The Elements of Astronomy: A TextbookGinn, 1919 - 508 стор. |
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altitude angle apparent astronomical astronomical units atmosphere axis azimuth binary bright celestial equator celestial sphere centre chromosphere circle comet constellation corona declination density determined diameter disc Dist distance Double Stars earth earth's orbit east eclipse equal equator equatorial eye-piece feet force globe gravity heat heavenly bodies horizon inches instrument Jupiter known latitude libration light longitude lunar lunar eclipse magnitude Mags mass mean measured meridian meridian circle meteoric method minutes moon moon's motion moving naked eye nearly nebula Neptune node object object-glass observations Observatory parallax perihelion period perturbations photographs photosphere planet pole Pole-star probably proper motion radius right ascension ring rotation satellites seen shadow sidereal sidereal period Sirius solar spectra spectroscope spectrum sun spots sun's synodic period telescope tides tion transit Uranus Ursa velocity Venus vernal equinox visible zenith
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Сторінка 18 - ... is the great circle in which the plane of the earth's equator cuts the celestial sphere. It is often called the "Equinoctial.
Сторінка 178 - The radius vector of each planet describes equal areas in equal times. (3) The squares of the periods of the planets are proportional to the cubes of their mean distances from the su» ; ie, £12 : ia2 : : «!3 : a28. This is the so-called "Harmonic Law.
Сторінка 30 - FIG. 10. — Determination of Latitude. An exact definition of the astronomical latitude of a place has already been given (Art. 40). It is (1) the angle between the direction of gravity and the plane of the equator, which is the same as the altitude of the pole. (2) It may also be defined as the declination of the zenith, as is clear from Fig. 10, where PB, the altitude of the pole, equals QZ (since PQ and ZB are each 90°), and QZ by the very definition of declination (Art. 31) is the declination...
Сторінка 219 - On it place a globe, two feet in diameter; this will represent the Sun; Mercury will be represented by a grain of mustard seed, on the circumference of a circle 164 feet in diameter for its orbit; Venus a pea, on a circle 284 feet in diameter; the Earth also a pea, on a circle of 430 feet; Mars a rather large pin's head, on a circle of 654 feet; Juno, Ceres, Vesta, and Pallas, grains of sand, in orbits of from 1000 to 1200 feet; Jupiter a moderate-sized orange...
Сторінка 152 - The heat-unit most used at present is the " calory," l which is the quantity of heat required to raise the temperature of one kilogram of water 1° C. ; and as the result of the best observations thus far made...
Сторінка iv - The eminence of Professor Young as an original investigator in astronomy, a lecturer and writer on the subject, and an instructor in college classes, led the publishers to present the General Astronomy with the highest confidence; and this confidence has been fully justified by the event.
Сторінка iv - Certain subjects, which, while they certainly ought to be found within the covers of every text-book of Astronomy, are perhaps not essential to an elementary course, have been relegated to an appendix. Where time allows, the instructor will find it advisable to include some of them at least in the student's work. A brief Uranography is also presented, covering the constellations visible in the United States, with maps on a scale sufficient for the easy identification of all the principal stars. It...
Сторінка 176 - Here, also, we find many writers, the older ones especially, bringing in the "projectile force," and saying that when a body moves in a curve, it does so " under the action of two forces ; one the force that draws it sideways, the other the 'projectile force' directed along its path." We repeat, this "projectile force" has no present existence nor meaning in the problem of a body's motion. Such a force may have put the body in motion long ago, but its function has ceased, and now we have only to...