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

primary standards for the units should be such that the calibration of the secondary standards can be made without excessive cost or time. A further study, however, suggests that ancient metrology was based on concepts and certain measured magnitudes of nature. Other desirable features were incorporated into their metrology. This is not to imply that all units were carefully defined and had a philosophical basis. Before discussing how ancient metrological units were based on natural philosophies the derivation of the modern definition of temperature will be described. Temperature can be measured or defined in terms of the length, the electrical resistance or any other physical property of a rod which varies with temperature and which can be readily and accurately measured. Such rods could be maintained for long periods in an environment such that the physical property used as the thermometric property would not change significantly. Temperature, however, is not defined in this manner. The reason is that there is no present day philosophical reason to choose one thermometric property over another or one rod material over another. Even though technically such an approach is practical, the lack of a philosophical justification has caused modern men to define temperature in terms of the pressure of an idealized gas or in terms of the efficiency of an idealized engine known as the Carnot engine. The person not familiar with present day theories might be led to conclude that temperature is not uniquely defined theoretically and cannot be determined in practice because unreal objects are required. To the physicist such an abstract way of defining temperature makes great sense because he believes this provides the best conceivable basis on which to structure an overall explanation of nature. This is the optimum choice of this era but not for all time. Man's ability to conceive the abstract, that is a relationship which he feels is perfect but which from his direct interaction appears only imperfectly, has allowed man to conceive of a universe with considerable order or one composed of many symmetries. This feeling of an underlying order may never die. It is not that man can prove it so but that he feels it must be so. The ancient expressed this feeling in animistic or vitalistic philosophies. The modern man expresses it with abstract mathematical symmetry properties or in laws which state that certain abstract entities are conserved. One has only to consider recent efforts of fundamental particle physicists to be convinced that the feeling is still strong that nature is describable in terms of symmetry principles. A discussion will now be given of certain ancient metrological units. The magnitudes assigned to these units were based on the following assumptions: 1. The ancients constructed sets of units related to each other by convenient ratios. 2. The units of one country were often related to those of other countries by simple ratios. Frequently these ratios were complementary fractions or one minus a unit fraction such as 6/7, 9/10, 24/25 and 80/81. The origin of this practice may be with the Egyptians who only had symbols for unit fractions; consequently, complementary fractions could be expressed relatively simply.