**Philippe van Lansberge** was a Flemish clergyman who wrote on mathematics and astronomy. He calculated $\pi$ to 28 places by a new method.

- He is known by the name Philip, often written as Philippe.
- Faced with this array of possibilities we will consistently use the form 'Lansberge'.
- He was born in Ghent in the Netherlands to parents Daniel van Lansberge, Lord of Meulebeke, and Pauline van den Honigh.
- At the time Philip was born, the Low Countries were part of the Spanish Empire, a Roman Catholic country that used the Inquisition to prevent any deviation from the beliefs laid down by the Church.
- It was there that Philip was educated, studying mathematics and theology.
- Lansberge could now return to his homeland and, in March 1579 he left London and returned to Ghent.
- However, in Saffelaere he had trouble with the bailiff, Gilles van Bastelaer, who wanted to prevent him from performing the duties of his ministry.
- Farnese allowed the Calvinists in Antwerp to leave peacefully after the siege and move to the north and this is what Lansberge did, moving to Leiden.
- In Leiden, Lansberge matriculated at the university and continued his studies of theology.
- Before we describe the contents of Lansberge's treatise, we note that his interest in astronomy, probably stimulated during his short stay in Leiden, led him to be dissatisfied with both Ptolemy and Copernicus.
- Van Lansberge's new proof for the cosine theorem for sides (in Book IV) marks the first time that the theorem appeared in print for angles as well as sides.
- But although Van Lansberge may lay claim to the discovery of the theorem for angles, sufficient evidence indicates that this theorem was known to Viète and to Tycho Brahe.
- On the whole Van Lansberge shows little originality in the content of his trigonometry, but his arrangement of definitions and propositions is less complicated and more systematic than that of Viète and Clavius.
- In 1597 there was an attempt to call Lansberge to be a minister in Amsterdam.
- In the end, despite the attempts of the church to call Lansberge to Amsterdam, the town authorities refused to sanction the appointment and Lansberge remained in Goes.
- It was a position which called for a militant attitude, and Lansberge certainly did not compromise.
- Lansberge thought himself entitled to tell the magistrate how to act.
- A vigorous attack on the leniency of the town government of Goes, which allowed people suspected of Catholic sympathies to stand for the magistracy, eventually led to Lansberge's downfall.
- Lansberge accepted that his time in Goes was over and moved to Middelburg where he spent the rest of his life.
- In Middelburg, Lansberge used his skill in medicine as well as publishing books on astronomy and continuing to make astronomical observations.
- In 1616 Lansberge wrote on π calculating it to 28 places using a new method.
- He thought that he had found a better approximation than that of Ludolf van Ceulen, who had used the Archimedean method of inscribed and circumscribed polygons and had carried the value of π to thirty-five decimal places in 1615.
- Lansberge's work on astronomy followed Copernicus's heliocentric theory although he did not seem satisfied with what Copernicus had presented.
- It gave Lansberge's theory of the sun, presented with many tables to allow calculation of the sun's position at any time and in any place on earth.
- However, when he was joined by an enthusiastic young astronomer Maarten van der Hove (who is better known by the Latin version of his name, Martinus Hortensius) in 1628, he quickly started publishing again.
- Helped by his young assistant, Lansberge published in 1628 a second edition of his 1619 work, a manual on the use of the astrolabe and the quadrant, then, in the following year, he published a popular account of his heliocentric theories in Dutch under the title Bedenckingen op den dagelyckshen, ende jaerlyckschen loop van den aerdt-kloot.
- The Dutch edition, written for those without mathematical skills, made quite an impact in Holland while the Latin translation was widely read and this soon led to Lansberge being strongly attacked by those opposed to the heliocentric theory.
- Of course, as a devout Christian, Lansberge had to explain why he was putting forward a theory which, apparently, contradicted the Bible.
- Among those who attacked Lansberge's work, one of the most vigorous of the anti-Copernicans was Jean-Baptiste Morin.
- Perhaps it would be fitting to look at the highly non-scientific world-view that Lansberge puts forward in the Bedenckingen clearly attempting to integrate the religious views of his day into his Copernican system.
- Now although Lansberge believed in a heliocentric system, he did not accept Kepler's ellipse theories and he published astronomical tables, based on circular orbits with epicycles, which he hoped would support Copernicus over Kepler.
- In 1632, the year of his death, Lansberge published Tabula motuum caelestium perpetuae, the astronomical tables that he had been working on for 45 years.
- The quality of Lansberge's tables, published five years after Kepler's Rudolphine Tables, were not immediately obvious at first.
- Many accepted that the later tables by Lansberge would necessarily be more accurate than Kepler's and for around ten years this belief continued.
- Despite the weaknesses in Lansberge's work, he still deserves much credit for bringing the ideas of Copernicus to a wide range of people who did not possess the mathematical background to read advanced texts.

Born 25 August 1561, Ghent, Spanish Netherlands (now Belgium). Died 8 December 1632, Middelburg, Netherlands.

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Astronomy, Origin Belgium

**O’Connor, John J; Robertson, Edmund F**: MacTutor History of Mathematics Archive