Is this the world's oldest known protractor?

For over a century, archaeologists have argued over the original purpose of the strange looking object shown above, which was discovered in 1906 in the tomb of the ancient Egyptian architect Kha. Now, an Italian physicist claims to have deduced the artifact's true function:She says it's the world's first known protractor.

If the strange-looking object doesn't immediately bring to mind a protractor — the flat, metal or plastic, typically half-disc drawing tool used to measure angles — don't be alarmed; since its discovery, it hasn't reminded anyone else of one, either. (Ernesto Schiaparelli, the archaeologist who first discovered the artifact, believed it to be the case for a balancing scale.)

But Amelia Sparavigna, a physicist at Turin Polytechnic in Italy, believes that the complex patterns adorning the object – long believed to serve merely as decoration — actually serve a functional purpose, as well. Sparavigna describes the patterns, pictured below, as follows:


The [inner]decoration of the object of Kha is quite complex: it has 16-fold symmetry, looking as a compass rose with 16 leaves. Outside this rose, there is a polygonal line of 18 corners, pointing outwards. They correspond to the same number of corners (pointing inwards). That is we have a [polygonal line] with 36 corners.

Is this the world's oldest known protractor?

The sixteen petals of the inner rose pattern divide the object's circular projection into sixteenths – an important fraction featured prominently in a system of calculation commonly used by ancient Egyptians. The Egyptians also placed great significance in the number 36, which they originally associated with the 36 small groups of stars (now call decans) that they observed appearing over the nighttime horizon throughout every rotation of the earth. According to Sparavigna:

The use of 1/16 fraction, the coincidence of the number of corners with that of decans, and the fact that the decoration was engraved on the instrument of an architect, [suggest] that this object had been used as a protractor instrument with two scales, one based on Egyptian fractions, the other based on decans

However, members of the archaeological community remain skeptical. Kate Spence, a Cambridge archaeologist who specializes in ancient Egyptian architecture, cites the lack of precision of the artifact's decorative markings as proof that the Egyptians would never have used the object as a measuring instrument, stating succinctly: "When the Egyptians want to be precise, they are."

You can read Sparavigna's original paper via Arxiv [PDF] (Spotted on New Scientist).