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 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 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 1960 and 1991)
1790 – French Academy of Sciences created the metric system 3 Requirements
# 1 Basic Standard = Earth unit of length is portion of Earth's circumference
#2 Internal Consistency Units for capacity (volume or space) and mass related to unit of length
#3 Ease of Use - Calculations Larger and smaller units created by multiplying or dividing basic units by factors of 10
Fundamental (Base) Units Based on object/event in nature SI system has 7 fundamental units Probably already know 4 of them Any guesses as to which ones you know?
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 meter = decimeter (dm) 1/100 of meter = centimeter (cm) 1/1000 of 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 used for all 7 fundamental units! Kilometer Milliliter Centigram Microsecond Nanokelvin
1790 - Jefferson Proposed decimal-based measurement system for United States Didn’t use prefix idea & 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 of: 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 = 100C = 373 K mp of H2O = 0C = 273 K
What is a mole? amount any substance that has as many elementary particles as number of atoms found in 0.012 kilogram of carbon-12
Prototype kilogram stored in vault in France