Galileo's Contemporaries

Galileo biographies leave the impression that Galileo's science was the only important science of his day. This is not true. His contemporaries were responsible for fundamental philosophical works that guided the future of chemistry and physics, several medical breakthroughs, the formation of the earliest scientific societies, the birth of brand new sciences and important early works on chemistry, magnetism, hydrology and electricity (see Galileo-Contemporaries-Timeline). They even made critical contributions to the technology of the telescope and the cosmology of planetary models (areas typically associated with Galileo). Many of these contemporaries were church scientists. This is not supposed to be. Galileo's clash with the church is often presented as a clash between the church and science (see Galileo's Battle for the Heavens).

Word Cloud - Scientific Citations

Since Galileo had many important contemporaries, where do we start? One place might be with the contemporaries that were being cited in the following century. The word cloud above is based on the 22 most cited scientists from several major European scientific reference works from 1758 [_1_] . The names in grey were Galileo's contemporaries.

The word cloud tells us that something, somewhere is horribly wrong. Galileo is missing! But so is Kepler and Tycho Brahe. Were the scientists of the 18th century guilty of poor judgement or is our modern fetish with Galileo overdone? Galileo's contemporary, Gassendi, a Catholic priest, was heavily cited. Gassendi is most famous for his attempt to revive atomism. Atomism was tremendously important to the future development of both physics and chemistry. The English scientists of the Royal Society from later in the century often referenced Gassendi in their own advocacy for atomism. The importance of atomism is not lost on modern scientists either. The quote below is from Richard Feynman, the Nobel Prize winning physicist:

If, in some cataclysm, all of scientific knowledge were to be destroyed, and only one sentence passed on to the next generation of creatures, what statement would contain the most information in the fewest words? I believe it is the atomic hypothesis (or the atomic fact, or whatever you wish to call it) that all things are made of atoms — little particles that move around in perpetual motion, attracting each other when they are a little distance apart, but repelling upon being squeezed into one another.

Gassendi became the voice of atomism for his age. Atomism needed a champion that was competent in philosophy in addition to math and science. Gassendi was a credible philospher, even to the point of getting into philosphical battles with Rene Descartes. He was also a very strict believer in the need for actual physical experimental support for scientific theories..moreso than Galileo. Galileo often supported his work with mind experiments instead of real physical experiments. Pierre Gassendi and another priest, Marin Mersenne, organized real experiments to test Galileo's theories where Galileo had settled for mind experiments.

Amongst the most commonly cited were several of Galileo's Jesuit contemporaries, Gaspar Schott, Giovanni Riccioli, and Claude-Francois Deschales. Riccioli and his fellow Jesuits carried Galileo's work on free fall a step further. Galileo had demonstrated important features of free fall. Riccioli took those demonstrations a step further and actually measured the acceleration due to gravity experimentally. This was done using a pendulum clock to measure the time of fall from the Torre Asinelli [_2_] . The view from the top of the Torre Asinelli shows a smaller tower that is about the height of the Tower of Pisa. Gaspar Schott made important contributions to the development of mechanical and hydraulic devices.

Torre Asinelli-Free Fall

Descartes was another famous contemporary of Galileo that is found in the word cloud. He made significant contributions to philosophy, mathematics, and science. His views sometimes clashed with Gassendi's, especially with respect to reducing what can be known to what can be sensed or inferred from the senses. His development of analytical geometry would be important to many scientific fields but especially to optics and astronomy. By the twentieth century, all the largest optical telescopes were reflectors using either hyperbolic or parabolic mirrors. Descartes analytical geometry was instrumental in their design. It might be argued that Descartes was more important to modern telescopy than either Galileo or Mersenne. Descartes also made contributions to physiology.

Medical Breakthroughs

Citations are a good start, but there is more to science than citations. There were several medical breakthroughs during Galileo's lifetime. Cesalpino discovered the roles of the veins, arteries and valves in blood circulation. This was followed by an even more accurate description of blood circulation by William Harvey. One medical breakthrough from the time is often overlooked. An expedition to the foothills of the Andes in Peru returned with a native medicine that was used to fight off chills. This medicine was sent back to the Collegio Romano in Rome. When this medicine, the Jesuit's Bark, was prescribed to malaria victims in Rome to control their chills, it was discovered that it was a remedy for the disease itself, not just the symptoms. Jesuit's Bark is rich in quinine, still used today to control malaria. This would have far reaching effects well into the future. The successful completion of the Panama canal is credited in part to the availability of quinine to control malaria.

