Seeds of a Tychonic Revolution: Telescopic Observations of the Stars by Galileo Galilei and Simon Marius

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Because early telescopic astronomers did not understand the spurious nature of star images formed by their telescopes, their observations of the stars yielded data that apparently confirmed the geocentric Tychonic world system. Both Galileo Galilei (1564–1642) and Simon Marius (1570–1624) obtained such data. Galileo backed Nicholas Copernicus (1473–1543) despite his data. Marius supported Tycho Brahe (1546–1601) on the basis of his data. KeywordsAristotle-Ptolemy-Nicholas Copernicus-Tycho Brahe-Galileo Galilei-Simon Marius-Aristotelian–Ptolemaic world system-Copernican world system-Tychonic world system-Airy disk-stellar observations-telescope-history of astronomy

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... This is argued by Simon Marius in his 1614 Mundus Jovialis. Marius, who also observed the telescopic stellar disks, states that they support the geocentric (or geo-heliocentric) hypothesis of Tycho Brahe (Graney 2010). ...
G. B. Riccioli's 1651 Almagestum Novum contains a table of diameters of stars measured by Riccioli and his associates with a telescope. These telescopically measured star diameters are spurious, caused by the diffraction of light waves through the circular aperture of the telescope, but astronomers of the time, including Riccioli and Galileo Galilei, were unaware of this phenomenon. They believed that they were seeing the physical bodies of stars. In the Almagestum Novum Riccioli uses these telescopically measured disks to determine the physical sizes of stars under both geocentric (or geo-heliocentric - Tychonic) and heliocentric (Copernican) hypotheses. The physical sizes obtained under the Copernican hypothesis are immense - dwarfing the Earth, the Sun, and the Earth's orbit; even exceeding the distances to the stars given by Tycho Brahe. Thus Riccioli felt that telescopic observations were an effective argument against the Copernican system. Comment: Revised version includes extended Table 4; better Airy pattern image for Figure 1; wording changes to improve clarity of the paper, especially so as to distinguish more clearly between star sizes seen through the telescope and calculated physical sizes of stars.
... Each believed that the disks yielded information about stellar distances. Interestingly, Marius concluded that the disks were evidence in favor of a Tychonic world system (Marius 1614: 48; Graney 2010), while Galileo used them to argue for a Copernican world system (Galilei Huygens argued that stars were merely points of light, as evidenced by their decreasing in size when a smoked glass was placed in the light path of a telescope (1659: 7; Roberts 1694). ...
Since the dawn of telescopic astronomy astronomers have observed and measured the "spurious" telescopic disks of stars, generally reporting that brighter stars have larger disks than fainter stars. Early observers such as Galileo Galilei interpreted these disks as being the physical bodies of stars; later observers such as William Herschel understood them to be spurious; some, such as Christian Huygens, argued that stars show no disks at all. In the early 19th century George B. Airy produced a theoretical explanation of star images sufficient to explain all historical observations, but astronomers were slow to fully recognize this. Even today conventional wisdom concerning stars and telescopes stands at odds to both historical observations and Airy's theory. We give a detailed analysis of both historical observations and Airy's theory, illustrating how Airy's theory explains the historical observations, from Galileo to Huygens to Herschel. We argue that the observations themselves appear in all cases to be valid and worth further study. Comment: This is a preprint of an Article eventually submitted for consideration in Annals of Science, which is available online at: The published version is available at
Cambridge Core - History of Science and Technology - Finding our Place in the Solar System - by Todd Timberlake
Hoyt & Schatten (1998) claim that Simon Marius would have observed the sun from 1617 Jun 7 to 1618 Dec 31 (Gregorian calendar) all days, except three short gaps in 1618, but would never have detected a sunspot -- based on a quotation from Marius in Wolf (1857), but misinterpreted by Hoyt & Schatten. Marius himself specified in early 1619 that "for one and a half year ... rather few or more often no spots could be detected ... which was never observed before" (Marius 1619). The generic statement by Marius can be interpreted such that the active day fraction was below 0.5 (but not zero) from fall 1617 to spring 1619 and that it was 1 before fall 1617 (since August 1611). Hoyt & Schatten cite Zinner (1952), who referred to Zinner (1942), where observing dates by Marius since 1611 are given, but which were not used by Hoyt & Schatten. We present all relevant texts from Marius where he clearly stated that he observed many spots in different form on and since 1611 Aug 3 (Julian) = Aug 13 (Greg.) (on the first day together with Ahasverus Schmidnerus), 14 spots on 1612 May 30 (Julian) = Jun 9 (Greg.), which is consistent with drawings by Galilei and Jungius for that day, the latter is shown here for the first time, at least one spot on 1611 Oct 3 and/or 11 (Julian), i.e. Oct 13 and/or 21 (Greg.), when he changed his sunspot observing technique, he also mentioned that he has drawn sunspots for 1611 Nov 17 (Julian) = Nov 27 (Greg.), in addition to those clearly datable detections, there is evidence in the texts for regular observations. ... Sunspots records by Malapert from 1618 to 1621 show that the last low-latitude spot was seen in Dec 1620, while the first high-latitude spots were noticed in June and Oct 1620, so that the Schwabe cycle turnover (minimum) took place around that time, ...
