Christopher Clavius SJ: astronomer, mathematician and educator


Christopher Clavius, S.J.  (25 March 1538 – 06 Feb 1612) was a German Jesuit known for his reform of the calendar, and a mathematician and gifted educator. He joined the recently founded Jesuit order in 1555 and was sent to Coimbra, Portugal, to pursue his studies. On 21 August 1560, he observed a sun eclipse, an event which convinced him to devote his life to mathematical and astronomical study. Following this eclipse observation, he went to Italy later in 1560 and studied theology at the Jesuit Collegio Romano in Rome. He was ordained in 1564. He remained at the Collegio Romano were he began teaching mathematics in the year of his ordination. In fact, except for a period in Naples around 1596 and a visit to Spain in 1597, Clavius was to remain Professor of Mathematics at the Collegio Romano for the rest of his life. He continued with his studies in Theology and became a full member of the Jesuit Order in 1575.

in 1579, he was elected as member by Pope Gregory XIII to the commission to oversee the reform of the calendar. The old Julian Calendar had been established by an edict of Julius Caesar in 45 BC.  Because the system of Julian years and leap years did not correspond exactly to the length of the astronomical year, dates of important Christian feasts had gotten out of alignment with the seasons. This commission adopted the ideas for calendar reform of Aloysius Lillius, with some modifications, and in 1582 Pope Gregory XIII promulgated the new calendar. Catholic countries quickly adopted the “Gregorian calendar,” but Protestant and Eastern Orthodox countries only slowly followed. In 1588, it became his role to explain and defend the calendar reform, and he did so in Novi calendarii romani apologia and subsequent works to counter arguments coming from Protestants, but also from astronomers and mathematicians.

Galileo Galilei was familiar with Clavius’s books, and he visited Clavius during his first trip to Rome in 1587. After that they corresponded from time to time about mathematical problems, and Clavius sent Galileo copies of his books as they appeared. Clavius was and remained a defender of the geocentric system although he was impressed by Galilei’s telescopic discoveries as he wrote in 1611, a year prior to his death.

His true and lasting influence was the adoption of rigorous mathematical curricula in Jesuit colleges, at a time when the importance of mathematics in natural science (then called “natural philosophy”) was widely underappreciated. He wrote widely used textbooks and influenced future generations of astronomers and mathematicians.

Image: Christopher Clavius. Line engraving by E. de Boulonois., Wikimedia


Thony Christie, A loser who was really a winner.

Christopher Clavius (1537-1612), The Galileo Project

J J O’Connor and E F Robertson, Christopher Clavius

Stephen M. Barr and Andrew Kassebaum, Important Catholic Scientists of the Past, Christopher Clavius (new on the website of the Society of Catholic Scientists)

Thony Christie, Christopher and the calendar

Thomas Aquinas: God, Chance and Necessity


“The effect of divine providence is not only that things should happen somehow, but that they should happen either by necessity or by contingency. Therefore, whatsoever divine providence ordains to happen infallibly and of necessity, happens infallibly and of necessity; and that happens from contingency, which the divine providence conceives to happen from contingency”

Thomas Aquinas:, Summa theologiae, I, 22, 4 ad 1.

I found these words some years ago in ‘Communion and Stewardship’ (Vatican Theological Commission, 2004, par. 69) and it was a game changer in how I reflect on God’s action in creation via evolution [1].

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John C. Eccles – In Evolution, Humans Remain Mysterious


On 27 January 1903, John C. Eccles (1903–1997) was born in Melbourne, Australia.

He was one of the most preeminent neurophysiologists of the 20th century, and he won the Nobel Prize in Medicine in 1963. His numerous popular works elucidate his vision of the human mind in which he supersedes materialist monism by the conception of the mind transcending matter. He wrote “The Human Mystery” (1979) and “The Wonder of Being Human” (1985).


