The Cosmic Vision of Ireland's Ancient Astronomers

The Cosmic Vision of Ireland's Ancient Astronomers

Dark Skies - Unraveling the cosmic vision of Ireland's Ancient Astronomers. An article by Anthony Murphy published as the cover story in the July 2008 issue of Astronomy & Space magazine. The article looks at some of the issues affecting our appraisal of the capabilites of the astronomer builders of 5,000 years ago and examines some of the evidence pointing towards a more complicated knowledge than is currently acknowledged. From Newgrange to Ireland's Stonehenge to the mountains of Sligo, we follow the cosmic trail left by our ancient ancestors.

Imagine yourself gazing up at the blackest of dark night skies, with the starry vault of heaven glistening like a myriad dewdrops catching the glint of strong sunlight, a speckled star show gleaming out from the dark roof of the cosmos. Visualise a night so clear and crisp, so devoid of atmospheric and light pollution that you feel you are in an astronomer’s dream, a sort of star-gazer’s paradise.

Welcome to the skies of the Neolithic.


Stars over Newgrange
Stars over Newgrange (Síd in Broga).


More than 5,000 years ago, the farming communities of the New Stone Age who lived on this island began the earliest known dedicated and proficient attempts to record astronomical observations they had made under such idyllic skies as those described above.

In places such as the Boyne Valley, the hills of Loughcrew in Meath and on the mountaintops in Sligo, stone structures which are considered to be among the world’s earliest astronomical observatories were built by communities who lived under night skies so clear that such views are impossible to glimpse today, except in the most remote corners of our planet.

The people of the Irish Neolithic were on a sort of cosmic quest – a life journey that saw the inevitable consequence of cyclical life patterns – corporeal death, and the ending of a chaotic physical existence. This cosmic quest was one which imagined that there was life beyond the corpse, that the soul could be “reborn”, and that the ultimate destiny of the spirit lay among the glittering stars of the nocturnal otherworld.

Thus, at places like the world-famous passage-mound of Newgrange science and religion came together with the construction of giant lithic edifices which tracked down large units of cyclic astronomical time and which also acted, perhaps, as entrances to the heavenly afterworld.

Newgrange is well known for its winter solstice alignment. On the shortest day of the year – and for a number of days before and after – the light of the rising sun enters into the passage and chamber of Newgrange through a specially constructed aperture over the door known as the “roofbox”.

The alignment was rediscovered by archaeologist Michael O’Kelly in 1967 and has since been trumpeted as one of the great achievements of the Stone Age architects who built similar structures on the periphery of Europe in remote prehistory. Every year, hundreds visit Newgrange at the solstice, and over 25,000 people now enter the annual “Winter Solstice Lottery”, with a lucky 50 entrants chosen to be present at this ancient light show deep in the cold, stony vault of this giant passage-tomb overlooking the Boyne.

But the fact remains that, impressive as the construction and engineering of Newgrange is, we are being grossly unfair to our exceedingly clever ancestors by suggesting they were adherents to a simple solar calendar, and that the height of their scientific knowledge was the ability to track down the solstices – and perhaps the equinoxes.


Milky Way and Venus over Newgrange
The Milky Way and Venus over Newgrange.


Evidence is emerging that these megalithic astronomers were far more advanced than we have accepted up to now.

The hypothesis which suggests the observational and scientific capabilities of the Stone Age astronomers were limited to the tracking down of solstices and equinoxes ignores the broader picture. It overlooks the fact that not only did the mound builders live under pristine night skies, but they were much closer to nature and the cosmos, living without the distractions of the modern age.

Such distractions – including television, computers, electronic devices, game consoles and many other things, even driving motorcars – prevent us from interacting with the cosmos. In fact, even conveniences such as artificial lighting and a solid roof over our heads are barriers between us and the natural world. Today, only the most devout observational astronomers enjoy an interaction with the heavens which bears any similarity to that enjoyed by our prehistoric forebears.

The greatest question, and one which arouses significant controversy in academic circles today, surrounds the level of expertise which the ancient astronomers might have been capable of under ideal viewing conditions and life patterns which meant the Neolithic farmers enjoyed many more hours under the stars than we do today.

