![]() ![]() Modern physics has depended on various standards of distance, defining a meter in 1960 as the distance between two ends of a particular platinum-iridium bar stored under controlled conditions and in 1983 as the distance traveled by light in a vacuum in 1 / 299,792,458th of a second. 1120 the king of England declared that the standard of length would be called a yard, defined by the distance from the tip of his nose to the end of his outstretched arm. These standards have changed over of the history of measurement. ![]() For physical properties, this problem has been successfully handled by simply defining the three basic units of measurement (length, mass, and time) according to agreed-upon standards. ![]()
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