1. The Metric System
Simple & Consistent

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

3. 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

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

5. 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!

6. 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 and 1991)

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

8. # 1 Basic Standard = Earth
unit of length is portion of Earth's circumference

9. #2 Internal Consistency
Units for capacity (volume or space) and mass related to unit of length

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

11. 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?

12. 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

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

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

15. 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)

16. 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 
micro
nanometer
10-9 n
nano

17. Prefixes used for all 7 fundamental units! Kilometer Milliliter
Centigram
Microsecond
Nanokelvin

18. Jefferson
Proposed decimal-based measurement system for United States
Didn’t use prefix idea & 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 distance from North pole to equator
1983: distance light travels in vacuum in 1/299,792,458 th of second

21. 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

22. 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

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

24. 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

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

26. Prototype kilogram stored in vault in France