Helicobacter pylori
The History of Measurement
Measurement
Measurement:
• the assignment of numbers to objects or events
• a type of quantitative observation made with a
measuring instrument
• includes both a number and a unit
The following physical properties can be measured:
 Length, Width, Height
 Mass (Weight)
 Volume (Capacity)
 Etc.
 Temperature
 Electric charge
 Density
 Viscosity
History of Measurement
• Measuring is an important part of everyday life.
• Objects were initially measured for convenience,
to aid commerce and prevent fraud.
• Early measurements were based on body parts
or common objects.
• The Egyptians among other civilizations were the first to
begin recording measurements (around 3200 B.C.)
Units of measurement are essentially arbitrary:
people make them up and then agree to use them.
Historical Units of Length
 Digit: the breadth of a finger
(Egyptian)
 Barleycorn: the length of a
barleycorn seed
 Inch: the width of a man’s
thumb or 3 barleycorns
 Foot: the length of a man’s foot
 Cubit: elbow to fingertip length
(Egyptian)
 Yard: nose to fingertip
 Mile: 5000 pedes (feet, Roman)
 League: 7500 pedes
Historical Units of Mass/Volume
 Grain: the weight of a
grain of wheat or
barleycorn
 Pound (libra): ~5000
grains (Roman) or
~7000 grains (English)
 Talent: 100 libra
 Stone: 14 pounds
(English/British)
 Troy Ounce: 1/12 of a
pound
 Carat: weight of a
carob seed
The Cubit
The cubit is the measure from your elbow
to the tip of your middle finger when your
arm is extended.
The cubit was the
measurement used
by the Egyptians to
build the pyramids.
The Palm
The palm is the width of your four fingers
when they are placed together.
The Fathom
The fathom is the measure from fingertip to fingertip
when your arms are stretched sideways as far as they
will go.
The fathom was used by sailors to measure the depth
of water so that boats would not run aground.
The Hand-span
The hand-span is the measure
from the tip of your pinky to
the tip of your thumb when
your hand is stretched out.
Hand-span was used
to measure the
height of horses.
People still describe
horses as being so
many hands high.
The Pace
The pace is the measure of distance from one step
to another. This unit was used by the Roman army
to judge speed.
The term is
still used
frequently
during
various
types of
foot races.
The Foot
A measurement equal to the
length of an individuals foot.
Feet are different…
King Henry I of England
defined a standard for
this measurement:
his foot was 12 inches long.
The Girth
The girth was the measurement around
one’s stomach (your belt measure).
Girth was used to
measure fishing line.
The term (not unit) is
still used by US Post
Office and refers to
package dimensions.
The Acre
The acre (“field” in Saxon) was a unit of area
equal to the size of a field that a farmer could
plow in a single day.
French word for acre means “day” and the German word
means “morning” or “day’s work”.
Problems with Early Measurement Systems
1. People have different sized body parts, as well as
there is a variety among common objects like grains.
Grain, India
Wheat
Barleycorn
2. Measurements are not accurate when dealing with
fractions.
Accuracy and Precision
• Accuracy is how close
a measured value is to
the actual (true) value.
• Precision is how close
the measured values
are to each other
(repeatability and
reproducibility).
• Bias is a built-in
(systematic) error
which makes all
measurements wrong
by a certain amount.
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Standard Measurement Systems
• Standard Systems are based on some standard
to measure against.
• Early standard systems often used body parts of the king
or ruler as the standard. When the king died, a new
measurement system would be created…
• 17th-18th century: apparent necessity for standardization
of weights and measures between nations who traded
and exchanged scientific ideas.
• At that time, every country had their own “standard”
system of weights and measures. England had three
different systems just within its own borders!
English Units Based Systems
• Imperial System of Measurement
(British Empire, 1824):
 Distance/Length: Inch, foot, yard, mile
 Volume: fluid ounce, pint, quart, gallon
 Area: Acre
 Weight/Mass (three different systems!): grain,
ounce, pound, ton
• US Customary System of
Measurement:
 Mostly same unit names
 Units are not identical! (1 US
gal=0.83 imp gal)
 Different units for liquid and dry
measures (liquid/dry ounce)
The Metric System
The metric system is an internationally agreed decimal
(based on power of 10) system of measurement.
