Paolo dal Pozzo Toscanelli

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Paolo dal Pozzo Toscanelli

Paolo dal Pozzo Toscanelli (* 1397 in Florence , † 1482 in Florence) was an Italian doctor, mathematician, astronomer and cartographer . He was busy u. a. with the idea that Asia could be reached from Europe by a western sea route. He became one of the pioneers in the discovery of America by Christopher Columbus in 1492 .

Life

He was the son of the doctor Domenico Toscanelli. From 1415 he studied mathematics, philosophy and medicine at the University of Padua . Here he made a lifelong friendship with Nikolaus Cusanus . Both graduated in 1424, Cusanus in law and Toscanelli in medicine.

Toscanelli spent practically his entire life in Florence, which was then the center of European science. His contemporaries regarded him as the leading scientist who was asked for advice, especially on mathematical problems, and a. by Regiomontanus and Cusanus. He taught Leon Battista Alberti and Filippo Brunelleschi in mathematics. He supported Brunelleschi with the calculations for the dome of the Cathedral of Santa Maria del Fiore in Florence. The titles of mathematical works he wrote are known from contemporary sources, but they have been lost.

The lunar crater Toscanelli and the asteroid (8209) Toscanelli are named after him.

Astronomical observations

The gnomon in Santa Maria del Fiore

In the 15th century, critical astronomers were concerned with the question of the extent to which the much-used table works such as the Alfonsine tables reflect the true planetary positions that are necessary for the creation of horoscopes and the calculation of Easter. Measurements with inadequate instruments indicated that sizes such as the skewness of the ecliptic change over time and that the length of the year in particular was incorrect. Around 1430 Ulugh Beg measured a value for the skewness of the ecliptic of 23 ° 30 '17 " at his excellently equipped observatory in Samarkand , less than the value handed down by Ptolemy 23 ° 51'. The wrong year length resulted in a shift in the vernal point of a few days, so that in a few years Easter was celebrated at the wrong time.All attempts to reform the calendar failed for a long time, also because of the argument that the measurements were inadequate.

Both the Council of Constance and the Council of Basel negotiated the question of calendar reform. In Basel, Nikolaus Cusanus , Toscanelli's friend, had headed a commission. In 1470 Cardinal Bessarion wrote a letter to Pope Paul II , who died in 1471. In 1475 Regiomontanus had calculated the dates of Easter in his Latin calendar using both ecclesiastical and astronomical methods and showed the discrepancies. He was then called to Rome for consultations by Pope Sixtus IV , where he died in 1476. In connection with these activities, Toscanelli was invited by the church to participate.

In 1468 (according to other sources not until 1475) Toscanelli and Alberti installed a gnomon in the Cathedral of Santa Maria del Fiore. They attached a pinhole camera at a height of 90 m in a southern window of the lantern on the dome and a meridian line in the Holy Cross Chapel in the northern transept to measure the cardinal points (solstices and equinoxes) and the length of the year. They were able to determine the declination of the sun at the solstices with an accuracy of 2 arc seconds and from this the inclination of the ecliptic to 23 ° 30 '. Further measurements were taken in 1510 when a new attempt at reform was made ( Nicolaus Copernicus was also asked to comment).

The gnomon was improved in 1755 by the Jesuit Leonardo Ximenes (1716–1786), who took measurements until his death. After an earthquake in 1895, the statics of the church were checked and no damage was found.

Comet observations

Toscanelli was the first European to leave detailed records of the course of cometary orbits. The manuscript Immensi labores et graves vigilie magistri Pauli de Toscanello super mensura comete describes his observations of the comets of 1433, 1449/50, 1P / Halley 1456K1, 1457 I and II and 1472 with illustrations . (The latter was also observed by Regiomontanus .) His Works were not printed and therefore remained largely unknown. Edmund Halley did not seem to be familiar with the observations.

