An issue of increasing interest both among scientists and among members of Congress and the general public is the assumed objectivity of scientific research. Yet historians and philosophers of science have argued in many places, most notably in Thomas Kuhn's Structure of Scientific Revolutions, that scientists' observations are necessarily shaped by the theory in which they are made. Psychologists have found as well that, if one expects to see something, then it may show up even if "objectively" it is not there. This is not an issue of deliberate distortion of scientific results, but rather a fact of life which scientists and the public must come to recognize. An important instance of how theory shaped an observation occurred in astronomy after World War I. A centuries-long dispute over whether spiral nebulae are galaxies beyond the boundary of our own galaxy or are actually within the Milky Way culminated in a debate between Adriaan van Maanen and Edwin Hubble at the Mount Wilson Observatory. Hubble, who went on to become one of the outstanding figures of 20th century science -- he even appeared on the cover of Time magazine -- argued that the appearance of Cepheid variable stars in the nebulae place the spirals far beyond the confines of our galaxy. Van Maanen, however, measured the rotation of spiral nebulae and placed them inside the galaxy. Over the course of many years of trying to reconcile the two observations, Hubble finally concluded that van Maanen had read his expectations into his data. In short, van Maanen's theory led him to "see" things which actually were not there. An interesting aspect of the debate between Hubble and van Maanen, in contrast to contemporary confrontational approaches to errors in scientific publications, is that it all occurred behind the scenes. Hubble, after discussions with the head of the Observatory and several colleagues, decided that it would be "ungentlemanly" and would have created an unseemly public controversy to confront van Maanen in public about his error. Only after a decade of effort, was he able to convince van Maanen of his mistake. Van Maanen eventually did acknowledge the correctness of Hubble's observations. In order for the full debate to be available for use by historians, philosophers, sociologists, and policy makers interested in the "objectivity" of scientific research, Dr. Hetherington will edit the entire set of unpublished manuscripts and additional correspondence dealing with the debate. He will also provide an historical introduction to these materials