In 1576 the English astronomer Thomas Digges (1546–95) published his English translation of Nicholaus Copernicus’s (1473– 1543) De Revolutionibus Orbium Coelestium together with a sketch of the Copernican universe under the heading “A Perfit description of the Cœlestial Orbes” (fig. 1). Because Digges’s sketch shows the planets circling the Sun, surrounded by an infinite expanse of stars, it is often hailed as a forerunner of the modern, scientific understanding of an infinite universe in which the Earth is but a speck.1 However, Digges was illustrating not the insignificance of Earth but the greatness of a universe of stars that testified to the omnipotence and magnificence of God. Ideas such as Digges’s played a prominent role in Copernican thought, so much so that Copernicans cited Divine Omnipotence to answer one of the most powerful scientific objections to the heliocentric theory. This Copernican use of religion to answer a scientific objection to heliocentrism greatly troubled one of the most prominent defenders of geocentrism, the Italian Jesuit astronomer Giovanni Battista Riccioli (1598–1671). The story of Digges, Riccioli, and the stars challenges the modern portrayal of the Copernican Revolution as being a contest of religion Thomas Digges’s representation of an infinite Copernican universe. versus science: geocentricism versus heliocentrism. It also raises questions about how historians and scientists, and in particular Catholic historians and scientists, could forget such a dynamic part of the history of ideas. Writers today commonly portray a Copernican infinite universe, such as Digges envisioned, as rendering irrelevant human beings or the Earth or even God—usually with reference to Giordano Bruno (1548–1600) being burned at the stake, supposedly for advocating such a universe. Consider, as a very recent example, some quotes from David Wootton’s newly published biography of Galileo, Galileo: Watcher of the Skies. Galileo was prepared to say that there is no way of telling whether the Universe is finite or infinite. This was dangerous territory. Bruno had argued that the universe was infinite, and that not only were the stars suns, but they were circled by innumerable inhabited planets (a view which would imply innumerable Christs, for each world would need its own saviour). Moreover, it was difficult to see how an infinite universe could be the work of a creator: an infinite universe must surely have existed (as Aristotle claimed) throughout eternity.2 And later: Indeed [heliocentrism] offered a view of the cosmos in which humankind, and the things that matter to humankind—love and hatred, virtue and vice, mortality and immortality, salvation and damnation—were irrelevant. Far from embodying a scheme of values, far from embodying a telos or purpose, Galileo’s universe appeared to be indifferent to moral and metaphysical issues, and even indifferent to our own existence. . . . Galileo’s greatest and at the same time most disturbing achievement was to recognize that the universe was not made for the sake of human beings, and that it teaches us nothing about right or wrong, and offers us neither salvation nor damnation.3 The largest illustration in Watcher, aside from the frontispiece portrait of Galileo himself, is Digges’s sketch of the infinite Copernican universe.4 The notion that the vastness of the Copernican cosmos indicates purposelessness and insignificance is so common today as to be cliché. Yet Copernicans apparently were of the mind that the vastness of the universe testified to human beings about the power and magnificence of God. Copernicus himself first connects the vastness of the universe to God. In the Copernican theory, the Earth changes position with respect to the stars as it circles the Sun. That motion should reveal itself in the stars, an effect known to astronomers as “annual parallax.” Yet no such parallax appears to the naked eye. To Copernicus, this indicates that Earth’s motion around the Sun is negligible compared to the distances to the stars, and in those vast distances is seen God’s handiwork. But that there are no such appearances among the fixed stars argues that they are at an immense height away, which makes the circle of annual movement or its image disappear from before our...
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Simon Marius - Werke und Literatur. (mit Pierre Leich) In: Wolfschmidt, Gudrun (Hg.): Simon Marius, der fränkische Galilei, und die Entwicklung des astronomischen Weltbildes. Hamburg: tredition science (Nuncius Hamburgensis, Beiträge zur Geschichte der Naturwissenschaften; Band 16) 2012, S. 364/365-377.
