Technikatörténeti szemle 9. (1977)

A MÉRÉS ÉS A MÉRTÉK AZ EMBERI MŰVELŐDÉSBEN című konferencián Budapesten 1976. április 27–30-án elhangzott előadások I. rész - Bowsher, H. F.: Régi mértékegységek fejlődése

of the earth's role and the sacredness of the circle or sphere. The most elaborate Greek model was proposed by Ptolemy. This model contained epicycle orbits which are generated by rolling circles on circles and also by assuming the earth need not be located at the center of a circle contained in the epicycle orbit of the celestial objects. This approach was attractive since it did not challenge many of the ancient concepts and yet so powerful that it ruled supreme for over a thousand years. Since Greek models of the universe did not challenge the basis on which previous metrology was developed, they introduced units highly related to former units. Consider, for example, the cubit of Propylae wich has the proposed value of 18.6624 English inches. This is 1/100,000,000 of the distance around the earth at the latitude which passes through the Temple of Propylae. It appears that this cubit has a geographical significance. Even Copernicus, who challenged the unique position of the earth within the solar system, and Kepler, who challenged the sacredness of the circle or sphere, did not introduce the philosophical concepts whicht will ultimately restructure metrology. Newton introduced the idea of a gravitational force as more fundamental than planetary motions since planetary motions are consequences of this force. Suddenly planetary motions seem to have no more significance than the motion of any other object. This radical concept has not yet found full expression in metrology. The metric system which is an improvement over previous systems is still rooted in the earth's dimensions. Philosophies developed recently are beginning to force changes in metrological thinking. The wavelength of a certain spectrum line of a certain excited gas is presently believed to have a more profound significance as a primary unit of length than some fraction of the earth's circumference; however, the forces opposing change have successfully resisted the introduction of a metrological system in which such a wavelength would be assigned a convenient value. The forces for retaining much from ancient metrology have been shown to be strong but the forces resulting from advances in scientific concepts and technological capabilities are persistent. Tables of Proposed Metrological Values The following tables contain proposed values of selected ancient units. The list is not intended to be complete but illustrates results which were obtained when the rules mentioned earlier were used in re-establishing the magnitudes of ancient units. It is apparent that the following metrological values are highly correlated. Certain ratios occur frequently between units of the same type as well as between units of different types when magnitudes are expressed in English units. A study of less rigidly defined ancient length units such as a day's journey, a day's march, a ship under oars and a ship under sails had indicated to me that these units were not uniquely defined; however, they were also not completely dependent on the weather, the physical condition of the traveler, terrain,