Archimedes’ Death Ray and Dante’s Inferno
The Real Story of How Galileo Ignited the Age of the Telescope
Although Galileo tried to avoid a conflagration, controversy rages to this day concerning the great astronomer’s role in fueling the 400-year-old so-called conflict between science and religion.
But there is another debate, although thankfully it is being conducted with far less angst and vitriol among historians and academicians, concerning the methods by which Galileo was able to improve upon an unusual optical device, invented in the Netherlands 400 years ago, which allowed faraway objects to be seen as if nearby.
Was Galileo’s dramatically rapid improvement of the telescope the pre-ordained product of a ruthlessly methodical and mathematical mind?
Or was it merely the fortuitous outcome of a desperate, opportunistic man; Berthold Brecht’s so-called hero: hell-bent on claiming fame and fortune to save himself and his family from economic collapse?
Perhaps it was a happy conjunction of both?
What do two highly-regarded historians have to say? According to William Shea, Galileo was a talented artisan, but “until his dying day he remained totally in the dark regarding the laws of optics that lay behind his success.” Albert Van Helden does acknowledge that Galileo was a brilliant experimenter—he did, after all, figure out that magnification was related to the focal lengths of the two lenses he employed in his fledgling instrument. But how did he do it? Trial and error. Ringing endorsements of Galileo’s prodigious knowledge of optical theory? Not exactly.
Yet, even after Galileo published his famous Siderius Nuncius, wherein he described how he improved the magnification and quality of the image in his telescope, no one could duplicate his efforts, not even Mr. Kepler—who was certainly no “lightweight.” So how was Galileo able to do it?
In his excellent and comprehensive article, “Galileo and the Telescope”, Tel Aviv professor Ya’acov Zik contends that Galileo’s improvements on the telescope weren’t accidental; that he undoubtedly understood the principles of the telescope. Galileo said as much in a letter he wrote to his brother-in-law just one week after his successful demonstration of his 8-power telescope from Campanile di San Marco in Venice- August 21,1609. He states unequivocally that his instrument “havere fondamento su la scientia di prospettiva”—in other words, it has its foundation in the science of perspective. Zik states that Galileo, being a mathematician, understood prospettiva very well. Measuring things was his forte. He had been tutoring students for years on the use of his military or geometric compass. Zik writes: “From his vast experience of taking measurements on the earth surface, Galileo knew that the proper way of representing or drawing objects is done by using a defined proportion scale. It is possible to manipulate the scale and the angle of vision without damaging the realistic representation as long as we are following the formal calculation rules, arithmetical or geometrical…
And here’s the intriguing part: Zik concludes that Galileo could easily draw the similarities between his problem and the model of describing a method to measure the height of a tower… using a mirror.
Measuring the height of a tower using a mirror? Why does this sound vaguely familiar? Recall the story of Archimedes’s burning mirror in the siege of Syracuse, sometimes called Archimedes Death Ray which was also supposedly used to defend Constantinople in 519 AD. Can you conjure up this image of Archimedes poised on top of a tall tower, directing a huge mirror which reflects the sun’s rays directly onto the Roman ships in the sea below, setting them ablaze once they were within bowshot.
Yet another Galilean scholar, Sven Dupre has argued that Galileo must have been familiar with the optical properties of concave mirrors in terms of the “punctum inversionis” as it was practiced in 16th century optics since he owned copies of Della Porta’s Natural Magic and DeRefractione and also Ausonio’s Theorica which describes not only the burning properties of a concave spherical mirror, but its image formation and location as well. It would not have been the first time Galileo used medieval texts for inspiration and instruction from fiery themes. Recall that Galileo established quite a name for himself as a mathematician early-on with the Medici’s. Just past his teenage years, Galileo impressed the Florentine Academy with his lectures on Dante’s Inferno. He solved a problem which had vexed all who had preceded him: how do you calculate the size and the shape of Hell? His solution eventually led to one of the most important discoveries in the history of science — the principle of scale invariance, or the idea that in nature, size matters. So is it so unreasonable to assert that perhaps only Galileo was uniquely endowed with the requisite knowledge to transform a toy Dutch spyglass into an instrument whose impact on the world would be of epic proportions?