Join CNN’s Surprise Idea science e-newsletter. Explore the universe with news on fascinating discoveries, scientific advancements and more.
CNN
—
To these gathering over the centuries at Stonehenge — the imposing prehistoric monument that has dominated Salisbury plain in southwest England for some 4,500 years — it was doubtless clear how the solar may have knowledgeable its design.
The central axis of the stone circle was, and nonetheless is, aligned with the dawn at midsummer and sundown at midwinter, the stones dramatically framing the rising and setting solar when days have been at their longest and shortest.
However do Stonehenge and doubtlessly different megalithic monuments around the globe additionally align with the moon?
The concept that Stonehenge was linked ultimately to the moon gained ground in the 1960s. Nonetheless, the idea hadn’t been systematically explored, stated Clive Ruggles, professor emeritus of archaeoastronomy within the faculty of archaeology and historical historical past on the College of Leicester.
This summer season, archaeologists are utilizing a little-known lunar phenomenon that occurs each 18.6 years to analyze as a part of their work in understanding why Stonehenge was constructed.
Lunar standstill
Just like the solar, the moon rises within the east and set within the west. Nonetheless, moonrise and moonset transfer from north to south and again once more within the house of a month. The northern and southern extremes additionally change over a interval of about 18 and a half years. The lunar standstill is when the northernmost and southernmost moonrise and moonset are farthest aside.
“The moon rise adjustments day by day and when you monitor this for a month you’d discover there’s a northern and a southern restrict past which the moon by no means rises (or units),” stated Fabio Silva, senior lecturer in archaeological modeling at Bournemouth College through e-mail.
“Should you have been to have a look at these limits over 19 years you’d discover them change like an accordion: they increase as much as a most restrict (the most important lunar standstill) after which begin contracting as much as a minimal restrict (the minor lunar standstill).”
This main lunar standstill is because of occur in January 2025, however from now till mid-2025, the moon could seem, to an off-the-cuff observer, to be unusually high and low within the night time sky throughout the lunar month.
“Should you’re in a kind of 19 years, then once in a while, you will notice the moon rising or setting a lot additional north or south than it does most occasions. Within the years in between you by no means see it there,” Ruggles stated.
Regardless of the phenomenon’s title, the moon isn’t really standing nonetheless throughout this era, he stated.
“What’s standing nonetheless is these limits, and the second of that taking place is in January subsequent yr,” Ruggles added. “However for a couple of yr both aspect, when you occur to catch the moon rise on the proper time, you’re going to see the moon rising exceptionally low (within the sky).”
Stonehenge is manufactured from two kinds of stone: bigger sarsen stones and smaller bluestones that type two concentric circles. Ruggles stated that Stonehenge’s station stones, which type a rectangle across the circle, roughly align with the moon’s excessive positions throughout the lunar standstill.
How this lunar alignment was achieved, whether or not it was by design and its potential goal are matters of debate that the staff needs to analyze.
Whereas there are not any written paperwork that make clear Stonehenge’s that means and significance, archaeologists have lengthy believed its photo voltaic alignments have been intentional. Such alignments have been recognized in lots of locations around the globe and would have been comparatively simple for historical builders to establish, on condition that data of the solar’s yearly cycle and its connection to the seasons would have been important to livelihood.
Nonetheless, it’s rather more troublesome to say whether or not Stonehenge actually has a connection to the lunar standstill.
“I don’t assume we are able to say definitively, however for me, there are some bits of proof that made me assume that it was deliberate,” Ruggles stated.
One clue was the truth that archaeologists have discovered cremated human stays clustered within the southeast, close to the place the southernmost moonrise will happen.
“I feel there there’s a chance that they have been conscious of that path of the moon after which that turned some form of sacred path,” Ruggles stated.
Since April, Ruggles and Silva, together with colleagues from Bournemouth College, the College of Oxford and English Heritage, the group that manages the positioning, have been documenting the moonrise and moonset at key moments when the moon is in alignment with the station stones. The moon was anticipated to align with the station stone rectangle twice a month from about February 2024 to November 2025, Silva stated.
“This can occur at completely different occasions of day and night time across the yr, with the moon being on the proper place on completely different phases every month,” Silva stated in a news release in April.
The staff needs to know what patterns of sunshine and shadow the moon creates at Stonehenge and whether or not they may need held that means to the individuals who constructed and used the monument.
Stonehenge isn’t the one megalithic monument doubtlessly linked to the lunar standstill.
In the USA, Erica Ellingson, emeritus professor of astrophysics on the College of Colorado Boulder, is investigating lunar alignments at Chimney Rock, a rocky ridge about 1,000 ft above a valley flooring in Colorado. The landmark options two giant pillar-like rocks that body the horizon.
Between the years 900 and 1150, ancestors of the Pueblo folks constructed multi-storied buildings and ritual areas on this difficult-to-access excessive place, with its dramatic view, Ellington stated, and it stays an vital website to the 26 Native American teams which have conventional or cultural ties to the realm.
“The extraordinary view of the sky between the dual pinnacles suggests an astronomical connection, however the hole is barely too far north for the Solar to ever shine by way of it. The Moon, nonetheless, could be seen to rise there when it’s near its most excessive northern place, throughout the main lunar standstill season,” she stated through e-mail.
Additional proof of moon-watching comes from tree-ring relationship of picket beams within the close by historical buildings, which signifies their building is linked with the dates of lunar standstills almost 1,000 years in the past, she added.
The Calanais Standing Stones, located on the Isle of Lewis in Scotland and erected earlier than Stonehenge, might also have a hyperlink with the lunar standstill, Ruggles stated.
Bradley Schaefer, professor emeritus within the division of physics and astronomy at Louisiana State College, stated he was deeply skeptical that historical folks have been conscious of the lunar standstill and constructed monuments aligned with it. Extra doubtless, he steered, it was a coincidence.
“Each historical website has dozens-to-hundreds of potential sightlines, and one-or-more will all the time level someplace close to to one of many 8 standstill instructions,” he stated through e-mail.
The lunar standstill is difficult for an off-the-cuff observer of the moon to acknowledge, he added, and is just actually seen in detailed knowledge on observations of the moonrise and moonset.
Whereas the shift within the moon’s place is delicate and historic data documenting the lunar standstill are uncommon and troublesome to interpret, Ellington stated she thinks the hyperlink is believable as a result of many historical folks watched the sky very carefully.
“A moon-watcher would have seen the moon begin to rise or set outdoors of those limits, shifting farther and farther out of bounds as the most important lunar standstill approached,” she stated.