Lenses and Waves

1653 - TRACTATUS 25
development of seventeenth-century dioptrics, with a particular emphasis on
the way questions regarding the telescope were addressed.
The telescope was made public when in September 1608 a spectacle
maker from Middelburg, Hans Lipperhey, came to The Hague to request a
patent for a “… certain device by means of which all things at a very great
distance can be seen as if they were nearby, …” 45 It was a configuration of a
convex and a concave lens fitted appropriately in a tube and turned out to
magnify things seen through it. The patent was denied, as within a couple of
week two other claimants turned up. It is doubtful whether Lipperhey had
made the invention himself. He may have learned it from his neighbour
Sacharias Janssen, who in his turn seems to have learned the secret of the
device from an itinerant Italian. 46 The history of the invention of the
telescope is an intricate one, in which Jacob Metius of Alkmaar was the first
to be publicly named its true inventor by Descartes. The first doubts were
raised in the 1650s through the publication of Pierre Borel. Huygens himself
was one of the first to perform some archival research on the matter,
claiming that the credit should go to either Lipperhey or Janssen. 47 The news
of the device spread quickly through Europe and by the summer of 1609
simple telescopes were commonly for sale in the major cities of Europe. 48
The news also reached the ears of scholars, who realized the device could
be of use in astronomical observation. Most successful among them was
Galileo in Venice, whose interest in the telescope was aroused in the spring
of 1609. He figured out how to make one and how to improve it. Among the
earliest telescopists, Galileo was the only one who not only knew how the
telescope could be improved, but also had the means to do so. In August, he
had made a telescope that magnified nine times, as opposed to the ordinary
three-powered spyglasses. A couple of months later he had made telescopes
that were even more powerful. 49 In this way, Galileo turned the spyglass into
a powerful instrument of astronomical observation. 50 He observed the
heavens and saw spectacular things: mountains on the Moon, satellites
around Jupiter, and more. In March 1610, he published his observations in
Sidereus nuncius. Galileo also sent a copy to the Prague court with a specific
request for a comment by Kepler. 51
In May, Kepler published his comment in Dissertatio cum nuncio sidereo. He
primarily responded to Galileo’s observations, but he also said a few things
about the instrument. In Sidereus nuncius, Galileo had explained its
construction and use, but he had left out any mathematical account. 52 In
45
Van Helden, Invention, 35-36; Galileo, Sidereus nuncius, 3-4 (Van Helden’s introduction).
46
De Waard, Uitvinding, 105-225; Van Helden, Invention, 20-25.
47
OC13, 436-437.
48
Van Helden, Invention, 21, 36.
49
Van Helden, Invention, 26; Galileo, Sidereus nuncius, 6, 9 (Van Helden’s Introduction).
50
Van Helden, “Galileo and the telescope”, 153-157.
51
Galileo, Sidereus nuncius, 94 (Van Helden’s Conclusion).
52
Galileo, Sidereus nuncius, 37-39.