This paper presents high-resolution images of the original document of the 24 February 1616 condemnation of the Copernican system as being "foolish and absurd in philosophy", by a team of consultants for the Roman Inquisition. Secondary sources have disagreed as to the punctuation of the document. The paper includes a brief analysis of the punctuation and the possible effects of that punctuation on meaning. The original document and its punctuation may also have relevance to public perception of science and to science education.
In 1651 the Italian astronomer Giovanni Battista Riccioli published within his Almagestum Novum, a massive 1500 page treatise on astronomy, a discussion of 126 arguments for and against the Copernican hypothesis (49 for, 77 against). A synopsis of each argument is presented here, with discussion and analysis. Seen through Riccioli's 126 arguments, the debate over the Copernican hypothesis appears dynamic and indeed similar to more modern scientific debates. Both sides present good arguments as point and counter-point. Religious arguments play a minor role in the debate; careful, reproducible experiments a major role. To Riccioli, the anti-Copernican arguments carry the greater weight, on the basis of a few key arguments against which the Copernicans have no good response. These include arguments based on telescopic observations of stars, and on the apparent absence of what today would be called "Coriolis Effect" phenomena; both have been overlooked by the historical record (which paints a picture of the 126 arguments that little resembles them). Given the available scientific knowledge in 1651, a geo-heliocentric hypothesis clearly had real strength, but Riccioli presents it as merely the "least absurd" available model - perhaps comparable to the Standard Model in particle physics today - and not as a fully coherent theory. Riccioli's work sheds light on a fascinating piece of the history of astronomy, and highlights the competence of scientists of his time.
In 1651 the Italian astronomer and physicist Giovanni Battista Riccioli (1598–1671) published his encyclopedic book, Almagestum novum, in which he presented seventy-seven arguments against the Copernican theory of the movement of the Earth, one of which foresaw an effect that physicists today attribute to the Coriolis force. Galileo Galilei (1564–1642), Isaac Newton (1642–1727), and Robert Hooke (1635–1703) investigated this argument, which raises significant questions about the nature of the opposition to the Copernican theory in the seventeenth century.
In 1615 Robert Cardinal Bellarmine demanded a "true demonstration" of Earth's motion before he would cease to doubt the Copernican world system. No such demonstration was available because the geocentric Tychonic world system was a viable alternative to the heliocentric Copernican system. On the contrary, recent work concerning early observations of stars suggests that, thanks to astronomers' misunderstanding of the images of stars seen through the telescope, the only "true demonstration" the telescope provided in Bellarmine's day showed the earth not to circle the Sun. This had been discussed by the German astronomer Simon Marius, in his Mundus lovialis, just prior to Bellarmine's request for a "true demonstration."
In January of 1616, the month before before the Roman Inquisition would infamously condemn the Copernican theory as being "foolish and absurd in philosophy", Monsignor Francesco Ingoli addressed Galileo Galilei with an essay entitled "Disputation concerning the location and rest of Earth against the system of Copernicus". A rendition of this essay into English, along with the full text of the essay in the original Latin, is provided in this paper. The essay, upon which the Inquisition condemnation was likely based, lists mathematical, physical, and theological arguments against the Copernican theory. Ingoli asks Galileo to respond to those mathematical and physical arguments that are "more weighty", and does not ask him to respond to the theological arguments at all. The mathematical and physical arguments Ingoli presents are largely the anti-Copernican arguments of the great Danish astronomer Tycho Brahe; one of these (an argument based on measurements of the apparent sizes of stars) was all but unanswerable. Ingoli's emphasis on the scientific arguments of Brahe, and his lack of emphasis on theological arguments, raises the question of whether the condemnation of the Copernican theory was, in contrast to how it is usually viewed, essentially scientific in nature, following the ideas of Brahe.
In Galileo's opinion, his most important argument for the Earth's motion was based on his theory of the tides that combined the Earth's rotation with its orbital motion so that it alternately accelerates and decelerates the sea. His theory deliberately ignored the Moon's influence, which at that time was generally regarded as occult. Galileo's confidence in his theory was strongly reinforced by its providing a mechanical model. That a theory that ignored the Moon's influence could seem plausible is confirmed by comparison with the theories of Bacon and Wallis. That Galileo's theory could seem plausible despite encountering difficulties is confirmed by comparison with Newton's theory, which is deeply flawed by its inclusion of a vertical response to the total tidal force. That many people now regard Galileo's theory as wrong is due to our having absorbed as natural Newton's idea of lunar attraction.
