Scattered over the heavens are millions of stars, each representing a certain degree of development. The cloud forms of the nebulae tell us of stellar origins; the white, yellow, and red stars illustrate the rise and decline of stellar life; and the Earth itself affords a picture of what may remain after light and heat have been extinguished.

The Study of Stellar Evolution: An Account of Some Recent Methods of, Astrophysical Research, Chapter 1 (p. 8), The University of Chicago Press. 1908