The name of the Cyrenean foot stems from the fact that this foot was used in particular in Cyrenaica , a landscape in eastern Libya with the ancient capital Cyrene . The city of Cyrene was founded in the 7th century BC. Founded by Greek settlers. The Cyrenean foot spread throughout Greek ecumenism , including in the mother country . It is also called the “little Ptolemaic foot” in the specialist literature .
Using the dimensions of the acropolis Parthenon , Jacques Foucherot (1746–1813) evaluated the Cyrenean foot at 308.597 mm; so to very close to 308.6 mm. The Kyrenean foot measures 308.7 mm seven-smooth . In fact, fluctuations of approx. ± 0.17% in the length dimensions - even for etalons - must be regarded as normal both in antiquity and in the Middle Ages . Its ratio to the Roman foot is 25:24. Thus, a 600-foot Cyrenean stadium is exactly as long as the 625-foot Roman stadium .
According to Eratosthenes, the circumference of the earth is the length of 252,000 stadia . If Eratosthenes meant a stadium of 158.76 m, that is, a stadium of 600 pous italikos , equal to 600 × 264.6 mm, then he calculated the circumference of the earth exactly - with reference to today's WGS 84 value. If, however, Eratosthenes meant any “other stadium”, his calculations are accordingly incorrect. Contemporary geodesists , such as the Berlin professor Dieter Lelgemann , assume that Eratosthenes actually calculated 252,000 × 600 × 0.2646 m, i.e. 360 × 3600 × 100 Cyrenean feet for his circumference of the earth.
The modern seven-smooth value of the Cyrenean foot
Modern historical metrology nowadays prefers the arbitrary value of exactly 308,700 µm. It is the seven-smooth multiple of the micrometer that corresponds to the 360,000. Part of a degree of latitude of the WGS 84 - Referenzellipsoides comes closest (with a relative error of less than 0.001%). The value is chosen a posteriori so that the measurement of the earth's circumference by Eratosthenes was as exact as possible. The fact that the value is seven- even avoids the occurrence of arbitrary decimal roundings when converting ancient measurements into SI units. The value is within the scope of the occurring variance also compatible with the statistical surveys of the ancient measures of length.
The ancient Olympic Stadium in Athens , like all Greek stadiums, measures 600 feet. Roman stadiums always measure 625 feet. Based on the seven-smooth value of 308.7 mm, the Athens Olympic Stadium - where the Cyrenean foot was also used - should actually measure 185.22 meters. In fact, it only measures 184.96 meters, i.e. exactly 26 centimeters less. Such minor deviations, here 0.14%, can be observed in general with pre-ancient measurements. In the case of ancient lengths, deviations of more than ± 0.17% are considered to be questionable, or it is then a different dimension with a different derivation.
Since the Kyrenean foot and the foot of the ancient Olympic Stadium in Athens are identical, the Kyrenean foot is sometimes called the "Olympic foot". This name is unclear, however, as the Olympic foot of the stadium to Olympia is different. This is in connection with the construction remen . Its ratio to the Athens Olympic foot, that is to say to the Cyrenean foot, is 72: 49√2.
The Kyrenean foot in relation to other units of the foot
The ratio of the Kyrenean to the English foot is exactly 7000: 6912, the latter number being 4 × 12 3 . If you take the English foot as a reference, you get a value for the Kyrenean foot of exactly 2 −3 × 3 −2 × 5 2 × 7 1 × 127 = 308.680 555 millimeters. Conversely, assuming the seven-smooth value of the Kyrenean foot, the result is an English foot increased by 1/15875 to 2 4 × 3 5 × 5 −4 × 7 2 = 304.8 192 mm. In production engineering, 1: 15 875, i.e. plus approx. 0.0063%, is within all tolerance values even in the high-precision range .
The English foot has not been used in science worldwide - including the USA - for many decades, but is still in use in some countries as the last representative of the old, highly composite number systems with their 5000 year old tradition. The legal value of the Austrian foot is only about 1/40 millimeter or 0.009% shorter than 128: 125 seven-smooth Kyrenean feet, while the old, widespread Rhine foot, 64:63 Kyrenean foot, later also called Prussian foot , here 0.25 Millimeters or 0.080% longer, which is also very well within the range of the old precision.
