Lectures on Astronomical Theories, Volumes 1-4Lovell Printing and Publishing Company, 1876 |
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Lectures on Astronomical Theories Associate Professor University of Alberta Canada John Harris No preview available - 2016 |
Common terms and phrases
aberration of light actual angle angular velocity antarctic circle aphelion apparent path appears arrived ascending assume assumption astronomical astronomical observation become belonging Biela's celestial sphere centre of gravitation centrifugal force comet commencement compound consequently consideration considered continually descend difference direction disc distance doctrine earth earth's orbit earth's perpendicular axis eclipse effect emersion equatorial plane equinoctial circle equinox ether evident explanation gravitating influence hemisphere Herschel's Outlines horizontal inclined axis Jupiter Jupiter's KUKL Lardner luminous magnitude manifested mass matter minutes moving north pole object oblique observed facts occultation occupied opposition orbital path orbital revolution oscillation parallax particles passing perihelion period phenomena planet Jupiter planetary position present quantity reason recede relatively Roemer seen shadow sidereal solar orbit solar system sound south pole space spot sun's axis sun's equator supposition surface synodic period terrestrial theory of light tion tube undulatory theory vertical motion visible visual ray
Popular passages
Page 20 - EF, with a velocity properly adjusted at every instant to that of the ball, while preserving its inclination to the horizon, so that when the ball in its natural descent reached...
Page 24 - Comets consist for the most part of a large and more or less splendid, but ill-defined nebulous mass of light, called the head, which is usually much brighter towards its centre, and offers the appearance of a vivid nucleus, like a star or planet From the head...
Page 23 - PQ, both fall on the extreme confines of the enlightened side. In this position, therefore, it is day over half the northern and half the southern hemisphere at once; and as the earth revolves on its axis, every point of its surface describes half its diurnal course in light, and half in darkness; in other words, the duration of day and night is here equal over the whole globe: hence the term equinox. The same holds good at the autumnal equinox on the position C.
Page 25 - Cassini describes the comet of 1()82 as being as round and as bright as Jupiter. On the other hand, instances are not wanting of comets furnished with many tails or streams of diverging light. That of 1744 had no less than six, spread out like an immense fan, extending to a distance of nearly 30° in length.
Page 20 - Suppose a shower of rain to fall perpendicularly in a dead calm ; a person exposed to the shower who should stand quite still and upright would receive the drops on his hat, which would thus shelter him ; but if he ran forward in any direction they would strike him in the face. The effect would be the same as if he remained still, and a wind should arise of the same velocity and drift them against him. Suppose a ball to fall from a point A (fig, 75...
Page 20 - RS, it is evident that the ball would, throughout its whole descent, be found in the axis of the tube } and a spectator referring to the tube the motion of the ball, and carried along with the former, unconscious of its motion, would fancy that the ball had been moving in the inclined direction R, S of the tube's axis.
Page 30 - F/ meet it at £ and if, and at a' and b'. Let c and c' be the points where the path of the satellite crosses the limits of the shadow, and h and h' the points where it crosses the extreme solar rays which pass along those limits.
Page 24 - Now, the temperature of any part of the earth's surface depends mainly, if not entirely, on its exposure to the sun's rays. Whenever the sun is above the horizon of any place, that place is receiving heat ; when below, parting with it, by the process called radiation ; and the whole quantities received and parted with in the year must balance each other at every station, or the equilibrium of temperature would not be supported. Whenever, then, the sun remains more than...
Page 21 - 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 26 - The smaller comets, such as are visible only in telescopes, or with difficulty by the naked eye, and which are by far the most numerous, offer very frequently no appearance of a tail, and appear only as round, or somewhat oval vaporous masses, more dense towards the...