Isinga Planetarium: a wonder of the world of great beauty in a house on the Frisian Channel

Isinga Planetarium: a wonder of the world of great beauty in a house on the Frisian Channel

Behind the distinctive neck gable of a canal house in Franeker lies one of the wonders of the world. Anyone who takes the stairs upstairs and enters the box-bed living room will be amazed. A miniature solar system from the 18th century built by Eze Eisinga is installed on a blue wooden roof in Berlin. It is the world’s oldest planetarium still operating in situ, and has just been upgraded to the World Heritage List by UNESCO.

It is a very beautiful sight. The fixed sun is drawn in the middle of the ceiling and is equipped with 24 pointed rays. Directly below it hangs a copper ball on a wire. The planets Mercury, Venus, Earth (with the Moon), Mars, Jupiter, and Saturn orbit that Sun. This time, the balls are close to the ceiling, and the half facing the sun is gilded, with suspension points that slowly slide through the openings.

The size of the planetarium is one in a trillion (a millimeter is actually a million kilometers), so everything can fit in the room. On the other hand, the orbital periods of the planets are precise: 88 days for Mercury, one year for Earth, and anyone who wants to see Saturn complete its orbit would have to stay 29 years and 164 days. A visit to this planetarium is an exercise in slowing down.

The planetarium in Eisinga’s living room is one-trillionth the size.

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Nine weights

Everything still functions as perfectly as it did when it was completed in 1781. To see how it works, you have to climb another flight of stairs to the attic under the gable roof. There is an overwhelming composition of the drive in which a lot of thought and craftsmanship are combined. It turns out that the planetarium runs on a pendulum clock with nine weights. It does not move the hands, but through a precise interaction of the cogwheels, it moves a series of wooden hoops and discs from which ten thousand hand-made nails protrude.

You can’t see any of it in the living room below. There the planets move silently, the seventh aperture shows the Earth’s current position in the zodiac, and the wall above the box bed gives the correct date with the corresponding times of sunrise and sunset. The planetarium was working (and working) so precisely that the planetary positions were still correct. He can also predict lunar and solar eclipses flawlessly to this day.

The creator of this Copernican work of art was Is Eisinga (1744-1828), a wool carder and a devoted lover of science. Then in 1774 Leeward Courant Reporting that on May 8 of that year, the sky would show a rare “conglomeration” of Jupiter, Mars, Venus, Mercury, and the Moon, the Frisian priest Elko Alta predicted from the pulpit that the Earth would be thrown out of its orbit and would die in the heat of the sun. Woe to man!

Panic also broke out in Franeker, Esenga’s hometown. Having an interest in mathematics and astronomy, the humble Al-Farizi knew better and after disaster did not strike, he decided to build a planetarium at home. In this way, the residents of Franeker and the surrounding areas could see with their own eyes on his roof that their patronage was completely unfounded.

Isinga had hoped to complete the project in six months, but it took seven years to complete in addition to his usual work. A look into the attic explains why. Two months before the planetarium was completed, German-British astronomer and composer William Herschel discovered a seventh planet after Saturn: Uranus. Adding it to Franeker was not an option: the ceiling was too small. From the beginning, Eisenga opened his planetarium to the public: following the conspiracy theory put forward by Pastor Alta, education was his motivation. In this sense, Frisianism was a product of the Enlightenment, when amateur researchers founded societies (the Dutch Society of Science was the first in 1752) in which they conducted experiments and discussed new theories of learning and entertainment.

The planets in Eisinga’s home were so accurate that Jan Henri van Swenden, a professor at the University of Franeker, compiled a comprehensive description of the planetarium and distributed it to astronomers in Europe. But it didn’t work perfectly. Temperature changes affected the accuracy of the clock and the motor core. In the manual that Isinga wrote for his sons – which is still useful more than two centuries later – he indicated that he would amend the order every ten to twelve years.

Gears in the attic. The planetarium operates on a pendulum clock with nine weights.

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Ace Esenga was a special person. Born in the village of Dronrib, as an inquisitive young man he walked to Franker every week to practice mathematics – a two-hour journey. At the age of sixteen, Eze published a massive book on mathematics, followed two years later by a book on astronomy. He also built sundials and drew tables showing the celestial positions of the planets. However, he succeeded his father in combing wool. After serving as a successful businessman, patriot and city councilor, he came into conflict with the princes in 1787 and fled to Gronau, just across the German border. After the arrival of the French in 1795, he was able to return to Franker and became a professor at the academy. Until Napoleon closed it in 1811.

The reason why UNESCO has granted the Eise Eisinga Planetarium World Heritage status is the original state in which it is located: the mechanism is still working, and the overall function has remained unchanged. Nowhere in the world is a working planetarium built in a historic building in a similar manner. It was purchased by King William I in 1825, and from 1922 it was converted into a wider museum.

The planetarium designed by Ace Isinga is an extraordinary manifestation of our desire for knowledge, our desire to understand how the universe works. It bridges the gap between astronomical research and hobby science, connecting the craftsman with the master. The result is an iconic precision instrument, an unparalleled creation in which science and art are heavenly fused.

Dirk van Delft is former director of the Rijksmuseum Boerhaave and professor emeritus of the Material Heritage of Natural Sciences.

The Eise Eisinga Planetarium is open daily during the summer period, but reservations are required. including:

Above Eisinga’s bed are the times of sunrise and sunset.

Photography by Bertel Kolthoff on behalf of the World Heritage Foundation

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