The Trilogy of TimeAstrolabium - Planetarium - Tellurium

by Marcus Hanke

How it all began …

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In 1983 Rolf Schnyder bought the watch manufacturing company Ulysse Nardin, which at that time was in immediate danger of bankruptcy. Ulysse Nardin had a tradition of watch making since 1846 and was famous for its high-quality chronometers not only built for private use, but also as navigational instruments used by several navies. During the Seventies the company became one of the many victims of the quick advance in watch technology and production. Millions of cheaply produced, accurate quartz watches flooded the market. This left the traditional mechanical watch, which was manufactured in a long and time consuming process with a lot of work done by hand, barely a chance to survive.

Nevertheless, Rolf Schnyder was convinced that the production of high-class mechanical timepieces still had a future. He also knew, that his newly acquired company would need something really spectacular to reintroduce its name into the exclusive league of the world’s best watch manufacturers. During the search for this specialty, Rolf Schnyder visited the workshop of a well-known watchmaker in Lucerne, Switzerland: Jörg Spöring. There, he noticed an extraordinary wall clock featuring an astronomical dial, a so-called astrolabe. Upon asking, he learned from the master that his apprentice, a certain Ludwig Oechslin, had constructed this clock. When Mr. Schnyder finally met this apprentice, he immediately asked him if it would be possible to create an astrolabe as small as a wristwatch. “Who would be interested in buying it?” was Oechslin’s laconic answer.

This was the start of not only a steady friendship, but also of an extraordinary co-operation. One result of it is presented in this book.

The Trilogy of Time

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The Trilogy of Time is also available as a limited set

Some Notes about the History of Astronomy

What Does Astronomy Have to Do With Measuring Time?

In fact, our common measuring of time is nothing more than the observation of basic astronomical events. What we call a ‘day’ is the time span during which the Earth rotates once around its axis. Very early already, mankind divided this span into shorter intervals, which made it possible to keep record of the time elapsed within a day. The time shown by our timepieces, be they worn on our wrists or hanging on the walls of our homes, is always the representation of a specific moment during that rotation of the Earth.

Since all watches are only a simple product of astronomy, it was logical that the two functions – observation of astronomical events and the measuring of certain time intervals – were combined into a single device. In the beginning these devices hardly could be identified as ‘clocks’: megalithic arrangements like those at Stonehenge in England and Carnac in France, or Egyptian and Mayan temples. All of these artifacts were erected for astronomical observations and calculations as well as being a place to celebrate.

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The megalithic alignments of Carnac in Brittany served as religious site as well as astronomical observatory.

The connection of astronomy, time and religion always was a very tight one. The first people noticed that the Sun rises and disappears in more or less regular intervals, that the Moon changes its face also regularly, and that the stars seemingly kept their positions eternally. Therefore, those celestial bodies became symbols for divine activities, which determined all life on Earth. People came to the belief that Sun, Moon and stars even were gods themselves, who needed to be worshipped. It consequently became increasingly important to dedicate rituals, held at specific times, to the gods. The architectural framework for the rituals became an instrument to determine the important moments by means of optical signs. Only on one or two days in a year, for example, (mostly the equinoxes) would the sunrays reach a specially marked stone or spot. To maintain the gods’ favour it was indispensable to celebrate the rituals at the exact time, which put the power of time into the hands of priests, who kept it for thousands of years. Until today, the Christian holiday of Easter Sunday is determined by astronomy. It is the first Sunday after the first full moon in spring.

Not only religious celebrations were held, following the accurate observation of astronomical cycles, but also daily life was influenced by these events. In ancient Egypt, it was noticed that the annual flooding of the Nile started shortly after the bright star Sirius appeared in the sky for the first time of the year (July 20th). This event determined the whole cycle of sowing and harvesting and therefore, the Egyptian year started with the appearance of Sirius.

After the multitude of gods assigned to the celestial bodies were replaced with the belief in the one God, astronomical timepieces not only kept their importance to calculate the correct times for ceremonies, but they gained an additional didactic function. The observation of Sun, Moon and the planets brought forward the insight, that their movements followed certain rules, which themselves could only be the result of God’s planning and his creation of the universe.

The huge astronomic clocks built in the Middle Ages and located in the churches had the purpose of demonstrating to all spectators the magnificent apparatus of the universe in which the Earth and man were placed in the centre with the universe rotating around just as it was planned and executed by the will of God. Therefore, the study of the celestial bodies, and the exposition of astronomical clocks were a means to discover mankind’s place in the universal order of things. They were instruments of philosophy and religion, and even instruments of indoctrination.

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The huge astronomic clock in the cathedral of Strasbourg, France, was built in 1572–74.

Given this importance, it is not astonishing that the clerical monopoly of time was soon challenged by the cities: During the 15th and 16th centuries, these had gained massive economic strength, and were eager to demonstrate their independence from the church. While the old church towers were a natural place to locate public clock displays, the magistrates of wealthy towns quickly erected their own clock towers. Huge astronomic clocks, such as the magnificent clocks in Padua (1434), Prague (1486), or Berne (1530) were placed in either the townhalls, or in dedicated clock-towers, and proved to the public, that the interpretation of the universe was not an entirely spiritual issue, left at the discretion of priests.

