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When it comes to strange requests, ‘Darling, do you mind if I saw up
the bedroom ceiling to build a planetarium?’ must rate pretty high. But
then Eise Eisinga, Dutch wool-comber by day and amateur astronomer by night,
was no ordinary petitioner. Nor was his wife a predictable character, as
her reply shows: ‘Yes, dear, as long as you don’t take more than seven years.’

The event that inspired Eisinga to begin his remarkable venture occurred
in 1774. In May of that year, an unusual alignment of planets was hailed
by the local minister as a sign that the end of the world was nigh. Eisinga
was fired by the desire to reassure his neighbours by pointing out that
this was mere scaremongering. So, with his wife’s blessing and working by
candlelight, this self-taught polymath embarked on an ambitious construction
project to transform his bedroom ceiling into a working scale model of the
Solar System, or orrery. The planetarium is now a museum, and national treasure.

Eisinga was born on 21 February 1744 in Dronrijp, near Franeker in the
northwestern province of the Netherlands called Friesland. His father was
a wool-comber and Eise followed him into this trade. Eisinga senior enjoyed
mathematics and geometry, and in his spare time made all kinds of ingenious
objects, including a piano and a cabinet organ. He was particularly interested
in designing sundials, which he sold as garden ornaments. He passed this
interest on to his sons, both of whom showed a talent for mathematics and
general science. The younger son, Stephanus, published some books on astronomy
and was interested in music, drawing and writing. He remained in Dronrijp
to work in his father’s wool-combing business.

Eise, the older brother, was encouraged by his father to carry on studying
after he had left primary school. Once a week he was allowed to leave his
wool-combing and walk to Franeker for lessons in algebra and Euclidean geometry,
from Willem Wytzes, a scholar of local repute. Wytzes later instructed Eise
in trigonometry, astronomy and the use of astronomical tables.

When Eisinga was 17 he met Wytse Foppes Dongjuma, a mathematician and
instrument-maker from Leeuwarden. Foppes, like Eisinga, came from an uneducated
background, but was intrigued enough by mathematics, astronomy and instruments
to teach himself. He stimulated the young Eisinga’s interest in astronomy
by allowing him, in June 1761, to watch the transit of Venus – the rare
sight of the planet passing in front of the Sun. (Transits of Venus occur
in pairs – Eisinga would have been able to watch another 8 years later.
The last pair occured in 1874 and 1882; and the next pair are due in 2004
and 2012.) The transit so inspired Eisinga that he produced drawings and
calculations of all the solar and lunar eclipses that would be visible from
Franeker between 1763 and 1800.

Eisinga married Pietje Jacobs in 1768 and moved to Franeker, into a
house called De Ooijevaar (The Stork), opposite the town hall. Here he
worked at his wool-combing, eventually employing several workmen. Once a
year he made a business trip to Leiden and would have lived and died a modest
Friesian had it not been for the minister, Eelco Alta, and his warning of
impending doom.

On 9 April 1774, a message appeared in the local newspaper announcing
that the end of the world was nigh. A rare alignment, or conjunction, of
the planets Jupiter, Mars, Venus and Mercury, as well as the Moon, was predicted
for the early hours of Sunday, 8 May 1774. This would, asserted the minister,
cause the Sun to burn up the whole Universe, including the Earth. It was
the Day of Judgment, continued the self-styled ‘lover of truth’, and there
was only one month to go. Further details could be obtained from a pamphlet
that the minister had written.

Despite the 18th-century growth of European interest in scientific matters,
most Dutch people, and especially those living in secluded farms and villages,
were ill-informed about science, being guided instead by a religion based
on the fear of God, Dutch Protestantism. Many of them worked on the land
or tended flocks of sheep for the wool industry, at that time an important
local source of income.

The newspaper announcement caused widespread alarm, which local printers
seem to have capitalised on. They worked overtime to produce and sell leaflets
that reprinted Alto’s warning alongside a plea for people to confess their
sins and prepare for the Day of Judgment, thereby fuelling the furore. Panic
reached such levels that the authorities felt obliged to intervene. All
pamphlets containing the minister’s announcement were confiscated, and a
notice was issued explaining that the planetary conjunction was perfectly
harmless, and would have no influence on the Earth’s course. An embargo
was placed on any publications relating to the conjunction until after 8
May.

Eisinga, for his part, decided to show people that there was nothing
to fear by persuading his wife to let him build a planetarium in his bedroom.
He designed the planetarium to occupy the entire ceiling, with the planets
suspended into the room from rods, which would move along grooves in the
ceiling to simulate the motions of their orbits. His wife gave him permission
to saw up parts of the ceiling and set him the time limit of seven years
to complete the project.

