A Timeless History
Tellurions grew out of the orrery. London maker John Rowley built one around 1713 for Charles Boyle, 4th Earl of Orrery, and the name stuck: a clockwork solar system turned by a handle. A tellurion keeps only three bodies — Sun, Earth and Moon — the ones whose motions explain sunrise, the seasons and the tides. Hartog van Laun of Amsterdam made this one around 1800; it later taught at the city's navigation school.
SourceWhipple Museum of the History of Science, Cambridge — whipplemuseum.cam.ac.uk · Rijksmuseum, NG-NM-11700 · Image: Rijksmuseum, Amsterdam
Science In Action
Rotation — Earth turns once a day; the side facing the Sun has daylight, the other side night • Tilt — the axis leans 23.4°, so the year-long orbit brings summer and winter, not any change in distance • Phases — the Moon circles Earth in 27.3 days, but new Moon to new Moon takes 29.5: Earth has moved on • Scale — the numbers cut into the two arms are real: 149,597,870 km to the Sun, 384,400 km to the Moon
SourceNASA Science — science.nasa.gov, Earth facts; Moon: lunar phases and eclipses · Image: NASA/JPL/USGS, Galileo, PIA00342
Arts
The orrery has its own famous painting. Joseph Wright of Derby, A Philosopher Lecturing on the Orrery, first shown in 1766: a lamp stands in for the Sun and lights the faces gathered round the brass rings, two children closest of all. Wright painted a science lesson the way others painted saints. William Pether's mezzotint of 1768 carried the picture across Europe.
SourceRoyal Museums Greenwich — rmg.co.uk · Derby Museums, the painting · Image: Rijksmuseum, RP-P-OB-33.704X
Applications Today
Classrooms — a tellurion is still the quickest way to show why summer is not “closer to the Sun” • Tides — tide tables are worked months ahead from the same Sun–Earth–Moon geometry • Eclipses — NASA has computed every solar eclipse from 2000 BCE to 3000 CE from these same three motions
SourceNOAA National Ocean Service — oceanservice.noaa.gov, Tides · NASA Eclipse Web Site — eclipse.gsfc.nasa.gov · Image: NASA/Aubrey Gemignani
Earth carries two tidal bulges at once, one facing the Moon and one opposite — hence two high tides a day.
Tafelplanetarium / Table orrery — planetarium, tellurium and lunarium in one instrument; wood, brass, ivory — Hartog van Laun (c. 1733–1815), instrument maker, Amsterdam — c. 1800–c. 1808 — Rijksmuseum, Amsterdam — gift of the Kweekschool voor de Zeevaart (Amsterdam nautical college) — NG-NM-11700