Newgrange tells us many useful facts about its builders. The most significant of these facts inform us that these builders were astronomers of sorts, that they were keen surveyors and engineers, that they were organised, devoted to a singular cause, and that they were capable of scientific endeavour, even if it was tinged with a spiritual undercurrent.

Nightly observations made over a couple of generations would yield many significant results. Surely, if the builders of the Boyne monuments could track down the sun to the days on which it “stood still” on the horizon – something not easily observable directly by the naked eye – they would easily have perceived that the moon also appears to “swing” along the horizon, and that it moved through phases and cycles which would obtrude themselves over the course of a period of careful observations?

Certainly, the Scottish engineering professor Alexander Thom, who studied hundreds of stone circles and similar monuments in Scotland and other parts of the UK, thought so. He believed that the 18.6-year “moon swing” cycle would become obvious to an observer “if in fact it had not been recognised from time immemorial”.

It is popularly accepted that Newgrange is a solar construct. In a similar fashion, it is widely acknowledged that Cairn T, another Stone Age “passage-tomb” at Loughcrew, County Meath, is aligned on the sunrise on the spring and autumnal equinoxes.

But it is helpful to consider a few more facts about the builders of these places. At Newgrange, there are 97 giant stones forming the kerb, and another 60 large stones forming the corridor of the passage and the upright orthostats of the chamber. If we could take away all of these huge stones, some of them weighing a couple of tonnes apiece, the total weight of material covering Newgrange is still estimated to be in excess of 200,000 tonnes.

Its builders brought stone from as far away as Dundalk Bay, 20 miles to the north, and the Wicklow Mountains, some 50 miles to the south. Yet, despite their awe-inspiring engineering capabilities, using unhewn rocks to form a light beam just 40 centimetres wide on the shortest day of the year, we are supposed to accept that these proficient astronomer-builders could not perceive the phases of the moon, the movements of the moon and planets through the zodiac, and the longer cycles such as the 18.6-year moon swing cycle and the 19-year Metonic Cycle. Something just doesn’t add up in our worldview of these incredible people. How could they carefully track down the solstices and equinoxes and yet not perceive the lunar cycles?

The crux of the problem (if you’ll excuse the constellation pun!) is that in considering the astronomical capabilities of the Neolithic farmers, we are projecting our own limited observational knowledge onto them. There is no doubt that the moon’s movements are complex. It cannot be denied that describing these movements is an onerous task. However, modern astronomers DO NOT, by and large, actually SEE what the moon does against the backdrop of the stars. No, we prefer to use telescopes to “zoom in” on the moon and its craters and seas, thus eliminating the wider sky scene which forms the backdrop against which the moon and planets perform their dance. Telescope astronomy cheats us into thinking we know more about the night sky. In essence, we end up actually knowing less.

Ask any amateur astronomer to describe the Metonic Cycle or give a competent definition of the 18.6-year moon swing cycle and you’ll likely be met with a blank stare. As a telescope astronomer of over 20 years, I found it difficult initially to grapple with the concepts surrounding the moon’s apparent meanderings among the stars. If only it behaved like the sun, following a clearly defined path through the zodiac constellations, life would be much easier!

In my quest to better unravel the complex movements of the moon, I had help from a retired American doctor, Charles Scribner, who had been observing the sky without a telescope since the 1980s and working out the movements of the moon – before the advent of cheap computer software which could simulate the same thing. Scribner saw the sky as it was seen by the ancient Irish astronomers – and was able to perceive very long-term cycles of the sky using comparatively short-term observation periods. In the space of twenty years, Scribner bridged a knowledge gap of five millennia.

A generation ago, the American artist Martin Brennan came to Ireland and made huge discoveries about the astronomical capabilities of the Irish Stone Age astronomers. He revealed that Dowth a sister site of Newgrange, had a chamber which was aligned on winter solstice sunset. He was the discoverer of Cairn T’s equinox alignment.

