The Total Solar Eclipse of 1869 as Stimulus for Adoption of Physical-astronomy Techniques in the United States

Abstract

In the United States, techniques that would one day be called astrophysical were applied later than elsewhere and comparatively suddenly. Their entry into US main-stream astronomy was motivated by a quasi-stochastic phenomenon: a total eclipse of the Sun visible between the contiguous borders of that country. In reaction to the upcoming event, the US Nautical Almanac Office in particular invested time, workforce, and a great deal of money into the measurements of physical astronomy, especially spectroscopy. This occurred although none of its employees had ever expressed—at least, in writing—expertise or even interest in the subject beforehand. Once adopted, physical astronomy, and the investigations it enabled, moved slowly, but steadily, into the mainstream of American astronomy despite objections from traditionalists. In the twenty-first century, spectroscopy and other physical astronomy techniques are essential tools for all astronomers.