How the Moon may have played a role in the building of Stonehenge

Two years ago, I was standing in the car park at the Stonehenge Visitor Centre on a cold, clear December evening.

I had only recently started working for English Heritage and it was a few weeks before the winter solstice.

The Sun was slowly setting, a large, bright-red sphere on the western horizon.

Just as it dipped below the horizon, I turned and was shocked to see another giant red orb rising above the eastern horizon – the Moon.

 It felt like a cosmic moment, the cycling of a glowing red orb that briefly dipped into the underworld to only rise again in triumph, and I was in awe.

Stonehenge's celestial foundations

In that instant, I realised why the wide open spaces of Salisbury Plain, where Stonehenge is located, have been a place for observing the skies for millennia.

As modern humans living in urban environments awash with light, sometimes we forget how prominent the night sky would have been to people in the past.

We know that the movements of the Sun, Moon and stars influenced our ancient ancestors, because around 5,000 years ago, at the end of the Neolithic (or New Stone) Age, the first farmers (who had arrived on British shores about a thousand years earlier) began to build extraordinary things. 

Monumental tombs, stone circles and henges were all developed on a grand scale, and as people transformed their world, they looked to the skies.

Many of these were aligned with the Sun on the solstices or equinoxes (when night and day are of equal length), including Stonehenge in England and Newgrange in Ireland.

These monuments were built not only to help track the yearly movements of the Sun, but also to connect to its regenerative power.

Stonehenge and the Sun

The Sun was of key importance to these early farmers, because the survival of their crops and animals relied on accurately predicting its movements over the course of the day and year.

Stonehenge, in particular, was carefully designed to align with the movements of the Sun.

When the circle was constructed 4,500 years ago, the enormous sarsen stones were precisely arranged to frame these key moments in the yearly cycle.

On the summer solstice the Sun rises over the Heel Stone and on the winter solstice it sets behind the tallest trilithon at the centre of the circle.

This central ‘Sun axis’ at the heart of Stonehenge suggests that it was a special place of worship and celebration created to enact this cosmic ritual.

But what role did the Moon play?

Stonehenge and the Moon

Astronomers have long studied the various possible astronomical alignments connected to Stonehenge.

While observations of the Sun’s connection to the monument go back to the 18th century, the Moon’s connection has been more ephemeral.

It was not until the 20th century that astronomers suggested there may be a possible link between Stonehenge and the Moon.

This was based on observations of the Moon alignment at another ancient monument, Calanais, on the Isle of Lewis off the west coast of Scotland. 

Around the same time that Stonehenge was being built, the standing stones and avenue making up the complex stone monument at Calanais were rearranged to align with the full Moon’s path from rising to setting.

Skimming the horizon, the Moon shines into the centre of the circle at the southern end of the Calanais monument as it sets.

Could the Moon have played a similar role at Stonehenge? 

At Calanais, this phenomenon only occurs every 18.6 years, during a two-year period called a major lunar standstill.

This is when the northernmost and southernmost positions of the Moon at moonrise and moonset are at their furthest apart along the horizon.

Marking time by the Moon 

Over the course of a year, the Sun follows a fixed cycle of changing positions in the sky. However, the Moon’s cycle is much more rapid.

Our view of the Moon varies over a period of 29.5 days as it changes from a thin white crescent to a full disc and back again to a thin crescent, until disappearing for three days.

Meanwhile, moonrise and moonset move from their northernmost to southernmost limits and back again in just 27 days. 

Through its phases, the Moon acts as timekeeper for societies around the globe, past and present.

As well as being the basis for early calendars, in Neolithic times it was also a source of light for nighttime activities such as hunting and farming.

Even today, some people still plant certain crops in the light of the full Moon, as it is thought to be beneficial to the plant’s development.

No doubt, the Moon had a similar significance in marking and observing the passage of time for the Neolithic people who built Stonehenge.

