Astronomy

A science of prehistoric antiquity, originating in the elementary needs of mankind. It is divided into two main branches, distinguished as astrometry and astrophysics; the former concerned with determining the places of the investigation of the heavenly bodies, the latter, with the investigation of their chemical and physical nature. But the division is of a quite recent date. The possibilities of antique science stopped short at fixing the apparent positions of the objects on the sphere. Nor was any attempt made to rationalize the observed facts until Greeks laboriously built up a speculative system, which was finally displaced by vast fabric of gravitational theory. Descriptive Astronomy, meanwhile took its rise from the invention of the telescope, and the facilities thus afforded for the close scrutiny of the denizens of the sky; while practical Astronomy gained continually in refinement with the improvement of optical and mechanical arts. At the present time, astrophysics may be said to have absorbed descriptive Astronomy, and astrometry necessarily includes practical research. But mathematical Astronomy, grounded on the law of gravitation keeps its place apart, though depending for the perfecting of its theories and the widening of its scope upon advances along the old, and explorations in new, directions. +