The Sun
Sundial
During the 16th century BC in a town in Egypt, gnomons which are shadow casting devices were used to divide the day up into large intervals. These gnomons were eventually combined with scales to produce a sundial. The sundial enabled people to tell time based on the length or direction of the shadow cast by the sun. Back then, sundials were very inaccurate. This was partly due to the fact that many people had not acknowledged that the summer hours are longer than those of the winter. Sundials were made based on the area in which it was to be used because the Sun farther away from the equator is lower in the sky than it is when the Sun is closer to the equator. This affects the length of the Sun’s shadow which therefore affects the understanding of whatever time it may be.
Clepsydra
The clepsydra was first invented around the time of 15th century BC. clepsydras were named after the Greeks. These objects appeared to have a container with a small hole in it’s bottom where water would seep through at a constant pace. The drip-drop of the water would be later what the tick-tock in clocks is now. These water clocks had marks on the outside that indicated hours. The time was dependent on the increase or decrease of water which filled the inside of the drum. The lines on the outside were different sizes so that they could accommodate the shorter length of hours in the winter than in the summer. The clepsydra was not used to measure hours but rather used to measure time allotted for a particular event. Clepsydras were used during the sunlit day, however no evidence has proven that this same device was used during the night.
Astrolabe
The astrolabe was believed to have been invented in the 2nd century A.D by Ptortemy. He was riding along on his donkey with a a celestial globe. He dropped it on the ground making it a 2-D celestial sphere. The astrolabe, also known as the “star grasper”, is a combination of movable plates. The rete and the tympan are the most significant of those. The rete shows the movements of the sun and the tympan shows the coordinates of the celestial sphere. The alidade and the rule, other parts of the astrolabe distinguished the altitudes of the stars. These devices were able to find location, distance, and of course, time. The astrolabe’s design is based on the map that was created in 150 BC by a Greek astronomer named Hipparchus. On this map, stars appeared in a perpendicular line all connected to a designated point on the plane. This map displayed where the stars were placed in relation to the Earth’s equator. However, for centuries this device was unable to accurately measure time. They also never became very popular due to the belief by some Christians that it was a tool of the devil. However, later it did play a key role in more accurate timekeeping devices such as the advancement of the sundial.
Candle Clock
The candle clock was first recorded having been used in the 9th century A.D. However, some people assume that it is much older. The candle clock was designed to with stand most affects of weathering that around this time may have proven harmful to such a device. These clocks were unable to the tell the actual time, but nevertheless, were able to tell how long an event may have been. This was done by the marks placed on both sides of the candle which identified periods of time. These candle clocks also served as timers when a nail was placed in an area that indicated the time that it was to be set off. When the wax around the nail melted, it enabled the nail to fall to a plate below.
Sandglass
The sandglass is believed to have been invented in Europe around the time of the 14th century. The sandglass appears to be two cup-like objects called glass vessels, connected at the center, or the orifice. The substance that makes its way from the first cup to the second cup could be of the following: powdered eggshell, marble dust, and sand. The passage between the first and the second cup is ten times wider than the single particle being used. Sandglasses were first used to measure cooking times. These instruments later proceeded to tell the time of many other events.
Mechanical Clock
The inventor and the time in which the mechanical clock was invented is yet to be discovered. Some believe it was invented during the 1270s in Europe. The mechanical clock works by a weight that is connected to a pole called a verge. This piece is constantly wound around the main gear shaft. As this happens, the weight is lowered due to the gravity which then rotates the barrel and this is what drives the escape and wheel. But what is really unique about this type of clock is the escapement, most commonly the verge-and-foliot. This escapement works by the verge mentioned above and the pallets which are two small, squarelike objects extended on the top and bottom. When the wheel turns the top pallet stops the escape wheel and makes the foliot oscillate. Not only does it move the verge-and-foliot, but it also loosens the grip of the top pallet. This then continues with the bottom pallet and then continues some more as it alternates pallets.
Spring-Driven Clock
It’s not entirely known, however some people suggest that the spring driven clock was invented in Europe in the early 14th century. They were basically a portable version of the mechanical clock. Despite advances in the time telling, these spring driven clocks were often very inaccurate. Thus many spring driven clocks contained a sundial or a compass. The mainspring, also the clock’s power,displayed problems when the force from the spiral balance spring was exerted. When this was done, the spring loosely unwound. The clock’s pace then varied as it ran fast when the spiral balance spring was fully wound, yet became slower as the spring began to release. In 1674 to 1675, a Dutch astronomer named Christian Huygens discovered a way to fix this problem. The way would make the spiral balance spring similar to the way in which the pendulum works in the pendulum clock. The balance spring would unwind and wind with always the same energy being produced by the mainspring.
Pendulum Clock
In 1656, the pendulum clock was invented by Christian Huygens. These time devices had advanced a great deal as now they could measure seconds. The discovery first began in the early 1580s when Galileo recognized that a pendulum could swing through a wide arc and a small arc at the same given time. In 1614 a year before Galileo was to pass away, he began to work at creating a pendulum that would remain in a constant motion. In 1656, a Dutch mathematician and astronomer named Christian Huygens took the pendulum and added a common escapement of this time to produce the first pendulum clock. In 1671, a new and improved escapement called the anchor escapement was invented that allowed for almost complete accuracy with the loss of just a couple seconds each day. Much later in 1906, the first pendulum clock was to be powered by an electric battery which was stationed in the clock.
Quartz Clock
The initial quartz clock was invented in 1927 by Warren A. Marrison and J.W Horton. Quartz crystals vibrate anywhere from thousands to millions of times every second. This happens because of the different electric fields the quartz crystal is faced with. In a watch, the electric current produced from the battery causes this vibration. The high frequency is reduced to a lower frequency that is transferred through a coil. It’s magnet then alternates back and forth and moves a small pinion that turns the crystal vibration into a mechanical movement. Before quartz clocks, a second had been defined as 1/86,400 of an average solar day (the average amount of time it took for one rotation of the Earth). However, new knowledge of a second helped scientists discover that the Earth’s rotation was an unreliable tool used to tell time. This new discovery was not altered in quartz clocks because of the change that took place in quartz crystals after long periods of time. In the quartz crystal, their was either a change in the back and forth motion or the vibrations. This was a result of either temperature changes, reoccurring effects of the vibrations, or the impurities in the quartz. Back then, these clocks were very space consuming. Nowadays, quartz clocks have advanced so much that they are found in all types of things such as calculators and computers. Quartz clocks are presently the most common tool used for timekeeping.
Cesium Atomic
During the year of 1955 in Britain’s National Physical Laboratory, the Cesium Clock was invented. The atomic clock was an invention that is so significant to our contemporary life. Without it we would be unable to do many things such as have communication and transportation.
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