Measurement is a process to attach a numerical value to an observation. This is done to be able to compare or order two or more such observations. Units of Measurement provide standards to compare against. For example, the metre is the standard unit to measure length. Before 1982, it was defined as the distance between two markers on a certain rod. Now scientists define the metre as the distance light travels in a certain time, in vacuum.Saying something has a length of 2 metres therefore means that it is exactly twice as long as that rod used to define the metre, or that light takes twice the time defined for a metre to travel that distance.This also makes it easy to say that something that is 3 metres long is longer than something else, that is only 2 metres long.Today, most units of measure fall into one of two systems. The older, imperial system uses the foot as a mesure of length, the pound as a mesure for weight and the second as a measure for time. There are other units as well. Most of the time 12 or 16 of the smaller unit make the bigger unit. This is difficult to remember, so there is
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