A Text-book of Astronomy |
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Common terms and phrases
altitude amount angle appear astronomers atmosphere attraction average axis body bright called century Chapter clock cloud cluster color comet constellation curve dark density determine diameter direction distance double stars earth earth and moon earth's orbit edge equal equator figure force full moon furnish greater heat horizon Jupiter Kepler's latitude law of gravitation light longitude lunar magnitude marked Mars mass measure meridian meteors miles Milky moon move nearly nebula node observations path perihelion period photographs photosphere planet Polaris pole position present produced proper motions radiant energy radius represent right ascension ring rotation satellites Saturn seen shadow shown in Fig side sidereal solar eclipse solar system space spectra spectroscope spectroscopic binaries spectrum spots star's stellar student sun-spot sun's sunlight surface telescope temperature tidal tion Uranus variable variable stars velocity Venus vernal equinox visible wave length
Popular passages
Page 45 - Every body continues in its state of rest or of uniform motion in a straight line, except in so far as it may be compelled by impressed forces to change that state.
Page 50 - Newton generalized the law of attraction into a statement that every particle of matter in the universe attracts every other particle with a force which varies directly as the product of their masses and inversely as the square of the distance between them; and he thence deduced the law of attraction for spherical shells of constant density.
Page 49 - To every action there is always an equal and contrary reaction ; or the mutual actions of any two bodies are always equal and oppositely directed.
Page 90 - Thirty days hath September, April. June, and November; All the rest have thirty.one, Save February, which alone Hath twenty.eight; and one day more We add to it one year in four.
Page 267 - Upwards of one hundred lay prostrate on the ground, some speechless, and some with the bitterest cries, but with their hands raised, imploring God to save the world and them. The scene was truly awful ; for never did rain fall much thicker than the meteors fell towards the earth ; east, west, north, and south it was the same.
Page 45 - Change of motion is proportional to the impressed force and takes place in the direction of the straight line in which the force acts.
Page 43 - The radius vector drawn from the sun to a planet sweeps equal areas in equal times. 3. The squares of the periodic times of the planets are proportional to the cubes of the semimajor axes of their orbits.
Page 79 - The Sun's rim dips; the stars rush out: At one stride comes the dark; With far-heard whisper, o'er the sea, Off shot the spectre-bark.
Page 89 - The moon by us to you her greeting sends. But bids us say that she's an ill-used moon, And takes it much amiss that you should still Shuffle her days, and turn them topsy-turvy ; And that the gods, who know their feastdays well, By your false count are sent home supperless, And scold and storm at her for your neglect.
Page 349 - Major, like the Minor, consists partly of large tracts and ill-defined patches of irresolvable nebula, and of nebulosity in every stage of resolution, up to perfectly resolved stars like the Milky Way, as also of regular and irregular nebulae properly so called, of globular clusters in every stage of resolvability, and of clustering groups sufficiently insulated and condensed to come under the designation of