The classic image of Galileo Galilei has the 16th century Italian scientist dropping two balls of differing weights from the Leaning Tower of Pisa and observing them hitting the ground at the same time. Though that scenario was probably no more than one of Galileo's thought experiments—his known tests involved rolling balls down inclines—it does illustrate his towering reputation as a scientific revolutionary. Galileo helped pave the way for classic mechanics and made huge technological and observational leaps in astronomy. Most famously, he championed the Copernican model of the universe, which put the sun at its center and the earth in orbit. The Catholic Church banned Galileo's 1632 book Dialogue Concerning the Two Chief World Systems, forced Galileo to recant his heliocentric views and condemned him to house arrest. He died in his Florence home in 1642.

Historians of science have long debated the exact nature of and motivations for Galileo's trial. War, politics and strange bedfellows obscure science's premier martyrdom story. Many of the documents historians use to try and untangle the mystery are mired in their own prejudices or were written long after the fact, or both.

Now the very first written biography of Galileo has been rediscovered. It offers a rare glimpse into what people thought about the trial only 20 years after Galileo's death and even suggests a tantalizing new explanation for why he was put on trial in the first place.

Following Galileo's death, his apprentice, Vincenzo Viviani, collected Galileo's books and correspondences and announced his intention to write the definitive history of Galileo. Due to Viviani's privileged position, most other would-be biographers deferred to him. But by the 1660s, Viviani still had not written his promised masterpiece.

Enter Thomas Salusbury, an English historian who in 1664 published his Galilean oeuvre, Mathematical Collections and Translations. Composed of two volumes, the collection contained translations of Galileo's various discourses, letters, and the first book-length depiction of Galileo's life.

Then in 1666, the Great Fire of London swept through the city. The book trade in particular was badly hit; many publishing houses became piles of ashes overnight. In the inferno, all but a single copy of Salusbury's biography were lost. Salusbury died at about the same time—possibly in the fire, or maybe from the plague. By late 1666, Mrs. Susan Salusbury was a known widow.

But the book lived on. It passed through various hands before, in 1749, it wound up in the private library of George Parker, Second Earl of Macclesfield, a respected amateur astronomer. The 1830s marked the last time that the book was directly quoted. After that, the trail goes cold. Historians searched the Macclesfield library again and again, only to wind up empty-handed, and most were resigned to the fact that the book was lost.

In 2003, Richard Parker, the Ninth Earl of Macclesfield, was evicted from the family castle following a bitter property dispute with the castle's management company, whose shareholders included his own relatives. The 30-year family feud precipitating the eviction was based on, as the presiding judge put it, simple "palpable dislike." Upon his ousting, the Earl auctioned off the contents of the castle's three libraries.

Nick Wilding, an associate professor of history at Georgia State University, heard the libraries were up for auction and immediately called the Sotheby's representative in charge of the affair. Wilding asked him, doubtfully, if in the collection he had chanced across a particular title: Galilaeus Galilaeus His Life: In Five Books, by Thomas Salusbury. "To my surprise, he said, 'Why, yes, actually. I've got it right here,'" Wilding recalls. He hopped on the next plane to London.

Perusing the tattered tome at Sotheby's auction house, Wilding became the first person to study Salusbury's mysterious biography of Galileo in almost 200 years. Inside the timeworn document itself, Wilding discovered clues that allowed him to piece together its elusive, seemingly cursed history.

Wilding discovered that the manuscript itself solves one mystery: why did this copy survive the Great Fire when its siblings were burned? The book is incomplete. It is missing a chunk in the middle and ends abruptly, mid-sentence, in the middle of the final of five books. And tellingly, some of the pages are full of proofreader's marks. For Wilding, these clues point to one conclusion: The copy that exists today was an incomplete version taken home by a proofreader, away from the fire's epicenter, and spared from the brunt of the disaster.

The text's curious state—unfinished and annotated—provided Wilding with insights into the overlapping worlds inhabited by Galileo, Salusbury and the publishing industry. Like many works of the time, it has its share of inconsistencies, partly because Galileo's apprentice Viviani controlled the firsthand evidence and Salusbury had to rely on secondary sources.

"Quite a lot of it is wrong," Wilding says. "But that makes it even more interesting for historians because you have to explain the mistakes as well as the facts." For example, Salusbury parrots rumors of the time that Galileo was an illegitimate child, and that his wife tore up many of his scientific papers at the request of a nefarious priest. Modern scholars know both claims are false; in fact, Galileo never even married. But these inaccuracies point to the rampant anti-Catholic, misogynistic sentiments of many in the Italian scientific circle at the time, Wilding says. "For them, it was, 'Bad priest! Stupid women!'"

