Petition For Metric In US Halfway To Requiring Response From the White House

Metric is every bit as arbitrary as imperial, it's just a bit easier to do unit conversions with them.

The metric system is not arbitrary. There is only one unit each of length, mass, volumes, etc. It is also coherent.

Coherence"

"Each variant of the metric system has a degree of coherence ? the various derived units being directly related to the base units without the need of intermediate conversion factors. For example, in a coherent system the units of force, energy and power are chosen so that the equations

? ? ? ? force = mass ? acceleration
? ? ? ? energy = force ? distance
? ? ? ? power = energy / time

hold without the introduction of constant factors. Once a set of coherent units have been defined, other relationships in physics that use those units will automatically be true - Einstein's mass-energy equation, E = mc2, does not require extraneous constants when expressed in coherent units.[18]

The cgs system had two units of energy, the erg that was related to mechanics and the calorie that was related to thermal energy so only one of them (the erg) could bear a coherent relationship to the base units. Coherence was a design aim of SI resulting in only one unit of energy being defined - the joule.[19]

In SI, which is a coherent system, the unit of power is the "watt" which is defined as "one joule per second".[20] In the US customary system of measurement, which is non-coherent, the unit of power is the "horsepower" which is defined as "550 foot-pounds per second" (the pound in this context being the pound-force), similarly the gallon is not equal to a cubic yard (nor is it the cube of any length unit).

The concept of coherence was only introduced into the metric system in the third quarter of the nineteenth century; in its original form the metric system was non-coherent - in particular the litre was 0.001 m3 and the are (from which we get the hectare) was 100 m2. A precursor to the concept of coherence was however present in that the units of mass and length were related to each other through the physical properties of water, the gram having been designed as being the mass of one cubic centimetre of water at its freezing point."

http://en.wikipedia.org/wiki/Metric_system [wikipedia.org]

Source: http://rss.slashdot.org/~r/Slashdot/slashdotScience/~3/YgL3ZZjDPhw/story01.htm

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