Tycho Brahe, the most prominent and accomplished astronomer of his era, made measurements of the apparent sizes of the Sun, Moon, stars, and planets. From these he showed that within a geocentric cosmos these bodies were of comparable sizes, with the Sun being the largest body and the Moon the smallest. He further showed that within a heliocentric cosmos, the stars had to be absurdly large - with the smallest star dwarfing even the Sun. (The results of Tycho's calculations are illustrated in this paper.) Various Copernicans responded to this issue of observation and geometry by appealing to the power of God: They argued that giant stars were not absurd because even such giant objects were nothing compared to an infinite God, and that in fact the Copernican stars pointed out the power of God to humankind. Tycho rejected this argument.
The science museum in Florence has two telescopes and a single lens attributed to Galileo. Tests conducted with modern interferometric equipment show that Galileo was able to obtain nearly perfect optical quality.
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Galileo found the Copernican heliocentric theory of the universe so persuasive owing to its mathematical elegance that he embraced it even when his theory of the tides stood in opposition to it. Further support for Galileo’s deep commitment to the Copernican heliocentric theory is found in his recently discovered unpublished observations of the double star Mizar in 1617, which exhibited no annual stellar parallax and hence indicated that the Earth does not move, in contradiction to the Copernican heliocentric theory. Further, Galileo did not mention this contradiction in his Dialogue Concerning the Two Chief World Systems of 1632. I conclude that he was so deeply committed to the Copernican heliocentric theory that he was unswayed even when observations undermined it, and I suggest that if he had published his observations on the double star Mizar, general acceptance of the Copernican heliocentric theory by astronomers would have been delayed even more than it was.
Galileo's conflict with the Catholic Church is well recognized as a key episode in the history of physics and in the history of science and religion. This paper applies a new, historiographical approach to that specific episode. It advocates eliminating the science and religion. The Church concluded that the plainest facts of human experience agreed perfectly with an omniscient God's revealed word to proclaim the earth at rest. Supported by the Bible, Galileo, God-like, linked the elegance of mathematics to truths about nature. The Church, in effect, resisted Galileo's claim to be able to think like God, instead listening to God himself - and paying close attention to what man himself observed. We can thus see that the phrase "Galileo's religion versus the Church's science" is as meaningful (or meaningless) as the usual designation "Galileo's science versus the Church's religion."
The Copernican Principle (which says the Earth and sun are not unique) should have observational consequences and thus be testable. Galileo Galilei thought he could measure the true angular diameters of stars with his telescope; according to him, stars visible to the naked eye range in diameter from a fraction of a second to several seconds of arc. He used this and the Copernican Principle assumption that stars are suns as a method of determining stellar distances. The expected numbers of naked eye stars brighter than a given magnitude can be calculated via Galileo's methods; the results are consistent with data obtained from counting naked eye stars. Thus the total number of stars visible to the naked eye as a function of magnitude would appear to Galileo to be data supporting the Copernican Principle.
Galileo Galilei had sufficient skill as an observer and instrument builder to be able to measure the positions and apparent sizes of objects seen through his telescopes to an accuracy of 2" or better. However, Galileo had no knowledge of wave optics, so when he was measuring stellar apparent sizes he was producing very accurate measurements of diffraction artifacts and not physical bodies.
Orbes according to the most aunciente doctrine of the PYTHAGOREANS, latelye reuiued by COPERNICVS and by Geometricall Demonstrations approued [1576]”; reprinted in Francis R
  • Thomas Digges
  • Cælestiall Johnson
  • Sanford V Larkey
3 Thomas Digges, “A PERFIT DESCRIPTION OF THE CÆLESTIALL Orbes according to the most aunciente doctrine of the PYTHAGOREANS, latelye reuiued by COPERNICVS and by Geometricall Demonstrations approued [1576]”; reprinted in Francis R. Johnson and Sanford V. Larkey, “Thomas Digges, the Copernican System, and the Idea of the Infinity of the Universe in 1576,” The Huntington Library Bulletin, No. 5 (April 1934), pp. 78-95
Edizione Nazionale Sotto gli Auspicii di Sua Maestà il re d’Italia. Vol. III. Parte Seconda (Firenze: 1890); reprinted Sotto l’Alto Patronato di S.M. il re d’Italia e di S 877; available online at <
  • Antonio Favaro
  • Ed Le
  • Di Galileo
The Observatory The missing material, which also includes his notes on Andromeda, would be located after the end of the Preface on page 373 and the beginning of PART I
  • The
  • Mundus
  • Jovialis
  • Simon
De revolvutionibvs orbium cælestium, Libri VI (Norimbergæ: Ioh. Petdrium, 1543); facsimile reprint
  • Nicolai Copernici
  • Torinensis
Edizione Nazionale Sotto gli Auspicii di Sua Maestà il re d’Italia. Vol. III. Parte Seconda (Firenze: 1890); reprinted Sotto l
  • Ibid
An Account of the Nebula in Andromeda,” Memoirs of the American Academy of Arts and Sciences
  • George P Bond
Mundus Iovialis Anno MDCIX, etc.: Die Welt des Jupiter im Jahre 1609, etc
  • Simon Marius
An Attempt To prove the Motion of the Earth from Observations (London: printed by T.R. for John Martyn Printer to the Royal Society at the Bell in St. Pauls Church-yard, 1674); facsimile reprinted in
  • Robert Hooke
De mvndi aetherei recentioribvs phaenomenis
  • Tychonis Brahe
Tychonis Brahe [Tycho Brahe], De mvndi aetherei recentioribvs phaenomenis. Liber Secvndis.
Seeds of a Tychonic Revolution page xxvi To appear in Physics in Perspective
  • Graney
Graney, Seeds of a Tychonic Revolution page xxvi To appear in Physics in Perspective. Not to be quoted or cited.
Orbes according to the most aunciente doctrine of the PYTHAGOREANS, latelye reuiued by COPERNICVS and by Geometricall Demonstrations approued
  • Thomas Digges
  • Perfit
  • Of
  • R Francis
  • Sanford V Johnson
  • Larkey
Thomas Digges, " A PERFIT DESCRIPTION OF THE CAELESTIALL Orbes according to the most aunciente doctrine of the PYTHAGOREANS, latelye reuiued by COPERNICVS and by Geometricall Demonstrations approued [1576] " ; reprinted in Francis R. Johnson and Sanford V. Larkey, " Thomas Digges, the Copernican System, and the Idea of the Infinity of the Universe in 1576, " The Huntington Library Bulletin, No. 5 (April 1934), pp. 78-95.
Thony Christie's comments from HASTRO- L Re: [HASTRO-L] Gilbert's universe; lack of evidence
  • Hastro-L Discussions
  • February
18 HASTRO-L discussions of February/March 2009; website <>. Thony Christie's comments from HASTRO- L, March 5, 2009, subject heading " Re: [HASTRO-L] Gilbert's universe; lack of evidence. "
1602); facsimile reprint idem, Tomus II
  • Vranibvrgi Danioe
Vranibvrgi Danioe, 1602); facsimile reprint idem, Tomus II. Scripta Astromica (Hauniae: In Libraria Gyldendaliana, 1915).
Die Welt des Jupiter im Jahre 1609, etc
  • Simon Marius
  • Mundus Iovialis Anno
Simon Marius, Mundus Iovialis Anno MDCIX, etc.: Die Welt des Jupiter im Jahre 1609, etc. [1614], edited by Joachim Schlör (Gunzenhausen: Schrenk-Verlag, 1988), pp. 42-55.
24 The 'Mundus Jovialis' of Simon Marius, translated by A.O. Prickard, The Observatory The missing material, which also includes his notes on Andromeda
  • A Pannekoek
  • History
  • Astronomy
Pannekoek, A History of Astronomy (New York: Interscience Publishers, 1961), p. 231. 24 The 'Mundus Jovialis' of Simon Marius, translated by A.O. Prickard, The Observatory, A Monthly Review of Astronomy 39 (1916), 367-381, 403-412, 443-452, 498-503. The missing material, which also includes his notes on Andromeda, would be located after the end of the Preface on page 373 and the beginning of PART I.
The Early Search for Stellar Parallax
  • Harald Siebert Galileo
  • Ramponi Castelli
Harald Siebert, " The Early Search for Stellar Parallax: Galileo, Castelli, and Ramponi, " Journal for the History of Astronomy 36 (2005), 251-271; especially 254-256.
Parte Seconda (Firenze: 1890); reprinted Sotto l’Alto
  • Ibid
  • Ed Favaro
  • Le Opere Di Galileo
  • Galilei
  • Torinensis Nicolai Copernici
The Starry Messenger [1610
  • Galileo Galilei
A PERFIT DESCRIPTION OF THE CÆLESTIALL Orbes according to the most aunciente doctrine of the PYTHAGOREANS, latelye reuiued by COPERNICVS and by Geometricall Demonstrations approued
  • Thomas Digges
Thony Christie’s comments from HASTRO-L
  • Hastro-L Discussions Of February