2.12: Galileo and the Beginnings of Modern Science

Galileo Galilei was both a controversial figure and one of the first scientists. Do these two things necessarily go together? That depends on who you ask. The world might not have been ready for science yet, but Galileo wasn’t going to let that stop him from sharing his thoughts about his observations.

Galileo was a meticulous observer, both in his work in understanding the motion of terrestrial objects and in his work discovering the movement of celestial objects. In terms of the impact of his work on the process of science as we know it today, it turns out that he had the greatest effect where he was the least controversial. Galileo is most famous in most circles for his contentious relationship with the Catholic church over the movement of the planets around the Sun (and the movement of moons around planets, some of which he was the first to ever observe). However, his overall contribution to the field of astronomy was not as influential as his contemporaries Tycho Brahe and Johannes Kepler. And though his instrumentation allowed him to see things that nobody else had ever seen before, the idea that the planets went around the Sun had been proposed by Copernicus a hundred years before (and even by some early Babylonian astronomers whose names are now lost to history).

Galileo’s greatest contributions to science lay in his work on understanding motion. Galileo was able to show that the increase in velocity of a falling object was proportional to the time it was falling (hence defining acceleration, and in all cases he observed constant acceleration). He was able to measure this through the use of a very long device of variable inclination that he rolled steel balls along. To keep track of time in the days before stopwatches, he devised an elaborate system of weighing the water released from a jug.

In both his work on astronomy and in the development of the field of kinematics, Galileo’s innovations were in the design and creation of novel instruments and in the meticulous observations he was able to make with those instruments. In astronomy he created telescopes. In kinematics he created the aforementioned inclined plane. Also important was his ability to observe these experiments with high precision. His ability to observe changes in velocity of an object rolling along an inclined plane was truly remarkable given the technology available to him at the time. Physics students of today often have trouble measuring as precisely as Galileo did back then, even with the technology that these students have available to them now! In addition to the new designs related to astronomy and kinematics, Galileo created more accurate thermometers, and compasses.

In addition to his groundbreaking work in instrumentation, observations, and experimentations, he needed to make sense of the data he was obtaining. For this, Galileo needed to have a comprehensive understanding of the mathematical techniques of the day. He did not really create new ways of thinking about math, but he needed to use the existing ways in order to formulate his idea. Galileo had a deep respect for the field of mathematics and was one of the first to claim that natural phenomena could be fully explained by mathematical principles.

There were several factors which lead to Galileo’s eventual trial and sentencing by the Inquisition. He had been instructed by the Inquisition to no longer write about heliocentrism in 1616. The Inquisition’s arguments against Galileo’s beliefs largely relied on the ideas of Kepler, which are still understood to be true today. (Kepler proposed an elliptical instead of circular orbit, which could be thought of as the Earth and Sun revolving around each other.) Galileo didn’t discuss heliocentrism again for decades, but did have a bitter dispute with a Jesuit about a comet in the meantime. Eventually Pope Urban VIII was elected, and based on their friendship Galileo thought he could now write about heliocentrism. However, the resulting work led to a new trial in 1633 which resulted in house arrest for the remainder of his life and a ban on any of his writings.

Galileo spent the last ten years of his life under this house arrest. It was during this time that he wrote about his work on kinematics which he had performed decades earlier: Two New Sciences. If he had not been so confined, he might not have taken the time to write down his greatest contributions to the field of science. On the other hand, everything he wrote at this point in his life was still being banned and he had to publish it in a non-Catholic country.

But perhaps Galileo’s greatest contribution is not just an aspect of science, but science itself. Albert Einstein called Galileo the father of modern science. Other prominent scientists have echoed this sentiment or said very similar things. (Although it should be noted that Galileo was not the only one focused on this line of thought. Other prominent researchers of the 17^th century include Francis Bacon, René Descartes, and Robert Boyle.) Prior to the work of Galileo, scientific thought in Europe was not distinct from religious and philosophical thought (as can be seen from its historical name: natural philosophy). It was perhaps mostly a curiosity within the fields of religion and philosophy that was beholden to the principles which governed these fields. The concept that it was possible to discover natural laws through the observations of nature was itself a novel concept and so it is not surprising that it would lead to some controversy. In our modern world, philosophy, religion, and science are their own separate fields but there are still those who sometimes conflate them. This is especially true when science discovers (or sometimes rediscovers) aspects of reality that other fields of understanding make false assumptions about as part of constructing their worldview. As we discussed in chapter 1, there are multiple ways of knowing, and science is only one of them. But science is the way of knowing best equipped to provide clarity on how natural processes work based on observations of those processes.