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15-4 Metric Measurements CH 15]

weights and measures. It was decided that the new system would be based on a natural physical unit
to ensure immutability (unchanging over time or unable to be changed.). The academy settled on the
length of 1/10,000,000 of a quadrant of a great circle of Earth, measured around the poles of the Immutability:
meridian passing through Paris; this is a longitudinal line. An arduous six-year survey led by, French Unchanging over
luminaries of their day, Jean Delambre, Jacques-Dominique Cassini, Adrien-Marie Legendre, and time or unable to
Pierre Mechain to determine the arc of the meridian from Barcelona, Spain, to Dunkirk, France, as be changed.
these two cities lie on the same longitudinal line, a meridional quadrant of the earth, and eventually
yielded a value of 39.37008 inches for the new unit to be called the “metre” (“meter” in the U.S.),
from Greek metron, meaning “measure” or “to measure.” Along with the Academy’s findings the
National Assembly also stipulated that their final solution should be at once simple, yet scientific.
Borrowing from Mouton, the commission established three basic principles:
1. The unit of length would be equal to a portion of the Earth's circumference. Meridian: A line
2. Measures for volume and mass would be derived from length, thereby ensuring between the poles
all units would have a relationship. with the same
longitude. A
3. Larger and smaller multiples of each unit would be created by multiplying and geographic
dividing by 10 and its powers. meridian, a line of
longitude, is the
This first incarnation of the metric system was officially adopted by France in 1795. Four years half of an
later, scientists fashioned standards for the meter and kilogram out of platinum. These, too, were imaginary great
circle on the
officially recognized by the French government and stored in a safe place so copies could be made as Earth's surface,
needed. terminated by the
In comparison, and as a reminder, the US Standard Units or the English system of measurement North Pole and the
include: South Pole,
 Length or distance in inches, feet, yards, and miles. connecting points
 Capacity or volume in fluid ounces, cups, pints, quarts or gallons. of equal longitude,
as measured in
 Weight or mass in ounces, pounds and tons. angular degrees
east or west of the
Terminology in the Metric System Prime Meridian.
Metric Prefixes
The metric system of measurement uses similar prefix terms for length (distance - meter), capacity
(volume - liter) and weight (mass - gram). The metric prefixes are a continuum to delineate small
units and big units of measure from a defined base unit.

Base
Kilo Hecto Deca Deci Centi Milli
unit

Bigger Units Smaller Units
Figure 15.2 To measure smaller or larger quantities, we use prefix
units derived from the metric units

There are units greater than the kilo such as those with the prefix’s of mega, giga and tera. Kilo
means 1,000, as a mega is 1,000 times of kilo. A giga is 1,000 times of mega and a tera is 1,000
times of a giga. You are probably familiar with these terms as they are used in computer memory for
RAM and hard drive configurations.

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