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Galileo’s story is always relevant

Illustration of the Italian astronomer, mathematician and natural philosopher Galileo Galilei, Circa 1630

In the seventeenth century, Galileo faced persecution for his heretical views on astronomy.Credit: Hulton Archive/Getty

Galileo and the Science Deniers Mario Livio Simon & Schuster (2020)

Is there room in the crowded canon for a new biography of Galileo Galilei? Astrophysicist Mario Livio is betting so. His Galileo and the Science Deniers aims to stand out by placing the original Renaissance man and his discoveries in modern scientific and social contexts. In particular, he argues, the charges of heresy that Galileo faced for his scientific claims in the seventeenth century have their counterparts in science deniers’ condemnations today.

Born in 1564 in Pisa, Italy, into an intellectual family of declining fortune, Galileo pursued medicine at the University of Pisa. But he soon abandoned his course to study mathematics, his enduring passion. The Universe, he famously wrote, “is written in the language of mathematics”. It was an argot that allowed him to break reliance on the Aristotelian cosmology prized by the Catholic Church, and to forge a new, quantitative study of nature.

In Pisa, Galileo delved into mechanics, using his observations to question accepted ideas about motion (although Livio reminds us that Galileo probably never conducted the famous experiment in which he supposedly dropped spheres from the city’s leaning tower and found that they fell at the same speed regardless of their mass).

In 1592, he moved to the University of Padua in Italy, an intellectually liberal environment happily beyond the jurisdiction of the Pope. Here, he began to discuss the revolutionary theory, proposed by Polish mathematician Nicolaus Copernicus in 1543, that rather than being the Universe’s fixed centre as Aristotle had insisted, Earth was in fact orbiting the Sun.

Livio structures his account partly around specific works, including Galileo’s 1610 The Sidereal Messenger, which described his major astronomical observations. While working in Padua, Galileo often visited the nearby port of Venice, where he was introduced to the ‘spyglass’, a new-fangled instrument from Holland that could be used to see ships approach. Galileo turned it to the heavens to make the discoveries that changed the course of astronomy, and launched his own fate.

In his first observations, Galileo saw that the Moon was not a smooth sphere, but was mountainous. This contradicted the church’s view that the heavens were pristine and unchangeable, unlike the corrupt, mutable Earth. He also saw satellites orbiting Jupiter, shooting a hole in the geocentric argument that if Earth were to move, it would lose its Moon.

In 1610, against his friends’ advice and in pursuit of more money, Galileo left the protective environment of Padua and moved to Florence to work for Cosimo II de’ Medici, the Grand Duke of Tuscany. Despite now living within the Pope’s sphere of influence, in 1632, Galileo published his book Dialogue Concerning the Two Chief World Systems, an imaginary debate between Salviati, an advocate of heliocentrism, and a witless geocentrist named Simplicio.

Putting the Pope’s view — that God’s universe is inherently unknowable — into the mouth of a fool was risky. Galileo’s fame and fortune rose, but so did the power and determination of his enemies, and the Holy Inquisition finally claimed him. In a riveting account of the trial, Livio describes how the Inquisition dismissed Galileo’s claim that the Dialogue was a balanced argument that ultimately rejected Copernicanism. On 22 June 1633, one of the world’s most venerated scientists was on his knees before its members, renouncing the errors and heresies inherent to Copernicanism.

Livio parses the considerable, and often ambiguous, evidence about Galileo’s life and trial, and comments on the conclusions reached by various historians. The official summary of the trial proceedings, he writes, “revealed a clear intention to present Galileo in the worst possible light”. Like others before him, Livio doubts claims that Galileo left the court defiantly muttering about Earth, “and yet it moves”.

Anthony Fauci, right, and U.S. President Donald Trump at the daily coronavirus White House briefing

Anthony Fauci and Donald Trump participate in the daily coronavirus task force briefing at the White House in Washington DC.Credit: Drew Angerer/Getty

The non-chronological zigzagging of the book can be hard to follow, but allows Livio to focus on themes, such as Galileo’s polymathy. He highlights Galileo’s lifelong study of the great Italian poets Dante Alighieri, Torquato Tasso and Ludovico Ariosto. And he notes that the astronomer’s drawing skills and knowledge of perspective allowed him to understand that the shadings on the Moon were shadows cast by mountains, and to depict them in lovely watercolours.

Livio is at his best when he discusses how Galileo’s scientific understanding compares with that of researchers today. Galileo suggested, for example, that comets might be optical phenomena caused by the reflection of sunlight by vapours released from Earth. We now know they are ‘dirty snowballs’ made of ice, rock, dust and frozen gases. Some of these components vaporize when they get close to the Sun, giving comets two tails: one of dust that reflects sunlight, and one of gas that glows as it ionizes.

And what of today’s science deniers? Livio briefly addresses how religion and business interests still conspire to attack evidence for evolution and anthropogenic climate change. In general, “processes that are not fully understood don’t constitute flaws”, he points out, but critics from creationists to Donald Trump discredit scientific arguments by exploiting gaps in knowledge. It’s a chillingly relevant theme, yet the parallels he draws between Galileo’s trial and contemporary science wars feel thin, and there’s a frustrating lack of examples to demonstrate the continuity of denialism through the centuries.

Nonetheless, Livio has added to the canon an accessible and scientific narrative, in which a profound love for Galileo shines through.

Nature 581, 27-28 (2020)



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