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Home > Dictionary of Science Quotations > Scientist Names Index P > Ptolemy Quotes

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(c. 100 - c. 170)

Greek astronomer who wrote the famous book of mathematical astronomy, known as the Almagest, which described the Ptolemaic (geocentric) universe.

Science Quotes by Ptolemy (5 quotes)

Engraving of Ptolemy, upper body, facing right, holding a cross-staff, from Robert S Ball, Great Astronomers (1906), page 9
Ptolemy (source)
All those who think it paradoxical that so great a weight as the earth should not waver or move anywhere seem to me to go astray by making their judgment with an eye to their own affects and not to the property of the whole. For it would not still appear so extraordinary to them, I believe, if they stopped to think that the earth's magnitude compared to the whole body surrounding it is in the ratio of a point to it. For thus it seems possible for that which is relatively least to be supported and pressed against from all sides equally and at the same angle by that which is absolutely greatest and homogeneous.
— Ptolemy
'The Almagest 1', in Ptolemy: the Almagest; Nicolaus Copernicus: On the Revolutions of the Heavenly Spheres; Johannes Kepler: Epitome of Copernican Astronomy: IV - V The Harmonies of the World: V, trans. R. Catesby Taliaferro (1952), 11.
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I do not profess to be able thus to account for all the [planetary] motions at the same time; but I shall show that each by itself is well explained by its proper hypothesis.
— Ptolemy
(c. 100 AD). From introduction to 'Hypotheses', translated into French by Abbé N. Halma, Hypothèses et époques des planètes de Cl. Ptolémée et Hypotyposes de Proclus Diadochus (1820), 41-42. As quoted, in English, in John Louis Emil Dreyer History of the Planetary Systems from Thales to Kepler (1906), 201. In French, “Je ne prétends pas pouvoir ainsi rendre raison de tous ces mouvemens à la fois; mais je veux montrer que chacun à part s'explique très-bien par son hypothèse propre.”
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 Ptolemy quote When I trace at my pleasure the windings
Conjunction of the moon, Venus and Jupiter (source)
I know that I am mortal by nature, and ephemeral; but when I trace at my pleasure the windings to and fro of the heavenly bodies I no longer touch earth with my feet: I stand in the presence of Zeus himself and take my fill of ambrosia, food of the gods.
— Ptolemy
Epigram. Almagest. In Owen Gingerich, The Eye of Heaven: Ptolemy, Copernicus, Kepler (1993), 4.
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Mortal as I am, I know that I am born for a day. But when I follow at my pleasure the serried multitude of the stars in their circular course, my feet no longer touch the earth.
— Ptolemy
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Therefore the solid body of the earth is reasonably considered as being the largest relative to those moving against it and as remaining unmoved in any direction by the force of the very small weights, and as it were absorbing their fall. And if it had some one common movement, the same as that of the other weights, it would clearly leave them all behind because of its much greater magnitude. And the animals and other weights would be left hanging in the air, and the earth would very quickly fallout of the heavens. Merely to conceive such things makes them appear ridiculous.
— Ptolemy
'The Almagest 1', in Ptolemy: the Almagest; Nicolaus Copernicus: On the Revolutions of the Heavenly Spheres; Johannes Kepler: Epitome of Copernican Astronomy: IV - V The Harmonies of the World: V, trans. R. Catesby Taliaferro (1952), 11.
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Quotes by others about Ptolemy (12)

