Definitions of TimeDefinitions of Time

Newton:Newton: “I do not define time, space, place and “I do not define time, space, place and motion, as being well known to all”motion, as being well known to all”

Time (Merriam–Webster dictionary):Time (Merriam–Webster dictionary): A period A period during which an action, process, or condition during which an action, process, or condition exists or continues.exists or continues.

Period (Merriam–Webster dictionary):Period (Merriam–Webster dictionary): An An extent of time. extent of time.

DefinitionsDefinitions of Distance of Distance

Newton:Newton: “I do not define time, space, place and motion, as “I do not define time, space, place and motion, as being well known to all.”being well known to all.”

Length (MW):Length (MW): a measured distance or dimension a measured distance or dimension

Distance (MW):Distance (MW): a measure of separation in space a measure of separation in space

Measure (MW):Measure (MW): the dimensions . . . of something ascertained by the dimensions . . . of something ascertained by measuringmeasuring

Dimension (MW):Dimension (MW): measurement of extension (as in length) measurement of extension (as in length)

““God’s Coordinate System”God’s Coordinate System”

““Absolute, true, and mathematical time . . . flows Absolute, true, and mathematical time . . . flows equably without regard to anything external; relative, equably without regard to anything external; relative, apparent, and common time is some sensible and apparent, and common time is some sensible and external measure of (time) by the means of motion, external measure of (time) by the means of motion, which is commonly used instead of true time; such as which is commonly used instead of true time; such as an hour, day”an hour, day”

““Absolute space . . without regard to anything external, Absolute space . . without regard to anything external, remains always similar and immovable. Relative remains always similar and immovable. Relative space is some movable dimension or measure of the space is some movable dimension or measure of the absolute spaces . . . Absolute and relative space, are absolute spaces . . . Absolute and relative space, are the same in figure and magnitude”the same in figure and magnitude”

Evolution of the meterEvolution of the meter

1 meter = 1 ten–millionth of the distance from the 1 meter = 1 ten–millionth of the distance from the equator to the North Poleequator to the North Pole

Distance between scratches on a bar kept in Serves, Distance between scratches on a bar kept in Serves, FranceFrance

1,650,763.73 wavelengths of orange light from 1,650,763.73 wavelengths of orange light from 8686Kr.Kr.

One inch = 2.54 cm One inch = 2.54 cm exactlyexactly

EvolutionEvolution of the second of the second

One second = 1/86,400 of a dayOne second = 1/86,400 of a day

Amount of time it takes a pendulum one meter long to Amount of time it takes a pendulum one meter long to swing from one side to the otherswing from one side to the other

9, 192, 631, 770 transitions between the hyperfine levels 9, 192, 631, 770 transitions between the hyperfine levels in in 133133Cs. (1967)Cs. (1967)

Means one Means one 133133Cs vibration is 109 ps (picoseconds)Cs vibration is 109 ps (picoseconds)

Derived Derived QuantitiesQuantities

Speed = distance Speed = distance ÷ time ÷ time

Acceleration = speed ÷ timeAcceleration = speed ÷ time

Force = mass × acceleration (Newtons)Force = mass × acceleration (Newtons)

Energy = Force × distanceEnergy = Force × distance

Speed of light is Speed of light is specialspecial

c = 3 c = 3 × 10× 1088 m/s = 186,000 miles/sec m/s = 186,000 miles/sec (measurement)(measurement)

Define c ≡ 299, 792, 458 m/s Define c ≡ 299, 792, 458 m/s exactlyexactly

One meter is distance light travels in One meter is distance light travels in 1/299,792,458 seconds ( = 3 ⅓ ns )1/299,792,458 seconds ( = 3 ⅓ ns ) ( = 30.66 ( = 30.66 133133Cs vibrations). Cs vibrations).

Modern Definitions of StandardsModern Definitions of Standards

1 second1 second = 9, 192, 631, 770 transitions in = 9, 192, 631, 770 transitions in 133133CsCs

Speed of lightSpeed of light = 299, 792, 458 m/s = 299, 792, 458 m/s ≈ 3 × ≈ 3 × 101088 m/s. m/s.

1 kilgoram1 kilgoram is the mass of a standard bar in France is the mass of a standard bar in France

1 meter1 meter = distance light moves in = distance light moves in ≈ 3⅓ ns. ≈ 3⅓ ns. (derived)(derived)