David S. P. Dearborn is an astrophysicist at the Lawrence Livermore National Laboratory, and co-editor of Archaeoastronomy: A Journal for Astronomy in Culture as well as Archaeoastronomy & Ethnoastronomy News. In addition, he is a founding member of ISAAC (the International Society for Archaeoastronomy and Astronomy in Culture), an organization promoting a professional standard in this interdisciplinary study that all too often suffers from spectacular claims involving more enthusiasm than evidence.
For more than 20 years, Dr. Dearborn has worked in collaboration with archaeologists to study the Inca and their uses of astronomy. In this interview from 1997, he and I discussed his work and the underpinnings of solid archaeoastronomical research.
Why did people study astronomy?
"The movements of the heavenly bodies are an admirable thing, well known and manifest to all peoples. There are no people, no matter how barbaric and primitive, that do not raise up their eyes, take note, and observe with some care and admiration the continuous and uniform course of the heavenly bodies." Bernabé Cobo (1653)
We know that astronomical observations must have predated writing. What kind of things do you use to determine that a particular structure (building or other monumental architecture) has an astronomical component, when you don’t have written records?
In the absence of historical or pertinent ethnographic information, there remains only archaeological data. Like most archaeological data, confidence grows with artifact frequency and functionality. For astronomy, these artifacts include imagery on all of the usual media, architecture, and perhaps even city orientation. One might expect there to be fewer observatories than workshops or cooking vessels, so arguments based on frequency suffer, leaving functionality as a critical component.
When dealing with architecture, astronomically significant orientations like the direction of a sun rise or set on the date of a solstice are most commonly looked for. The place on the horizon where the sun stops and turns in its annual journey is obvious, and immediately establishes an accurate annual calendar. Observation of the equinoxes requires an additional level of sophistication (and suggest an additional partition of the year), so are more difficult to argue.
While the claims for a precise megalithic astronomy have been substantially discredited, the solsticial orientations of Stonehenge and Newgrange are generally accepted. The tremendous labor and resource investment represented by their construction suggests that the sun and its annual motion were of substantive and fundamental interest to the builders. Even though they included an astronomical function, I would not characterize these sites as observatories in the modern sense (a place where a specialist monitors astronomical objects). I suspect that a society ready to expend the effort to construct a monument like Stonehenge, also supported some level of specialist, but that is conjecture. The workshop/observatory of such specialists are likely to be small and difficult to identify. Fortunately for archaeologists interested in how societies organize themselves, ceremonial structures like Stonehenge are possibly more interesting than mere observatories.