Many hours of calculations were necessary before Eisinga could begin
making and assembling the mechanical parts – all work which had to be done
in his spare time and by candlelight. The first problem he faced was his
bed. He had designed and ordered a clock with a pendulum that was to oscillate
60 times every minute. The clock was to be both the driving and regulating
force of his planetarium. Its pendulum was, however, so long that it could
not clear the box bed, forcing him to change his plan and shorten the pendulum,
which then oscillated 80 times per minute. This meant more calculations
and a recalibration of his instruments.

Eisinga’s design incorporated over 100 gears and pinions. The complexity
and resistance of such a mechanism required eight weights to keep the equipment
moving. These extra weights, all regulated by the clock, had to be rewound
at intervals varying between once a week and every five years. The beams
of the house, like the bed, obstructed the working of some of the mechanisms,
and Eisinga had to design around them.

In the meantime, he was asked to serve in several civic posts, and became
a member of the town council and an officer in the Civic Guard, an appointment
that later forced him to flee the region temporarily. As a tax collector,
he used his arithmetic skills to draft a series of lists for simplifying
trade calculations, which were printed in 1778 for use among merchants and
tradespeople. Even though these duties took up precious time that he wanted
to devote to the planetarium, Eisinga nevertheless managed to complete the
main mechanical work within four years, and the entire planetarium after
the allotted seven.

Eisinga made most of the parts and gears for the planetarium out of
wood, with the help of his father and workmen. There are a few brass wheels,
which were made by a clockmaker. Eisinga constructed a false wooden ceiling
behind which most of the driving mechanism is hidden. The ceiling represents
a scale plan of the extent of contemporary knowledge of the Solar System,
with the Sun and the planets Mercury, Venus, Earth, Mars, Jupiter and Saturn
revolving around it. (Uranus (1781), Neptune (1846) and Pluto (1930) had
not been discovered then, and so were not represented – a stroke of luck
for Eisinga who would otherwise have had to have moved to a much larger
house if he had wanted to include them to the same scale.) Though the planets
are not represented to scale, their orbits are – to a scale that is now
the equivalent of about 1 millimetre to 1 million kilometres. They are
all driven at their natural rate of rotation; so the model of the Earth
takes 365 days to complete one revolution, and that of Saturn, 10 760 days.

ECCENTRIC ORBITS

In the centre of the ceiling, Eisinga painted a large star to represent
the Sun. Around the Sun, there are six circular but eccentric grooves cut
in the ceiling, through which the planets are suspended from the end of
metal rods. The planets do not rotate about their own axes. On the side
facing the Sun, they are painted gold. The Earth, Saturn and Jupiter are
accompanied by their satellites, but only the Moon is designed to revolve
and rotate about its parent planet, the Earth.

Although the planets followed circular orbits in the eccentric grooves
of his ceiling, Eisinga emphasised that their natural paths are elliptical
by painting letters on the ceiling to show the nearest and farthest points
of their orbits to the Sun. He also indicated the proportions of their orbits
that lay above and below the ecliptic plane – the slice of sky made by
the Earth’s orbit around the Sun.

Outside Saturn’s orbit, Eisinga cut a seventh groove in the ceiling
for a pointer that completes one rotation in 365 days. The pointer indicates
the date and the position in the signs of the zodiac. In leap years, this
pointer has to be moved back one day. Eisinga left instructions on how to
do this; it involves crawling between the two ceilings, ‘taking care not
to set the place alight with the candle’.

A rectangular hole is cut out of the ceiling, through which is visible
part of a wooden disc that shows the current year. At the end of each year,
at approximately 4 pm, the disc starts moving and by the next morning the
new year has appeared. The disc has to be repainted every 22 years, as this
is the maximum number of years that could be fitted on the disc at any one
time. This is done right up to the present year, using Eisinga’s original
disc.

Eisinga also constructed a number of dials to indicate the travel of
the Moon, including its position and hour of setting. Above the bed cupboard
Eisinga built a planisphere, about 50 centimetres in diameter. This instrument
indicates the apparent motions of the Sun and the fixed stars as seen from
Franeker. Eisinga added the explanation above this dial, which says: ‘Schijnbare
beweging der zon en vaste IIII’ (The apparent motion of the Sun and fixed
IIII). The sentence breaks off because he did not have enough space to spell
out the Dutch for stars, sterren. On either side of the planisphere are
dials indicating the times of sunrise and sunset.