Lunar standstill

But the Moon also has a further cycle that is far longer.

Over several years, the limits of moonrise and moonset themselves gradually change, until they reach the point where the northernmost and southernmost moonrise and moonset positions are at their maximum distance apart on the horizon.

This two-year period is what is known as a major lunar standstill, or lunistice, and it only occurs every 18.6 years.

Once a major standstill is reached, the distance between northernmost and southernmost moonrise and moonset can be exceptionally far apart, and it stays that way for around two years. 

This is a rare celestial event and when it occurs it presents a once-in-a-generation opportunity for us at Stonehenge to explore the connection between the monument and the Moon.

Standstill at Stonehenge

The artist and sculptor Henry Moore, in awe seeing Stonehenge for the first time in the autumnal moonlight, remarked: "Moonlight, as you know, enlarges everything, and the mysterious depths and distances made it seem enormous."

The Moon transforms the way we see the world and, just over a hundred years after Moore’s nocturnal visit, the Moon illuminated Stonehenge once again but now from its most southerly position, just as the summer solstice Sun set.

A massive beam of light suddenly floodlit the stones and dominated the sky – the triumph of the Moon over the Sun!

The thing that is remarkable is that on a major lunar standstill, the Moon rises and sets in a place on the horizon that the Sun never reaches.

Early farming communities would have tracked the movement of the Sun on the horizon across the year.

So the appearance of the Moon further north and south than the extremes of the Sun may have been highly significant.

Perhaps this would have been a moment when the lunar deity was stronger than the solar one.

It is believed that these distinct lunar movements may have been observed during the early phase of Stonehenge, potentially influencing the later monument’s design and purpose.

A long history

This is the intriguing thing about Stonehenge. It's not simply one monument, but rather a special place that people transformed and added meaning to over many generations. 

In its earliest phases, around 5,000 years ago, Stonehenge was a circular earthwork surrounded
by a bank and ditch.

This became an ancestral cemetery and people began burying cremated human remains, animal bones and grave goods for the dead in the ditch.

Burials also took place in 56 regularly spaced pits called the Aubrey holes (after the antiquarian John Aubrey who first recorded them), arranged around the inner circumference of the circular earthworks.

These pits may originally have housed upright timber posts or stones as part of the earliest monument at Stonehenge.

Stonehenge became the largest Neolithic cremation cemetery in Britain, a place of commemoration and mourning.

This was several centuries, around 500 years, before the large stones were put up at Stonehenge.

Notably, many of these cremations were concentrated in the southeast of the monument, aligning with the most southerly rising position of the Moon, where three timber posts were also set into the bank.

Was there a symbolic link between the Moon and these ancestral burials or the bones of the cremated dead in the earliest version of Stonehenge?

It’s one of the questions being investigated over the major lunar standstill.

Secrets of the stones

Around 500 years later, a massive renovation project took place at Stonehenge and the familiar form of its stone circle started to take shape.

The large sarsen stones and smaller bluestones were placed into concentric circles, arranged to mark the position of the annual summer and winter solstices.

Outside the stone circle were four small stones called the Station Stones, of which only two remain.

These may have helped measure out the large sarsen circle when it was being built, but they also marked out a large rectangle that appears to relate to the Moon.

The long axis of this rectangle aligns in the direction of the southernmost moonrise at the major lunar standstill and (looking the opposite way) the most northerly moonset.

Researchers have debated whether this was deliberate and, if so, how it was achieved and what its purpose might have been.

Interestingly, the likelihood that the Station Stones were employed to measure out the sarsen circle, five centuries after the site was first used for cremations, suggests an enduring connection between the lunar cycles and the architecture of Stonehenge.

This lunar standstill, we are seeking answers to whether Stonehenge was designed and built with the movements of the Moon in mind, and whether the possible alignments between the stones and the Moon were intentional.

This article appeared in the June 2025 issue of BBC Sky at Night Magazine