The Metric System Simple & Consistent

Measurement up to 1790: Not a pretty picture! Measurement requires standard and until 1790’s every region had own standard

Standards “standard: something used as comparison for measuring” standard must: be available for everyone to use to check measurements be something in nature that is same everywhere never vary

1585 – Simon Stevin Introduced use of decimals in Europe Predicted universal introduction of decimal coinage, measures and weights

1670 – Gabriel Mouton 1st to propose decimal system of measurement based on size of earth Earth-based standard: 1 of longitude The earth is standard available to everyone! What an idea!

Systeme International (SI) based on metric system invented in 1790* Originally, earth-based standards Volume & mass linked to length Larger & smaller multiples of each unit related by powers of 10 *updated every few years (particularly in in 1960 and 1991)

1790 – French Academy of Sciences created the metric system 3 Requirements

Basic Standard = Earth 1. unit of length is portion of Earth's circumference

Internal Consistency 2. Units for capacity (volume or space) and mass related to unit of length

Ease of Use - Calculations 3. Larger and smaller units created by multiplying or dividing basic units by factors of 10

Fundamental or Base Units Based on object or event in nature The SI system has 7 fundamental units You already know 4. What are they?

7 Fundamental Quantities of SI Abbreviation Name Quantity m meter Length kg kilogram Mass s second Time K kelvin Temperature mol Mole Amount of Substance cd candela Luminous Intensity A ampere Electric Current

Derived Units Combinations of fundamental units Examples: Speed (meters/second) Area (Length x Width) Volume (Length x Width x Height) Density (Mass / Volume)

Ease of Use - Names Larger & smaller multiples of same unit named by series of prefixes relating to base unit

Smaller Units 1/10 of a meter = decimeter (dm) 1/100 of a meter = centimeter (cm) 1/1000 of a meter = millimeter (mm) Larger Units 10 meters = dekameter (dam) 100 meters = hectometer (hm) 1000 meters = kilometer (km)

Prefixes in the SI System Use Power Value Symbol Prefix Gigabyte 109 1,000,000,000 G Giga Megamillion 106 1,000,000 M Mega kilometer 103 1,000 k Kilo decimeter 10-1 0.1 d deci centimeter 10-2 0.01 c centi millimeter 10-3 0.001 m milli micrometer 10-6 0.000001  micro nanometer 10-9 0.000000001 n nano

Prefixes prefixes can be used with all 7 fundamental units! Kilometer Milliliter Centigram Microsecond Nanokelvin

1790 - Jefferson Proposed decimal-based measurement system for United States Didn’t have prefix idea and system had too many names

1792 – U.S. Mint Produced world’s first decimal currency (one dollar = 100 cents)

What is a meter? 1790: 1/10,000,000 th of distance from North pole to equator 1983: distance light travels in vacuum in 1/299,792,458 th of second

What is a Liter? defined as cube measuring 10 centimeters on each side (1000 cm3) Liter based on meter, which is based on Earth 10 cm 10 cm 10 cm

What is a kilogram? defined as mass 1 Liter water at 4°C Why water? kilogram is based on liter, which is based on meter, which is based on Earth 10 cm 10 cm 10 cm

What is a second? originally defined as 1/86,400th of average solar day Now: defined in terms of electron transitions in Cs-133

What is a Kelvin? Kelvin is defined in terms of water & absolute zero 0 K = Absolute zero bp of H2O = 100C = 373 K mp of H2O = 0C = 273 K

What is a mole? amount of any substance that has as many elementary particles as the number of atoms found in 0.012 kilogram of carbon-12

Prototype kilogram stored in vault in France