The Metric System

1. Simple & Consistent The Metric System

2. Measurement up to 1790:Not a pretty picture! • Measurement requires a standard and until about the 1790’s every region had it’s own standard

3. Standards • “A standard is something that is used as a comparison for measuring” • The standard must be available for everyone to use to check measurements • means a standard should be something in nature that is the same all over the earth • The standard must never vary

4. 1585 – Simon Stevin • Introduced the use of decimals in mathematics in Europe • Predicted the universal introduction of decimal coinage, measures and weights

5. 1670 – Gabriel Mouton • 1st to propose the decimal system of measurement based on the size of the earth • Earth-based standard: 1 of longitude The earth is a standard available to everyone! What an idea!

6. Systeme International (SI) • Based on the 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 in 1960

7. 3 Requirements 1790 – French Academy of Sciences created the metric system

8. Basic Standard = Earth • The unit of length was to be a portion of the Earth's circumference

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

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

11. 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?

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

13. Derived Units • Combinations of fundamental units • Many, many derived units • Examples: • Speed or meters/second • Area or Length X Width • Volume or Length X Width X Height • Density or Mass / Volume

14. Ease of Use - Names Larger & smaller multiples of each unit named by a series of prefixes relating them to the base unit

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

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

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

18. 1790 - Jefferson • Proposed a decimal-based measurement system for the United States • Didn’t come up with the prefix idea and his system had too many names

19. 1792 – U.S. Mint • Produced world’s first decimal currency (one dollar = 100 cents)

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

22. What is a Liter? • Liter defined as cube measuring 10 centimeters on each side, or 1000 cm3 • Liter based on meter, which is based on Earth 10 cm 10 cm 10 cm

23. What is a kilogram? 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

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

25. What is a kelvin? The 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

26. What is a mole? • amount of substance which has as many elementary particles as there are atoms in 0.012 kilogram of carbon-12

27. Prototype kilogram in France