metric+system

Quantitative observation did not have a well-established, standardized system until the late 1600's.

This arrived in the Middle Ages in Europe with the invention of the metric system.
 * One of the more important books preceding the metric system was "[|The Tenths]", written by Simon Stevin. He predicted that the development of a uniform system of measurement and currency would occur soon.
 * In 1670, Gabriel Mouton developed a system of measurement that had unit prefixes in powers of ten, and was a precursor to the modern metric system.
 * John Wilkins described the meter and a fully functional metric system of measurement in 1668 in England, of all places, but it was rejected and would not ever be used in England.

Eventually the metric system would be accepted in most European countries, and is now the standard in measurement in almost all countries but England and the US. Having a standard system of measurement allowed scientists to share data and to understand others' experimental results in a much easier fashion.

The modern metric system has a number of //base units//:
 * for distance, the [|meter] (m), which is now defined as the distance light travels in a vacuum in 1/299,792,458 second.


 * for volume, the [|liter] (L), which is actually defined, using the meter, as one cubic decimeter.


 * for mass, the [|gram] (g), defined as the mass of one cubic centimeter of pure water at 4 degrees Centigrade. It is also based on a one kilogram platinum-iridium alloy metal cylinder seen below.


 * for pressure, the [|atmosphere] (atm), defined as the average yearly atmospheric air pressure in Paris, France.


 * for temperature, the [|centigrade] scale (also Celsius), whose reference points are the freezing and boiling points of pure water; also used is the [|Kelvin] scale, which refers to absolute zero and the triple point of pure water. Both are equivalent in scale.


 * for amount, the [|mole], which is based on Avogadro's number: measured as the number of carbon-12 atoms in exactly 12 grams of pure carbon-12, which is equal to 602,214,179,000,000,000,000,000 particles.




 * for energy, the [|Joule], defined as the the work done by the force of one newton over the distance of one meter.

The metric system uses prefixes to alter the scale of the above base units by powers of ten. The following table depicts some important metric prefixes. Here is a Word version of this table:
 * Prefix: || Abbreviation: || Relation to Base (1): || Power of Ten: || Example of its use: ||
 * giga || G || 1,000,000,000 || 10^9 || gigahertz processor ||
 * mega || M || 1,000,000 || 10^6 || megapixel camera ||
 * kilo || k || 1,000 || 10^3 || kilogram ||
 * (base) || (none) || 1 || 1 || gram, liter, meter, etc. ||
 * centi || c || 1/100 || 10^-2 || centimeter ||
 * milli || m || 1/1,000 || 10^-3 || milliliter ||
 * micro || μ || 1/1,000,000 || 10^-6 || micrometer ||
 * nano || n || 1/1,000,000,000 || 10^-9 || nanosecond ||

Check out this interactive Scale of the Universe to help visualize these prefixes.


 * Some Metric to English Comparisons**

__Distance:__ · One meter is roughly one yard · There are about two and a half centimeters in an inch · One mile contains about one and a half kilometers

__Mass:__ · There are a little over two pounds per kilogram · One pound is nearly equal to 500 grams

__Volume:__ · There are about 4 liters in one gallon · One quart is about equal to one liter

__Temperature:__ · The boiling point of water is 212 F, or 100 C, or 373 K  · The freezing point of water is 32 F, or 0 C, or 273 K   · Absolute zero is 0 K, or -273 C, or -460 F

__Pressure:__ · One atmosphere is almost 15 psi

__Energy:__ · There are about 4 joules in one calorie

Here is a worksheet on metric units and prefixes: