GREEK PACE = 2½ FEET ROMAN PACE = 5 FEET

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3 HAND

4 296 mm

5 GREEK PACE = 2½ FEET ROMAN PACE = 5 FEET

6 1000 (MILLE) PACES = 1 MILE (5000 FEET)

7 QUEEN ELIZABETH I CHANGED THE MILE FROM 5000 FEET TO 5280 FEET 5280 FEET = 40 FURLONGS

8 1 ACRE Amount of land that could be ploughed in 1 day. 22 yards x 220 yards Each furrow is 220 yards 220 yards is 1 furrow long 1 furlong

9 1 YARD Finger-tip to nose Yard / 2 = half-yard Yard / 4 = span Yard / 8 = hand Yard / 16 = finger

10 1 BARN Area of Uranium nucleus square metres kilo-barn mega-barn milli-barn micro-barn ( Outhouse ) yocto-barn ( Shed )

11 ENGLISH MILE 5280 FEET SCOTTISH MILE 5952 FEET IRISH MILE 6720 FEET COUNTRY MILE INDETERMINATE USUALLY LONGER THAN ANY MEASURED MILE

12 It s just a mile and a bit!

13 Seeds are of a consistent size Step 1 Fill with seeds Step 2 Count the seeds

14 Carob seed Greek: kerátion Modern: Carat

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16 Comparison to a known weight on a balance. Easy to cheat. System of Inspections. System of standards

17 Pound Latin: Pondus = Weight Slug = lbs (1 standard gravity = ft/s) Stone = 14 lbs lb unit : Roman Libra = standard weight 325g

18 Day & Night Morning & Afternoon High & low tide

19 Day & Night Morning & Afternoon High & low tide Coffee or Wine

20 Need to reference a more specific time of day. Sundial Water clock Hour glass

21 The DAY was divided into 12 hours, being easily divisible by 2, 3, 4 & 6 Thus the 3 rd hour, the 6 th hour and the 9 th hour were mid-morning, noon and mid-afternoon.

22 14 th century clockwork 1 hour = 1 day/24 Babylonian base 60 Divisible by 2,3,4,5,6,10 &12 Latin: pars minuta prima (first very small part) pars minute secunda (second very small part) = Minutes & seconds

23 I ll be there in a jiffy!

24 I ll be there in two shakes! A SHAKE in one step in a nuclear reaction. About 10 billionths of a second.

25 Atomic Clocks (suggested by Lord Kelvin in 1879) Accurate to 1 in (1 second in 31 million years)

26 Why do we need accurate time? Navigation Latitude: Use the sun, moon or stars Longitute: Need the time of day 17 th century clocks had to be adjusted daily. Conditions at sea made them worse.

27 John Harrison H2 39 kg 50 years to develop H1 34 kg H4 1.4 kg Lost 5.1 seconds in 81 days H3 Bimetallic strip Caged roller bearing

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29 1 metre 1 Pascal 1 Newton per square metre

30 Early thermometers used alcohol. But Non-linear expansion. In-accurate over wide range.

31 1714 Gabriel Fahrenheit made tubes thin enough to use mercury. His design became the standard.

32 HOW MANY DEGREES? HUMAN BODY TEMPERATURE ISAAC NEWTON 12 FREEZING POINT OF WATER

33 HOW MANY DEGREES? HUMAN BODY TEMPERATURE DANIEL FAHRENHEIT 12 SECTIONS OF 8 DIVISIONS = 96 F FREEZING POINT OF BRINE

34 HOW MANY DEGREES? BOILING POINT OF WATER 212 F DANIEL FAHRENHEIT 32 F FREEZING POINT OF WATER

35 HOW MANY DEGREES? BOILING POINT OF WATER ANDERS CELCIUS 0 C 100 C FREEZING POINT OF WATER

36 HOW MANY DEGREES? BOILING POINT OF WATER 100 C CARL LINNAEUS 0 C FREEZING POINT OF WATER

37 HOW MANY DEGREES? BOILING POINT OF WATER 100 C TWO CENTURIES BEFORE INTERNATIONAL ACCEPTANCE IN THE 1960s 0 C FREEZING POINT OF WATER

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39 QUALITATIVE THE MOON IS VERY BRIGHT COMPARITIVE YOUR EYES ARE AS BRIGHT AS THE MOON

40 1860s LIGHT MEASUREMENTS BY COMPARISON RUMFORD RITCHIE

41 MID 20 th CENTURY ELECTRONIC LIGHT MEASUREMENTS WERE NOW SUBJECTIVE BUT NEEDED A UNIT INTENSITY CANDLEPOWER BY COMPARISON TO A STANDARD CANDLE ILLUMINANCE FOOT-CANDLE COMPARISON TO A CANDLE 1 FOOT AWAY

42 THESE UNITS WERE REFINED AND REDEFINED INTENSITY CANDELA The luminous intensity, in a given direction, of a source that emits monochromatic radiation of frequency hertz and that has a radiant intensity in that direction of watt per steradian. ILLUMINANCE LUX 1 lumen per square meter LUMEN 1 candela times angle (sr) (Roughly the light emitted by 1 candle)

43 A FOOT-CANDLE

44 Alessandro Volta Michael Faraday Georg Ohm Andre-Marie Ampere Charles Coulomb

45 LEYDEN JAR

46 LEYDEN JAR

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50 NOT RELATED TO A COUNTRY EASILY REALISED BASED ON A NATURAL MEASUREMENT

51 1791 metre = 1/ th of ¼ of a terrestrial median

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53 Triangulation measurements from Dunkirk to Barcelona by Pierre-François Mechain & Jean-Baptiste Delambre

54 1 metre 1 decimetre 1 litre 1 kg 1 dm 3 1 litre water kilogram greek/latin one thousand small weights

55 1799 ARCHIVES OF THE REPUBLIC DEDICATED TO ALL MEN AND ALL TIMES

56 METRE REDEFINED 1960: ,73 times the wavelength of orange radiation from the krypton 86 atom in vacuum. 1983: the distance travelled by light in vacuum in 1/ of a second.

57 B.I.P.M RESEARCH INTO OTHER FIELDS

58 B.I.P.M RESEARCH INTO OTHER FIELDS

59 KILOGRAM REDEFINED In terms of the Plank constant. Two methods: Number of atoms in a silicon sphere. Watt balance. Redefinition scheduled for the General Conference on Weights and Measures in 2018

60 UNITY AT LAST 2018 all SI units will be defined in terms of fundamental quantities of nature SI units are internationally accepted at least by the science and engineering communities.

61 TRADITIONS DIE HARD

62 TRADITIONS DIE HARD

63 Cheers!

64 GUY SNELLING INTERCAL CALIBRATION WHERE IT COUNTS

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