It is considered to be one of the most elegant experiments in history. A young Galileo Galilei (1564-1642) creates atmospheres of different masses from the top of the tower of Pisa in front of an astonished audience consisting of professors, scientists and students from his university. But it is possible that the scene never took place.
The only good thing is that if it had happened, it would have taken place somewhere between 1589 and 1592, when Galileo was a professor of mathematics at the University of Pisa. None of the Italian writings refer to these experiments. The only source of information is a few lines in a biography written in the year 1654 (twelve years after the death of Galileo and more than sixty after the alleged experiment) by Vincenzio Viviani (1622-1703), his personal assistant during his life. last three years of life. This was only published in 1717:
During his years as a professor in Pisa, Galileo did not publish work on his research, although he did make a large number of notes about his studies of the fall of bodies in a medium. All this material was not published for the first time until the end of the 19th century in the text De motu.
In view of the existing evidence, there is no consensus among scholars about the history of science about the authenticity of the anecdote. During the last century, publications appeared that argued both for and against his truthfulness.
According to researcher Michael Segre, the first criticisms of two important Galileo scientists: Rafaello Caverni, a Florentine priest (in an encyclopedic work of six parts between 1891-1900), and Emil Wohlwill, an engineer and historian of German science (in two articles published in 1903 and 1905).
Both felt that the story of Viviani contradicted what had appeared in the writings of Galileo himself. Caverni believed that the fault was Galileo's, who had lied when he told the story to Viviani, while Wohl believed that Viviani had invented the story and that there was no other information in the biography of the wise person who it had supported. That is why it would never have taken place.
However, in two works published in 1916 and 1917, the student of the life and work of Galileo, Antonio Favaro, argued against the objections of these two authors. He pointed out that his criticism was based on works that Galileo had not published, perhaps because he was not very happy with the results. He pointed out that these investigations had not necessarily taken place during his stay in Pisa (1589-1592), so the passages that contradicted Viviani might not have been from that time.
He acknowledges that Viviani has occasionally distorted a fact in his biography of the Italian genius.
On the other hand, it is also true that De motu Galileo mentions seven times the possibility of conducting experiments from a high tower, although it does not give names or give an accurate experimental description. On one occasion, he says, "That's something I've tried many times." All this, however, still does not constitute direct evidence that the experiment has taken place.
This was almost twenty years, until in 1935 a book was published by Lane Cooper, an English professor at Cornell University. In it, doubts are again raised about the truthfulness of Viviani's story.
The author bases his conclusions on two points: on the one hand, in the analysis of the different versions that circulated throughout history; it indicates that this appears in a very schematic way and that there are contradictions between versions.
On the other hand, in the study of the letters exchanged between Galileo and the professor of mathematics of the University of Pisa Vincenzio Renieri in March 1641. In these letters he told him that he had dropped spheres of different sizes and densities from the top of the Tower of Pisa and which reached the ground at different times. These results were in contradiction with the story of Viviani, who claimed that they immediately reached the ground. It should be noted that on that date Viviani was already the personal assistant of the elderly (and completely blind) Galileo, so he had access to this correspondence.
Many new documents have been studied since then, but none shed light on the mystery. One of the latest contributions to this controversy can be found in the biography that Stillman Drake published in 1978, a reference to the study of the works of the Italian sage.
Despite the absence of evidence, Drake believes that the Pisa Tower experiment has taken place. Viviani only started writing the memories Galileo told her when she received the letter from Ranieri, although she admits she finds it hard to understand that in his old age Galileo suddenly remembered a fact he had never mentioned before.
Drake also suspects that Viviani himself wrote the letter of reply to Ranieri, including the passage of the tower. If this letter is preserved, this would be the definitive proof of the correctness of the story, but unfortunately this letter was not found.
In short, the story is based on a sentence of two lines in the biography written by his personal assistant (known to have falsified some information, such as the date of birth), according to the old man's alleged reminder of an event that has half occurred a century before that. That, together with the contradiction with what is stated in the letters of Ranieri, and the lack of more testimony of the time, doubt the authenticity of the passage.
Precisely for that reason, a recently published book states without any impediment that "the reason that none of the supposed witnesses of Galileo & # 39; s unique execution of the top of the tower mentioned it is that it did not occur" .
On the other hand, the story of Viviani must be understood in the context of the seventeenth century. The moment biographies were written, truthfulness was less important than decorating the character's image by anecdotes, sometimes invented or decorated.
There are even authors, including the great philosopher and historian Alexander Koyré, who go one step further and believe that Galileo did not perform the experiments elaborated in De motu. They were, in fact, mental experiments.
In any case, the question is no longer just whether the Pisa Tower experiment took place or not, but the fact that Galileo Galilei, in reality and contrary to what is said in the books, did not want to prove exactly that "bodies of at the same time, "and that he was not the first to question Aristotle's ideas about the fall of bodies.
José Manuel Montejo Bernardo: assistant professor of medicine. Department of Educational Sciences, University of Oviedo
Originally published in The Conversation.