Metric System Simple & Consistent

Measurement up to 1790: not a pretty picture! measurement requires a recognizable standard for all but… until 1790’s every region had own standards

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 allows for parts of a whole 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 (major changes in 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/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 UNIT 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 US cons: no prefixes & too many names

1792 – U.S. Mint produced world’s first decimal currency (one dollar = 100 cents) 100 cents in dollar 4 quarters in dollar 10 dimes in dollar 20 nickels in dollar can see how this can be confusing: names not related to each other no consistency with parts of dollar

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 defined now 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 any substance that has as many particles as # atoms found in 0.012 kg of carbon-12

prototype kilogram stored in vault in France