American Heritage® Dictionary of the English Language, Fourth Edition
- adj. Of or relating to the astronomer Ptolemy.
- adj. Of or relating to the Ptolemies or to Egypt during their rule.
Century Dictionary and Cyclopedia
- Of or pertaining to Ptolemy; relating to one or all of the line of Ptolemies, rulers of Egypt from the end of the fourth to the first century b. c.
- relating to the Alexandrian geographer and astronomer Ptolemy (see below).
- He represented the deferent by the circle, thus giving it a breadth too great. This circle remained in an eccentric position, whence it was called the eccentric, as well as the deferent and the orbit.
- Instead of supposing the moving radius, TD, to describe equal areas in equal times, he drew a line to D, the attachment of the epicycle with the deferent from E, really corresponding to the empty focus of the ellipse, but called by him the center of the equant, and be supposed this line ED to turn with an equable motion so as to describe equal angles in equal times. This made an observable error only in the case of Mars. It made a tolerable approximation to the elliptic motion, which excited the admiration of Kepler, and it shows that Ptolemy aimed at something much better than a mere harmonic analysis of the motions of the planets.
- He not only made the epicycle circular, but he placed its center upon the deferent, thus virtually neglecting the eccentricity as well as the ellipticity of the earth's orbit in its effects on the apparent places of the exterior planets.
- He made the planet revolve in its epicycle so as to describe in equal times equal arcs measured from the perigee of the epicycle, as if the earth's motion were affected by the eccentricity of the orbit of the other planet.
- And he made the planet come to the perigee of its epicycle when it was just opposite the mean place of the sun, instead of the true place. Other still more serious falsities affected his theories of the inferior planets and of the moon. Yet, notwithstanding all these errors, Ptolemy's theory satisfied pretty closely, in the cases of all the planets except Mercury and the moon, such observations as could be made in his time. In his phrase, it “saved appearances.” The Ptolemaic theory continued in vogue until Copernicus (in 1543) explained the relations between the motions of the planets and that of the sun, and thus supplied a method for determining the relative magnitudes of the different planetary orbits. But the system of Copernicus did not in itself represent the phenomena any better than that of Ptolemy; and it was not until the great work of Kepler on the motions of Mars, published in 1609, that the real truth was known. The Almagest remains, however, a model of scientific investigation, most admirable for the genius with which it manages not only the astronomical problems attacked, but also those of pure mathematics.
- adj. Of or pertaining to the Ptolemies, rulers of Hellenistic Egypt.
- adj. Of or pertaining to the astronomer Claudius Ptolemy.
GNU Webster's 1913
- adj. Of or pertaining to
Ptolemy, the geographer and astronomer.
- adj. of or relating to the geocentric Ptolemaic system
- adj. of or relating to the astronomer Ptolemy
“The highest level of technology used in Ptolemaic Egypt was employed in support of religion, most likely to reinforce the existing social structure, and was never developed in ways that could be used by any sizable fraction of the society for societally productive goals.”
“Other extremely technological devices were developed in Ptolemaic Egypt, including remote-controlled steam engines that opened temple doors and magnetically levitated statues in those temples.”
“This system became known as the Ptolemaic system and predicted the positions of the planets accurately enough for naked-eye observations.”
“The system of Ptolemy, called the Ptolemaic universe, prevailed in astronomy for nearly fifteen hundred years, until the modern model of the solar system, with the sun at the center and the planets in motion, was developed from the ideas of Copernicus.”
“Hephaestio of Thebes (ca. 415), and the Ptolemaic, which is followed by Porphyrius (ca. 250), Paul of”
“Ptolemies, called the Ptolemaic, had hitherto been used, with some slight alterations; but Copernicus, an eminent astronomer, born at”
A Catechism of Familiar Things; Their History, and the Events Which Led to Their Discovery. With a Short Explanation of Some of the Principal Natural Phenomena. For the Use of Schools and Families. Enlarged and Revised Edition.
“To an uninstructed observer, the apparent motion of the heavenly bodies round the Earth would naturally lead him to conclude that, of the two theories, the Ptolemaic was the correct one.”
“Ptolemy's name is, however, most widely known in association with what is called the Ptolemaic theory.”
“This so-called Ptolemaic system of astronomy fitted in very nicely with the language of the”
“The greatest astronomer of ancient times was Hipparchus, and to him the system known as the Ptolemaic system is no doubt largely due.”
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