Etched into the kerbstones of Knowth, the third of the three major mounds of the Boyne, Brennan saw markings which he revealed were recordings of apparently complex lunar movements. He dubbed one stone the “Calendar Stone” and on its surface he saw 22 crescent shapes and 7 circular shapes – a total of 29, perhaps representing the 29 days of the synodic lunar month. Indeed, three of the crescents were apparently obscured by a large spiral pattern, and Brennan postulated that this represented the three days during which the moon is lost in the glare of the sun.

Alexander Thom, whose major works were published in 1967 and 1971, went against the grain of popular academic thought when he suggested the stone builders of Scotland could perceive the long lunar cycles. But he went further, even suggesting that the stone engineers could predict eclipses. Today, four decades after the publication of these works, Thom’s ideas remain widely unpopular among UK academia. Yet our own studies of the Irish astronomers suggest that there could have been a skilled lunar astronomy wrapped up in the sophisticated stone observatories of ancient times.


Stars over Dowth
Stars over Dowth.


At Dowth, for instance, there are two chambers which accepted light from both the sun and moon. The previously-mentioned southern chamber, which is illuminated by the light of the setting winter solstice sun, is more precisely aligned on something which Thom called the “major standstill” of the moon. In effect, the major lunar standstills are like solstices, and signify those times in the moon-swing when the rising and setting positions of the moon are at their most extreme. The major standstill risings and settings fall outside the extreme azimuth positions of the solstice sun – by over ten degrees. This means that at its maximum extremes, the moon rises and sets further north and further south than the solstice suns, something which would have been very noticeable to an ancient astronomer who has familiarised themselves with the various rising and setting positions of the sun and moon over a period of time.

The northern chamber at Dowth was accurately oriented towards the “minor” standstill of the moon, when the limit of the moon’s declination takes it from +18.5 degrees to –18.5 degrees, well within the declination of the solar standstills.

Dowth has a total of 115 kerbstones. Doubling this number results in 230, which is the number of synodic lunar months in one 18.6-year moon-swing cycle. On a kerbstone on the eastern side of the great cairn, there are markings which may resemble an attempt to “draw” a total eclipse of the sun on stone.

Even the legend of Dowth talks about the coming of a sudden darkness, a blackening of the sky which may have signified a total eclipse of the sun.

While eclipses of the sun are difficult to observe, occurring as they do along a narrow strip of the earth, eclipses of the moon are both predictable and observable in many cases. It seems that the study of eclipses was at least one intent of the megalithic builders of ancient Ireland.

While the great monuments of the Bend of the Boyne stand relatively intact today after more than five millennia, other great monuments have vanished. One such magnificent structure was Ireland’s Stonehenge near Dundalk, in County Louth. This huge arrangement of stones and earth was recorded by the astronomer and draftsman Thomas Wright in 1748. He described the monument as a “very great work” comparable with Stonehenge in England. If it were there today, it would outshine Stonehenge, and probably Newgrange, as one of the great monuments of the world. Sadly though, Ireland’s Stonehenge was demolished, almost every trace of it removed from the face of the earth. Some time between Wright’s visit and the early 1900s, the huge triple-ringed stone circle vanished from existence.

However, not every trace has been removed. The so-called “footprint” of Ireland’s Stonehenge has been detected by archaeologists, and a brief note about the site in an old archaeological journal described it as an ancient “school of astronomy”.

On the mountains around Sligo are dotted the remains of an enormous Stone Age legacy. A large number of cairns, including the well-known Queen Medb’s Cairn, form a vast archaeological landscape dating right back to the Neolithic. One of the Sligo cairns, Cairn G at Carrowkeel, has a roofbox similar to that at Newgrange. Megalithic researcher Martin Byrne says the cruciform chamber of Cairn G can be illuminated by light from the sun and moon. The hill upon which Queen Medb’s Cairn is located is called Knocknarea, meaning “Hill of the Moon”.

All over the country are sprinkled the remains of a vast stone system which has at its heart a cosmic design. At Saint Patrick’s chair at Boheh, County Mayo, observers can watch the setting sun apparently “roll” down the side of Croagh Patrick. This happens on two dates in the year – April 18th and August 24th, dates which, along with the winter solstice, divide the year neatly into three parts.