If the Lord Almighty had consulted me before embarking upon his creation, I should have recommended something simpler.
Remarking on the complexity of Ptolemaic model of the universe after it was explained to him.
(circa 1250 A.D.) As atttributed, in John Esten Keller, Alfonso X, El Sabio (1967), Preface.
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It was not just the Church that resisted the heliocentrism of Copernicus. Many prominent figures, in the decades following the 1543 publication of De Revolutionibus, regarded the Copernican model of the universe as a mathematical artifice which, though it yielded astronomical predictions of superior accuracy, could not be considered a true representation of physical reality: 'If Nicolaus Copernicus, the distinguished and incomparable master, in this work had not been deprived of exquisite and faultless instruments, he would have left us this science far more well-established. For he, if anybody, was outstanding and had the most perfect understanding of the geometrical and arithmetical requisites for building up this discipline. Nor was he in any respect inferior to Ptolemy; on the contrary, he surpassed him greatly in certain fields, particularly as far as the device of fitness and compendious harmony in hypotheses is concerned. And his apparently absurd opinion that the Earth revolves does not obstruct this estimate, because a circular motion designed to go on uniformly about another point than the very center of the circle, as actually found in the Ptolemaic hypotheses of all the planets except that of the Sun, offends against the very basic principles of our discipline in a far more absurd and intolerable way than does the attributing to the Earth one motion or another which, being a natural motion, turns out to be imperceptible. There does not at all arise from this assumption so many unsuitable consequences as most people think.'
from Letter to Christopher Rothman, 20 Jan 1587
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And from this such small difference of eight minutes [of arc] it is clear why Ptolemy, since he was working with bisection [of the linear eccentricity], accepted a fixed equant point… . For Ptolemy set out that he actually did not get below ten minutes [of arc], that is a sixth of a degree, in making observations. To us, on whom Divine benevolence has bestowed the most diligent of observers, Tycho Brahe, from whose observations this eight-minute error of Ptolemy’s in regard to Mars is deduced, it is fitting that we accept with grateful minds this gift from God, and both acknowledge and build upon it. So let us work upon it so as to at last track down the real form of celestial motions (these arguments giving support to our belief that the assumptions are incorrect). This is the path I shall, in my own way, strike out in what follows. For if I thought the eight minutes in [ecliptic] longitude were unimportant, I could make a sufficient correction (by bisecting the [linear] eccentricity) to the hypothesis found in Chapter 16. Now, because they could not be disregarded, these eight minutes alone will lead us along a path to the reform of the whole of Astronomy, and they are the matter for a great part of this work.
Astronomia Nova, New Astronomy (1609), ch. 19, 113-4, Johannes Kepler Gesammelte Werke (1937-), Vol. 3, 177-8.
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Had I been present at the Creation, I would have given some useful hints for the better ordering of the universe.
Remarking on the complexity of Ptolemaic model of the universe after it was explained to him.
Footnote: Carlyle says, in his History of Frederick the Great, book ii. chap. vii. that this saying of Alphonso about Ptolemy's astronomy, 'that it seemed a crank machine; that it was pity the Creator had not taken advice,' is still remembered by mankind, — this and no other of his many sayings.
In John Bartlett and Nathan Haskell Dole (Ed.), Familiar Quotations: A Collection of Passages, Phrases, and Proverbs Traced to Their Sources (1914), 954.
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Copernicus, the most learned man whom we are able to name other than Atlas and Ptolemy, even though he taught in a most learned manner the demonstrations and causes of motion based on observation, nevertheless fled from the job of constructing tables, so that if anyone computes from his tables, the computation is not even in agreement with his observations on which the foundation of the work rests. Therefore first I have compared the observations of Copernicus with those of Ptolemy and others as to which are the most accurate, but besides the bare observations, I have taken from Copernicus nothing other than traces of demonstrations. As for the tables of mean motion, and of prosthaphaereses and all the rest, I have constructed these anew, following absolutely no other reasoning than that which I have judged to be of maximum harmony.
Dedication to the Duke of Prussia, Prutenicae Tabulae (1551), 1585 edition, as quoted in Owen Gingerich, The Eye of Heaven: Ptolemy, Copernicus, Kepler (1993), 227.
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Because a fact seems strange to you, you conclude that it is not one. ... All science, however, commences by being strange. Science is successive. It goes from one wonder to another. It mounts by a ladder. The science of to-day would seem extravagant to the science of a former time. Ptolemy would believe Newton mad.
In Victor Hugo and Lorenzo O'Rourke (trans.) Victor Hugo's Intellectual Autobiography: (Postscriptum de ma vie) (1907), 322.
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It’s only through honesty and courage that science can work at all. The Ptolemaic understanding of the solar system was undermined and corrected by the constant pressure of more and more honest reporting.
In essay, 'The Origin of the Universe,' 6. Written after hearing Stephen Hawking's lecture (2006) at Oxford, about the origin of the universe.