“The amazing success of the theory of evolution has protected it from significant critical evaluation in recent times. However, it fails in a most important respect. It cannot account for the existence of each one of us as unique, self-conscious beings.”
(The Human Mystery, 1979)

Baptiste-Julien d’ Omalius d’ Halloy and Charles Darwin


On 15 January 1875, Baptiste-Julien d’ Omalius d’ Halloy, a Belgian geologist, died at age 91. He was an early proponent of evolution and one of the pioneers of modern geology who determined the stratigraphy of the Carboniferous and other rocks in Belgium and the Rhine provinces, and also made detailed studies of the Tertiary deposits of the Paris Basin.

In the third edition of On the Origin of Species published in 1861, Charles Darwin added a Historical Sketch giving due credit to naturalists who had preceded him in publishing the opinion that species undergo modification, and that the existing forms of life have descended by true generation from pre-existing forms. This included d’Halloy :

“In 1846 the veteran geologist M. J. d’Omalius d’Halloy published in an excellent, though short paper (‘Bulletins de l’Acad. Roy. Bruxelles,’ tom. xiii. p. 581), his opinion that it is more probable that new species have been produced by descent with modification, than that they have been separately created: the author first promulgated this opinion in 1831.”

He was a practicing Catholic during his long and active life, and was characterized by his loyalty and devotion to the Church. He insisted on the harmony between faith and science, making this the subject of his oration on the occasion of the golden jubilee of the Belgian Academy in 1866.

Was Nikola Tesla a Christian? – An "enlightening" answer


Nikola Tesla (10 July 1856 – 7 January 1943) was born in Smiljan, Crotia. His father was a Serbian Orthodox priest. He was a pioneer in fields such as electricity, radio and x-rays. Tesla had 300 patents under his name by the time he died in 1943 (in New York) and is revered by some as one of the most important scientific brains of the late 19th and early 20th century.

But was he a Christian? I doubted this, taking him as a vaguely a religious person with strong Serbian-Orthodox background.  And than to my surprise, I found this icon of Nikola Tesla in a church in Trebinje, Republica Srpska, and posted it to the SMF fb-page.

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Giuseppe Piazzi: Discoverer of Minor Planet Ceres



Giuseppe Piazzi (1746–1826) was an Italian Catholic priest of the Theatine order, mathematician, and astronomer.  He founded and directed what is now known as the Palermo Astronomical Observatory. He also directed the construction of the observatories in Naples and Capodimonte. Piazzi also published a catalogue of 6,748 stars, the “Praecipuarum stellarum inerrantium positiones mediae ineunte saeculo XIX.”

On 01 January 1801, he discovered the first asteroid, Ceres (now called a “dwarf planet” or “minor planet”). In his astronomical catalog, he also identified 61 Cygni as a good candidate for studying parallax, which later led to important research by Friedrich Wilhelm Bessel (1784–1846). The lunar crater Piazzi was named after him in 1935.

Christian Women in Science


To close the year 2019, I have introduced a new category that will allow you to browse all the amazing Christian Women in Science, starting at the Middle Ages up to 21st century that are presented on this blog: it is a long list, and there is more to come!

Why is it important to present ‘Christian Women in Science’?

In the introduction to my article on Mary Anning, Marie Buckland and Charlotte Murchison, three early paleontologists, I said:

“Women are still minorities in the sciences, and we should change that in the 21st century.  Although there is no “magic bullet” to close the gender gap in science, everyone who studies the problem agrees on one thing—the importance of female role models in changing girls’ perceptions of themselves. As a female scientist, I have to agree. But at the same time, I am a Christian female scientist, and young girls need to know that it’s possible to be both.

What constitutes a ‘Christian Woman in Science?

In an earlier post, I identified two characteristics:

(1) they have had an impact on the science and/or scientific education at their time and
(2) there is some kind of proof that their Christian faith – in whatever faith tradition, Catholic, Protestant or Orthodox – was important to their personal life.

Or in other words: female scientists whose life was informed, transformed and inspired by their faith.