BOURNEMOUTH, United Kingdon – New research on Stonehenge published this week in the academic journal, Antiquity, suggests that the ancient structure functioned more as a calendar than previously thought.
The alignment of the axes of the megalith stones is well known. Those are aligned with the summer and winter solstices. The sarsen stones of Stonehenge perfectly align with the rising sun on the mornings of the solstices. Their careful alignment traced the movement of the sun and as such they have been understood to have important ceremonial purposes.
The new research offers insights that Stonehenge had more extensive calendar functions.
Previous research had proposed these calendar functions but how they worked and aligned was unclear. The earliest such proposal for the early Twentieth century suggested the stones held a “May Calendar” based on “clock-stars,” others had suggested a calendar that identified the solstices and equinoxes plus some cross-quarters like Lammas and Imbolc. Others, like the idea of a “Celtic Calendar”, have been discredited.
The new research looks at the placement and size of the sarsens and bluestone monoliths in the circle. The different types of stones are believed to have been introduced into Stonehenge at different times. The first bluestones were placed some 3,000 years ago and the sarsens 2,500 years ago.
Stonhenge [Photo Credit: Manny Tejeda y Moreno]
Bluestones were erected first, and the sarsens added later. Professor Timothy Darville of Bournemouth University noted the previous researchers had observed that “All the extant stones have been shaped and dressed. Through either selection or modification, most widen towards the top in a type of entasis to create the optical illusion of straight-sidedness.”
Professor Darville took a new look at the layout of Stonehenge and found a pattern suggesting a calendar function.
“The clear solstitial alignment of Stonehenge has prompted people to suggest that the site included some kind of calendar since the antiquarian William Stukeley,” said Professor Darvill in a statement. “Now, discoveries brought the issue into sharper focus and indicate the site was a calendar based on a tropical solar year of 365.25 days.”
Darville wrote that “The core of the year is represented by the Sarsen Circle.” Each of the 30 upright sarsen stones that held the lintels represent a solar day. Certain distinctive stones in the circle mark the start of three 10-day weeks that formed a month. This numerology created a 12-month calendar of 30 days.
Summary of the way in which the numerology of sarsen elements at Stonehenge combine to create a perpetual solar calendar. Non-sarsen elements have been omitted for clarity (drawing by V. Constant).
Then the trilithons structures that are formed by two large vertical stones supporting a horizontal third stone were arranged in a horseshoe shape in the center of the site. The trilithons represent the five extra days needed to match the 365-day solar year. Finally, four smaller stones that lay outside the Stonehenge circle form a rectangle to keep track of leap years, adding an extra day every four years.
“An intercalary month of five days and a leap day every four years were needed to match the solar year. “The intercalary month, probably dedicated to the deities of the site, is represented by the five Trilithons in the centre of the site,” said Professor Darvill, “The four Station Stones outside the Sarsen Circle provide markers to notch-up until a leap day.”
Darvill wrote that “Making the solar calendar a perpetual one, in which the days, decans and months keep pace with the seasons and the movements of the sun to describe a tropical solar year with accuracy, requires periodic adjustment, specifically, the addition of one day every four years to create a leap-year of 366 solar days. The four Station Stones provide a means of keeping tally so that a sixth day could be added to the intercalary month every fourth year.”
But the new research raises additional questions about the origin of the solar calendar. The 10-day pattern and extra months have been adopted by many cultures in the Eastern Mediterranean.
“Such a solar calendar was developed in the eastern Mediterranean in the centuries after 3000 BC and was adopted in Egypt as the Civil Calendar around 2700 and was widely used at the start of the Old Kingdom about 2600 BC,” said Professor Darvill.
The new research raises the possibility the calendar of Stonehenge was imported through contact or influence from one of these cultures. Future research, particularly the tracking of ancient DNA and the discovery of new archeological artifacts may help us better understand the connections between these cultures.
For example, the Amesbury Archer, an early Bronze Age man whose grave was discovered during excavations for a housing development in May 2002. Radiocarbon dating of his bones found he had been raised at the time sarsens and tritholons were installed at Stonehenge. However, the Archer’s tooth enamel suggested he originated in the Alps of central Europe.
“Finding a solar calendar represented in the architecture of Stonehenge opens up a whole new way of seeing the monument as a place for the living,” Darvill said, “A place where the timing of ceremonies and festivals was connected to the very fabric of the universe and celestial movements in the heavens.”
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