kepler to prove his theory, Galileo Galilei. Using the telescope he had constructed in 1610, Galileo discovered the four moons of Jupiter. Their existence showed that the Earth could not be the only body around which other bodies revolved. Galileo also confirmed the calculations done by Copernicus and Kepler. But even in his day, Europe was not ready for the heliocentric system. Galileo was dragged before the Inquisition to justify his assertions. In order to avoid execution, he renounced the Copernican theory. It was not until another 50 years had passed that Isaac Newton succeeded in providing the final proof of the heliocentric theory. Using his law of gravity, he explained and calculated the orbits of the planets on the assumption they were ellipses as Kepler had predicted. He published his results in his grand breaking work Philosophiae Naturalis Principia Mathematica, the Mathematical Principles of Natural Philosophy. It was a long time before the Pope and the Roman Catholic Church finally accepted the Copernican theory. Not until 1822 was De Revolutionibus Orbium Coelestium removed from the index.