## The disc of Nebra

The superposition of gold leaf inlays and the origin of the gold used to decorate the disk let us think that its creation required four stages:

### First stage

At the origin, the disc contained 32 small golden discs set in a star pattern, a waxing moon crescent and a wide disc in gold representing the full moon or the sun. The fact that 32 solar years (of 365 days) correspond to 33 lunar years (of 29.5×12 = 354 days) leads us to deduce that the central disc represents both lunar and solar forms.

A single cluster of stars can be distinguished among the small golden discs. Composed of 7 discs located between the crescent and the full moon, it evokes the 7 stars of the Pleiades visible to the naked eye. In contrast to the current era, the Pleiades constituted, at the Bronze Age, a distinct constellation from the Taurus.

In accordance with the Gregorian calendar and commentaries of the archaeologist Harald Meller and astronomer Wolfhard Schlosser, the moon and the Pleiades appeared together in the sky of the northern hemisphere twice a year. The Pleiades set on March 10^{th}, shortly after the new moon preceding the full moon of spring and rose on October 17^{th} at full moon of fall (consult the site Himmelsscheibe von Nebra

in German). They probably marked the cycle of sowing and harvesting in many societies of that era. Consequently, the Pleiades were visible from October 17^{th} to March 10^{th}, which corresponded to a length of 145 days out of the 365 days of the year (=0.4).

### Second stage

Next, two lateral golden arcs were added. To do this, a small golden disc on the left side was moved towards the right and two small golden discs on the right side were covered. The small golden discs were reduced to the number of 30 henceforth.

The lines joining the opposing ends of both arcs make an angle of 82°. This value corresponds to the angle formed by the diagonals of the “solstitial rectangle” determined by the position of the sunrise and sunset at solstices. This angle depends on the astronomical data of the era and the latitude of the place of the discovery of the disc (φ = 51.3°) ^{1}.

Let us note that the diagonals of the rectangle intersect inside the wide golden disc that, in this case, no longer acts as the moon, but the sun.

### Third stage

The following modification consisted in adding a golden arc turned towards the Pleiades in the lower part of the disc. Now, this arc is inscribed in a circle, internally tangent to the disc and going through its centre. Moreover, it is seen from the centre of this circle at an angle about 145° out of 360° of the circumference of the circle it is inscribed in.

If we compare the length of the golden arc inscribed in the circle with the length of the visibility of the Pleiades during the year, we note that they represent a proportion close to 0.4. It follows that the relative length of the golden arc corresponds to the relative length of the visibility of the Pleiades in the sky of the northern hemisphere.

In other words, the meaning of the golden arc is firstly astronomical and not symbolic. Attaching the image of the “solar Boat” crossing the world of darkness to it does nothing but complete the astronomical meaning. In fact, symbols often rely on a representation of cosmic order to suggest a reality of supra-cosmic order.

### Fourth stage

The last stage of the realization of the disc consists in piercing its circumference with 39 or 40 equidistant holes. In fact, the damaged part of the edge of the disc could have contained one or two holes according to various authors. As the spacing between holes is not completely regular, they are probably more the outcome of an empirical process than an exact calculation. Nevertheless, such a calculation gives an average value of 2.58 cm (hypothesis 39 holes) or 2.51 cm (hypothesis 40 holes). Knowing that the current inch measures 2.54 cm, these values suggest the use of a unit of measure corresponding to the **inch** of the region at the Bronze Age ^{2}.

While putting his thumb on the edge of the disc after a hole to mark the following one, the person, empowered to work on the disc, introduced a new approach to the astronomical location. **The man crowned the geometrical representation with a digital one** based on the choice of a unit of measure ^{3}.

We can deduct from all this that each of these stages added something important to this authentic astronomical instrument. Its symbolism will appear more clearly with the study of the site of Goseck.