Eisinga Planetarium
Encyclopedia
Orrery
An orrery is a mechanical device that illustrates the relative positions and motions of the planets and moons in the Solar System in a heliocentric model. Though the Greeks had working planetaria, the first orrery that was a planetarium of the modern era was produced in 1704, and one was presented...
, a working model of the solar system
Solar System
The Solar System consists of the Sun and the astronomical objects gravitationally bound in orbit around it, all of which formed from the collapse of a giant molecular cloud approximately 4.6 billion years ago. The vast majority of the system's mass is in the Sun...
. It was built from 1774 to 1781 by Eise Eisinger in Franeker
Franeker
Franeker is one of the eleven historical cities of Friesland and capital of the municipality of Franekeradeel. It is located about 20 km west of Leeuwarden on the Van Harinxma Canal. As of 1 January 2006, it had 12,996 inhabitants. The city is famous for the Eisinga Planetarium from around...
. The "face" of the model looks down from the ceiling of what used to be his living room, with most of the mechanical works in the space above the ceiling. It is driven by a pendulum clock
Pendulum clock
A pendulum clock is a clock that uses a pendulum, a swinging weight, as its timekeeping element. The advantage of a pendulum for timekeeping is that it is a resonant device; it swings back and forth in a precise time interval dependent on its length, and resists swinging at other rates...
, which has 9 weights or ponds. The planets move around the model in real time, automatically. (A slight "re-setting" must be done by hand every four years to compensate for the February 29th of a leap year
Leap year
A leap year is a year containing one extra day in order to keep the calendar year synchronized with the astronomical or seasonal year...
. The orrery includes a display for the current time and date. The plank that has the year numbers written on it has to be replaced every decade.
In addition to the basic orrery, there are displays of the phase of the moon and other astronomical phenomena. It is listed as a Rijksmonument
Rijksmonument
A rijksmonument is a National Heritage Site of the Netherlands, listed by the agency Rijksdienst voor het Cultureel Erfgoed acting for the Dutch Ministry of Education, Culture and Science.-History and criteria:...
, number 15668.