A Treatise on AstronomyHarper & brothers, 1893 - 346 pàgines |
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Altres edicions - Mostra-ho tot
Frases i termes més freqüents
altitude angle aphelion apparent diameter appear asteroids astronomers axis binary stars body bright called celestial celestial equator celestial sphere centre centrifugal force circle comet computed conjunction constellation declination density describe determine difference diminished direction disturbing force diurnal diurnal motion earth earth's orbit earth's shadow eccentricity eclipse equal equator feet fixed stars full moon globe gravity greatest height Hence horizon horizontal parallax hour increased inequality inferior conjunction inferior planet interval Jupiter latitude less light limb longitude lunar magnitude mass mean distance Mercury meridian millions of miles moon's orbit move nearly Neptune node nucleus observations parallax passes penumbra perihelion period planet pole pole star portion position radius refraction represent revolution revolve right ascension ring rotation satellite Saturn seen semi-diameter sidereal solar spots sun's attraction sun's disc supposed synodical period tang telescope tide tion transit triangle Uranus velocity Venus visible zenith
Passatges populars
Pàgina 128 - RULES TO KNOW WHEN THE MOVEABLE FEASTS AND HOLYDAYS BEGIN. EASTER DAY, on which the rest depend, is always the First Sunday after the Full Moon which happens upon, or next after the Twenty-first Day of March ; and if the Full Moon happens upon a Sunday, Easter Day is the Sunday after.
Pàgina 64 - ... 1864, his diameter was 31' 31".8. Find the relative distances of the sun at these two periods. Ans. 0.96698. Ex. 2. On the 1st of April, 1864, the apparent diameter of the sun was 32' 3".4. Find the ratio of its distance to the distances in July and January. Ans. 0.98357 and 1.01716. 112. The earth's orbit is an ellipse. — By observations of the sun's apparent diameter continued throughout the year, we find that the true form of the earth's orbit is an ellipse, having the sun in one of the...
Pàgina 139 - ... at last brought down to the ground; and the greater the velocity is with which it is projected, the farther it goes before it falls to the earth. We may therefore suppose the velocity to be so increased, that it would describe an arc of 1, 2, 5, 10, 100, 1000 miles before it arrived at the earth, till at last, exceeding the limits of the earth, it should pass into space without touching it.
Pàgina 130 - Join SC, and, because SB and Cc are parallel, the triangle SBC will be equal to the triangle SBc, and therefore also to the triangle SAB. By the like argument, if the centripetal force acts successively in C, D...
Pàgina 28 - By actual measurement of a degree of latitude in different parts of the earth, it is found that the equatorial diameter is longer than the axis or polar diameter by 26 miles : the former being about 7924 miles; the latter about 7898 miles,* and that the form of the earth is that of an oblate spheroid resembling the annexed figure, in which pp, is the axis and eq the equator.
Pàgina 71 - Ad is found to be 42° 31' 47". The difference between AD and Ad is 2° 28' 13", or 9m. 52.8s. in time; and this is about the greatest amount of the equation of time, due to the obliquity of the ecliptic.
Pàgina 298 - Virginis ; not only on account of the length of its period, but by reason also of the great diminution of apparent distance, and rapid increase of angular motion about each other, of the individuals composing it. It is a bright star of the fourth magnitude, and its component stars are almost exactly equal. It has been known to consist of two stars since the beginning of the eighteenth century, their distance being then between six and seven seconds ; so that any tolerably good telescope would resolve...
Pàgina 197 - ... the semi-major axis. The eccentricities of most of the planetary orbits are so minute that, if the form of the orbit were exactly delineated on paper, it could not be distinguished from a circle except by careful measurement.
Pàgina 55 - ... most curious effects of atmospheric refraction is the oval form of the disks of the sun and moon, when near the horizon. This arises from the unequal refraction of the upper and lower limbs. The latter being nearer the horizon is more affected by refraction, and therefore raised in a greater degree than the upper limb, the effect of which is to bring the two limbs apparently closer together, by the difference between the two refractions. The form of the disk is therefore affected as if it were...
Pàgina 73 - Protestant countries the reform was not so readily adopted, and in England and her colonies it was not introduced till the year 1752. At this time there was a difference of 11 days between the Julian and Gregorian calendars, in consequence of the suppression in the latter, of the intercalary day in 1700. It was therefore enacted by Parliament that 11 days should be left out of the month of September...