File:Elements of astronomy with explanatory notes, and questions for examination (1855) (14595940428).jpg

Identifier: elementsofastro00broc (find matches)
Title: Elements of astronomy ... with explanatory notes, and questions for examination
Year: 1855 (1850s)
Authors: Brocklesby, John, 1811-1889
Subjects: Astronomy
Publisher: New York, Farmer, Brace & co.
Contributing Library: The Library of Congress
Digitizing Sponsor: The Library of Congress

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cs near the poles the arctic41 (northern) and 1. The axis of the earth is at right angles (90°) with the plane of theequator. The plane of the ecliptic being inclined to that of the equator abouttwenty-three and one half degrees, it must therefore be inclined to the axisabout sixty-six and one half, degrees since sixty-six and one half added totwenty-three and one half equals ninety. 2. Precession and nutation will of course produce a very slightdisplacement. 3. The figure is here drawn as if the plane of the ecliptic was viewedobliquely, the orbit of the earth therefore, appears more eccentric than itactually is. 4. Arctic (northern.) From the Greek word, arktos meaning bear,because the north pole of the heavens is in the constellation called the bear. What is the extent of the inclination of the earths axis to the ecliptic 1 Explain whythe earths axis is directed to the name points in the heavens notwithstanding the earthrevolves about the sun ? Explain the figure. THE SEASONS. 117
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118 THE EARTH VIEWED ASTRONOMICALLY. antarctic1, (southern) or polar circles. The lines drawnin each globe from C, parallel to CSlC, indicate the posi-tion of the plane of the ecliptic with respect to that of theequator. 201. Spring. At the vernal equinox, (March,) whenthe earth is in Libra,2 the circle of illumination extends tothe two poles,3 the sun is in the plane of the equator, andis seen from the earth in this plane. As the earth rotateson its axis every point upon its surface is then half thetime of one rotation in darkness, and the other half inlight. In this position of the earth, the days and nightsare therefore equal all over the globe. 202. Summer. When the earth is in Capricorn at thenorthern summer solstice*, (June,) the axis being un-changed in direction, the north pole is presented towardsthe sun, and the circle of illumination extends beyond thepole N to the arctic (northern) circle, while in the south-ern hemisphere it falls short of the south pole S, reachingonly t

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