Maximilianus Hell (1720-1792) - Munin

II.1.1 THE PHENOMENON AND ITS PLACE IN CONTEMPORARY ASTRONOMY
A transit, or passage of Venus in front of the Sun as seen from Earth, is a rather rare
astronomical phenomenon. The first transit of Venus to be observed by means of astronomical
equipment took place in 1639. Since then, transits of Venus have occurred in the years 1761,
1769, 1874, 1882 and 2004. The next transit will take place on 5-6 June 2012, but after that
no transits of Venus will occur until 2117 and 2125. Thus, a passage of Venus is not for every
generation to witness.
The 1639 transit of Venus made no immediate impact and (as far is known) was only
observed by two amateur astronomers in the English countryside. 10 By contrast, the pre-
calculated transits of 1761 and 1769 attracted massive interest from the entire world of
learning. Indeed, they became major events of eighteenth-century science, attracting lavish
funding and propelling scientific expeditions into remote regions. The principal reason was
that the transits of Venus were seen as unique opportunities to measure the distance between
Earth and the Sun, a coveted measure in the „quantifying spirit‟ of the Enlightenment. Early
on in the seventeenth century, Johannes Kepler‟s (1571–1630) ground-breaking work on the
orbits of the planets had laid the foundations that enabled skywatchers to be prepared for
spectacular events, such as transits of Venus. 11 The Newtonian theory of gravitation and
10 The observers were Jeremiah Horrocks (c. 1618–1641), observing from outside Liverpool, and his friend
Simon Crabtree (1610–1640), observing from the Manchester area. Horrocks, who had foreseen the event, has
recently been hailed as the “Father of British Astronomy” (Aughton 2004, title page), a rather odd suggestion,
since Horrocks‟ manuscript Venus in Sole Visa was left unpublished until it was sent out of the country and
eventually printed by the famous astronomer Johannes Hevelius (Jan Heweliusz, 1611–1687) in Danzig
(Gdansk, modern Poland) in 1662. Only then did the Fellows of the Royal Society of London become aware of
Horrocks‟ achievement (Hevelius 1662, pp. 111-181; cf. Aughton 2004, pp. 3-7). See also Posch & Kerschbaum
2005 and Chapman 2005 for illuminating studies of Horrocks and his place in the history of European
astronomy.
11 Kepler issued a pamphlet in 1629 asking “sailors navigating the Ocean”, as well as “learned men living in
America, the Mexican and neighbouring provinces”, along with European Professors of Mathematics and such
magnates as would “have the otium allowing them to take part in the pleasure of these celestial spectacles; in
sum, all and every one who cares for celestial matters”, to prepare for two spectacular events he foresaw for
November and December of the year 1631 – a transit of Mercury and a transit of Venus in front of the Sun
(Kepler, Admonitio ad Astronomos … 2 nd ed. 1630, pp. 12-13: “Satis hoc est caussæ, ut adhorter omnes & singulos,
non naucleros tantum, qui Oceanum navigabunt, doctósve viros, qui Americam, qui Mexicanam & vicinas
provincias habitant; sed Europæos quoque, Professores Mathematicos in Academiis constitutos, Magnates
etiam, qvibus otium ad hæc spectaculorum cœlestium oblectamenta suppetit; denique universos, qvibus cœlestia
curæ sunt [...]”). Kepler himself passed away before the events took place, but the French Professor of
Mathematics, Pierre Gassendi (1592–1655) responded to Kepler‟s admonition and observed the transit of
Mercury from Paris on 7 November 1631. He also tried to observe Venus passing in front of the Sun a month
later, but failed to do so because that transit took place during the night and therefore (as we now know) was
invisible in Paris (Gassendi, Mercurius in Sole visus, et Venus invisa Parisiis, Anno M.DC.XXXI. orig. 1632 =
Gassendi 1658, pp. 499-510; cf. Maor 2000, p. 42 n. 2; Marlot 2004, p. 61). See also Hughes 2005a for an
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