Western sea route to the rear of India

Toscanelli tried to find out how big the Atlantic was and how long it would take to cross it. In order to be able to calculate this, however, he had to know the size of the earth as well as the extent of Europe and Asia. In particular, the expansion of Asia was not known at the time. He studied all travelogues like Marco Polo's travelogue Il Milione and talked to well-traveled merchants like Niccolo di Conti and himself envoys of the Emperor of China. Even so, Toscanelli incorrectly calculated the western distance between Asia and Europe. He finally came to the conclusion that India was closer to the west than via the eastern route around Africa, which the Portuguese later found. In addition, he had no inkling of the existence of another continent.

The occasional assertion that Toscanelli was one of the first scholars to recognize that the earth was spherical, in contrast to most of his contemporaries, who would have believed it to be a flat disk, is false. In reality, the spherical shape of the earth's body has been known since ancient Greece and was also taught throughout the Middle Ages (→ flat earth ). The books by Aristotle , Ptolemy or the Naturalis historia by Pliny , which clearly teach and justify the spherical shape of the earth, were among the standard textbooks of science in the 15th century. No contemporary of Toscanelli's even rudimentary education would have thought the earth was a flat disk. Eratosthenes already measured the circumference of the earth quite precisely to 252,000 stages. However, the length of a stadium was not correctly recorded.

Map of Toscanelli

Toscanelli made his planisphere as early as 1457 , a map of the world in which the outlines of Europe are comparatively correct, the southern extent of Africa is grotesquely small, and northern Asia is largely separated from India and China by two large mountain ranges, the Urals and the Hindu Kush. Japan ( Cipangu ) has already been drawn, the Strait of Malacca not yet. In 1474 Toscanelli drew another map showing the western route to Asia and sent it to his friend, Canon Fernão Martins in Lisbon. He then passed it on to Alfonso V , the then King of Portugal. The king, however, paid no heed to Toscanelli and his theory.

However, Christopher Columbus turned to Toscanelli after hearing something about a letter to Martins. Toscanelli sent him two letters. The first informed him of the contents of the letter of 1474 to Martins, in the second he expressly encouraged him to go west to India. In the first volume of his Critical Investigations , Humboldt reproduces Toscanelli's words to Columbus as follows: "I praise your wish to sail west, and I am convinced that you have recognized from my earlier letter that the undertaking you have in mind and would like to carry out is not as difficult as one is used to believe; on the contrary, the way, that is, the crossing from the western coasts of Europe to India, can safely take place on the railway which I have indicated to you if, like me, you had had the opportunity to deal with a great number of people who have been to these lands. Be assured that you will find there powerful kingdoms, great cities and rich provinces. " Toscanelli estimated the distance between Portugal and China at 5,000 nautical miles with a stopover on the mythical island of “ Antilia ” and on Cipangu, so that “no large expanses of water to be crossed” remained.

The Chinese ambassador

Historians have long tried to find out who the Chinese ambassador to Pope Eugene IV mentioned in the letter to Columbus was. In 2005, the business journalist (and studied historian) Tai Peng Wang suggested that this embassy could be in connection with the 7th voyage of the Chinese overseas fleet under Admiral Zheng He in 1433. Emperor Xuande had ordered in 1430 that the fleet built by his grandfather Yongle should announce his accession to the world. A delegation separated from the fleet in Calcutta in 1433 and continued the journey with Arab sailors to Mecca, Cairo and Florence. The papal court stayed in Florence from 1433, so that Toscanelli could meet the embassy.

literature

Individual evidence

  1. ↑ Ralf Kern: Scientific instruments in their time . Volume 1. Cologne, 2010. p. 116.

Web links

Commons : Paolo dal Pozzo Toscanelli  - Collection of images, videos and audio files
personal data
SURNAME Dal Pozzo Toscanelli, Paolo
ALTERNATIVE NAMES Toscanelli, Paolo del Pozzo
BRIEF DESCRIPTION Italian doctor, mathematician, astronomer and cartographer
DATE OF BIRTH 1397
PLACE OF BIRTH Florence
DATE OF DEATH 1482
Place of death Florence