The Church and the Early Telescope

On October 29 2002, the Public Broadcasting System of the United States first aired a biography of Galileo titled "Galileo's Battle for the Heavens". The program's accompanying website stated "...Despite myriad embellishments, however, most optical telescopes in use in the 21st century derive from the two types developed in the 17th century by Galileo and Newton, on whose shoulders all astronomers, both amateur and professional, stand today.". In fact, the Galilean telescope was a dead-end; its popularity barely outlasted Galileo himself. Most astronomical telescopes today derive from two types developed in the 17th century...but not by Galileo and Newton. Most modern telescopes trace back to developments by Christopher Scheiner and Laurent Cassegrain, both 17th century Roman Catholic priests, and Johannes Kepler, the great astronomer. The irony here is that the writers of the biography had clearly portrayed the church throughout as 'battling' science. It should surprise no-one that the priests' contribution to the development of the early telescope was never mentioned in the program or on the accompanying website (see Galileo's Battle for the Heavens).

The Matthew Effect is a tendency discussed by historians where credit for discoveries or inventions is incorrectly attributed to already famous scientists. There is probably no better example of this effect than the history of the early telescope. There were many scientists who made critical contributions to the development of the early telescope (see Timeline of the Telescope). Popular histories typically only discuss two, Galileo and Newton. Those excluded include famous thinkers such as Kepler and Descartes and several Roman Catholic priests.

There were several advances in theoretical optics and telescope construction during Galileo's lifetime that would impact the development of telescopes for centuries to come. Oddly, Galileo was not involved in any of these advances. His importance to the history of the telescope lies in the fact that he made the use of telescopes respectable in science. This on its own is a very important contribution. His skill as an artisan, especially polishing lenses, also resulted in telescopes that were a considerable improvement over those that preceded him. Florence, Galileo's birthplace, had been the pre-eminent center for lens-making in Europe since the late thirteenth century (see Timeline of the Telescope Year:1289). But beyond this, it is difficult to name one advance made by Galileo in the theory or construction of telescopes that is in use today. That is not true of the church scientists of his day; especially the Jesuits.

The scientists who had the greatest influence on the future of optics and telescope construction from Galileo's day were Johannes Kepler, Rene Descartes, Wilebrord Snell, Father Marin Mersenne, Father Bonaventura Cavalieri, Father Christopher Scheiner and Father Christopher Grienberger. The first three developed a theoretical foundation for refraction and reflection that would be built upon in the following centuries. The four fathers made critical contributions to the technology of telescopes. All of their contributions are still in use today. Fathers Marin Mersenne and Bonaventura Cavalieri together would propose the basic geometric shape that would be used in modern (reflecting) research telescopes (see Reflecting on History). Father Christopher Scheiner, a Jesuit, would be the first to construct a modern astronomical telescope, using theory proposed by Johannes Kepler. Christopher Grienberger, a Jesuit colleague of Scheiner's, would propose an extremely sophisticated method of mounting telescopes to better follow celestial bodies as they arc through the night sky. Father Scheiner would use Grienberger's equatorial mount to produce the finest celestial images of the early seventeenth century. The contributions of Father Nicolo Zucchi, another Jesuit, may not have been as important as the scientists listed above, but he was able to demonstrate that using telescopes combining lenses and mirrors was viable. This was in 1616, 50 years before Newton's famous reflecting telescope. He was the master craftsman who also built refracting telescopes for Johannes Kepler at the request of the Jesuit order (see Jesuits and the Telescope).

The contributions of church scientists continued well after Galileo's death. Father Laurent Cassegrain, a french priest and contemporary of Isaac Newton, was the first to propose a design for reflecting telescopes that is commonly used in modern research telescopes. The Hubble Space Telescope and many of the largest research telescopes in the world are Cassegrain reflectors. In an ironic twist that is so common in history, Isaac Newton was one of the leading critics of the young priest's design. Here is what Newton had to say about the Cassegrain design:

You see therefore, that the advantages of this design are none, but the disadvantages so great and unavoidable, that I fear it will never be put in practise with good effect [_1_] .

Laurent CassegrainChurchTelescopeJesuitsChristopher ScheinerKeplerNewton

Copyright Joseph Sant (2019).

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Sant, Joseph (2019).The Church and the Early Telescope. Retrieved from


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1. Newton, Isaac, The Newton Project, The Newton Project, http://www.newtonprojec... ,
The aggressive response by Isaac Newton and another famous contemporary scientist, Christopher Huygens, to the Cassegrain design is an object lesson in the history of science. Historically, science has not always been a game that has been played with kid gloves. There has been good reason for scientists to fear publication of their material. Copernicus is known to have feared the reaction of his contemporary scientists to his work. Considering the treatment given Cassegrain, his fears were not out of place.