There is a connection between the discovery of the Jesuit's Bark and the Galileo Affair. Pope Urban VIII and the Jesuits of the Collegio Romano figure prominently in discussions of the Galileo Affair. They did reject Galileo's cosmology. They weren't rejecting science, just as Galileo wasn't rejecting science when he rejected Kepler's planetary model. It was Pope Urban VIII that motivated the Jesuits to conduct a global search for native medicines. It was the Collegio Romano that received these remedies and it was the Jesuit Cardinal Lugo, that arranged that 'clinical trials' be conducted on Jesuit's Bark in Rome (see The Jesuit's Bark).

Everyday Science

We often take the sciences that have become part of everyday life for granted. One such science is acoustics. The birth of the science of acoustics is often traced back to Harmonicorum Libri by Marin Mersenne. This is the same priest who is responsible for Mersenne primes. Harmonicorum Libri, was also used to introduce designs for telescopes based on mirrors rather than lenses. This was over thirty years before Newton's reflecting telescope. Mersenne's most surprising role was only discovered after his death. From letters in his possession, it was clear that Mersenne had been acting as a clearinghouse for scientific communication between many of the great mathematicians and scientists of the day. The Mersenne Circle included Descartes, Gassendi, Fermat, Hobbes, Beeckman, van Helmont, and both Etienne and Blaise Pascal.

Acoustics isn't the only thing we take for granted. We can use Google and Bing maps without thinking about how the maps are made. We can arrange to Skype with someone on the other side of the world on a certain month, day and hour knowing that the other person would know the same calendaring system. We can do this largely due to the advances made by Galileo's contemporaries.

Many web map services, including Google Maps, use some version of Mercator projection. The first map made using a Mercator projection was published in 1569 by Gerardus Mercator. It was a radical, useful and important advance. Maps are made by projecting a 3-dimensional spherical surface onto a 2-dimensional surface. They must distort some element of the original relation between points. Mercator's genius was that this projection distorted the sizes of land bodies and distances in the northern and southern extremes of the globe but preserved the angles between two points. This meant that if you drew a line between two points, the angle formed should be your heading. This made it extremely useful for nautical navigation. The other systems did not have this feature.

Most of the world uses the Gregorian calendaring system. The creation of the Gregorian system was one of the first "big science" programs. Many scientists and mathematicians were consulted on the creation of the calendar. By the time Galileo was born the European (Julian) calendar was a mess. Equinoxes would fall on different dates depending on the century. More important to the church was that the date for Easter was migrating since it was tied to the spring equinox. Pope Gregory XIII assembled some of the greatest scientific and mathematical minds of the time to see if the Julian calendar could be improved upon. The Gregorian calendar removed 3 leap years every 400 years and reset the date for the vernal equinox to what it would have been in 325 C.E. That was enough reduce the error from 10 minutes a year in the Julian calendar to 26 seconds a year in the new Gregorian calendar. Initially, only Catholic countries adopted the calendar but by 1760, most of Europe, Catholic or Protestant, had adopted it. From then, its use spread around the world. The importance of having a common calendar for commerce and communication is often overlooked.

Important experiments are not always done by important scientists. One important experiment was conducted by Carmelite friars in Seville, Spain, before Galileo had reached the age of 10. They had acquired an exotic tuber native to the equatorial mountain regions of South America. They wanted to see whether the plant could be used to feed the poor in the region. There were risks; the stem and leaves of the plant were poisonous and if the tubers themselves were allowed to go green they also became poisonous. But it was known that the Native Americans in South America were using the tuber as food and that Spanish sailors had used the tuber as rations on trips across the Atlantic. The other problems with the plant was that it had a bland taste and that the plant was adapted to 12 hours of daylight, not the long summer days of Europe. The experiment was successful enough that the Carmelite friars took the plant to Northern Italy and started growing it there. Within two centuries, hybrids had been developed that could handle the long summer days of Northern Europe. Today the tuber, now known as the potato, is the fourth largest cash crop in the world. It is being used to feed many more than just the poor of Seville.

Optics is important in our daily lives due to cameras and projectors, not telescopes. Modern cameras and projectors derive from the camera obscura and pin-hole cameras. Several of Galileo's contemporaries (both scientists and artists) made productive use of this technology. Camera obscura had been around for centuries but their use with lenses was new. Christopher Scheiner, and his Jesuit colleague, Grienberger, used an astounding combination of camera obscura, telescope, and the newly invented equatorial mount to observe sunspots. The device (shown below) was 22 metres long.

