Tuesday, May 20, 2008

Greek astronomy texts

From Saint Anselm College a look at some of the original documents on Greek astronomy.

Greek Astronomy

One of the most powerful creations of Greek science was the mathematical astronomy created by Hipparchus in the second century B.C. and given final form by Ptolemy in the second century A.D. Ptolemy's work was known in the Middle Ages through imperfect Latin versions. In fifteenth-century Italy, however, it was brought back to life. George Trebizond, a Cretan emigre in the curia, produced a new translation and commentary. These proved imperfect and aroused much heated criticism. But a German astronomer, Johannes Regiomontanus, a protege of the brilliant Greek churchman Cardinal Bessarion, came to Italy with his patron, learned Greek, and produced a full-scale "Epitome" of Ptolemy's work from which most astronomers learned their art for the next century and more. Copernicus was only one of the celebrities of the Scientific Revolution whose work rested in large part on the study of ancient science carried out in fifteenth-century Italy.

  • Byzantine Astronomical Collection

    In Greek, Before 1308

    In the thirteenth and fourteenth centuries, a number of recent Arabic and Persian astronomical works were translated into Greek by scholars who traveled to Persia under the Ilkhanid Empire. One short and confused treatise, translated by Gregory Chioniades, describes Tusi's lunar theory, illustrated, not altogether correctly, in this figure along with Tusi's device for producing rectilinear from circular motions. A part of the planetary and lunar theory of the astronomers of Maragha was later utilized by Copernicus, though scholars do not know how he gained access to this material.

  • Ptolemy, Almagest

    In Latin, Translated by George Trebizond, ca. 1481

    George Trebizond, one of the notable Greek scholars who came to Italy in the early fifteenth century, made a new translation of the "Almagest" from the Greek for Pope Nicholas V between March and December of 1451. Due to a dispute about the quality of Trebizond's commentary on the text, the translation was never dedicated to Nicholas. This very elaborate manuscript of the translation, with the figures drawn in several colors, was dedicated to Pope Sixtus IV by George's son Andreas. These pages show Book VI Chapter 7, on the computation of the duration of solar and lunar eclipses.

  • George Trebizond, Commentary on the Almagest

    In Latin, ca. 1482

    During the same nine months that George Trebizond made his translation of the "Almagest," he also wrote a commentary as long as the original text. The commentary was severely criticized, however, which resulted in a falling out with Pope Nicholas V. This opulent manuscript was dedicated to Pope Sixtus IV by George's son Andreas along with Vat. lat. 2055 of the translation. These pages contain a large figure of the model for the planet Mercury, shown at its least distance from the earth, with a list of Mercury's parameters and distances, and then the beginning of the treatment of Venus in Book X.

  • Nasir ad-Din at-Tusi, Tadhkira

    In Arabic, Fourteenth century

    Nasir ad-Din at-Tusi was among the first of several Arabic astronomers of the late thirteenth century at the observatory of Maragha in Persia who modified Ptolemy's models based on mechanical principles, in order to preserve the uniform rotation of spheres. This early Arabic manuscript contains his principal work on the subject, the "Tadhkira fi ilm al-Haya" (Memoir on Astronomy). The figure shown here is his ingenious device for generating rectilinear motion along the diameter of the outer circle from two circular motions.

  • Georg Peurbach and Johannes Regiomontanus, Epitome of the Almagest

    In Latin, Late fifteenth century

    The "Epitome of the Almagest" was written between 1460 and 1463 by Georg Peurbach and Johannes Regiomontanus at the suggestion of Cardinal Bessarion. It gave Europeans the first sophisticated understanding of Ptolemy's astronomy, and was studied by every competent astronomer of the sixteenth century. The illustration here shows the distance of the sun from the earth as 1210 terrestrial radii (about 4,800,000 miles), which is too small by a factor of twenty, but gives a solar parallax (the maximum displacement due to observing the sun from the surface rather than from the center of the earth) of less than 3 minutes, still well below the limit of observational accuracy.

  • Ptolemy, Geography

    In Greek, Fifteenth century

    Ptolemy's "Geography" contains instructions for drawing maps of the entire "oikoumene" (inhabited world) and particular regions, along with the longitudes and latitudes of about eight thousand locations in Europe, Africa, and Asia. The maps in manuscripts of the "Geography," however, date only from about 1300, after the text was rediscovered by Maximus Planudes. There are two versions, the A recension with twenty-six large regional maps, and the B recension, displayed here, with sixty-four smaller regional maps and four large additional maps. Shown here is the additional map of Europe which reveals Ptolemy's systematic exaggeration of west to east distances, particularly in the eastward extension of Scotland and the west to east slope of Italy.

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