Renaissance men - excerpt from the first chapter of the book "History of Science" by John Gribbin

The book was published by "Aliyat HaGeg Books and Yediot Books". From English: Dafna Levy. * The subchapters: "The Exit from the Darkness", and "The Elegance of Copernicus"

The exit from the darkness

The Renaissance is the period when the people of Western Europe lost their respect for the ancients and realized that they could contribute to civilization and society no less than the Greeks and Romans did. To modern eyes, the bewilderment is not that this happened, but that it took so long for the people to free themselves from their inferiority complex. The detailed reasons for this great delay are beyond the scope of this book, but anyone who has visited the sites of classical civilization around the Mediterranean can take a look at the things that made people in the "dark" Middle Ages (roughly speaking, AD 900-400), and even in the days of Late Middle Ages (1400-900), to feel as they felt. Buildings such as the Pantheon and the Colosseum in Rome inspire awe even today, and in the days when all the knowledge to build such buildings was lost, they probably looked as if they were built by another species of humans - or by the hands of gods. With so many physical evidences of the supposed divine ability of the ancients, and with the rediscovery of texts that came from Byzantium, proving the intellectual ability of the ancients, it was only natural to believe that intellectually they were far superior to the ordinary mortals who came after them, and to accept the teachings of the ancient philosophers Like Aristotle and Euclid as if they were Torah from Sinai. Since the Romans contributed very little to the discussion that today we would call a scientific view of the world, during the Renaissance the conventional wisdom about the nature of the universe remained almost unchanged since the great days of ancient Greece, about 1,500 years before Copernicus appeared on the scene. And yet, once the truth of these ideas was questioned, progress was incredibly fast - after 1,500 years of stagnation, less than 500 years have passed from the time of Copernicus to the present day. It may sound like a cliché, but it is nevertheless true to say that a typical tenth-century Italian would have felt at home in the fifteenth century as well, but a fifteenth-century Italian would have found the twenty-first century less familiar to him than Italy in the days of the Roman Empire.

The elegance of Copernicus

Copernicus himself was an intermediate figure in the scientific revolution, and in one important respect resembled the ancient Greek philosophers more than the modern scientist. He did not perform experiments nor did he make his own observations of the sky - at any rate, not to any significant extent - and did not expect anyone else to try to put his ideas to the test. His big idea was only an idea, or what today is sometimes called a "thought experiment", which presented a new and simpler way to explain the same pattern of behavior of the heavenly bodies that was explained using the more complicated method invented (or published) by Ptolemy (Claudius Ptolemy). If a modern scientist has a bright idea about how the universe works, his first goal will be to find a way to test the idea through experiment or observation, to find out how successful it is as a description of the world. But the key step in the development of the scientific method was not made in the fifteenth century, and it never occurred to Copernicus to test the idea he came up with - his mental model of the way the universe works - through new observations that he himself would make, or to encourage others to make new observations. To Copernicus, his model was better than Ptolemy's because it was, in modern terms, more elegant. Elegance can often be a reliable touchstone of a model's usefulness, but it is not infallible. However, in this case it turned out in the end that Copernicus' intuition was correct.

There is no doubt that Ptolemy's method lacked elegance. Ptolemy (sometimes called Ptolemy of Alexandria) lived in the second century AD and was educated in Egypt, which has always been under the cultural influence of Greece (as the very name of the city where he lived according to the records). Very little is known about his life, but among the works he left for posterity was a large treatise on astronomy, based on 500 years of Greek astronomical and cosmological thought. The book is generally known by its Arabic name, Almagest, which means "the greatest", and it gives some idea of ​​its status in the following centuries; Its original Greek title simply describes it as a "mathematical collection". The astronomical method he describes is far from being Ptolemy's own idea, although he seems to have modified and developed the ideas of the ancient Greeks. However, unlike Copernicus, it seems that Ptolemy himself made extensive observations of the movement of the planets in addition to what he drew from the observations of his predecessors (he also drew important star maps).

