The Cambridge Course of Elementary Physics: Astronomy. Part third, Part 3 |
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Common terms and phrases
angle appear ascertained astronomers atmosphere attraction axis balls called Cavendish Experiment celestial celestial pole circle comet computed conjunction constellation curved density described diameter direction disc Dominical Letter draws earth eclipse Epact equal equator equinoxes exactly Figure fixed star force of gravity gravity acts heavenly bodies heavens Hence Herschel horizon hour inches inclined inferior conjunction inferior planets interval inversely John Herschel Jupiter known length light luminous lunar magnitude Mars mass mean distance measured Mercury meridian miles MINOR PLANETS moon moon's motion mountain move naked eye nebula Neptune observed opposite orbit oscillation parallax particles pass path pendulum planet polar distance pole position proper motion proportion pull revolution revolve ring rotation satellites Saturn seen shadow side sidereal period spots square straight line sun's superior planet suppose surface synodical period tance telescope tion triangle Uranus velocity Venus vibrations visible weight
Popular passages
Page 192 - These phenomena agree with the supposition that the stars of our firmament, instead of being scattered in all directions indifferently through space, form a stratum, of which the thickness is small, in comparison with its length and breadth ; and in which the earth occupies a place somewhere about the middle of its thickness, and near the point where it subdivides into two principal laminae, inclined at a small angle to each other.
Page 187 - Their names are Aries, Taurus, Gemini, Cancer, Leo, Virgo, Libra, Scorpio, Sagittarius, Capricornus, Aquarius, Pisces; the whole occupying a complete circle, or broad belt, in the heavens, called the Zodiac.
Page 213 - ... is a compound pendulum, consisting of a heavy weight hung from a fixed point by means of a rod of wood or metal. The particles of such a pendulum must of course be at different distances from the point of suspension, and must therefore tend to vibrate in different times. Hence the time of vibration of the whole pendulum will not be the same as that of a simple pendulum of the same length. The compound pendulum may be regarded as consisting of as many simple pendulums as it contains particles....
Page 161 - Having despaired of reconciling the actual state of the planetary system with any theory he could form respecting it, he hazarded the conjecture that a planet really existed between the orbits of Mars and Jupiter, and that its smallness alone prevented it from being visible to astronomers.
Page 278 - Idler; the other six being inserted in different characters, to denote the other six days of the week. Now, since a common Julian year contains 365 days, if this number be divided by 7 (the number of days in a week), there will remain one day. If there had been no remainder, it is...
Page 255 - To shew this, suppose that the mine reached half-way to the centre of the earth. Then (since the volumes of spheres vary as the cubes of their diameters) the quantity of matter nearer to the earth's centre than the bottom of the mine would be only one-eighth of the whole quantity of matter in the earth. But the attraction of a quantity of matter at the earth's centre would be more powerful on a body at the bottom of a mine than on one at the top, in the inverse ratio of the squares of the distances...
Page 42 - ... that the squares of the periodic times of the planets are to each other as the cubes of their mean distances from the sun...
Page 133 - OM' is about four thousand miles shorter than OM. Notwithstanding the moon is much nearer when at the zenith than at the horizon, it seems to us much larger at the horizon. This is a pure illusion, as we become convinced when we measure the disc with accurate instruments, so as to make the result independent of our ordinary way of judging. When the moon is near the horizon, it seems placed beyond all the objects on the surface of the earth in that direction, and therefore farther off than at the...
Page ii - COMPANY, in the Clerk's Office of the District Court of the District of Massachusetts. UNIVERSITY PRESS : WELCH, BIGELOW, & Co., INTRODUCTION BT THE TRAN8LATOR.
Page 123 - SO), which he considered as an equatorial zone ; it was from the direction of these bands that he deduced the inclination of the axis of rotation. Besides this, during the crescent phases many observers...