Jesuit-Telescope-Camera Obscura

The Early Telescope

Galileo is commonly associated with the telescope. It was Galileo who demonstrated that the telescope was much more than a toy for the rich. It was a valuable instrument for astronomy and an early warning system for the military. He also raised the bar on telescope manufacture, very quickly producing telescopes that were much more powerful than the telescopes of the Dutch originators. But there was a serious flaw in Galileo's designs. A flaw so great that the design had met its practical limit even before his death. As astronomers attempted to increase the power of the Galilean telescope the field of view quickly decreased to the point where the telescope was of little use (see Jesuits and the Telescope). The picture of the moon below shows what would be seen by a 20x Galilean telescope (the inner circle) and what would be seen by a 20x Keplerian telescope (the outer circle).

Galileo/Kepler Field of View

The problems with the Galilean telescope meant that the future of the telescope lay in the hands of Galileo's contemporaries. Johannes Kepler proposed a design that would so dominate in astronomy that it became known as the astronomical telescope. Kepler's design was initially ignored. It was the Jesuit Christopher Scheiner and his colleagues that were the early champions of the design. Two priests, Marin Mersenne and Bonaventura Cavalieri, would propose telescope designs employing mirrors instead of lenses ( see Reflecting on History). During the nineteenth century important reference works identified Marin Mersenne as the inventor of the reflecting telescope [_3_] . Today we have the awkward situation where astronomers are using reflecting telescopes based on a design Mersenne published in 1636 ( see Reflecting on History), while textbooks assign the invention of the reflecting telescope to Isaac Newton in 1668 or James Gregory in 1663. The designs below are taken from Mersenne's 1636 publication.

Mersenne Telescopes-Harmonie Universelle

Kepler is important to science for more than his telescope design. He developed an important treatment of optics and a set of laws for planetary motion that is still taught in schools today. He also advocated that the tides were caused by the moon. Sadly, he was largely ignored by Galileo. Had he recognized Kepler's work it may have saved him the embarassment of trying to use tides to prove the motion of the earth and the futility of trying to make a planetary model work with perfect circles when ellipses were required. Nothing was going to change Galileo's mind about Kepler. Kepler's planetary model made very specific predictions. One was that Mercury should pass directly between the sun and earth on November 7, 1631 ( this is known as a Transit of Mercury). This was about a year before Galileo's trial. Pierre Gassendi had arranged an international experiment by sending brochures to important astronomers warning about the upcoming event. The transit was witnessed by Gassendi and others on November 7, 1631 within minutes of the time predicted. Galileo did state why he chose to ignore Kepler. He did not want to seek out "the nuggets of real gold in Kepler's heap of dross" [_4_] .

The Real Tower of Pisa Experiments

Perhaps the most famous experiment in the history of science is the Tower of Pisa experiment. Most people know the legend. Galileo, when a young professor at the University of Pisa, climbs the Tower of Pisa in front of an audience of professors and students. In a direct challenge to the stodgy Aristotelian professors of the day, he proceeds to drop balls of unequal weight to show that they hit the ground at the same time. There is a growing consensus that this experiment was a myth (see Myth 1. The Tower of Pisa Myth). There isn't any evidence that the story was known or told in Galileo's lifetime. As with many myths, it has a germ of truth. There is documented evidence of two different professors from the University of Pisa conducting a free fall experiment from the Tower of Pisa in Galileo's lifetime. Giorgio Coresio conducted his experiment in 1612 and Vincenzio Renieri in 1641. Coresio was trying to prove that Aristotle was right, and felt he did so (since in his experiment the heavier ball reached the ground before the lighter one). Renieri was an Olivetan monk and close friend of Galileo. Vincenzio was not trying to disprove Aristotle. He was trying to disprove the work of the Jesuit, Niccolo Cabeo. Cabeo believed that two objects of different weights dropped from a height would reach the ground at the same time with the same velocity. This was based on observing the free fall experiments of Baliani. Vincenzio's experiment contradicted that of the Jesuit (probably through experimental error). Galilean biographies are often presented as symbols of the clash between church and science and they often reference this famous myth. It is ironic that one of the real Tower of Pisa experiments was conducted by a monk to settle a dispute with a priest.

Breaking with the Past

Today, Galileo's clash with the church is of more interest than his astronomical work. A variety of very simple explanations explain this clash. One explanation is that Galileo openly challenged Aristotelian thought and that the church hierarchy was deeply tied to an Aristotelian world view. Galileo was neither unique nor more extreme in his criticism of Aristotle than many of his contemporaries. The Mersenne Circle was anti-Aristotelian and it was co-ordinated by a priest. Probably the most severe critic of Aristotle in the circle was another priest, Pierre Gassendi. Gassendi wasn't quibbling with individual observations or specific scientific theories of Aristotle, he was challenging the very fundamentals of his philosophy and world-view. The explanations sometimes caricature what it meant to be an Aristotelian. Aristotle had proposed that the speed of the fall of an object was proportional to its weight. That doesn't mean that is what Aristotelians believed. One Aristotelian contemporary of Galileo was Giuseppe Moletti. Galileo replaced Moletti at the University Padua after Moletti died. Moletti conducted a series of free fall experiments when Galileo was still a child and had concluded that heavy and light objects fall at the same speed. Moletti's experiments were a textbook example of good experimental design because he repeated the trials to control for shape, material and volume. Being an Aristotelian didn't mean you have to believe everything Aristotle said. A similar situation exists today. Today you might classify most biologists as 'Darwinists' (or neo-Darwinists). None of these biologists believe in evolution by natural selection as Charles Darwin originally proposed it in 1859 (see Mendel and Darwin).

