Image of the Nebra Sky Disc of the European Bronze Age period
Archaeo-astronomy steps out from shadows of the past
Shorter article is outlined below
The 3,600 year old Sky Disk of Nebra is the world’s oldest image of the cosmos.
It caused a world-wide sensation when it was brought to the attention of the German public in 2002, having been discovered at Mittelberg in the state of Saxony-Anhalt two years earlier.
A group of German scientists has deciphered the meaning of one of the most spectacular archaeological discoveries in recent years: The mystery-shrouded sky disc of Nebra was used as an advanced astronomical clock.
The purpose of the sky disc of Nebra dating from 1600 BC is no longer a matter of speculation.
A group of German scholars who studied this archaeological gem has discovered evidence, which suggests that the disc was used as a complex astronomical clock for the harmonization of solar and lunar calendars.
The disc maps 32 stars, including the Pleiades, as they appear in reference to a local mountain on the horizon, the Brocken. The Mittelberg (‘Central Hill‘) enclosure is oriented in such a way that the sun seems to set every equinox behind the Brocken, the highest peak of the Harz mountains. The nearby Ziegelroda forest is said to contain around 1,000 barrows.
The 252 metre high Mittelberg hill in the Forest is 180km southwest of Berlin.
Since the Mittelberg is near the German town of Nebra, the star map has been dubbed the “Nebra Disc.”
“This is a clear expansion of what we knew about the meaning and function of the sky disc” – archaeologist Harald Meller.
Unlike the solar calendar, which indicates the position of the earth as it revolves around the sun, the lunar calendar is based on the phases of the moon. A lunar year is eleven days shorter than the solar year because 12 synodic months, or 12 returns of the moon to the new phase, take only 354 days.
The sky disc of Nebra was used to determine if and when a thirteenth month — the so-called intercalary month — should be added to a lunar year to keep the lunar calendar in sync with the seasons.
“The functioning of this clock was probably known to a very small group of people” – Harald Meller.
The 32-centimeter-wide (12-inch) bronze disc that weighs about 2 kilograms, with gold-leaf appliqués representing the sun, the moon, and the stars is the oldest visual representation of the cosmos known to date. A cluster of seven dots has previously been interpreted as the Pleiades constellation as it appeared 3,600 years ago.
The explanation of the disc’s purpose sheds new light on the astronomical knowledge and abilities of the Bronze Age people, who used a combination of solar and lunar calendars as important indicators for agricultural seasons and passage of time.
“The sensation lies in the fact that the Bronze Age people managed to harmonize the solar and lunar years. We never thought they would have managed that” – Harald Meller.
According to astronomer Wolfhard Schlosser of the Rurh University at Bochum, the Bronze Age sky gazers already knew what the Babylonians would describe only a thousand years later.
“Whether this was a local discovery, or whether the knowledge came from afar, is still not clear” – Wolfhard Schlosser .
Ever since the disc was discovered within a pit inside a Bronze Age ringwall, archaeologists and astronomers have been puzzled by the shape of the moon as it appears on the disc.
It may have been used to time plantings and harvests.
On the left and right sides are two long arcs. These span about 80 degrees each. The difference between sunrise on the summer solstice and on the winter solstice is 82.7 degrees at this latitude, as is the difference between the sunsets on the two solstices. The two arcs are said to represent the portions of the horizon where the sun rises during the year. (The gold coating on the left arc, representing sunset, has fallen off and is lost).
Between the two arcs are a full circle and a crescent. The crescent obviously represents a crescent moon, while the large circle may be the sun or a full moon. (The gold on the sun/full moon circle is damaged). In the background are 23 stars dotted in an apparently random pattern, and one group of seven stars which is said to represent the Pleiades star cluster (the Seven Sisters or M45). X-Rays indicate that under the gold of the right arc are two more stars, so it is likely that the two arcs were added some time after the other features.
“I wanted to explain the thickness of the crescent on the sky disc of Nebra because it is not a new moon phase” – Ralph Hansen, Hamburg astronomer .
In his quest to explain why the Nebra astronomers created a sky map with a four or five days old moon on it, Hansen consulted the “Mul-Apin” collection of Babylonian documents from the 7th and 6th centuries B.C.
These cuneiform writings represent, according to Hansen, a compendium of “astronomic knowledge from the earliest times.” They also contain a calculation rule for the crescent that looks strikingly similar to the one from Nebra.
According to the ancient Babylonian rule, a thirteenth month should only be added to the lunar calendar only when one sees the constellation of the moon and the Pleiades exactly as they appear on the Nebra sky disc.
The disc was originally smeared with rotten eggs. These would have caused a chemical reaction on its bronze surface, which would have turned the disc’s background a deep violet colour simulating a night sky out of which the gold-embossed stars would have shone.
The third arc on the disk is also highly interesting. The ancients did not understand how the sun could set in the west and end up in the cast the next morning. Representations of a disk in a ship, from Bronze Age Egypt and Scandinavia, reveal an age-old belief that a ship carried the sun across the night sky. The Nebra disk is the first evidence of such a faith in central Europe.
The sky disc of Nebra was found near Europe’s oldest observatory in Goseck.
It is a solar observatory built ca 4900 BCE.
Nearby excavations of wood-and-clay houses have turned up a variety of grains and evidence of domesticated goats, sheep, pigs and cows. Farmers reached this part of the world some 500 years before they built the solar observatory. Although these earliest Neolithic agriculturists most likely measured only the sun’s movements, over millennia they came to quantify the lunar cycle and the positions of constellations.
The Bronze Age astronomers would hold the Nebra clock against the sky and observe the position of the celestial objects. The intercalary month was inserted when what they saw in the sky corresponded to the map on the disc they were holding in their hands. This happened every two to three years.
But the German researchers also discovered that in the 400 years that the disc was in use, its status had evolved. The perforations on the edge of the object as well as a ship that was later added to the map suggest that the knowledge about the lunar calendar’s shortage of days was lost along the way.
“That means, that in the end the disk became a cult object” – Harald Meller.
The disc was found on July 4, 1999 from two convicted grave robbers. In February, 2002 it was bought along with two swords, two axes, chisels and armlets, from art fencers in a police operation in Switzerland.