At Baltray, a village near the mouth of the Boyne in County Louth, there are two seemingly innocuous standing stones. One of these stones forms an alignment with the Rockabill islands, some 13.5 miles away. At dawn on the winter solstice, the sun rises close to these islands. Back in the Stone Age, it would have been rising precisely over Rockabill.

At Drombeg Stone Circle in County Cork, there is an alignment with a notch in the hills where the winter solstice sun sets. On the summit of Slieve Gullion in County Armagh is a cairn which has a chamber oriented also to the winter solstice sunset.


Milky Way
There are many names for the Milky Way in the Irish tradition and in mythology.


It is abundantly clear that solar astronomy was practiced in Stone Age Ireland. What is not quite so clear, as stated already, is the extent of the lunar and stellar study.

There are hints in Irish mythology that the people who existed here in prehistory had their own star groupings. Some of these Irish constellations of antiquity are the same as those we know today. For instance, there is evidence to suggest the ancient astronomers saw the constellation we know today as Cygnus as a swan. They saw Taurus as a bull and Gemini as twins. They had no lion for Leo, instead knowing this huge constellation as the Cú – the “hound”.

Many stories of supernatural giants, warriors and god-like heroes conjure up images of the constellation we call Orion. Indeed such characters as Nuadu Silver-Hand, Amergin Bright Knee, Cúchulainn, Fionn Mac Cumhaill and Lugh were probably inspired by this giant anthropomorphic constellation.

There is evidence too that monuments were laid out along straight lines across huge distances. Many of these alignments correspond with astronomical events, such as solstices or star risings and settings.

Some monuments have chambers which point towards others. Newgrange, which has significant swan mythology associated with it, has a cross-shaped chamber which points towards Fourknocks, a smaller passage-tomb near the Meath-Dublin border. Fourknocks, in turn, has a cross-shaped chamber which, back in the Neolithic, pointed towards the rising place of Deneb, the main star in the swan constellation Cygnus.

In looking at structures which are as old as 5,000 years ago, one has limited evidence to study. Evidence often presents itself in the form of clues and pointers, rather than hard physical artefacts or definitive data. We have no textbook from the Neolithic which tells us how and why these monuments were built.

What we do have are pieces of a jigsaw, a giant astronomical jigsaw. If we can put enough of these jigsaw pieces into place, the larger picture eventually emerges. That picture suggests that the simple solar astronomy acknowledged to have been inherent in the design of some stone structures was complemented by a significant lunar and stellar knowledge deep in prehistory.

While much of what the remarkable people of the Stone Age did remains shrouded in mystery, a light has emerged from the obscurity of prehistory. That light signifies a quest for knowledge and a great understanding of the cosmic principle, which saw that life on earth was influenced by the great cycles of the heavens.

Perhaps the day is coming when we can truly appreciate what these outstanding people achieved. Their skies were darker and clearer than ours. They lived under the stars and among nature. Their enormous structures have stood the test of time. Some, like Newgrange, continue to function accurately. Perhaps their cosmic quest was eventually rewarded in the dim mists of the past. Today, we who are the descendants of these people have only the barest understanding of their knowledge and capabilities. Our own cosmic view is concealed by the trappings of modern life, and by the pollution which obscures the heavens from our eyes.

Now, only in our dreams is it possible to envision their wonderfully dark skies. Despite our apparent technological mastery, we are still reduced to humility by their achievements.

Anthony Murphy is a journalist, writer and astronomer who co-authored the book “Island of the Setting Sun – In Search of Ireland’s Ancient Astronomers” with artist Richard Moore. He is currently working on a revised and expanded second edition of the book which is due to be published in June. He is the creator of, a very popular website about ancient Ireland and its myths and astronomy.

Note: Some of the concluding text above was used in the preface to the second, revised and expanded, edition of Anthony Murphy and Richard Moore's book Island of the Setting Sun - In Search of Ireland's Ancient Astronomers.

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