Earth's circumference mile in the seventeenth century and the metre in the eighteenth. Earth's polar circumference is almost exactly 40,000 km because the metre was originally calibrated on this measurement (1/10-millionth of the distance between the poles and the equator), which is almost exactly 21,600 nautical miles (being defined as one minute of a degree – i.e. 360 multiplied by 60). It has been described as "the single most important measurement" of the Earth, assuming the Earth to be a sphere (the Earth is an technically an ellipsoid, albeit with just 0.3% flattening). Earth's circumference lines are the foundation of the coordinate
Theory of conjoint measurement to some kind of unit difference. Each level of "P" is a difference between the levels of "A" and "X". However, it is not clear from the literature as to how a unit could be defined within an additive conjoint context. proposed a scaling method for conjoint structures but he also did not discuss the unit. The theory of conjoint measurement, however, is not restricted to the quantification of differences. If each level of "P" is a product of a level of "A" and a level of "X", then "P" is another different quantity whose measurement is expressed as a