But the most striking finding might not be an error at all. Salusbury presents a novel motivation for Galileo's infamous trial, Wilding says. If people know anything about Galileo's trial, it's usually that the church disapproved of his advocacy of the idea that the earth orbits the sun. In many people's minds, Galileo is a kind of martyr figure for science and a cautionary tale against allowing religious authority to trump scientific inquiry.

"There's been a very long discussion about the trial—what happened, who won—and to some extent that's still going on today," Wilding says. "The usual interpretation is that this was the great rift between science and religion. You've got this arrogant scientist up against a dogmatic church, and in that head-ramming, the pope's going to win."

Not that modern scholars give much credence to the traditional science-vs.-religion interpretation of the trial. Most Galilean researchers today agree that politics played a much bigger role than religious closed-mindedness, but there is spirited disagreement about the specifics. Some think the pope was angry at being parodied by Galileo's character Simplicius in Dialogue Concerning the Two Chief World Systems­. Other scholars have suggested that church leaders felt Galileo had tricked them into granting him a license to write the book by not revealing its Copernican leanings. But "Salusbury's explanation is kind of refreshingly new," Wilding says.

It goes like this: In the middle of the Thirty Years' War between the Holy Roman Empire and almost every major power in Europe, tensions were high between Tuscany and Rome. The Tuscan Duke of Medici had refused to aid Rome in its war efforts against France. Pope Urban VIII decided to punish the Duke by arresting the Duke's personal friend, Galileo.

Whatever its motivation, the Roman court found Galileo guilty of heresy and placed him under house arrest. He spent the first five years of his sentence in a small house near Florence, where he continued to publish work on the science of motion, and the next—and last—four years of his life confined to another home in Florence closer to his doctors.

"No other historian in the 350 years after the trial has ever proposed the theory" that the Pope persecuted Galileo to punish the Duke of Medici, Wilding says. Written only 20 years after Galileo's death, the newfound biography represents one of the earliest explanations for the trial ever recorded. "To me, it feels right," Wilding says. The idea "might provide some closure to a still-festering wound."

But Wilding admits that Salusbury himself could be projecting his own interpretations on the event. That's the view Galilean historian Paula Findlen, at Stanford University, takes. To her, the accuracy of Salusbury's claims is less interesting than the fact that Salusbury is claiming them at all. "It's interesting to see how people at that time, from outside Italy, are starting to reconstruct Galileo's life," Findlen says. It shows that people immediately recognized the importance of Galileo, of his works and of his trial. And not only did they grasp the significance, they also suspected that politics was at the root of the trial, even then. "Even if you disagree with Salusbury's interpretation, it reinforces the idea that people knew there was something deeply political about the whole thing."

Mario Biagioli, a Harvard historian of science, says that perhaps the most exciting thing about Wilding's findings is the indication of England's early interest in Galileo. Biagioli sees the instant fascination with Galileo as an early sign of progressive thinking within the scientific revolution. "In a sense, the myth of Galileo derives from his early works and biographies—they're part of his canonization," he says. At this time, England's fledgling Royal Society, a scientific organization that Salusbury tried in vain to join, was looking to establish its patron saints, Biagioli explains, and Galileo seemed to fit the bill. Salusbury's decision to write a biography of Galileo may reflect the desire to reach across borders and solidify science as a worldwide affair.

But if there was so much interest in Galileo, why did the Salusbury biography ever disappear in the first place? Why didn't anybody make copies of the single remaining manuscript? Findlen suggests that, at some point, interest in Galileo waned. Maybe it was the canonization of English scientists such as Francis Bacon, or perhaps the availability of later Galilean biographies, but "you have to conclude that at some point, [the biography] became obscured." Then missing. Then lost. Then finally found again.

But some scholars worry that the book may disappear again. In 2006, Sotheby's sold it for £150,000 to an anonymous private collector. In his last encounter with the biography, Wilding slipped a note inside the cover asking that its new owner contact him so that it might be studied further. Ultimately, he'd like to see it wind up in a museum.

"It would be sad if things ended here, if it was lost again and kept in a private library for another 300 years," Wilding says. But he's hopeful that the more people talk about the biography, the more it comes up in public and scholarly discussions, the more likely it will be that the new owner will release the book to the public domain. "There does seem to be something of a curse on it," Wilding says. "I suppose I should start fearing fires and plagues at this point."