Chair: Sven Dupré

Vincent Ilardi

This paper discusses recently discovered documentary and archaeological evidence on the early history and development of eyeglasses, published in my book, Renaissance Vision from Spectacles to Telescopes, (Philadelphia, 2007). Most of the documentary evidence comes from depositories in Milan, Pisa, Florence, Rome, and London in the form of account books, customs records, diplomatic and private correspondence. 

Archaeological remains have been found predominantly in digs located in Germany, England, and Holland.

Rolf Willach, Independent Scholar, Switserland

The development of the telescope follows a long path over many centuries, beginning with the magnifying lens in its simplest design. These were rock crystals that were mainly produced for embellishment and decoration. Examples from early recorded history until the High Middle Ages are examined to reveal the technology of their making.

From these earliest times different pathways developed, beginning with the grinding of crystals for the liturgical art crafts in the workshops of monasteries, and ending with the invention of the spectacle. 

After that, the development of the spectacle and the technique used for grinding, from the early fourteenth until the seventeenth century is discussed and demonstrated with a lot of carefully examined examples.

It also becomes clear that the inventions discussed here were made possible only by practical experiments, insights made by real chance and an intensive interaction between the prevailing cultural and political evolutions in old Europe.

Coffee break 

Yaakov Zik and Giora Hon, Department of Philosophy, University of Haifa, Israel 

The introduction of the telescope as a scientific instrument into astronomy was of signal importance for the development of modern science. The received view holds that the first spyglass was assembled without any theoretical understanding how it magnifies. Artisans who had the first telescopes which magnified 3 or 4 times knew nothing—so the historical argument goes—of the principles by which this instrument worked and never managed to improve their magnifying power. However, Galileo who first used the instrument as a scientific tool did improve the power of magnification up to 30 times. It is therefore even more intriguing to hold that Galileo increased the power of magnification on no theoretical basis since the traditional knowledge of the optics of his day was not suitable to the analysis of system of lenses.

We offer an alternative view on this puzzling situation. Our interpretation rests essentially on the fact that Galileo was the first scholar to apply successfully the telescope to astronomical observations. A working astronomical telescope is a complex optical device consisting of a tube, lenses and aperture stops. In order to turn the telescope into a high-quality magnifying device, one has to find solutions to problems such as: How does the telescope magnify? Can one reduce image defects? How can one improve (in modern terms) resolution? And how does one produce adequate lenses? We argue that these problems cannot be solved by accidentally stumbling upon a complex procedure.

The telescope magnifies distant objects by presenting them to the eye in a greater angle than the angle subtended by the naked eye. This fundamental ratio between visual angles was known to opticians and mathematicians, among them Galileo, from the application of surveying instruments for measuring the height of remote objects using a mirror. We submit that the theory of the telescope was developed through analogical reasoning based on the phenomenon of reflection in mirrors which was extended to refraction in lenses. In spite of the fact that no adequate theory of refraction was available, Galileo could have applied such an analogy to help understand the working of the telescope and thus improve its magnification, making it a revolutionary scientific instrument.

Giuseppe Molesini, Istituto Nazionale di Ottica Applicata, Florence, Italy

In the course of the last two decades, a significant part of the 17th Century telescope optics remaining in Italy (mainly at the Institute and Museum of the History of Science in Florence) has been submitted to optical tests in research laboratories, in order to assess the lens quality and retrieve any information that might be useful to science historians. The investigation is still in progress. A number of interesting results have already come to light, showing that the lens quality that could be obtained at that time was extraordinarily good; in particular, the “broken objective lens” of Galileo housed in Florence turned out to be almost perfect as to optical performance. Such a high quality was achieved both in terms of lens surface, figuring, and polishing, and in terms of purity and homogeneity of the glass material. In this paper, the most significant outcome of this research will be reviewed, and results of recent measurements will be reported. In particular, aspects related to glass quality will be discussed, pointing out the critical problem of glass homogeneity. Defective glass could not be detected until the lens was polished and tested, and even then the causes of failure could probably not be understood. Current analysis is devoted to find out the chemical composition and the physical properties of the glass material, as an aid to locating the lenses and the telescopes more precisely within their historical framework.

Lunch 

Chair: Rob van Gent, Department History and Philosophy of Science, Utrecht University 

Mario Biagioli, Harvard University, Cambridge, USA

Following the trajectory of the telescope from it early emergence in the Netherlands to Galileo's discoveries of 1610 and his move to the Medici court, I want to discuss the different venues for reward open to instrument makers at this time. In particular, I want to look at the different opportunities provided by "IP-like" tools like the privilege for invention that Hans Lipperhey applied for in the Netherlands, by pensions for inventors (which both Lipperhey tried to obtain), and by the use of intriguing instruments as tools for accessing princely patronage networks.

Marvin Bolt, Adler Planetarium & Astronomy Museum, Chicago/USA

& Michael Korey, Mathematisch-Physikalischer Salon, Dresden State Art Collections, Dresden/Germany

The broad influence of the telescope in the decades following its discovery has often been recounted, but remarkably few telescopes securely datable to the first half of the 17th century survive. The presenters discuss their recent success in identifying several unknown or forgotten early telescopes and posit a promising setting in which to search for more. They also describe a portable optical tool kit which they have used to examine and document the optics of the telescopes held in some leading American and European collections as well as their initial efforts toward a comprehensive survey of early extant refractors.

Tea break

Eileen Reeves, Department of Comparative Literature, Princeton University, USA

This paper will address a historiographical problem usually treated with decorous neglect, the curious contrast between the rapid diffusion of news of the Dutch telescope across Europe, and Galileo Galilei’s belated acquaintance with reports of the instrument. It will propose a new explanation for the apparent gap between the emergence of the telescope in Middelburg in late September 1608, and the astronomer’s tardy encounter with a rumour that had clearly made its way to his friend Fra’ Paolo Sarpi in Venice by November of that year. Arguing that Galileo and Sarpi, among other contemporaries, mistakenly imagined that the new device involved a combination of lens and mirror, this paper details the several reasons for their error, the wealth of discussions concerning telescopic mirrors, and the longevity of Galileo’s association with such mirrors in the popular imagination.

Albert van Helden, Em. Utrecht University / Rice University, USA

In Galileo's hands, the humble spyglass was made into a research instrument, and in turn it made him into a public Copernican. In this paper I will examine how each discovery challenged the existing world order and tended to modify Copernicus's heliocentric system. These early telescopes had their limitations, and I will attempt to shed some light on those on the basis not of the optics, but of the observations themselves.

Reception with drinks at the Old Middelburg Town Hall with speech by the Mayor of Middelburg 

End of Afternoon session 

[Diner at own expense] 

Commemoration also for the general public

 

21:15-22:00

Drinks