Mechanical Watches

The mechanical watch revolutionized timekeeping by counting regular oscillations. These oscillations are generated by a pendulum that gives the pendulum clock its name and by the balance wheel in the wheel clock. These mechanisms release the armature at equal intervals, which in turn allows the rest of the clock's mechanism to rotate the hands a little further over the dial to indicate the time. Pendulum clocks were invented in the 17th century. Its pendulum was built in such a way that it oscillates about 1 time per second, thus setting the rhythm of the clock. Their mechanics kept going with the help of weight trains. However, environmental influences and friction in the gearbox ensured that these clocks were inaccurate between a few minutes and 10 seconds per day and had to be adjusted regularly. For this purpose, a noon indicator was often used – a sundial that was only used to indicate the noon time.

Around the same time, the wheel clock with balance wheel was invented, which was usually made as a pocket watch. Their accuracy was often not much better than that of the pendulum clock. Since longitude can only be reliably determined in seafaring with the help of an accurate clock, the wheel clock was further developed. In 1750, it was possible in England to improve the inaccuracy to 1 second per day by increasing the precision in the production of the wheel clock. Especially in the face of adverse environmental influences, spring-driven movements with a balance wheel were increasingly used instead of pendulums. With the spread of the railway in the 19th century, minute-by-minute timekeeping also became important in everyday life.

 

Quartz Clocks

The advances in physics and chemistry in the 19th century and the discovery of quantum mechanics in the 20th century ensured that timekeeping also became more and more accurate. For example, it was realized that the accuracy of clocks depends on how short the time intervals are that have to be counted before the mechanics can indicate that a second has passed. Today, timekeeping in everyday life is dominated by quartz watches. They measure time by counting the vibrations of a quartz crystal. A quartz element oscillates 32,768 times per second and thus serves as a "pendulum". This time signal is used in the quartz clock to control an electromechanical or a fully electronic counter. Clocks with dials and hands, as well as LED and LCD displays, can be used to display the time. With a deviation of only a few seconds per month, quartz clock surpasses mechanical clocks many times over in accuracy.

Today's smartwatches are computers worn on the wrist that not only measure time with a quartz clock but can synchronize with a time signal transmitted by radio. They display the time on an OLED display as an image of a clock face.

 

Atomic Clocks

The most accurate clocks today are atomic clocks. They also use quartz crystals to measure time, but they are much better shielded from environmental influences. For example, the temperature in the clock, the air pressure and external vibrations are precisely controlled. In addition, the properties of cesium (¹³³Cs) are used. When excited, this element oscillates 9,192,631,770 times per second and is used in the atomic clock to correct timekeeping based on the quartz crystal. This achieves an accuracy at which the clock deviates by only 1 second in several million years. The synchronization of several atomic clocks around the world together forms the basis for the official universal time – called UTC, Universal Time Coded.

 

Timekeeping for positioning

In 1978, the first GPS satellite was launched into space. This marked the beginning of the age of satellite navigation, which is another application of the atomic clock. Each navigation satellite has a very accurate atomic clock on board and constantly transmits on a certain frequency how late it is on its clock. On Earth, the time signals from at least four satellites are picked up and calculated by a GPS-enabled device. Since the speed of light is finite and the orbits of the individual satellites are known, the distance between the satellite and the receiver can be calculated from the time that has elapsed since the signal was sent. The location of the GPS device on Earth can be calculated from three such distances - accurate to within a few centimeters, depending on the satellite operator. The time signal must be very accurate, as a time difference of just one microsecond already corresponds to a distance difference of 300 meters.

In addition to the GPS system, which is operated by the United States, Europe operates the Galileo system, the Russian Federation operates the GLONASS system, and the People's Republic of China operates the BEI-DOU system.

 

The sculpture

Time moves along the arrow of time only in one direction. Humans have always tried to describe this process and have developed different ways of measuring time. The sculpture below artistically describes how sun and lunar calendars, sundials and mechanical clocks, hourglasses and atomic clocks are used for this purpose.

 

500 m to the last station

212 m to Pluto

 

Information about the sundials at the courthouse

These sundials are the award-winning design by Sybille Vogel and Karl Schwarzinger and were painted on the south side of the Reutte district court in 2000 by the Fachschule für Kunsthandwerk und Design in Elbigenalp under the direction of Ernst Hornstein on behalf of the cultural initiative HUANZA. The sundials of different epochs are assigned symbols that are intended to characterize the respective zeitgeist.

1. Prayer clock (top left):

In the monasteries, sundials were used to determine prayer times from about the 7th century onwards. The turn to spirituality and mysticism that the medieval prayer clock stands for is symbolized by the triangle with the divine eye and one of the oldest symbols of Christianity, the fish.

2. Antique sundial (bottom left):

The sun itself was to be at the center of the ancient sundial. The high esteem for science and wisdom in antiquity is expressed by the owl and the geometric division of the dial. Until the advent of the wheel clocks (14th century), the so-called "temporal hours" were the bourgeois measure of time. The time of day was divided into 12 equal parts from sunrise to sunset: 1st, 2nd, 3rd hour, etc.

3. Sundials for true local time (top right):

The clock of the last centuries is decorated with a scroll, which is a symbol of renewal. With the introduction of the wheel clocks, there was a change to the so-called equinoctial hours. The time from midnight to midnight was divided into 2 x 12 equal hours. The measure of time is called true solar time or local time. This measure of time was no longer used from the beginning of the 19th century because it is uneven. It has been replaced by a uniform mean solar time.

4. Sundial for our hours of use (bottom right):

Today's timekeeping is shown by the modern zone clock. Since the end of the 19th century, we have been living all over the world with zone times that are based on mean solar time and are tied to zone meridians. With the figure-eight loops, you can read the CET and daylight savings time directly. In winter, readings are taken on the loop at the top left, in spring at the bottom right, in summer at the bottom left and in autumn at the top right.

Common elements in all ages are birds that may migrate from continent to continent, from season to season and eternally from earth to sky.