The state of astronomy in about 1880

In those early years in London, while carrying out her many literary commitments, Agnes Clerke soon realised how far astronomy had advanced since she had studied it in Ireland.

That decade had been a time of unprecedented progress. Until the mid-nineteenth century astronomy had been principally concerned with the positions and movements of the heavenly bodies. Astronomers recorded with ever greater precision the paths of the planets against the background of the distant ‘fixed’ stars in order to understand their motions in space and to predict their future locations. They also searched for slight shifts in the positions of the stars themselves in order to discover their distances and their motions through space. For this purpose they produced star charts and compiled massive catalogues, but worried little about the nature of the stars themselves.

The motions of the planets around the sun had been elucidated by Isaac Newton in the seventeenth century in his great law of gravitation. Since Newton's time, more refined mathematical applications of that law were capable of explaining intricate details of the movements of the various bodies in the solar system caused by their gravitational influences on each other. Academic astronomers, who worked on these problems, tended to be mathematicians. Other astronomers specialised in studying the appearances of the sun, moon and planets through the telescope. The stars themselves, however, being enormously distant tiny points of light, appeared to be beyond the grasp of earthly observers.