It was originally introduced by France in 1799.
Modern "Metric system" term
is a synonym for "SI" or the
"International System of Units“
(1960)—the official system of
measurement in almost every
country in the world.
Metric System Basics
• The metric system was built around three base units
that corresponded to a certain kind of measurement:
 Length = meter
 Volume = liter
 Weight (Mass) = gram
• Decimal multiplicative prefixes were added to base
units to make up the full range of metric system:
 Milli + meter = millimeter
 Kilo + gram = Kilogram
• Historically, prototypes of base units were kept in the Archives
Nationales in France with copies manufactured and distributed
among other 17 countries - members of The Metre Convention
of 1875.
Decimal System
• The decimal numeral system (also called “base ten”) has ten
as its base and is most widely used by modern civilizations.
•
Decimal notation is the writing of numbers in a base-10
numeral system:
• A forerunner of modern European decimal notation was
introduced by Simon Stevin in the 16th century.
Example: 73.248 =
• In the Metric System, multiples and sub-multiples of all units
follow a decimal pattern.
US Customary/Imperial
Metric
1 foot = 12 inches
1 yard = 3 feet
1 mile = 1760 yards
1 centimeter = 10 millimeters
1 meter = 100 centimeters
1 kilometer = 1000 meters
Area
1 sq. foot = 144 sq. inches
1 sq. yard = 9 sq. feet
1 acre = 4840 sq. yards
1 sq. centimeter = 100 sq. millimeters
1 sq. meter = 10000 sq. centimeters
1 sq. kilometer = 100 hectares
Mass
1 ounce = 437.5 grains
1 pound = 16 ounces
1 stone = 14 pounds
1 gram = 1000 milligrams
1 kilogram = 1000 grams
1 tonne = 1000 kilograms
1 cu foot = 1728 cu inches
1 cu yard = 27 cu feet
1 pint = 20 fluid ounces
1 gallon = 8 pints
1 cu decimeter = 1000 cu centimeters
1 cu meter = 1000 cu decimeters
1 liter = 1 cu decimeter
1 hectoliter = 100 liters
Length
Volume
Conversion of Units
• For the same quantity measured, we can convert
units using an equivalence statement which shows
the relationship between the units (called conversion
factor):
 within a certain system of units
 in different systems of units
• Within the Imperial System, equivalence statements
do not follow any regular pattern.
• Consequently, conversion factors from the Imperial
System to the Metric System and vice versa do not follow
a regular pattern either…
• Within the Metric System itself, by design, conversion
factors are always a power of 10.
US Customary/Imperial
Metric
Metrication of the World
France, 1st
not yet!
Currently USA is the only country (and perhaps also Burma
and Liberia) that does not use Metric System.
Metric System in the USA
• The metric system has been officially
sanctioned for use in the United States
since 1866, but it remains the only country
that has not fully adopted the metric system
as its official system of measurement.
• Metric System was only partially adopted,
mostly in Science (but not Manufacturing…).
How good is “partially”?
Gimli Glider
July 23, 1983: Air Canada Flight 143
(Boeing 767-233 jet), ran out of fuel
at an altitude of 41,000 feet (12,000
m), about halfway through its flight
from Montreal to Edmonton.
The crew were able to glide the aircraft
safely to an emergency landing at Gimli
Industrial Park Airport. None of the 61
passengers were seriously hurt.
Investigation: fuel loading
was miscalculated due to a
misunderstanding of the recently
adopted metric system which
replaced the imperial system.
destination
origin
Loss of NASA orbiter
NASA's Mars Climate Orbiter
lost on September 23, 1999.
Cost: $125 million.
The spacecraft insertion trajectory
came too close to the planet; the
Orbiter disintegrated upon entering
the upper Martian atmosphere.
For a key spacecraft operation,
Lockheed Martin engineering team
used Imperial units of measurement
while the NASA's team used more
conventional Metric system…