I visited this tWHS in April 2022. I must say that the Netherlands in general really has a treasure trove of quaint well-presented little museums. I truly can't see how this little gem, dubbed as the world's oldest working planetarium, won't make it on the WH list just like the splendid Plantin Moretus, Ir. D.F. Woudagemaal or the Rietveld Schröder House.

The facade of the Eise Eisinga house in Franeker, Friesland, was built on a canal well before 1768 (this date can be seen on the stone of the facade but it's actually the year in which the facade was replaced). Overall the facade is quite plain with the usual gable roof. The nearby coffee shop is much more ornate with a lovely Art Nouveau interior. However, the highlight and OUV of this tWHS lies mainly in the living room literally converted into a fully working solar system model with the sun in the centre and the planets known at that time circling around it. The outer three planets, Uranus, Neptune and Pluto are missing as they had not been discovered by the time the model was built.

Entrance now costs 6 euros and whenever there are enough people, a lovely knowledgable old lady closes the living room door, fetches a long bamboo stick, and gives a brief explanation on the planetarium or orrery in Dutch, English or German. I revisited the room more than a couple of times practically listening to the explanation in three languages as I wanted to take photos without people in the way and also because I wanted to observe the incredible little details on the ceiling. The mechanism of the planetarium is visible upstairs but be careful not to bump your head if you're tall. What is incredible, is that Eise Eisinga did all this as a hobby! He was a full-time worker in his father's woolcombing business, and he also picked up his father's interests in astronomy and mathematics. He was so inquistive that at the age of 15 his self-study enabled hime to write a 650 page book on mathematics. Some original sheets are on display in the museum.

In his free time, Eise Eisinga put his knowledge of astronomy and mathematics to good use in May 1774 when panic erupted among the local people due to a doomsday prediction made by Eelco Alta. Eise had the knowledge it took to build a model of the solar system in his living room. His aim was to show that there is no reason for such fears. Once he had generated his initial concept for the model, and thanks to his knowledge from the woolcombing mills, it took him only 7 years to build it. To fit the model of the solar system into his living room, Eisinga had to reduce it in scale by a factor of one trillion. This meant that one millimetre on his ceiling represents one million kilometres. In addition to the solar system itself, with slits sawed in the ceiling with metal pins passing through them, he introduced all kinds of dials that could be used to derive real-time information about the solar system such as a date indicator, dials for the day of the week and the year, lunar dials, a celestial chart, zodiac signs, . He also fitted a cupboard bed, a wardrobe (make sure to have a look at the different original weights hanging from the mechanism upstairs) and an oven, literally to be able to live in his living room.

The balls used to represent the planets and the moons are gilded on one side to represent the illumination of the sun, and painted black on the other to represent night. Although the distances between the planets are shown at the correct scale, the balls representing the planets themselves are not; if built to scale, the Earth would be so small as to be invisible to the naked eye. In reality, the planets move in orbits that are not circles but ellipses with the sun in the centre of each one. Thus, for each planet Eisinga marked its farthest point away from the sun by the letters VP (verste punt, farthest point) and the closest point to the sun by the letters NP (nearest point). The figures indicated with the white circles drawn around the orbit of each planet indicate the planet's position in relationship to the ecliptic plane. This means that by looking at the celing, in theory one could tell where to look in the sky to find a certain planet and whether it is above or below the ecliptic plane, hence visible or not according to where you're looking from and when.

Equally exciting is the planetarium mechanism upstairs, just above the living room ceiling. All the planets, pointers and clocks are driven by an extensive system of wooden disks with around 6,000 hand-wrought iron pins serving as cogs. This entire mechanism is controlled by a pendulum clock with a single weight (shortened by Eisinga to avoid having a pendulum in the cupboard bed and upsetting his wife!). This clockwork, however, merely regulates the speed at which the mechanism turns. The power to turn it comes from 8 weights connected to the main axles that eliminate almost all resistance. The pendulum swings at a rate of 80 times a minute. Over the course of a year, the pendulum has to be adjusted somewhat due to temperature fluctuations; but Eisinga had it all thought through as he even left notes for future caretakers on how to maintain and operate the planetarium mechanism.

All in all I really enjoyed my visit and would also recommend both the coffee shop next door and the museum's small cafeteria and terrace. I combined it with a visit to the Drents Museum (to finally see the whole Frida collection on loan from the Dolores Almeda Museum in Mexico City) and a visit the 3 Dutch Colonies of Benevolence of Veenhuizen, Frederiksoord and Wilhelminaoord in Drenthe.