The June 2020 issue of Physics Today features an image of the Nebra Sky Disk as the illustration for a book review by Bernie Taylor (page 53). The sky disk is one of the earliest depictions of recognizable astronomical objects and relationships. Researchers have analyzed the disk extensively and debated about when it was created and where it was found. The disk had been used for generations, and elements were added to it over the years.1
The 30-centimeter disk originally featured elements that appear to be stars, the Sun or a full Moon, and a crescent Moon. Two golden arcs (one of which is now missing) were later added to the rim, which may have changed the disk’s function. It has been posited that those arcs represent the distances the sunrise and sunset travel between solstices at the latitude where the disk was purportedly found in 1999 near Nebra, Germany.
Added later to the disk was another arc with two distinct lines along its length and many shorter ones radiating from its sides. Some have interpreted the object to be a mythical boat that ferries the Sun across the sky, with the short engraved strokes representing the oars.2
Images of the disk are often oriented so that the third arc is on the bottom, emphasizing the possibility that the symbol represents a boat. But if the two side pieces indeed represent the extent of sunrises and sunsets throughout the year, then the disk is meant to be viewed as though the edge represents the horizon, as with modern overhead sky charts. If that is the case, the disk’s iconography might be interpreted differently.
The disk could be depicting the star cluster nearly midway between the side arcs—often thought to be the Pleiades—in the sky to the south, as it would sometimes appear from the area around Nebra. The object often thought to be a Sun boat then would be a fuzzy swath, low in the sky and to the north. I propose that it was intended as a representation of the aurora borealis, which would have made periodic appearances in Nebra. That would agree with the observational nature of the rest of the disk.
