Newcomb looked to astronomy’s future

Among the comments we received in response to our article “Simon Newcomb, America’s First Great Astronomer” (Physics Today, February 2009, page 46 ) are a number of inquiries about an often repeated quotation attributed to Simon Newcomb: “As far as astronomy is concerned, it must be confessed that we do appear to be fast reaching the limits of our knowledge.” An internet search brings up hundreds of sites that present this quotation as an example of how short-sighted, and wrong, even the most renowned scientists, inventors, and other learned people can be. But few sites include a proper reference to the quotation, let alone put it into context.

Newcomb first made the comment as part of a speech titled “The Place of Astronomy Among the Sciences,” ¹ which he presented at the dedication of a new astronomical observatory at Syracuse University in New York on 18 November 1887. A more complete quotation is, “It would be too much to say with confidence that the age of great discoveries in any branch of science has passed by: yet, so far as astronomy is concerned, it must be confessed that we do appear to be fast reaching the limits of our knowledge. True, there is still a great deal to learn.”

Newcomb was talking about the “old astronomy” that focused almost entirely on cataloging celestial objects—stars, planets, moons, asteroids, comets—and computing their motions. In the same talk he also said that “all the geometry and astronomy, all the phenomena of the motions of the heavenly bodies are already reduced to one general law.” He was referring to Newton’s universal law of gravitation, which he then accepted without reservation. As we pointed out in our article, and in more detail in our book, ² Newcomb later began to question Newtonian physics as he struggled with the discrepancies in the motions of Mercury. Ultimately, his findings provided an immediate test of Einstein’s theory of general relativity.

It is important to realize that Newcomb was not including “new astronomy,” generally referred to today as astrophysics, in his assessment of the outlook for future discoveries about the universe. Just two paragraphs later in the printed version of his talk, he explicitly refers to the “new science of physical astronomy,” states that “the study of the stellar spectrum is a worthy one,” and mentions his curiosity about whether the spectrum of Sirius will change as the star goes through various stages of its life.

Newcomb’s interest in learning about the universe never waned, and he argued strongly for the pure pursuit of knowledge, saying that it seemed almost as if the secrets of nature would be revealed “only to those who investigate from a love of nature herself.”