Study of the Nebra Sky Disc got off to a dramatic start. This Bronze Age artefact was discovered on the summit of the Mittelberg hill, Germany, in 1999. The metal disc had been carefully placed upright in the ground, but reportedly did not enter the earth alone. Instead, it formed part of a larger hoard, which also included pairs of bronze swords, axe-heads, and armlets. Yet the finders of this impressive cache were metal detectorists operating illegally, and it was only a police sting operation that allowed these objects to receive archaeological attention. The results of this research, and its implications for the level of astronomical knowledge available in Bronze Age Europe, are nothing short of extraordinary. Equally fascinating is the way the design of the disc was reimagined over time, to encode new information and beliefs on its face. Such is its sophistication that the artefact has been likened to a portable Stonehenge, making it entirely appropriate that the Sky Disc is currently one of the highlights of the British Museum’s The world of Stonehenge exhibition. Like many of the objects on show, the Nebra Sky Disc offers elegant testimony to a mobile, connected, and sophisticated prehistoric world.
There is a tendency for celebrity ancient artefacts to be smaller than viewers expect. Not so the Nebra Sky Disc. At 32cm in diameter it has an imposing presence, while the final form of the symbols speckling its face manages to be both mysterious and oddly contemporary. Neil Wilkin, exhibition curator, has compared the result to a smiling, winky-face emoji. In the absence of an instruction manual, attempts to understand the meaning of the symbols arranged on this instrument inevitably involve a degree of guesswork. Even so, there are widely accepted interpretations of the broad meaning of the images. To stick with the emoji metaphor, the winking eye is a crescent moon, while the other eye is either a full moon or the sun. Indeed, it may have been read as both at different points in the past. Feathery lines projecting from the ‘smile’ resemble the stylised oars of a mythological solar boat, which was believed to ferry the sun through the heavens. The ‘freckles’ are stars, with the group of seven probably representing the cluster known as the Seven Sisters or Pleiades, which is visible in the European night sky from October to March. Finally, an arc of gold was added to the edge of the disc beside the winking eye, while the traces of a second arc that has been removed can be made out on the opposite side. Together, these elements hint at an astonishing breadth of knowledge.
As originally conceived, the face of the Sky Disc only incorporated the two ‘eyes’ and assorted stars. This potentially encoded information that would have been of key significance to ancient farming communities. Keeping track of the seasons is essential for growing crops, while the regular cycles of the moon offered a handy way to measure months. Because the lunar and solar years are different lengths, though, any calendar based on the moon needed to be periodically reset. One way of doing this, which is recorded on a 7th- or 6th-century BC tablet from Babylon, involves making observations of the moon and the Pleiades. The Babylonian text notes that the reappearance of the Pleiades in October normally coincides with a full moon. If a crescent moon a few days old appears next to the Pleiades in the springtime sky, though, a leap month should be added every third year. As the face of the Sky Disc seemingly shows the Pleiades sandwiched between a full and crescent moon, it could have acted as a pictorial equivalent of the Babylonian tablet. ‘This is a complex and sometimes contentious feature of the Sky Disc’s function,’ says Neil. ‘It does require a leap of faith, but personally I think it’s a compelling argument. If true, it’s totally mind-blowing, because this is knowledge that we just didn’t think they had.’
The first alteration to the Sky Disc involved adding the gold arcs to its sides. You can see how the surviving strip on the left side of the disc overlies two earlier stars, while on the right side a third star was moved to nudge it away from the now-missing arc. Taking the disc as a circle, these two strips match the 82.5° length of the horizon where the sun rises and sets between the two solstices. Intriguingly, the Mittelberg would have made a particularly good observatory for monitoring the sun’s progress along the horizon, as the summer solstice sunset occurred behind the highest peak in a mountain range 90km distant.
If the first two iterations of the disc encoded impressive knowledge of celestial cycles, the third was of a different order. This was when the solar boat was added. ‘It is similar to the sort of motif you get in the Scandinavian and Nordic Bronze Age,’ says Neil. ‘What’s fantastic is that it’s a concept you also find much further afield in Mesopotamia and Egypt. So, what we’re seeing is really an object that was seemingly – for want of a better word – quite scientific, shifting into something that is more mythological. Perhaps, if it originally did have that leap year significance, some of that has now been forgotten. Instead, it’s been transformed into something quite different, which revolves around belief more than knowledge.’
‘The next change is when perforations were made around the edge of the disc, including through the solar boat. Where analysed, traces of gold have been found in these holes, so it looks like gold rivets were used to attach the disc to something. Was it carried on a banner or even attached to a shield? It’s difficult to know, but rock art in Scandinavia shows sun symbols being held up during ceremonies.’ After this fourth phase of use, the disc was detached from its backing and the missing arc torn away, presumably as a prelude to its burial on the Mittelberg.
Forging the firmament
If the celestial cycles and mystical motifs discernible on the disc suggest information could travel over long distances, assessing the metal used to create this instrument delivers a similar message. The bronze disc itself would originally have appeared black – like the night sky – and seemingly incorporated copper extracted in the Austrian Alps. The gold used to make the moons and stars has been traced to the Carnon valley in Cornwall, posing all sorts of questions about how it travelled across Europe to become part of the Sky Disc. Was it part of a reciprocal trade in raw materials, or could it have been recycled from an earlier gold object? Either way, Cornwall was not the only source of gold exploited for the Sky Disc, as the arcs that were later added to its sides made use of material from Romania.
Another curious connection concerns the paired implements reportedly buried with the Sky Disc. The presence of double sets of artefacts is also a classic feature of high-status ‘princely’ burials that are found in Germany. ‘Some of the objects in them are very similar to – and have connections with – Bronze Age objects found in the Stonehenge landscape,’ says Neil. ‘This is a very old idea that was explored by Stuart Piggott in the 1930s. The point is that you find things like miniature halberds in graves around Stonehenge. During the period these were buried, full-sized halberds were rare in England but an important weapon and symbol of prestige and identity in Central Europe, including among contemporary communities in Germany. So here, too, there are suggestions of connections occurring across vast distances.’
The objects buried with the Sky Disc are also of crucial importance for dating it. They point firmly to the instrument being deposited around 3,600 years ago, but some scholars have questioned a connection that depends on the testimony of the metal detectorists. Severing this link would allow a later, perhaps even Iron Age date for the Sky Disc. ‘A lot has been written about this,’ says Neil. ‘From my point of view, what it comes down to is whether the disc sits at the beginning or the end of the Bronze Age, as the proposed Iron Age date would still be Late Bronze Age by the standards we use. While it wouldn’t shock me if that later date turned out to be correct, I think the case for an Early Bronze Age date is strong. In the UK we are familiar with metal-detecting finds, whereas in parts of Europe it is banned, and lots of specialists working there find it hard to believe that information from metal-detecting can be taken for granted. Here, because we’ve had the Portable Antiquities Scheme recording metal-detecting finds for years, we’ve begun to accept that most things are as described. The point that I’d stress, though, is that even the late end of the possible date spectrum for the disc doesn’t diminish one of the most important ancient objects ever found in Europe.’
FURTHER INFORMATION The Nebra Sky Disc and associated hoard can be seen alongside a stunning array of prehistoric artefacts at the British Museum’s The world of Stonehenge exhibition until 17 July 2022. For further details, including ticket prices, see www.britishmuseum.org/exhibitions/world-stonehenge The Sky Disc is also discussed in the publication accompanying the exhibition: D Garrow and N Wilkin (2022) The world of Stonehenge, London: The British Museum Press. £25, ISBN 978-0714123486 CWA is grateful to Neil Wilkin and Maxwell Blowfield.