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The astronomic clock at the town hall of Prague, Czech Republic (1486)

Views of the World

When we observe the Sun’s path in relation to the stellar sky during a year, it seems that the Sun rotates around the Earth, which is positioned in the centre of the universe. This conclusion was made very early and found its way into the old texts about the creation of the world. It was scientifically explained mainly by the Egyptian mathematician and astronomer Ptolemy during the 2nd century AD.

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The geocentric view of the solar system as Ptolemy defined it.

His geocentric system of the universe was adopted by the Catholic Church and fiercely defended, even when scientific proof, that the Sun is the centre, around which the Earth is rotating, was brought forward by Nicolaus Copernicus in his book “De revolutionibus”, published in 1543. Consequently, Copernicus and other defenders of his heliocentric system ran into serious trouble with the Church. Galileo Galilei had to publicly retract his support of the Copernican theory. Giordano Bruno was even burnt on the stake by the Inquisition. Too far away was the new theory from the traditional dogma about the Earth’s position in the known universe. It seemed blasphemy to consider that God’s final and finest creation, mankind, was not the centre of the world.

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The heliocentric or Copernican system.

Even when the heliocentric model finally was adopted, there were still too many apparent inconsistencies and contradictions. The movement of certain planets just did not follow the predictions, which were based on the assumption that all celestial bodies moved in perfect circles. The impression, that the universe was a gigantic automaton created by God, and followed strict divine laws, prevailed. Moreover, as a special privilege from God, man was enabled to use the same laws to recreate the universe in a small scale as astronomic automatons in mechanical clocks.

It was Johannes Kepler, who finally delivered a serious blow against this conception, when he proved that the planets moved along ellipses rather than perfect circles. Sir Isaac Newton, with his gravitational laws, demonstrated that so many different gravitational influences have an effect on the planets’ movements, and that it is merely impossible to predict them by means of strict and eternally valid formulas. Suddenly, it became meaningless to reproduce the universal movements by means of automatons, and the importance of the mechanical astronomical clocks as a means of scientific, as well religious demonstration and education quickly vanished.

Celestial Mechanics 101

Sun and Earth

The Rotation of the Earth

The Earth rotates around its own axis, causing the impression that the Sun rises in the morning, passes its zenith at noon and sets in the evening which is followed by a period of darkness, the night. This complete cycle is one day, the basic time interval which can be defined by astronomic events. In ancient times, the definition of the day had already been established as the period between two zeniths of the Sun. By means of a simple stick in the Earth, it was easy to determine that the Sun had reached its highest point, when the shadow cast by the stick had its shortest length. However, different cultures placed the beginning of a new day on different times, be it the sunrise, the sunset or the noon. In the Roman Empire, the day changed at midnight, which was a difficult issue, since no astronomical event helped to determine this exact time.

The possibility to count days alone was not enough though, and a more detailed subdivision was needed. This was achieved by dividing daylight and night into twelve hours each, totalling twenty-four hours per complete day. The twelve hour interval was already introduced in ancient times, since the number twelve was a sacred number in nearly every old culture. In Rome, the twelve daylight hours started at sunrise, the twelve nighttime hours at sunset. The apparent problem with this subdivision is that the Earth’s rotation axis is not at a right angle to its orbit around the Sun, but it is slanted some 23 degrees. This angle is responsible for the change of the seasons and the different lengths of light and dark periods during the year. Therefore, the old method to measure the daytime, the so-called ‘apparent solar time’, accepted different lengths of the hours. During winter, the twelve night-time hours were much longer than the twelve daytime hours, and vice versa during summer. Consequently, night and day hours varied in their lengths, between 75 and 44 minutes. Only at the two equinoxes did they last equally long, 60 minutes. It is clear that this system of measuring time implies differences as soon as the geographical location is changed. Due to the Earth’s rotation, places in the East experience sunrise and sunset earlier than those in the West, resulting in a considerable difference at larger distances. Since the average circle of social relations at that time was very small, caused by the lack of long range communication assets and fast means of transportation (around 1500, a journey from Venice to Lissabon lasted about 46 days!), this difference was hardly noticeable. The system of using the apparent solar time was convenient to use and easy to understand for all people, who normally did not possess clocks, but were well aware of sunrise and sunset as daytime constants.

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One complete rotation of the Earth needs 23 hours and 56 minutes. Since the Earth in the meantime has moved along its path around the Sun, its angle of illumination has changed too, so the time span between noon A and noon B is four minutes longer.

The introduction of reliable mechanical clocks during the late 15th century made these flexible hour lengths problematic, since the hours they measured were all equally long. For that reason, the ‘mean solar time’ was introduced, then designated ‘Italian hours’, after the region of their first general use. This way of time measurement was independent from sunrise and sunset, and is still used today. So the clocks first had to ‘invent’ the regular hours before they could display them. For the people this was a drastic change and made necessary the use of tables and sophisticated instruments (astrolabes for example) to translate the hours shown in mean solar time into the traditional apparent solar time.

Nevertheless, the definition of a day being the time between two noons is still problematic, since it does not reflect the true rotational period of the Earth.

If a certain point on Earth’s surface is marked, and the time span needed for one complete 360 degrees-rotation of this point is measured, it is about four minutes shorter than twenty-four hours. However, since the Earth itself has travelled a certain distance on its orbit around the Sun during the 24-hour-period, it has to rotate a bit more than 360 degrees until the same point has noon again. The time needed for a true 360 degree rotation of the Earth is called a “stellar day”.