Page:Popular Science Monthly Volume 66.djvu/301



HE investigator in any field of knowledge must, as the price of success, both comprehend the general principles underlying his special problem, and give constant care to its details. Yet it is well, now and then, to leave details behind and consider the bearing of his work upon the science as a whole. Whether our subject is that of determining the accurate positions of the stars, or their radial velocities, the orbits of the planets, or the constitution of the sun, we are making but minor contributions to the solution of the two great problems which at present compose the science of astronomy. These problems, perhaps the most profound in the realm of matter, may be stated thus:

1. A determination of the structure of the sidereal universe; of the form of that portion of limitless space occupied by the universe; of the general arrangement of the sidereal units in space; and of their motions in accordance with the law of gravitation.

2. A determination of the constitution of the nebulæ, stars, planets and other celestial objects; of their physical conditions and relations to each other; of the history of their development, in accordance with the principles of sidereal evolution; and of what the future has in store for them.

The first problem has for its purpose to determine where the stars are and whither they are going. It has been ably treated under the head of astrometry.

The second seeks to determine the nature of the heavenly bodies—what the stars really are. This field of inquiry is well named, astrophysics.