When we think of the revolutionary thinkers of the past, we often think of them as inventive thinkers, people who look at the world in a fundamentally different way from what came before, who depart radically from their predecessors to usher in a new era. Copernicus and Galileo, who are credited (perhaps in slightly overstated fashion) with entirely recontextualizing our place in the universe, are thought of in this way, but the reality is that most seemingly revolutionary thinkers were less people who ran in a different direction from everyone else, and more people who saw the trail ahead more clearly and could take the next few steps for us. We saw that in our review for On the Revolutions of the Heavenly Spheres, wherein Copernicus connected his arguments for a heliocentric cosmos to similar assertions by ancient thinkers going back to the classical Greeks.
More than Copernicus, Galileo is often depicted as a scientific firebrand deliberately courting controversy with the Church, emblematic of the mindset of leaving the old, stale ways behind in favor of what is new. Great insights and radical leaps usually don’t occur in a vacuum, though, even if the contributing steps are sometimes invisible. What looks like invention in retrospect often reveals itself to be innovation upon closer examination. Ivan Malara recently brought us several steps closer to understanding Galileo as an innovator, rather than an inventor.
The details of his finding will be published soon in a paper being reviewed by the Journal for the History of Astronomy, but the findings are already being widely reported, including in this article from Science: “Galileo’s Handwritten Notes Found in Ancient Astronomy Text.” In it, Malara details his discovery of a manuscript of The Almagest in which are contained annotations in Galileo’s handwriting. They reveal the attention Galileo paid to this foundational work of the Ptolemaic cosmology, and how he “broke with Ptolemy’s cosmos because his mastery of [Ptolemy’s] reasoning convinced him that a heliocentric system would better fulfill Ptolemy’s own mathematical logic.”
Remember, the Ptolemaic system was originally less a claim that the Earth was the actual center of the universe, and more an attempt to geometrically explain astronomical observations in a geocentric coordinate system. Copernicus, and others before him, found the math significantly simpler if the coordinate system is heliocentric instead of geocentric, since the geocentric coordinate system requires invoking complex barycenters, epicycles, and other intricacies to account for the observations. Galileo’s astronomical observations advanced the argument from a geometric concern to a physical one.
Of course, there is a sense in which the whole argument is somewhat silly. In an infinite universe, the “center” is meaningless. Even today, astronomers and others working in related fields use all kinds of coordinate systems centered in all kinds of places depending on the desired application. In working with satellites, I use a variety of geocentric coordinate systems, but I’ll occasionally need to use a heliocentric coordinate system, or even something exotic, like a coordinate system centered on the Moon, or on Mars, or (one time) on one of Mars’ moons. For these projects, each of those became the apparent “center of the universe.” All of which is probably only interesting if you happen to make a hobby of astrodynamics and orbital mechanics.
What is more interesting, though, is the finding of Galileo’s annotations in The Almagest and the insights we can derive about his thinking and approach therefrom. If nothing else, it’s a reminder that even the most inventive changes often look more like innovation. It’s all a matter of perspective.
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