History of measurement of time

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History of measurement of time by Mind Map: History of measurement of time

1. Sundial

1.1. Shadow clock

1.1.1. http://www.gmat.unsw.edu.au/currentstudents/ug/projects/yj/sundial.htm

1.2. Egyptians

1.3. 1500 BC

1.4. Better accuracy than obelisks

1.4.1. Sharper shadow line

1.4.2. Larger sundial

2. Obelisks

2.1. Egyptians

2.2. 3500 BC

2.3. Cast shadows from the sun

2.3.1. Years shortest day

2.3.2. Years longest day

3. Using Sun

4. Using Stars

4.1. Egpytians

4.1.1. Improved sundial

4.1.2. Merkhet

4.1.2.1. Oldest astronomical tool

4.2. 600 BC

4.3. String and weight on the end

5. Using Water

5.1. Clepsydras

5.2. Oldest found in tomb

5.2.1. Egyptian King Amenhotep I

5.2.2. 1500 BC

5.3. 325 BC

5.3.1. Greeks started using

5.4. Regular dripping of water

5.4.1. Narrow opening

5.4.2. Accumulate water in a reservior

6. Mechanical Clocks

6.1. Medieval Europe

6.2. Wheels and gears turn by weights

6.3. Pointer attached to wheels marked the hours

6.4. http://www.fi.edu/time/Journey/Time/Escapements/inmechanclk.html

6.5. Sprint powered clocks

6.5.1. Peter Henlein of Nuremberg

6.6. 1582

6.6.1. Galileo

6.6.2. Pendulum used to measure small amount of time interval

6.7. 1721

6.7.1. George Graham

6.7.2. Pendulum accuracy to within a second a day

7. Quartz Clocks

7.1. Electric property of quartz crytsal

7.2. Interaction between the mechanical stress and electrical causes the crystals to vibrate

7.3. First digital watch ever

7.3.1. Black Watch

7.3.2. 1975

7.3.3. Sinclair company