Few ancient monuments are shrouded in as much mystery as Stonehenge, the eerie prehistoric temple situated in southern England, which began construction nearly 5,000 years ago. Its builders and designers left no written words behind to explain its significance to them, nor do we know what it was used for all those years ago.
From modern analyses, we’ve learned that ancient Britons hauled these megaliths – many of which weigh upwards of 20 tonnes – from quarries some point far away from the Stonehenge site.
We also know that the structure is aligned with the Sun at summer and winter solstice. But the significance of this to the people themselves is largely lost.
The one thing experts were really puzzled about, at least until now, was whether Stonehenge was built not only to be aligned with the Sun – an impressive feat for a society which was yet to invent the wheel – but also with the Moon.
On 21 June 2024, a team of experts are hoping to answer exactly that, as a once-in-a-generation major lunar standstill begins.
Its significance? Prof Michael Parker Pearson, an expert on British Later Prehistory at University College London, tells BBC Science Focus that if Stonehenge is aligned with this event, it would show that its builders “were tying together the movements of the Sun and Moon in a kind of Neolithic grand unified theory.
“With all of Stonehenge's stones hauled from far away (unique amongst Britain and Ireland's 900 stone circles) and with so many people buried at Stonehenge, this would have been a monumental attempt to unify people, ancestors, land and cosmos.”
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What is a major lunar standstill?
During a major lunar standstill, which happens only every 18.6 years, the Moon reaches its most extreme northern and southern positions in the night sky. Imagine the Moon rising and setting much further north and south than usual, making a wider arc across the night sky.
This might seem similar to how the Sun's path changes throughout the year, reaching its northernmost and southernmost points at the summer and winter solstices. Indeed, the word ‘solstice’ derives from the Latin words ‘sol’ and ‘stice’, literally meaning ‘Sun standstill’.
However, there's a key difference between a lunar standstill and the Sun’s. The Earth's tilt relative to the Sun causes the solstices to happen at more or less the same points each year.
In contrast, the Moon's orbit has a tilt too, but this tilt changes slightly over time. That's why the Moon's most extreme northern and southern positions shift over 18.6-year cycles, creating this dramatic major lunar standstill effect that will take place over the next year or so.
During the major lunar standstill, each month the Moon's highest point in the sky can be higher than the summer Sun's peak, and its lowest point can be lower than the winter Sun's lowest point.
- You can catch the southernmost moonrise of the major lunar standstill at Stonehenge on the English Heritage YouTube channel, where it will be streamed on 21 June at 9:30pm BST (4:30pm EDT in New York City, 1:30pm PDT in Los Angeles).
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What’s Stonehenge got to do with it?
Stonehenge’s alignment with the summer and winter solstices is well known, with crowds gathering each year to mark the events at the site. But its connection with the harder-to-track lunar cycles is less well understood by experts.
Research believe that between 3000 and 2500 BCE, before the large stones were brought to the site, burials and cremations were taking place there.
Many of them were clustered in the direction of the southernmost rising position of the Moon during major standstills, and three timber posts were set into the bank at this position.
Later, four so-called ‘Station Stones’ were brought to the site, forming a rectangle at its centre.
“The four Station Stones align with the Moon's extreme positions, and researchers have debated for years whether this was deliberate, and – if so – how this was achieved and what might have been its purpose,” says Prof Clive Ruggles, emeritus professor of archaeoastronomy at Leicester University.
The Station Stones themselves were likely employed to measure out the iconic ‘sarsen circle’ which was added around 500 years after the first burials at the site, English Heritage says.
So, if they are connected to the lunar standstill, it would suggest a more fundamental role for the Moon in the architecture of the entire Stonehenge than was previously thought.
To find out whether the lunar standstill was indeed at the heart of Stonehenge’s conception, academics from Oxford, Leicester and Bournemouth universities plan to study the event from now until its end in 2025.
“Unlike the Sun, tracking the Moon's extremes isn't straightforward, requiring specific timing and weather conditions,” says Dr Amanda Chadburn, an archaeologist from the University of Oxford.
“We want to understand something of what it was like to experience these extreme Moonrises and sets and to witness their visual effects on the stones (for example, patterns of light and shadow), and consider modern influences like traffic and trees, and to document all of this through photography for future study.”
About our experts
Mike Parker Pearson is Professor of British Later Prehistory at the Institute of Archaeology, University College London (UCL). After gaining a BA in European Archaeology at Southampton University in 1979, he was awarded a PhD at Cambridge University in 1985. He worked as an Inspector of Ancient Monuments for English Heritage until 1990. From then on, he lectured in the Department of Archaeology & Prehistory at Sheffield University where he was given a professorial chair in 2005, which he held until moving to UCL in 2012. He is a Fellow of the British Academy.
Clive Ruggles is an emeritus professor of archaeoastronomy at Leicester University. From 2008 to 2018 Ruggles coordinated the IAU’s Astronomy and World Heritage Initiative jointly with UNESCO and he continues to advise governments on potential World Heritage nominations relating to astronomy. In 2017, he was awarded the Royal Astronomical Society’s Agnes Mary Clerke Medal for a “lifetime of distinguished work in the overlapping areas of archaeology astronomy and the history of science”.
Amanda Chadburn is a professional archaeologist and historic environment adviser. She started her professional career in local government and joined English Heritage in 1987 where she worked in various casework and policy roles. She has taught archaeology and heritage management at the Universities of Bristol, UCL and Oxford, and co-supervised PhD students at the Universities of Bristol and Huddersfield.
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