The History of

TimekeepingKaren Isabelle SoaresKarla Natalia Queiroz

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Using the Sun

noon

sunsetsunrise

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Sundial Clocks

Oldest type of clock Also called sun

clocks

The shadow points to a number

Depend on the sun

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Water Clocks Around 4,000 B.C. Babylon, Egypt, India or China Water traveled through a tube Tell time during the night

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Dividing the Year into Months

12 Moon cycles in a year Greeks divided the year in 12 months

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Dividing the Year into Days

They divided the month in 30 days 360 Days in a year 360 Degrees in a circle

90°

180°

270°

360°

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Dividing the Day into Hours Egyptians and Babylonians Sunrise to sunset in 12 hours, sunset to sunrise also in

12 hours Whole day in 24 hours

+

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Minutes and Seconds

Sumerian Sexagenary Sistem

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Mechanical Clocks

Invented in medieval Europe

Common in churches and monasteries

“Clock” is from the Latin word “clocca”

One time-keeping hand

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Spring-powered Clocks Around 1500 Became very popular among the rich Was the precursor to accurate timekeeping

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Pendulum Clocks Developed by Christian Huygens around 1656 Pendulum clock had a minute hand Used to swing a lot (about 50 degrees) They stopped running after a while and had to be

restarted

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Quartz Crystal Clocks Based on an electric property of the quartz crystal When you apply voltage, or electricity, and pressure, the

quartz crystal vibrates or oscillates at a very constant frequency.

Very precise

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Time Zones In 1884, delegates from 25 countries divided the world

into time zones. The delegates divided the 360 degrees of the Earth into

24 zones of 15 degrees each. In the United States, there are four time zones: Eastern,

Central, Mountain, and Pacific.