Popular Astronomy: A Concise Elementary Treatise on the Sun, Planets, Satellites and Comets |
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angle Annual variation aphelion apparent diameter ascending node asteroids astronomers attraction celestial celestial sphere centrifugal force circle circular clock comet computed conjunction determined direction discovered discovery disk disturbing DUDLEY OBSERVATORY earth earth's orbit eccentricity ecliptic entire equal equator exact examination exerted fact fall figure fixed stars globe gravitation heavenly bodies heavens hence Hipparchus hypothesis inclination inferior conjunction instruments Jupiter Jupiter's Kepler law of Kepler laws of motion light line of nodes Longitude lunar major axis Mars mass Mean distance measure Mercury meridian millions of miles moon moon's orbit move nearly observation Observatory pass perihelion period of revolution phenomena planet planetary orbits pole position precisely present problem radius reached retrograde revolution in days revolving ring rotation round satellites Saturn seen Sidereal revolution space sphere spots sun's center surface telescope tion transit Uranus velocity Venus vernal equinox visible visual ray weight worlds
Popular passages
Page 308 - The third, viz. that the squares of the periodic times are proportional to the cubes of the mean distances...
Page 209 - THE general reasoning presented in the preceding chapter can only be reduced to exact application after having obtained the numerical values of the quantities demanded in the investigation. The mathematician may assume these quantities at his pleasure, and with the assumed weight of his sun, and planets and satellites, and with their assumed distances, and with the assumed directions and intensities of the impulsive forces, he may master, by analytical reasoning, all the circumstances attending the...
Page 181 - ... the elements of a particle of water, for instance, is subject to an attractive and a repulsive force, acting in contrary directions, the centres of action of which are reciprocally opposed. The action of each force in relation to a molecule of water situated in the course of the electric current is in the inverse ratio of the square of the distance at which it is exerted, thus giving (it is stated) for such a molecule a constant force-\-.
Page 118 - a singular phenomena connected with the snow-zone, which, so far as I know, has not been noticed elsewhere. On the night of July 12, 1845, the bright polar spot presented an appearance never exhibited at any preceding or succeeding observation. In the very centre of the white surface was a dark spot, which retained its position during several hours, and was distinctly seen by two friends who passed the night with me in the observatory. It was much darker, and better defined than any spot previously...
Page 350 - ... from the centre of the sun, had necessarily an absolute velocity greater than the molecules of the inferior part which is nearest it, the rotatory motion, common to all the fragments, must always have been in the same direction as the orbitual motion.
Page 186 - ... modern terms, they knew the " law of the inverse ratio of the square of the distance from the centre of the revolution." Some have thought, that in Empedocles's system the foundation of Newton's was to be found ; imagining, that under the name of
Page 57 - Venus lies, this plane, passing, as it does, through the sun's centre, it is clear that at every inferior conjunction of the planet there might be seen a transit of Venus, while at every superior conjunction the planet would be occulted, or hidden, by passing actually behind the disc of the sun. It happens, however, that the plane of the orbit of Venus does not coincide with the plane of the ecliptic, or earth's orbit. These planes are inclined to each other, under an angle of 3° 23' 28"-5, one...
Page 300 - Thus the law of universal attraction becomes pure Metaphysics if we withdraw from it the verifiable specification of its mode of operation. Withdraw the formula " inversely as the square of the distance and directly as the mass," and Attraction is left standing a mere
Page 350 - ... after their division one of these fragments has been sufficiently superior to the others to unite them to it by its attraction, they will have formed only a mass of vapor, which, by the continual friction of all its parts, must have assumed the form of a spheroid flattened at the poles and elongated in the direction of its equator. Here, then, are rings of vapor left by the successive retreats of the atmosphere of the sun, changed into so many planets in the condition of vapor circulating round...
Page 119 - In the early part of the evening," he says, "the small bright spot seemed to be partly buried in the large one. After the lapse of an hour or more my attention was again directed to the planet, when I was astonished to find a manifest change in the position of the small bright spot. It had apparently separated from the large spot, and...