In the 1960's some scientists began to look at Stonehenge in a new light. It seemed that if you took all the precession survey data about the locations of the stones and filled in holes on the Stonehenge site, and put them into a computer (a very new research tool back then) all sorts of wonderful things began to emerge.
If this survey data was run alongside modern astronomical programs, for instance, it appeared that the original builders of 2600 BC were sophisticated astronomers whose neolithic observatory on Salisbury plain could be used not only for finding the sunrise point on a midsummers day, but also for making calendars, predicting eclipses and all manner of other things too. Indeed, Stonehenge - along with many other ancient stone circles scattered around Great Britain and Europe - appeared to be not only an ancient observatory but also an astronomical computer.
It seemed that the key to the mystery of Stonehenge had been found at last. Let's not forget that this mystery was itself ancient. The 12th-century historian Geoffrey of Monmouth had speculated about Stonehenge origin, the Jacobean architect Inigo Jones believed it to be a Roman ruin, while John Aubrey and William Stukeley performed the first surveys and excavations in the decades after 1670. Indeed it was Aubury and Stukeley with their then total ignorance of pre-Roman Britain and its inhabitances who first suggested the druids as likely builders, and sadly this myth has stuck.
In the late 18th century, James Douglas recognised the midsummer sunrise alignment and concluded that Stonehenge must have been an ancient solar temple. A century after him, the monument became the hobby of the great solar physicist Sir Joseph Norman Lockyer, who made the first accurate surveys and argued that its builders must have processed astronomical knowledge.
Lockyer's Stonehenge... Astronomically Considered (1909) in many respects set the scene for that observatory approach to the monument, which reached its peak with the computer and which attempted to date it to 1680 BC using astronomical criteria.
By the 20th century Stukeleys, imaginary druids had become proto-English gentlemen with a flair for architecture and astronomy. Nowadays most scholars regard the discoveries of the 1960's as over-optimistic. It is true that the monument does appear to be orientated towards sunrise and sunset, but people are much more cautious about stating what the original builders knew or intended. So Stonehenge's mystery remains.