Thesis at the University of Colorado at Boulder in December 1961 titled "The Stratospheric Solar Aureole". After obtaining his PhD, Eddy went into teaching, while maintaining an active research schedule to maintain his credentials. He studied spectral lines and worked on infrared spectroscopy. Interdisciplinary work Eddy received much criticism from within the astronomy community for his interdisciplinary work on Native American medicine wheels, which showed how they were used as calendars and observatories. It also earned him criticism from archaeologists at first, although his work was eventually accepted, and later documented in National Geographic and as a guest on TV and radio programs. As a teacher, he frequently used historical examples to show his students that not so long ago nobody knew more than they did about solar physics. This led him to do a lot of research in the history of his own field, particularly covering records of past eclipses and sunspot counts, whereupon he discovered the records of Edward Maunder and others demonstrating that there was indeed long term variability in solar activity. Eugene Parker of the University of Chicago, when promoting his theory of the existence of a solar wind, exposed Eddy to Maunder's work on sunspot records. Solar minimum paper In 1976 Eddy published a paper in Science titled "The Maunder Minimum" where, using the nineteenth century works of Edward W. Maunder and Gustav Spörer, he identified a 70-year period from 1645 to 1715 in which solar activity was extremely low. In making the case for the anomaly, he gathered and interpreted data from a wide variety of sources, including first-hand accounts from extant historical observations of the Sun going back to the telescopic observations of Galileo and other contemporary scientists of the 17th and early 18th centuries; from historical reports of the aurora borealis observed in past centuries in Europe and the New World; from visual observations of sunspots seen with the unaided eye at sunrise and sunset in dynastic records from the Orient; from existing descriptions of the eclipsed Sun; and from measurements of carbon-14 in dated tree-rings. In the last of these, which can be used as a proxy indicator of solar activity, he found evidence of other similar periods of solar quiescence in the distant past, the most recent an even longer 90-year span, from about 1460 until 1550, which he named the Spörer Minimum. Both the Maunder and Spörer minima fell