AstronomyH. Holt, 1890 - 366 pagina's |
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Veelvoorkomende woorden en zinsdelen
altitude angle angular distance apparent position appear astronomical atmosphere attraction axis brighter brilliant called celestial equator celestial meridian celestial pole celestial sphere centre circle comet constellation determine diameter direction disk diurnal motion diurnal orbit earth earth's surface east eclipse equator figure fixed stars force gravitation Greenwich heat heavens Hence HERSCHEL horizon hour-angle inferior conjunction Jupiter KEPLER kilometres known latitude light longitude lunar magnitude Mars mass mean distance mean solar measured Mercury meteoroids meteors miles months moon moon's move naked eye nearly nebulæ Neptune node noon north pole north-polar distance object observer orbit parallax particle pass period phenomena photosphere planet radius rays refraction revolution revolves right ascension ring rotation satellites Saturn seen shadow sidereal sidereal day solar system spectroscope spectrum sun's supposed telescope terrestrial theory tion transit Uranus vapor variable stars velocity Venus vernal equinox visible zenith
Populaire passages
Pagina 119 - that every particle of matter in the universe attracts every other particle, with a force whose direction is that of the line joining the two, and whose magnitude is directly as the product of their masses, and inversely as the square of their distances from each other.
Pagina 116 - To every action there is always opposed an equal reaction: or, the mutual actions of two bodies upon each other are always equal, and directed to contrary parts.
Pagina 115 - The change of motion is proportional to the motive force impressed; and is made in the direction of the right line in which that force is impressed.
Pagina iii - Aims to furnish a tolerably complete outline of the astronomy of to-day, in as elementary a shape as will yield satisfactory returns for the learner's time and labor. It has been abridged from the larger work, not by compressing the same matter into less space, but by omitting the details of practical astronomy, thus giving to the descriptive portions a greater relative prominence. From THE CRITIC: " The book is in refreshing contrast to...
Pagina 109 - law of equal areas." (3) The squares of the periods of revolution of any two planets are proportional to the cubes of their mean distances from the sun.
Pagina 320 - ... and, calling this a sidereal stratum, an eye placed somewhere within it will see all the stars in the direction of the planes of the stratum projected into a great circle, which will appear lucid on account of the accumulation of the stars; while the rest of the heavens, at the sides, will only seem to be scattered over with constellations, more or less crowded, according to the distance of the planes or number of stars contained in the thickness or sides of the stratum.
Pagina 176 - Its satellite system also deserves careful observation, especially in respect to the eclipses which occur; since we find in them a measure of the time required for light to cross the orbit of the earth, and so of the solar parallax, and also because, as has been already mentioned, they furnish a test of the constancy of the earth's rotation. The photometric method of observing these eclipses, first instituted by Professor Pickering at Cambridge in 1878, and since re-invented by Cornu in Paris, has...
Pagina 115 - Every body continues in its state of rest, or of uniform motion in a right line, unless it is compelled to change that state by forces impressed upon it.
Pagina 104 - KEPLER (born 1571, d. 1630) was a genius of the first order. He had a thorough acquaintance with the old systems of astronomy and a thorough belief in the essential accuracy of the Copernican system, whose fundamental theorem was that the sun and not the earth was the centre of our system.
Pagina 95 - The declination of a star is its angular distance north or south of the celestial equator, measured along the hour cirele through the star.