The basis of Ptolemy's method was the idea that the heavenly bodies must move in perfect circles, simply because circles are perfect shapes (here is an example of how elegance does not necessarily lead to truth!). At that time five planets were known (the planet Mercury, Venus, Mars, Saturn and Jupiter), as well as the Sun, the Moon and the stars. In order for the observed movements of these celestial bodies to conform to the requirement of perpetual motion in perfect circles, Ptolemy had to make two major revisions to the basic idea that the Earth is at the center of the universe and everything else revolves around it. The first correction (which was thought of long before) was that the motion of a certain planet could be described as turning in a small perfect circle around a point which itself circled in a perfect circle around the Earth. The small secondary circle (a kind of "wheel within a wheel") is called an epicycle. The second correction, which was probably perfected by Ptolemy himself, was that the great crystal spheres, as they were known in Shemmen ("crystal" in this context simply means "invisible"), which carry the heavenly bodies around in circles, do not actually revolve around the earth but around a set of slightly deviated points from the earth and are called "equant points", which differ from one celestial body to another. The earth was still considered the central object in the universe, but everything else revolved around aquant points, not around the earth itself. The large circle centered at the aquant point is called a deferent.

The model proved itself in this respect that it could be used to describe the apparent movement of the sun, the moon and the planets against the background of the planets of Saturn, i.e. the fixed stars (fixed in the sense that they all kept the same pattern while moving together around the earth), which themselves were considered connected to the sphere In a crystal outside the system of the crystal balls that carried the other celestial bodies around the relevant aquant points. But no attempt was made to explain the physical processes that drove everything in this way, nor to explain the nature of the crystal spheres. Furthermore, the method was often criticized as being too complicated, while the need for aquant points caused discomfort among many thinkers - this raised doubts about the assertion that the earth is the center of the universe. There was even a hypothesis (already put forward by Aristarchus in the third century BC, and it came up again and again in the centuries after Ptolemy) that the sun might stand at the center of the universe, and the earth revolved around it. But such ideas did not find favor, mainly because they stood in open contradiction to "common sense". Of course, it is impossible for the solid earth to move! This is one of the clear examples that one must be careful not to rely on common sense if one wants to know how the world works.

Two specific things pushed Copernicus to propose something better than Ptolemy's model. First, each planet, in addition to the Sun and the Moon, requires a separate reference in a model that takes into account its own offset from the Earth and its own epicycles. There was no comprehensive and consistent description of things that would explain what was happening. Second, there was a specific problem that people had been aware of for a long time, but usually swept it under the rug: the offset of the Moon's orbit from the Earth, necessary to account for the change in the apparent speed of the Moon's movement across the sky, was so great that the Moon was considered much closer. to the land on certain days of the month compared to other days - so that apparently its size must change considerably (and can be calculated), which clearly did not happen. In a sense, since Ptolemy's method does provide a prediction that we could test with observations, it fails this test and is therefore not a good description of the universe. Copernicus didn't think exactly so, but the moon problem must have prevented him from accepting Ptolemy's method.

Nicolaus Copernicus entered the picture at the end of the fifteenth century. He was born on February 19, 1473 in the Polish city of Torun on the banks of the Vistula River, and was first called Nicolaus Copernicus, but later changed his name to Latin (a common practice at that time, especially among the humanists of the Renaissance). His father, a rich merchant, died in 1483- or 1484-, and Nikolaus grew up in the house of his mother's brother, Lukas Wachenrode, who was appointed bishop of Ermland. In 1491 - (only a year before Christopher Columbus's departure for his first voyage to the New World), Nikolaus began his studies at the University of Krakow, and then discovered - probably for the first time - a serious interest in astronomy. In 1496 he moved to Italy and studied law and medicine there in addition to normal classical studies, and mathematics in Bologna and Padua, before receiving a doctorate in ecclesiastical law from the University of Ferrara in 1503. Copernicus, befitting a man of his time, was largely influenced by the humanist movement in Italy and studied the classical studies associated with this movement. Indeed, in 1519 he published a collection of poetic letters by the writer Theophilus Simocata (a seventh-century Byzantine), which he translated from the Greek source into Latin.

When Copernicus completed his doctorate, his uncle Lukas already appointed him a priest at the Frombork Cathedral in Poland - a clear case of nepotism that arranged for him a comfortable and lucrative position, which he held until the end of his days. But only in 1506 did Copernicus return permanently to Poland (which gives us an idea of ​​how few the job requirements were), where he worked as his uncle's doctor and as his secretary until Lucas's death in 1512. After the death of his uncle, Copernicus paid more attention to his duties as a man of religious law, he practiced medicine and held junior civil positions, which nevertheless left him more than enough time to persist in his interest in astronomy, but his revolutionary ideas about the place of the earth in the universe had already taken shape by the end of the first decade of the sixth century ten.

Tomorrow, the third and final part of the book: the continuation of the work of Copernicus

The introductory chapter to the book "The History of Science" by John Gribbin