Dawn of February 17, 1600, Campo de’ Fiori, Rome. A man is burned alive by order of the Holy Inquisition, between the insults of his enemies and the silence of his terrified friends and followers. His name, Giordano Bruno, a visionary defender of Copernican heliocentrism. Condemned for his heretical theology, he affirmed that there are innumerable suns in our universe, and infinite earths like ours that revolve around those stars, in the same way that our planet revolves around our Sun.
Just ten years later, Galileo Galilei discovered four satellites of Jupiter with his telescope. And also some silhouettes around Saturn, which we now know were its rings. Galileo was not the first person to look at the night sky through a telescope, but he was the first capable of doing it systematically and rigorously, of interpreting his observations and, in particular, of disseminating his discoveries to the society around him. time .
Bruno’s execution at the stake serves as an introduction to the historical context of Galileo’s times, a time of darkness, prejudice and persecution of ideas contrary to established dogmas. Giordano Bruno was convicted by a court led by Cardinal Roberto Bellarmine, the same inquisitor who a few years later also participated in the first of two trials against Galileo. And it is this context, in my opinion, that gives more value to the publication of the book Dialogues on the two maximum systems of the world , Ptolemaic and Copernican, an essay that is usually considered as the first example of the genre of written scientific popularization .
“Dialogues”, a popular play
Galileo began writing the Dialogues in 1624 and finished his manuscript in 1630. That year he traveled to Rome to initiate permissions for its publication with his publisher. According to his biographers, Galileo decided to take advantage of the accession to the papacy in 1623 of an apparently more liberal thinker, Pope Urban VIII, and opted to capture his ideas and discoveries through a work of popularization. It passed the filter of ecclesiastical censorship , but not without first modifying numerous paragraphs and even the title.
Finally, Dialogues Concerning the Two Chief World Systems was published in Florence on February 22, 1632, with the Roman and Florentine imprimatur. It was written in Italian , when the language of science at that time was Latin, and it was addressed to the general public . But the most striking thing was the style, in the form of a conversation between three characters: Salviati, who represented the Copernican vision of Galileo; Simplicio, defender of the geocentric vision of Ptolemy; and Sagredo, neutral arbiter of the debate on the movement of the universe around the Sun. The Venetian palace of the latter character was the location chosen by Galileo to stage the four days that the Dialogues lasted.
The full title of this work was Where in the conversations of four days the two maximum systems of the Ptolemaic and Copernican world are discussed, neutrally proposing the philosophical and natural reasons of both sides . A whole declaration of intentions, which remained only in the title. Because, far from neutrality, the clear dialectical winner in these conversations was always Salviati, defender of Copernicus , who ruthlessly refuted every argument of Simplicio, the obtuse defender of Aristotle.
On the first day of the Dialogues , the protagonists discuss the laws of motion of heavy bodies. They comment on the characteristics of sunlight that is reflected by the Moon and Salviati attacks Aristotle’s dogmatic proposal on the incorruptibility and perfection of celestial bodies. The next day, the debate turns to the relative motion of the Earth. Salviati exposes his famous thought experiment about what would happen in a ship whose mast dropped a stone while the ship moved and ends the day with the defense of some concepts of Kepler related to the orbits of the planets. On the third day, the discussion shifts to the newly discovered stars , with Salviati very critical of the arguments in a book he has read overnight and encourages Simplicio to draw a map of the arrangement of the known planets, starting with Mercury and Venus, so you can see that they really revolve around the Sun. Sunspots are also mentioned, which Galileo discovered years ago, and they are proof of the spherical geometry of the Sun. Something that would confirm Copernicus’ hypothesis. And the fourth and last day of the dialogues ends with the theme of the tides . Galileo believed that the accelerations and decelerations of the Earth caused the tides, ruling out the possible effect of the Moon. Something we now know was wrong.
In the Dialogues we find many of the resources that are still used in popular science books. An example is this fragment, in the mouth of Salviati, with analogies and a characteristic literary style that could well have been written by a contemporary author.«[…] Ptolemy and his followers present another experience, similar to that of projectiles. It deals with objects that, separated from the Earth, remain in the air for a very long time, such as clouds and flying birds. Since these cannot be said to be transported by the Earth, because they are not attached to it, it does not seem possible that they can follow the speed of the Earth, rather it should seem to us that they are all moving very quickly towards the West. And if we, carried by the Earth, cover our parallel, which is at least sixteen thousand miles, in twenty-four hours, how will the birds be able to follow that race? While, on the contrary, we see them fly without any noticeable difference, both towards the east and towards the west and towards any other part. In addition to this, if while running on horseback we feel the wind whipping us quite strongly in the face, shouldn’t we feel a great perpetual wind from the East, carried away with such rapid running against the air? And yet you don’t feel any similar effect.”
This other fragment with reflections that are at the height of a metaphorical lyricism worthy of Dante or Petrarch also serves as an example:
“Those who exalt so much incorruptibility and inalterability, etc., I think they are forced to do so by the desire they have to live long and the terror of death; and without considering that if we were immortal it would not be up to us to come into the world. They deserve to find themselves a head of Medusa, which will transform them into statues of opal or diamond, to achieve the perfection they do not have.
The Wrath of Rome: Book Ban
A few months after the publication of the Dialogues, as soon as the book arrived in Rome from Florence, it aroused anger among Galileo’s former enemies. The distributed copies, a few hundred, were withdrawn. And the publisher was formally warned to be banned from printing. Pope Urban VIII , who before ascending to the papacy declared himself an admirer of Galileo, going so far as to dedicate a laudatory poem to him, was furious when he read the book and interpreted that the foolish Simplicio could actually be a character inspired by him. Something that we still do not know if it was true or, what seems more likely, a mere conjecture hinted at by the pope’s advisers. The first surprised by the commotion and scandal was Galileo, who after going through all the paperwork to publish his book came face to face with his ban, his persecution and the subsequent legal process. Some very influential people of the time close to Galileo went to ask Urban VIII for explanations, but he dismissed them stating that he had been deceived by his former friend. The book was included in the Index librorum prohibitorum , a catalog of publications considered pernicious by the Catholic Church and whose reading was prohibited. It was not removed from that list until almost two centuries later, in the year 1822.
Bringing knowledge to the people
Galileo was a pioneer in opening science to a broader community , explaining his arguments clearly and rigorously, demonstrating each of the facts he exposed with simple experiments and using simple language. In the Dialogues , he left us a lesson on the functioning of the scientific mind and on how to unite thought and observation. But also something that is very important, science taught us to count . Although he defends Copernicus, he does not authoritatively try to prove that Copernicus was right. He wasn’t so presumptuous because he knew that wouldn’t work, plus he would never be accepted.
He left on the stage where the protagonists of his Dialogues participated all the objections that were affirmed in his time against the movement of the Earth. He put all the arguments and contradictions on the table and turned on the light. And he left it to the reader (who did not know Latin) to come to his own conclusions. That was what really bothered the ecclesiastical authority, the audacity to bring the light of knowledge to the people , contrary to what happened with the rest of his work, which, being directed to a more specialized sector, did not have that persecution and sentence.
Education and the dissemination of science are key actions to provide society with the rational thinking we need to face the problems of our world. I believe that Galileo was well aware of the importance of this fact and, for this reason, the Dialogues are considered the beginning of popular science, understood as the art of making scientific knowledge accessible to the general public.
