''The latter part of the nineteenth century ushered in two new technologies – photography and spectroscopy. For the first time since humans began to observe the heavens, astronomers could study the motions and physics of stars. The spectroscope allowed astronomers to study the stars' chemical composition and their velocities in the line of sight. Photography provided permanent recording of images that astronomers could measure and analyze in detail. These dramatic changes marked the beginnings of a shift away from the older tradition of positional astronomy toward study of the physics of celestial objects. A new field of research – astrophysics – was born.''
In Crelinstein, Einstein's Jury, pp. 9-10.