James Freysinger in USMA 15437 wrote an excellent letter to National Geographic, but I must quibble with your physics.
>By clinging to your obstinate use of obsolescent units you missed out >on the chance to point out that this very speed of light quantity is >now the basis for the definition of the global unit for length--the >meter. That, with the use of light to define the second, would have >made an interesting point in the section, namely, two of the seven base >units in the modern metric system are based on measurements of light. >And yet a third base unit is defined for the sake of measuring the >luminous intensity of light. Three out of seven is a pretty good score >in my book! The second was determined by astronomical observatiions, without reference to the speed of light. The speed of light was determined by reference to the metre and the second. In 1983 the Conf�rence g�n�rale des poids et mesures inverted this relation and defined the metre in terms of the speed of light. Joseph B. Reid 17 Glebe Road West Toronto M5P 1C8 Tel. 416 486-6071
