1. Metric System
Simple & Consistent

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

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
allows for parts of a whole
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 (major changes in 1960 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/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
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

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)

17. 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

18. Prefixes used for all 7 fundamental units! kilometer milliliter
centigram
microsecond
nanokelvin

19. 1790 - Jefferson proposed decimal-based measurement system for US
cons:
no prefixes
& too many
names

20. 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

21. 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

22. 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

23. 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

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

25. 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

26. What is a mole?
amount any substance that has as many particles as # atoms found in kg of carbon-12

27. prototype kilogram stored in vault in France