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Yet the widespread [planetary theories], advanced by Ptolemy and most other [astronomers], although consistent with the numerical [data], seemed likewise to present no small difficulty. For these theories were not adequate unless they also conceived certain equalizing circles, which made the planet appear to move at all times with uniform velocity neither on its deferent sphere nor about its own [epicycle's] center … Therefore, having become aware of these [defects], I often considered whether there could perhaps be found a more reasonable arrangement of circles, from which every apparent irregularity would be derived while everything in itself would move uniformly, as is required by the rule of perfect motion.
From Nicholaus Copernicus, Edward Rosen (trans.), Pawel Czartoryski (ed.) 'Commentariolus', in Nicholas Copernicus: Minor Works (1985), 81-83. Excerpted in Lisa M. Dolling, Arthur F. Gianelli and Glenn N. Statile (eds.) The Tests of Time: Readings in the Development of Physical Theory (2003), 40.
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Napoleon and other great men were makers of empires, but these eight men whom I am about to mention were makers of universes and their hands were not stained with the blood of their fellow men. I go back 2,500 years and how many can I count in that period? I can count them on the fingers of my two hands. Pythagoras, Ptolemy, Kepler, Copernicus, Aristotle, Galileo, Newton and Einstein—and I still have two fingers left vacant.
Speech (28 Oct 1930) at the Savoy Hotel, London in Einstein’s honor sponsored by a committee to help needy Jews in Eastern Europe. In Albert Einstein, Cosmic Religion: With Other Opinions and Aphorisms (1931), 31.
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I have always felt that astronomical hypotheses should not be regarded as articles of faith, but should only serve as a framework for astronomical calculations, so that it does not matter whether they were right or wrong, as long as the phenomena can be characterized precisely. For who could possibly be certain as to whether the uneven movement of the sun, if we follow the hypotheses of Ptolemy, can be explained by assuming an epicycle or eccentricity. Both assumptions are plausible. That’s why I would consider it quite desirable for you to tell something about that in the preface. In this way you would appease the Aristotelians and the theologians, whose opposition you dread.
From surviving fragment of a Letter (20 Apr 1541) answering a query from Copernicus as to whether he should publish his book (De Revolutionibus). From the German in Leopold Friedrich Prowe, Nicolaus Coppernicus (1883), Vol. 1, Part 2, 521-522. Translated from Prowe by Webmaster using web resources. Original German: “Hypothesen nicht als Glaubens-Artikel zu betrachten seien, sondern nur als Grundlage für die astronomischen Rechnungen zu dienen hätten, so dass es nicht darauf ankomme, ob sie richtig oder falsch seien, wofern sich nur die Erscheinungen dadurch genau bestimmen liessen. »Denn wer dürfte uns wohl darüber sichere Auskunft geben, ob die ungleiche Bewegung der Sonne, wenn wir den Hypothesen des Ptolemaeus folgen, durch Annahme eines Epicykels oder der Ekcentricität zu erklären sei. Beide Annahmen sind gestattet. Daher würde ich—so schliesst Osiander—es für recht wünschenswerth erachten, wenn Du hierüber in der Vorrede etwas beibrächtest. Auf diese Weise würdest Du die Aristoteliker und die Theologen milder stimmen, von denen Du befürchtest, dass sie heftigen Widerspruch kundthun werden.«” Compare Latin text, from Johannes Kepler, 'Apologia Tychonia', Astronomi Opera Omnia (1858), Vol. 1, 246: “De hypothesibus ego sic sensi semper, non esse articulos fidei, sed fundamenta calculi ita ut, etiamsi falsae sint, modo motuum φαινομενα exacte exhibeant, nihil referat; quis enim nos certiores reddet, an Solis inaequalis motus nomine epicycli an nomine eccentricitatis contingat, si Ptolemaei hypotheses sequamur, cum id possit utrumque. Quare plausibile fore videretur, si hac de re in praefatione nonnihil attingeres. Sic enim placidiores redderes peripatheticos et theologos, quos contradicturos metuis.”
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They say that Ptolemy once asked him [Euclid] whether there was in geometry no shorter way than that of the elements and he replied, “There is no royal road to geometry”.
In (Edition Friedlein, 1873), Prol. II, 39.
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Newton’s theory is the circle of generalization which includes all the others [as Kepler’s laws, Ptolemy’s theory, etc.];—the highest point of the inductive ascent;—the catastrophe of the philosophic drama to which Plato had prologized;— the point to which men’s minds had been journeying for two thousand years.
In History of the Inductive Sciences, Bk. 7, chap. 2, sect. 5.
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 Ptolemy quote When I trace at my pleasure the windings
Conjunction of the moon, Venus and Jupiter (source)

See also:
  • Ptolemy - biography from Great Astronomers (1895)
  • Ptolemy - context of quote “When I trace at my pleasure the windings” - Medium image (500 x 250 px)
  • Ptolemy - context of quote “When I trace at my pleasure the windings” - Large image (800 x 400 px)
  • Ptolemy’s Almagest, by Ptolemy translated by G.J. Toomer. - book suggestion.
  • Booklist for Ptolemy.

Carl Sagan Thumbnail In science it often happens that scientists say, 'You know that's a really good argument; my position is mistaken,' and then they would actually change their minds and you never hear that old view from them again. They really do it. It doesn't happen as often as it should, because scientists are human and change is sometimes painful. But it happens every day. I cannot recall the last time something like that happened in politics or religion. (1987) -- Carl Sagan
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