Sidereal Messenger
Galileo Galilei, 1610
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A short pamphlet in which Galileo reports what he saw when he turned a telescope he had improved on the sky in 1609 and early 1610. He describes a Moon with mountains and valleys, far more stars than the eye can see, a Milky Way made of faint stars, and four small bodies that change position beside Jupiter night after night and so must circle it. He names them the Medicean Stars for the Medici. The translation here adds Kepler's reply and a note on the later history of the book.
Where it happens
- Padua Galileo was professor of mathematics here, and the dedication is dated from Padua on 12 March 1610.12
- Venice The Venetian Republic employed Galileo, and the first printing of Sidereus Nuncius appeared here in 1610.2
- Middelburg Home of the spectacle-maker Hans Lippershey, whose 1608 patent attempt marks the first telescopes.1
- Florence Galileo wanted to return here under Medici patronage, and Kepler's Discussion was printed here in 1610.12
- Prague Kepler published his work on Mars here and heard of Galileo's discoveries while at Rudolph II's court.2
- London The Latin text was reprinted here in 1653, the copy Carlos later found and translated.2
Through time
- 1608Hans Lippershey tries to patent the telescope in the Netherlands.1
- 1609Galileo learns of the invention and builds improved telescopes.12
- 1610Sidereus Nuncius is published on 13 March; Kepler answers it later in the year.12
- 1611Kepler's Narrative reports observations that confirm Galileo's, and his Dioptrics preface discusses the telescope.2
- 1653Carlos later found this London volume at Christ's Hospital and translated Galileo's text from it, which is the edition on this site.2
Who is in it, and behind it
Galileo Galilei author
Mathematician at Padua who built the telescope used for these observations and published the results in March 1610.12
Cosimo II de' Medici patron
Grand Duke of Tuscany and Galileo's former pupil, to whom the book is dedicated; the Jupiter moons are named after his family.1
Johannes Kepler subject
Astronomer who answered the book with a Discussion in 1610 and supported its findings, although he had no telescope to check them.2
Edward Stafford Carlos translator
Translated the Latin into English after finding the 1653 London volume among old books at Christ's Hospital.2
Hans Lippershey subject
Middelburg spectacle-maker who tried to patent the telescope in the Netherlands in 1608.1
Giuliano de' Medici subject
Tuscan ambassador at the court of Emperor Rudolph II who carried Galileo's invitation to Kepler to correspond.2
What it is about
A rough, mountainous Moon
Galileo reads the jagged terminator as proof that the Moon has mountains and valleys, and judges the peaks to be at least four miles high.1
More stars than the eye sees
Through the telescope he counts far more stars in Orion and the Pleiades, and concludes that the Milky Way and nebulae are masses of tiny stars.1
Moons around Jupiter
Four points of light shifting along a line beside Jupiter persuade him they orbit it, a model for the Copernican system.12
Patronage in the naming
Calling the moons the Medicean Stars won Galileo a Medici post, though the name did not last.1
Others must repeat the sight
Doubters blamed lens defects, so the announcement pushed astronomers toward independent reproduction of observations.1
In its own words
About five years ago I was engaged in preparing a catalogue of the ancient books which belong to Christ’s Hospital.
IN the present small treatise I set forth some matters of great interest for all observers of natural phenomena to look at and consider. They are of great Introduction.interest, I think, first, from their intrinsic excellence; secondly, from their absolute novelty;
Let me speak first of the surface of the Moon, which is turned towards us. For the sake of being[15] understood more easily, I distinguish two parts in it, which I call respectively the brighter and the darker. The brighter part seems to surround and pervade the whole hemisphere;
But beyond the stars of the sixth magnitude you will behold through the telescope a host of other stars, [41]which escape the unassisted sight, so numerous as to be almost beyond belief, for you may see more than six other differences of magnitude, and the largest of these, which I may call stars of the seventh magnitude, or of
I therefore concluded, and decided unhesitatingly, that there are three stars in the heavens moving about Jupiter, as Venus and Mercury round the Sun; which at length was established as clear as daylight by numerous other subsequent observations.
Actual sight testified that there is a certain bright heavenly body which we call the Moon. It was demonstrated from the laws of optics that this body is round; also Astronomy, by[80] some arguments founded upon optics, had built up the conclusion that its distance from the earth is about sixty semi-diameters of the earth.
The shape of the book
9 chapters, 26,104 words. Point at a bar.
How it came to be here
Galileo was a mathematics professor at Padua in the service of Venice when he heard of the Dutch spyglass in 1609 and built better ones. He rushed the results into print in Latin, dated from Padua in March 1610, and dedicated them to Cosimo II de' Medici in hope of a post at Florence. It was the first published scientific work based on telescope observations, and the Jupiter moons gave support to the Copernican system. Edward Stafford Carlos translated it after finding the 1653 London printing in a school library at Christ's Hospital.
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Sources
Text: PG 46036 | translator: Edward Stafford Carlos. US public domain (Project Gutenberg licence).