Page 1316 : NEBULAR HYPOTHESIS — NEEDLE
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Keeler at Lick Observatory, to a substance not yet discovered on the earth. The brightest of all nebulas is the one in the girdle of Andromeda; the one in the sword-handle of Orion can also be seen at times by the naked eye. Planetary nebulæ are those which show a more or less well-defined disc. It is not impossible that nebulæ are merely stars in their early stages of development, later to pass through the phases of planetary nebulæ and nebulous stars. See Schemer’s Astronomical Spectroscopy, translated by Frost.
Neb′ular Hypoth′esis is a theory advanced by three different men, Swedenborg (1688–1772), Kant (1724–1804) and Laplace (1749–1827), to account for the observed facts of planetary motion. The more important phenomena to be accounted for are these: (1) The orbits of all the planets are nearly circular and lie all nearly in one plane. (2) The direction of revolution about the sun is the same for all planets. (3) Except in the case of Uranus and Neptune, the direction of rotation of the planet on its axis is the same as its direction of revolution. (4) The larger planets rotate (not revolve) more rapidly. (5) The plane of rotation is not very different from the plane of the orbit. (6) The satellites generally have a direction of revolution which coincides with that of the planet’s rotation. To explain this rather orderly state of affairs it was supposed that the matter now constituting this solar system was at some earlier date in its existence distributed in the form of an immense nebula; and that, as this nebula condensed and therefore increased its rate of rotation (while preserving a constant moment of momentum), the centrifugal force became so great that some of the outer portions of the nebula were set free. That is, the centrifugal force reached a point where it balanced the attraction of the rest of the nebula. The portions thus set free, whether as a ring or as a “hump,” condensed still farther and formed the earlier planets. As the concentration of the original nebula proceeded, the rate of rotation kept on increasing and again “threw off” or set free other planets. So also with the planets themselves; as they became more and more compact, their rate of rotation increased sufficiently for them to set free their satellites.
In a general way this hypothesis satisfactorily explains the six facts enumerated above. With later modifications it explains even many of the anomalies of the solar system. See Laplace. For recent criticism of this hypothesis see article by Moulton in Astrophystcal Journal, Vol. II. (1900).
Neck′ar, a river in Germany, flowing through Württemberg and Baden; it is one of the largest tributaries of the Rhine, rises on the eastern slope of the Black Forest, and pursues a winding course for 250 miles until it enters the Rhine at Mannheim. It is navigable for about half its lower length. Tübingen, Heidelberg, Heilbronn and Cannstatt are on its banks.
Neck′er, Jacques, a financier and minister of France, was born at Geneva, Sept. 30, 1732. At 15 he went to Paris as a bank-clerk, and in 1762 founded the London and Paris Bank of Thellusson and Necker. He entered public life as a syndic of the French East India Company and minister of the republic of Geneva at Paris, and about this time married. In 1773 he received the French Academy prize for a eulogy on Colbert, and won great recognition by his Essai sur le Commerce des Grains in 1775. This was an answer to the free-trade arguments of Turgot. After having loaned some money to the government, he was made director of the treasury in 1776 and director-general of finance in 1777. For five years he labored to improve the financial condition of France by readjusting the taxes, establishing state-guaranteed annuities and the present system of government pawnshops. His methods displeased the queen, however, and his publication of the Compte Rendu, a statement of the financial condition of France, in 1781, was made the cause of his dismissal. He thereupon withdrew to Geneva, but returned in 1787 and defended his Compte Rendu, for which he was banished from Paris. He was recalled to his office in September, 1788, but, while winning popularity through recommending the summoning of the states-general, he proved wholly incompetent during the storms of the Revolution. He declined the aid of Lafayette and Mirabeau, and on July 11, 1789, was ordered to leave France, but after the fall of the Bastille, three days later, he was recalled, only to resign voluntarily in September, 1790. He retired to his estate near Geneva, and died there on April 9, 1804. See The Private Life of M. Necker by Madame de Stael, his famous daughter.
Nec′tar, the name given by most of the Greek and Roman poets to the drink of the gods. Homer describes it as of a red color, and says that continued use of it was supposed to insure immortality. The sprinkling with nectar was supposed to confer perpetual youth, and it was used, in figure of speech, as meaning everything delightful and pleasant to the taste.
Nee′dle. The sewing-needle must be one of the oldest implements used by man. Bone needles with eyes are found in the reindeer caves of France, and on the sites of the prehistoric lake dwellings of central Europe have been found many “eyed” needles of bone and of bronze, but only one of iron. Ancient bronze
Image: Fig. 1
