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| First to discover the solar spots | |
| « [ ] Our Lynx Academician, first among others, discovered and observed the solar spots, in the same way as he discovered many other celestial novelties during the year 1610, while still lecturing on Mathematics in Padua. Here, and later on in Venice, he discussed about these matters with many people, some are still alive. A year later he also showed these spots to a number of people in Rome, as asserted in the first of the Sunspot Letters addressed to Mark Welser, Duumvir of Augusta. [ ] » | |
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| Even the Sun must endure the unforeseen events of the sub-Lunar world | |
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Against the opinion of people too much cautious
and too much convinced of the heavenly unchangeability, it was asserted,
for the first time, that such spots were of a substance that quickly generated
and dissolved itself. These spots could be observed contiguous to the Solar
body and revolving about it, or, ending up
their roundabouts, dragged along by the Solar globe itself that revolved
around its center in about one month. At the beginning, it was thought
that this motion was created by the Sun itself revolving about an axis
perpendicular to the plane of the ecliptic, as the arcs outlined onto the
Solar disc by these spots appeared to the
eye, as straight lines parallel to the plane of the ecliptic.
These spots were also partially impaired by casual, roaming and irregular
motions which affected them. These violent and chaotic motions scattered
the spots all around, at times heaping them up together, at times setting
them apart. Some spots even split into many spots, creating most extravagant
figures. [
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« Now returning to the subject, I say that the things discovered in the heavens in our time are and have been such that they can give complete satisfaction to all philosophers. For, both on the individual bodies and in the general expanse of the heavens, we have seen and still see phenomena similar to those which we call generation and destruction among us: excellent astronomers have observed many comets generated and dissolved in the regions above the Lunar orb (1), as well as the two new stars of the years 1572 and 1604, located without any doubt much higher than any planet; and on the face of the Sun itself, by means of the telescope, we see the production and decomposition of dense and dark substances very similar in appearance to clouds on the Earth, and some of which are so large that they far exceed not only the Mediterranean basin, but also all Africa and Asia. Now, Simplicio , what do you think Aristotle would say and do if he were to see these things? [ ] » (1) here reference is made to Tychos observations carried out on the parallax of comets. This parallax was not measurable, therefore, comets were outside the orbit of the Moon. On the contrary, the parallax of the Moon was detectable with the instruments that were available at the time... |
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| The borders of
these spots are irregular ... the spots are not spherically shaped ...
they rotate in less than a month |
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From the same change of shape, one gathers
that none of the spots are stars or other bodies with a spherical shape.
For, of all shapes, only the sphere is never seen foreshortened and must
always be represented as perfectly round. So, if any particular spot were
a round body, as all stars are considered to be, it
would appear equally round near the middle as well as near the edge of
the Solar disc; on the other hand, the fact
that they appear so foreshortened and narrow near the edge but wide and
large near the middle assure us that they are layers of small depth or
thickness in relation to their length and width.
In regard to the recent observation that after definite periods the exact same spots return, you should not believe it, Simplicio, and the person who told you this wants to deceive you; in fact, notice that he has been silent about those which are generated and dissolved within the face of the Sun, far from the circumference and that he has said nothing about the foreshortening, which proves conclusively their being contiguous to the Sun. What truth there is in the return of the same spots, you can read about in the aforementioned Letters; that is, some spots occasionally last such a long time that they are not decomposed in the course of only one Solar rotation which occurs in less than a month. [ ] » |
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| Selected passages from: Galilei,
Galileo, «Le opere di Galileo Galilei
: edizione nazionale sotto gli auspici di sua maestà il re d'Italia».
Volume VII, see: Liber Liber.
From: "Progetto Manuzio", an initiative of Liber Liber. A non-profit cultural association, open to everybody who is willing to collaborate. It promotes and circulates electronic versions of all kind of artistic and intellectual expressions. For more information see: http://www.liberliber.it/ Bibliography: Galileo On the World Systems - translated by Maurice A. Finocchiaro- University of California Press |
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