-
1500 BCE
The Sundial
One of the earliest time-keeping devices, the sundial uses the sun to determine time. A primitive form was first used by the Egyptians to measure work hours and shift times. Most forms used some type of shadow casting object to cast a shadow on a marking. This marking was assigned a specific time in order to give a time. Sundials could be made from virtually anything, as long as it was solid and could cast a shadow.
https://www.britannica.com/technology/sundial -
1400 BCE
Water-Based Clocks
These clocks were developed around the same time as the Sundial, and were first used by the Babylonians. They relied on the flow of water into a vessel to measure time. The vessel would have markings indicating a given time. Water clocks picked up where sundials fell short, in that they could operate independently of sunlight. They could also operate as timers, another shortcoming of the sundial.
http://www-history.mcs.st-and.ac.uk/HistTopics/Water_clocks.html -
Sep 30, 800
Candle Clock
The candle clock was most likely developed by King Alfred the Great, of England. It determined time by measuring the burning of a candle, by placing a candle next to a set of markings.
https://www.sciencenews.org/article/brief-history-timekeeping -
Sep 30, 1300
The Verge and Foliot Mechanism
The Verge and Foliot Mechanism is generally considered as having been the first mechanical clock. IT used rotational force to measure time, and moved some object a uniform amount per "tick." This made it one of the most accurate time keeping methods of its time.
http://www.uh.edu/engines/epi1506.htm -
Sep 30, 1510
Spring-Based Clock
Introduced by Peter Henlein, the Spring-Based Clock was a precursor to more modern mechanical clocks. They operated by using a spring as the watch mechanism. As a result, the movement of the watch would slow down until it was rewound. The clock was also quite small, being able to be placed on some form of necklace. Henlein's spring movement served as an ancestor to more modern pocket watches. http://abt.cm/2cGJWxw (Had to use a URL shortener) -
Pendulum Clock
Based off of Galileo's observations of pendulum and oscillatory movement, the Pendulum clock relied upon the movement of a pendulum to keep time. While Galileo may have designed the basis for the clock, it wasn't until 1656 that it was actually built by Christian Huygens, a dutch scientist. The pendulum was quite complex, and as a result of its complexity, could keep time to around 10 second per day. Improvements would later be made.
http://abt.cm/2cGJWxw (Had to use a URL shortener) -
Quartz Clock
Unlike earlier clocks, the quartz clocked relied upon electricity. They work by measuring the oscillatory motion of an electrically charged quartz crystal. The oscillation produce small electrical charges, which are often used to power small motors. This meant that they were accurate everywhere, regardless of environment or gravitational force (In the case of Pendulum clocks). Quartz clocks are still commonly used today in wrist watches.
http://www.explainthatstuff.com/quartzclockwatch.html -
The Atomic Clock
First introduced in the 1940s the atomic clock is one of the most advanced time keeping methods to date. Modern variants work by measuring the oscillations of individual cesium atoms, 9,192,631,770 of which is considered one second. Using these clocks, time can be measured to within one second per few million years.
http://science.howstuffworks.com/atomic-clock3.htm