One of Galileo's contemporaries, Jose Acosta, highlights the problems with simplistic analyses of the Galileo affair. Explanations of the Galileo Affair include Galileo's criticisms of Aristotle, the fact that he chose to write his works in his native tongue (Italian) instead of the Latin, and that his work conflicted with a literal interpretation of the Bible. Acosta's most famous work, Historia natural y moral de las Indias, was written in Spanish, his native tongue. The book was so popular that it was quickly translated into other languages. It dealt with the astronomy, meteorology, flora, fauna, medicines and social customs of South America. Amazingly, he predicted a land bridge with Asia centuries before the Bering Strait was discovered. Acosta's observations in South America contradicted Aristotle's writings. Unlike Galileo, Acosta never ran into trouble with the church, and he was a Jesuit priest. The reasons for Galileo's problems are likely more complex than many would want them to be. We are reminded of H.L. Mencken's quote, "For every complex problem there is an answer that is clear, simple, and wrong.".

Europe didn't have to wait for either Galileo or his contemporaries to realize Aristotle or Ptolemy weren't infallible. Aristotle had proposed that the equator was a ring of fire that was a barrier to navigation between the north and south hemispheres. By the 1470's Portugese mariners had crossed the equator and did not encounter a ring of fire. Ptolemy had proposed that the Indian Ocean was land-locked so that it would not be possible to navigate to India by sea. In 1488 Bartholomew Diaz rounded the Cape of Good Hope and proved that the Indian Ocean can be reached by sea. Many European maps from the early 1500's onward were graphic reminders of how wrong these great philosophers could be. The first map below is a Ptolemaic map and the second is a Spanish map (by Diego Ribeiro) from 1529.

Galileo biographies often lionize him by presenting him as a lone champion for experimentation and science. Any timeline of science from the period (Galileo-Contemporaries-Timeline) will show that this is not true. The advances included the revival of atomism (which underpinned the future of physics and chemistry) and cures for diseases that were the scourge of Europe. Contributors to these advances came from all across Europe. Although many were from the well-to-do middle class, many others were Roman Catholic clergy.

GalileoContemporariesKepler Tycho Brahe GassendiChurchMarin MersenneDescartesRiccioliJesuitsGregorian CalendarAcousticsOpticsPotato

Copyright Joseph Sant (2019).

Cite this page.

Sant, Joseph (2019).Galileo's Contemporaries. Retrieved from


<a href="">Galileo's Contemporaries</a>

1. Andrzej K. Wroblewski, , Are we ready for common history of science?, http://www.2iceshs.cyfr... ,
This is a call by the author for Europe to develop a common history of science. He demonstrates quite convincingly that there really isn't one history of science but several different ones, based on nationality and language group. In the presentation he discusses an exercise he performed of developing a citation index for science in 1758 from several respected Scientific publications from the English, German and French-speaking areas of Europe. Newton had the second highest number of citations with 94. Musschenbroek had 100. Musschenbroek had recently made important contributions to electrostatics including developing the Leyden jar. These include Schott(49), Descartes (43), Gassendi (35), Dechales (28), and Riccioli(26). Gaspar Schott, a Jesuit, made contributions on mechanical and hydraulic devices, including the first description of a universal joint. Riccioli wrote widely on astronomy and dynamics.

2. I. Bernard Cohen, W. W. Norton and Company, 1985, The birth of a new physics, , 97
Cohen mentions that Galileo's estimate of the acceleration due to gravity has been calculated to be 467 cm/sec/sec versus the actual value of 980 cm/sec/sec. The estimate produced by the Jesuit experiment from the Torre Asinelli was 914 cm/sec/sec.

3. Francis Lieber,ed., Carey and Lea, Encyclopedia Americana, Vol. 12, , 170
Quote:'The reflecting telescope was invented by father Mersenne, a Frenchman, in the middle of the seventeenth century'

4. Max Caspar, Courier Dover Publications 1993, Kepler, , 137
Caspar refers to this quote from an article by Rosen in the footnotes of his discussion as to why Galileo may have chosen to ignore Kepler through the last three decades of his life.