Rare lunar event may reveal Stonehenge’s connection to the Moon

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For those who have gathered over the centuries in Stonehenge – the imposing prehistoric monument that dominated Salisbury Plain in southwest England for around 4,500 years – it was probably clear how the sun could have influenced its design.

The central axis of the stone circle was, and still is, aligned with midsummer sunrise and midwinter sunset, the stones dramatically framing the rising and setting sun when the days were longer and longer. short.

But do Stonehenge and potentially other megalithic monuments around the world also align with the moon?

The idea that Stonehenge was somehow linked to the moon gained ground in the 1960s. However, the concept has not been systematically explored, said Clive Ruggles, emeritus professor of archaeoastronomy at the University of Leicester’s school of archeology and ancient history.

This summer, archaeologists are using a little-known lunar phenomenon that happens every 18.6 years to investigate as part of their work to understand why Stonehenge was built.

Lunar standstill

Just like the sun, the moon rises in the east and sets in the west. However, the rising and setting of the moon moves from north to south and vice versa within the space of a month. The northern and southern extremes also change over a period of about 18 and a half years. Lunar standstill occurs when the northernmost and southernmost moonrise and sunset are furthest apart from each other.

“The moonrise changes every day and if you follow this for a month, you will notice that there is a northern limit and a southern limit beyond which the moon never rises (or sets),” said Fabio Silva, senior professor of modeling archaeological site in Bournemouth. University by email.

“If you were to look at these limits over 19 years, you would notice that they change like an accordion: they expand to a maximum limit (the largest lunar standstill) and then begin to contract to a minimum limit (the smallest lunar standstill ).”

This major lunar standstill is expected to happen in January 2025, but from now until mid-2025, the moon may appear, to a casual observer, to be unusually low and high in the night sky during the lunar month.

“If you are in one of these 19 years, every now and then you will see the moon rising or setting much further north or south than most of the time. In the intervening years, you never see it there,” Ruggles said.

Despite the phenomenon’s name, the Moon does not stay still during this period, he said.

“What is stuck are these limits, and the time when that will happen will be January of next year,” Ruggles added. “But for about a year on either side, if you happen to see the moon rise at the right time, you will see the moon rising exceptionally low (in the sky).”

Stonehenge is made of two types of stone: larger sarsen stones and smaller blue stones that form two concentric circles. Ruggles said the Stonehenge station stones, which form a rectangle around the circle, roughly align with the extreme positions of the Moon during lunar standstill.

How this lunar alignment was achieved, whether it was intentional and its potential purpose are topics of debate that the team wants to investigate.

Probing Stonehenge’s celestial connections

Although there are no written documents that clarify the meaning and importance of Stonehenge, archaeologists have long believed that its solar alignments were intentional. Such alignments have been identified in many places around the world and would have been relatively easy for ancient builders to identify, given that knowledge of the sun’s annual cycle and its connection to the seasons would have been essential for subsistence.

However, it is much more difficult to say whether Stonehenge actually has a link to the lunar standstill.

“I don’t think we can say for sure, but to me there is some evidence that makes me think it was deliberate,” Ruggles said.

One clue was the fact that archaeologists found cremated human remains clustered in the southeast, near where the southernmost moonrise will occur.

“I think there is a possibility that they were aware of the direction of the moon and so it became a kind of sacred direction,” Ruggles said.

Since April, Ruggles and Silva, along with colleagues from Bournemouth University, the University of Oxford and English Heritage, the organization that manages the site, have been documenting the rising and setting of the moon at key moments when the moon is aligned with the stones of the station. The moon was expected to align with the station’s stone rectangle twice a month from February 2024 to November 2025, Silva said.

“This will happen at different times of the day and night throughout the year, with the moon in the right place in different phases each month,” Silva said in a press release in April.

The team wants to understand what patterns of light and shadow the moon creates at Stonehenge and whether they could have had meaning for the people who built and used the monument.

Other monuments with a possible lunar connection

Stonehenge is not the only megalithic monument potentially linked to the lunar standstill.

In the United States, Erica Ellingson, professor emeritus of astrophysics at the University of Colorado at Boulder, is investigating lunar alignments at Chimney Rock, a rocky ridge about 300 meters above the floor of a valley in Colorado. The landmark features two large pillar-shaped rocks that frame the horizon.

Between the 900s and 1150s, the ancestors of the Pueblo people built multistory buildings and ritual spaces on this hard-to-reach high site with a dramatic view, Ellington said, and it continues to be an important site for 26 Native American groups. who have traditional or cultural ties to the area.

“The extraordinary view of the sky between the twin pinnacles suggests an astronomical connection, but the gap is too far north for the Sun to shine through. The Moon, however, can be seen rising there when it is near its most extreme northern position, during the main lunar standstill season,” she said in an email.

Other evidence of moon sighting comes from tree ring dating of wooden beams in nearby ancient buildings, which indicates their construction is linked to lunar standstill dates nearly 1,000 years ago, she added.

The Calanais Standing Stones, situated on the Isle of Lewis in Scotland and erected before Stonehenge, may also have a link to the lunar standstill, Ruggles said.

Bradley Schaefer, professor emeritus in the department of physics and astronomy at Louisiana State University, said he is deeply skeptical that ancient people were aware of the lunar standstill and built monuments in line with it. Most likely, he suggested, it was a coincidence.

“Each ancient site has dozens to hundreds of potential sightlines, and one or more will always point somewhere near one of the eight strike directions,” he said in an email.

Lunar standstill is difficult for a casual Moon observer to recognize, he added, and is only really visible in detailed data on observations of the Moon’s rising and setting.

Although the change in the Moon’s position is subtle and historical records documenting the lunar standstill are rare and difficult to interpret, Ellington said he thinks the link is plausible because many ancient people observed the sky very closely.

“A moon watcher would have seen the moon begin to rise or set outside these boundaries, moving further and further outside the boundaries as the main lunar standstill approached,” she said.

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