This is the story of a very important 14th-century astrarium and its exceptional reconstruction. It was the pinnacle of medieval horology and the perfect practical implementation of Ptolemaic theory.

Statua rappresentante Giovanni Dondi, From the collection of: National Museum of Science and Technology Leonardo Da Vinci

Giovanni Dondi dell'Orologio was born in Chioggia in 1318. In 1342, his family moved to Padua, where his father introduced him to the study of science, and to medicine in particular.

In 1354, Dondi became a professor of medicine, and then of astrology and astronomy, at the University of Padua. From 1362 to 1365, Dondi taught at the University of Pavia, which was founded by Charles IV, Holy Roman Emperor, on April 13, 1361.

The University patron, Galeazzo Visconti, coerced students in the State of Milan to study there.

Statua rappresentante Giovanni Dondi, From the collection of: National Museum of Science and Technology Leonardo Da Vinci

During his time in Pavia, Dondi also served as astrologer and physician to the prince.

After having lived in Florence, Rome, and Padua again, Dondi settled in Pavia in 1379, when Visconti called on him to look after his son.

From 1379 until his death, he regularly taught in Pavia, as a royal physician and astrologer rather than professor, receiving an annual salary of 2,000 florins.

He went to look after Prince Antonietto Adorno, the 6th Doge (duke) of Genoa, the same citywhere it is said that he died in February 1389.

La ricostruzione dell’Astrario di Giovanni Dondi, Luigi Pippa, From the collection of: National Museum of Science and Technology Leonardo Da Vinci

Giovanni Dondi's Astrarium puts Ptolemaic theory into practice.

In the Ptolemaic system, the Earth is at the center of the (then-known) universe, while so-called fixed planets and stars move around it in a determined direction, regardless of their proper motion.

La ricostruzione dell’Astrario di Giovanni Dondi, Luigi Pippa, From the collection of: National Museum of Science and Technology Leonardo Da Vinci

It was built as an instrument to map the position of celestial bodies, which were believed to determine humankind's destiny.

Pagina del “Tractatus Astrarii” di Giovanni Dondi, Giovanni Dondi, From the collection of: National Museum of Science and Technology Leonardo Da Vinci

The original astrarium was built by Giovanni Dondi in the second half of the 14th century.

Pagina del “Tractatus Astrarii” di Giovanni Dondi, Giovanni Dondi, From the collection of: National Museum of Science and Technology Leonardo Da Vinci

The precise period is a bone of contention. It was first dated as 1348–64, then subsequently that period was refuted by new arguments and moved by around 20 years to 1365–80.

The new date range, in any case, still places the astrarium at the pinnacle of medieval horology.

The astrarium was taken to the Visconti Castle Library in Pavia, but from the middle of the 16th century, all traces of it were lost.

The object was last heard of in 1529, when Charles V, King of Spain and Emperor of the Holy Roman Empire, arrived in Italy.

At the time, it was reported to be in bad shape and needed of maintenance. Presumably it was destroyed in the years shortly after.

Pagina del “Tractatus Astrarii” di Giovanni Dondi, Giovanni Dondi, From the collection of: National Museum of Science and Technology Leonardo Da Vinci

Reconstruction of the astrarium was possible thanks to Giovanni Dondi's manuscript "Tractatus Astrarii," in which he described the design and its construction phases.

Pagina del “Tractatus Astrarii” di Giovanni Dondi, Giovanni Dondi, From the collection of: National Museum of Science and Technology Leonardo Da Vinci

This treatise is one of the first technical and scientific works of its kind and is stored in the Capitular Library of Padua.

Pagina del “Tractatus Astrarii” di Giovanni Dondi, Giovanni Dondi, From the collection of: National Museum of Science and Technology Leonardo Da Vinci

In the treatise, Dondi gives a detailed description of all the designs and the construction phases, as well methods for setting the various faces, reading devices, and instructions for the maintenance of the mechanism.

Luigi Pippa durante la ricostruzione dell'Astrario di Giovanni Dondi, Luigi Pippa, From the collection of: National Museum of Science and Technology Leonardo Da Vinci

The reconstruction of Giovanni Dondi's Astrarium was carried out between 1961 and 1963 by Luigi Pippa, a Milanese clockmaker, with the financial support of Innocente Binda.

Luigi Pippa durante la ricostruzione dell'Astrario di Giovanni Dondi, Luigi Pippa, From the collection of: National Museum of Science and Technology Leonardo Da Vinci

The reconstruction was completed for the National Museum of Science and Technology in Milan.

The astrarium still belongs to its collection.

Luigi Pippa durante la ricostruzione dell'Astrario di Giovanni Dondi, Luigi Pippa, From the collection of: National Museum of Science and Technology Leonardo Da Vinci

Pippa writes: "The actual completion of the astrarium took place in March 1963, after 20 months of intense work, during which I faced grueling problems beyond my ordinary knowledge. I was also hindered by my modest laboratory equipment. However, I managed to overcome these difficulties, albeit with many struggles."

La ricostruzione dell’Astrario di Giovanni Dondi, Luigi Pippa, From the collection of: National Museum of Science and Technology Leonardo Da Vinci

The astrarium is a very complex mechanism that indicates the position and movement of celestial bodies. It consists of 9 faces: 7 on its upper section and 2 on its lower section.

La ricostruzione dell’Astrario di Giovanni Dondi, Luigi Pippa, From the collection of: National Museum of Science and Technology Leonardo Da Vinci

On the upper section, 5 faces indicate the annual movement of the then-known planets (Mercury, Venus, Mars, Jupiter, and Saturn), one marks the movement of the sun, and the other, that of the moon.

La ricostruzione dell’Astrario di Giovanni Dondi, Luigi Pippa, From the collection of: National Museum of Science and Technology Leonardo Da Vinci

On the lower section, there is a face for the time and a face to predict lunar eclipses, also known as the node line.

La ricostruzione dell’Astrario di Giovanni Dondi, Luigi Pippa, From the collection of: National Museum of Science and Technology Leonardo Da Vinci

In the center of the astrarium is the calendar wheel, which completes one turn every year. This indicates the day of the week, the name of saints, the dominical letter, and the length of the day in hours and minutes.

Meccanismi dell'Astrario di Giovanni Dondi, Luigi Pippa, From the collection of: National Museum of Science and Technology Leonardo Da Vinci

The working mechanism of the astrarium is a mechanical clock. The gears are set in motion by a falling weight attached to a cable, wound around the large wooden cylinder at the base.

The reconstruction of Giovanni Dondi's Astrarium continues to be one of the highlights of the exhibitions at the National Museum of Science and Technology in Milan.

Credits: Story

Exhibition by
Museo Nazionale della Scienza e della Tecnologia
Leonardo da Vinci

Via San Vittore 21
Milano

www.museoscienza.org

Credits: All media
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