from The American Heritage® Dictionary of the English Language, 4th Edition
- adj. Of or relating to the astronomer Ptolemy.
- adj. Of or relating to the Ptolemies or to Egypt during their rule.
from Wiktionary, Creative Commons Attribution/Share-Alike License
- adj. Of or pertaining to the Ptolemies, rulers of Hellenistic Egypt.
- adj. Of or pertaining to the astronomer Claudius Ptolemy.
from the GNU version of the Collaborative International Dictionary of English
- adj. Of or pertaining to Ptolemy, the geographer and astronomer.
from The 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.
from WordNet 3.0 Copyright 2006 by Princeton University. All rights reserved.
- adj. of or relating to the geocentric Ptolemaic system
- adj. of or relating to the astronomer Ptolemy
Sorry, no etymologies found.