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Why build a planetarium?

Scientists assume our world's phenomena are an orderly consequence of the interactions among the objects. Science is the process of building models of these interactions. In 1686 Isaac Newton published his Principia, providing a general conceptual model that made sense of the motions observed in our solar system. The various mechanical models that comprise the Botjes planetarium exhibit many of the straightforward and the subtle features of Newton's conceptual model as applied to our solar system. It serves as a real-time calculator, from which can be read the positions in the sky of the stars, moon, sun, and planets, and from which can be inferred the phases of the moon and the timing and nature of eclipses.

The power of this particular model is underscored by its durability: the planetarium is over 130 years old, and yet predicts movements as well as it did the day it was completed. That the device was intended for the long term is clear from the inclusion of the planet Uranus, discovered just 75 years before construction began. The motion of this planet is so gradual that it has completed just over one and a half revolutions since the planetarium was set in motion.

Models and Superstition

More specifically, planetariums have been constructed as an antidote to superstition. Eise Eisinga began building a planetarium in 1774, after an unusual conjunction of planets that spring led to fear about the impending doom of the earth (see descriptions at the Eisinga Museum websites, both official and unofficial). Wildrik Botjes may have been inspired by Eisinga, working less than a century later and only sixty miles away. The mechanical planetarium counters a fearful view of a random future with a reassuring view of an orderly process. The Botjes family held firm Christian convictions, and the scientific view of an orderly universe is consistent with the New Testament description of Christ as "upholding the Universe by his word of power." (Hebrews 1.3, RSV).

The tradition of planetarium building has been continued today by software writers. These planetariums replace the mechanical with the virtual, and their likelihood of lasting more than a century is slight. Nonetheless their power to compute past and future along with the present and their accessibility via the internet (for example at the Weather Underground) make them a worthy and valuable extension of the tradition.

Publications about Wildrik Botjes and his planetariums (with links where available)

  • Bartelds, J. C. E., March 1930, in the Nieuw Nederlandsch Biografisch Woordenboek, eds. P. C. Molhuysen, P. J. Blok, and K. H. Kossmann, Leiden, part 8, pp. 188-189 "Botjes, Wildrik". [A two paragraph biographical synopsis of Wildrik Botjes (in Dutch).]
  • Beekman, George W. E. 1985, Zenit, Volume 12., Nos. 7-8, pp. 250-251, "Botjes' Planetarium in Franeker". [An account of the donation of Botjes' second planetarium to the Eise Eisinga Planetarium (in Dutch).
  • Havinga, Egbertus, van Wijk, Walter Emile, and D'Aumerie, J. F. M. G. 1928, 424 pp., "Planetarium-Boek: Eise Eisinga". [A book on planetariums published (in Dutch) on the occasion of the 100th anniversary of the death of Eise Eisinga. It includes description of the planetariums of Wildrik Botjes on pages 374 and following.]
  • Kalamazoo Morning News, August 4, 1896, p. 8. "Wonderful Machine: Showing Complete Movement of Solar System" [A local newspaper account of the arrival of the Botjes Planetarium in North America].
  • Menninga, Clarence 2013, presentation at the 2013 Annual Meeting of the American Scientific Affiliation, (July 19-22), "Wildrik Botjes Planetarium". [The link is a pdf of the presentation slides.]
  • Menninga, Clarence 2013, Watch & Clock Bulletin Vol. 55/4, No. 404, (July-August), pp. 361-370. "A Miniature Planetarium Powered by a Chauncey Jerome Chronometer" ( [This article gives an overview of the operation of the planetarium and provides details on the restoration work done in 1988 and in 2012-2013.]
  • Schulhof, Marc, May 18, 1992, Grand Rapids Press, "Calvin's gift planetarium is on display". [A local newspaper account of the arrival of the Botjes Planetarium at Calvin College and its restoration to working order by Clarence Menninga.]

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