“Galileo personifies revolutionary historical change”

February 11, 2014

Interview with Max Planck Director Jürgen Renn on the importance of the Italian scholar who was born 450 years ago

Galileo Galilei was born on 15 February 1564 in Pisa. The philosopher, mathematician, physicist and astronomer continues to fascinate both experts and lay people today. This year, science historians are revisiting his life and work while the media celebrates his 450th birthday. Jürgen Renn, Director at the Max Planck Institute for the History of Science, spoke about the importance of Galileo to Helmut Hornung.

Why is Galileo still of interest in the context of research today?

Galileo, like no other scientist, personifies revolutionary historical change and the birth of modern science. Since Galileo’s time, science has not only made rapid progress, it has also become an ever-greater part of our lives. Moreover, the relationship between knowledge and application has often been problematic since Galileo.

Science can stand for enlightenment and emancipation; however, it can also be used in the interest of power. Both factors were already becoming apparent in Galilei’s day. Thus, by understanding the revolutionary change heralded by Galileo from an historical perspective, we can also better understand our own situation: How did modern science develop and how does it relate to our lives? This remains a key topic.

To what extent did Galileo shape the history of science?

Thanks to his public support for Copernicus’ teachings and, above all, due to the trial which the church subjected him to for this support, Galileo was a legend in his own time. His further development of the telescope and his astronomical discoveries – in particular those of the craters and mountains on the moon and the Jupiter moons – earned him worldwide renown. The Jesuits spread his fame to China. His research on mechanics, the discovery of the law of the pendulum, the law of gravity and the parabolic trajectory laid the foundations for classical mechanics.

In science history, his research was long associated with a paradigm change that marked the advance from the Middle Ages to the scientific modern age. Today, we know that this advance did not depend on a single scientist and was the result of a long-term development that also had a crucial influence on economic, political and social change.

The young Galileo gave lectures on such topics as “On the Shape, Location and Size of Dante’s Inferno” at the Florentine Academy. Was Galileo a mystic? Or was he merely a child of his time?

In some respects, Dante was a scientific pioneer in his own right. His Divine Comedy is a marvellous synthesis of medieval scientific knowledge, which he made accessible to a wide audience through its literary presentation in the Italian vernacular.

With his lectures, Galileo followed this tradition of literary-scientific popular education. This was one of the secrets of his success: He was part of a broad, cosmopolitan culture that was equally interested in science, art and literature; a culture, for which the philosophical questions concerning the nature of world were closely related to scientific and practical problems. On the Shape, Location and Size of Dante’s Inferno reflects this close relationship.

Which of his works is most important in your view?

It depends on which aspect of his work is in the spotlight. Galileo was a gifted author, astronomer, philosopher, mathematician, engineer and physicist. In his day, these occupations were not as strictly separated as they are today. His works are correspondingly multi-faceted. His Starry Messenger of 1610 presented new astronomic observations of significance for the history of humanity - and was probably the first scientific bestseller.

The Dialogue Concerning the Two Chief World Systems, which was published in 1632, is without doubt Galileo’s literary masterpiece. It comprises an ingeniously composed conversation about Copernicus’s heliocentric system and Ptolemy’s geocentric system, which was supported by the church. It has just one drawback: Galileo’s supposed main proof of the superiority of the heliocentric system rests on a theory of tides that overlooked the main factor at work here, the role of the moon.

My personal favourite is the Discorsi of 1638, the debates about two new sciences. This work is Galileo’s scientific legacy and contains his most important contributions on mechanics, which are also presented in the form of a dialogue that enables us to draw important conclusions on Galileo’s own path to knowledge.

What is the origin of Galileo’s insights?

Galileo stood at the interface of different traditions. This enabled him to link elements of knowledge that had previously been separate from each other and, in this way, attain new insights. He studied medicine and, as a young man, explored the Aristotelian philosophy of nature and the medieval scholastic tradition in detail. He was also familiar with the Renaissance tradition of the artist-scientist-engineer.

He explored contemporary technology and was able to draw and calculate like other contemporaries whose main profession was art or military architecture. He admired the work of the ancient mathematician and physicist Archimedes, with whose help he aimed, in his youth, to reform Aristotelian natural philosophy. The fact that these efforts at reform would ultimately result in the surpassing of the Aristotelian system is in the very nature of such processes of change.

What is new in Galileo’s approach? Is it really, as is often claimed, the combination of mathematical methodology and experimentation?

Actually, Galileo didn’t develop any new approach, in any case as the starting point of his achievements – at best it emerged as their result. He experimented and applied mathematical methods. But this was neither new nor decisive. Galileo’s work displays notable similarities with that of other contemporaries. Thomas Harriot, who also directed the telescope at the moon and discovered the laws of gravity, is considered an English Galileo. This clearly shows that what’s involved here is not individual revolutionary discoveries, but the transformation of an entire system of knowledge.

The starting point was provided by the basis shared by Galileo and his contemporaries, which drew on, among other things, the ancient traditions of Aristotle and Archimedes. They also shared the challenge posed by contemporary technology, firearms and ballistics, shipbuilding and architecture, and machinery with wide-ranging applications.

The attempts to understand the new technology using old concepts gradually transformed the inherited system of knowledge. New concepts emerged on the boundaries, which eventually moved to the centre of a new system of knowledge, that of classical physics. It was a Copernican process, in which a lot of inherited knowledge structures remained intact, but were newly arranged, like the planets in the Copernican system.

The “case of Galileo”, that is his trial by the Inquisition in 1633 is viewed as the starting point for the separation of the church and science. How do you see this relationship today?

The “case of Galileo” was the result of complicated political processes surrounding the conflict between church hegemony and secular power. These processes were complicated, because there was no consensus within either the church or the secular powers and they did not form united fronts. It should not be forgotten that the church was an important pillar of science at the time. From Albertus Magnus and Thomas Aquinas on, it had united Christian teaching with Aristotelian philosophy and had thereby established the intellectual basis for a comprehensive worldview that was predominantly based on science as it was understood back then.

At the same time, in Galileo’s day, Christian orders like the Jesuits played a key role in the dissemination of scientific education. However, despite the complexity of these historical processes, there was a basic conflict between the striving of science for knowledge and the interest of the church authorities in the control and limitation of the rapidly accumulating knowledge – a conflict that came to a head in the judgement against Galileo.

This conflict persists to the present day, in principle. However, it cannot be resolved through the absolute separation of power, moral values and knowledge, and their allocation to different societal instances, which must then seek a balance. Just as science is not only the precondition of power, and should also be that of morality, moral reflection should be as integral to power as it is to science. The case of Galileo shows us that we cannot completely separate the spheres of knowledge, power and morality from each other.

Interview: Helmut Hornung

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