Even before Eisinga had finished his work and before he had time to
paint the newly built planetarium, he had to deal with curious visitors.
One of these was Jan Hendrik van Swinden, professor of physics at the former
University of Franeker. He visited Eisinga on numerous occasions and was
instrumental in spreading the news about the planetarium to scientists outside
the Netherlands. Van Swinden was aware of the rewards offered to other home-taught
innovators, such as Eisinga’s British contemporary, John Harrison, the Yorkshire
carpenter who received Pounds sterling 20 000 for perfecting the marine
chronometer, and he was keen to promote this genius in his native town.
As a result, a steady stream of interested people called at Eisinga’s house.
Eisinga collected their signatures in a total of six books that are still
kept in the planetarium museum.

Van Swinden was asked to give his scientific opinion about the device
to the authorities of the University of Franeker. He spoke in the highest
terms of Eisinga’s masterpiece, and tried to persuade them to ask Eisinga
to build a larger planetarium for the university. But nothing came of this
idea, partly because the request happened to coincide with the town mayor’s
presentation to the university of an orrery made by the British instrument
makers, Wright and Cole. Instead, the town authorities gave Eisinga enough
to buy himself a silver coffee pot and teapot, which were unceremoniously
delivered to him by the silversmith’s assistant.

In 1784 Eisinga drafted a full description of his planetarium for his
two sons, so that they would be able to look after the mechanism properly.
This description is still used by present-day curators when they need to
investigate the intricate machinery between the two ceilings and reset the
dials. Eisinga was only 40 at the time, but he may have realised that he
would never get the chance to build a bigger planetarium.

POLITICAL EXILE

Eisinga might have felt inclined to spend the rest of his life contemplating
the ceiling in his bedroom, but politics interfered. In 1787 civil war raged
in the north west of the country, and Eisinga, as an officer in the Civic
Guard, was forced to flee eastwards and abandon his beloved home-cum-planetarium.
He spent the next five years in exile at Visvliet, a village in the neighbouring
province of Groningen, until peace was restored and he could return to Franeker.
During these years his first wife died, and he remarried. His house had
been occupied in his absence and he had to wait before he could move in
again. He returned in 1796 and was soon spending all his free time restoring
his planetarium after nine years of neglect.

The remaining years of his life were spent wool-combing and dreaming
about more mechanical devices. He made many drawings and calculations, and
was appointed to several important civic positions. He was also asked to
assist with the restoration of the University of Franeker, another victim
of the political troubles. His dreams of building a larger planetarium were
never realised, despite several attempts by eminent visitors to encourage
him. In 1818, King Willem I and Prince Frederik of the Netherlands paid
him a visit; the crown prince, who became Willem II, came again two years
later.

As the years went by, Eisinga became increasingly concerned with the
fate of his masterpiece, which had miraculously survived both rebellion
and neglect. Although the many attempts, by others, to attract greater fame
for Eisinga proved unsuccessful, his anxiety about the future of his planetarium
met with more sympathy. Through the influence of eminent Friesians, the
planetarium was purchased by the state in 1825 and an allowance was given
to the family to continue to live in the house. Eisinga moved to the house
next door, while his son continued to live in the original house with the
planetarium. Between the two houses is a small path that leads to the wool-combing
building behind. Painted on the arch at the entrance to this path are the
words ‘Voersint eer Ghy begint’ (Look before you leap). No one seems to
know if this is Eisinga’s personal motto, or one added later reflecting
on the folly of the bedroom planetarium – the painstaking calculations
required for its construction and the time-consuming maintenance needed
for its upkeep.

Eisinga died in 1828 and was buried, as he wished, in Dronrijp, the
village of his birth. In 1859 the house was given by the state to the municipality
of Franeker, and his descendants continued to live there and look after
the planetarium until 1922. Since then the bedroom has been a museum, open
to the public and cared for by the state.

It has not been recorded whether Eisinga’s attempts at educating his
fellow citizens paid off, but a visit to his well-preserved and still accurate
planetarium is more than a lesson in astronomy. It is also a chance to contemplate
a monument to perseverance and dedication.

Marjolein Allen-Wytzes is the librarian at the Isaac Newton Institute
for Mathematical Sciences of the University of Cambridge. Willem Wytzes,
Eisinga’s early tutor, is one of her ancestors. The Eise Eisinga Planetarium
in Franeker is open all year round; telephone (31-5170) 3070 for details.