The Celatone: Galileo’s Forgotten Failure
On a breezy September morning in 1617, legendary astronomer Galileo Galilei was fastened into a chair, secured to a small boat, floating in a pool of water, on the deck of a ship in the Tuscan port of Livorno.
Strapped to his head was a helmet with a telescope welded to its eyeslit. He called the device the ‘celatone’ and he was convinced that it would make him one of the richest men in Europe. He was wrong.
The problem Galileo was trying to solve was one of longitudinal navigation. It was one he had struggled with for five years already and, when he died twenty-five years later, he still wouldn’t have an answer.
The longitude problem had gone unsolved for more than 1,500 years, since the Greeks first proposed splitting the Earth into a grid of latitudinal and longitudinal lines in the 3rd century BC.
Astronomers found you could determine your latitude by using the Sun’s altitude at the equator as a standard. Tables of the Sun’s altitude were drawn up, showing how high it would be on each day of the year. When you compared your view of the Sun to that in the table you could establish how far north or south you were from how far above or below the standard the Sun appeared to be.
But until Galileo discovered four moons orbiting Jupiter in 1610 there hadn’t been an equivalent celestial marker to find how far east or west you lay on the planet’s surface. By fixing a ruler to the side of his telescope, Galileo found he could chart with great accuracy the regular phases of Jupiter’s moons. With one eye he observed the moons through the glass and, with the other, relate their distance to the planet. Galileo had found a universal clock in the heavens.
Galileo realised Jupiter’s moons could be used to establish a standard celestial time, much as the height of the Sun at the equator established a standard altitude. Astronomers knew that the Earth completed a full 360° rotation on its axis every day, meaning that within a 24 hour day every hour the Earth rotates by 15°. When you look at two locations’ local time you can establish their longitudinal distance from one another.
Pisa encounters noon six hours ahead of Dhaka each day, so there is 90° of separation between Pisa and Dhaka. So, if Galileo set celestial time to the phases of Jupiter’s moons when viewed from Pisa, a sailor could always know what time it was in Pisa by looking at Jupiter, he could then determine his longitude by comparing that to his local time.To put it roughly, if Jupiter reads 12PM and your sundial reads 3PM then you are at 45° longitude.
It wasn’t simply intellectual interest that spurred Galileo’s experiments — there was a lot of money at stake. In 1598 King Philip III of Spain established a perpetual pension of 6,000 ducats for whoever could devise a solution to the longitude problem, particularly a solution that could be used at sea. That works out at about £350,000 per year.
The king offered such a large sum because determining longitude would rewrite the routes sailors took to cross the world’s oceans. Ships had to follow latitudinal (east-west) routes to avoid getting lost in the middle of the sea with no landmark to guide them. If their destination was north-east of their starting point they had to head east till they hit land and then follow the coast northwards. Weeks were lost travelling in this manner.
Galileo sent a chart of Jupiter’s motions and a description of Jovian navigation to the court in 1612. It was quickly dismissed. When the king first created the pension, his court had rewarded inventors before their submissions were tested. As a result, the court had been inundated with proposals of astral navigation, bizarre machines, and ideas that held no water. The court quickly learnt not to throw any more money at theories.
So Galileo had to prove his method worked. In the winter of 1616 he began work on the celatone. The helmet was designed to allow any sailor to do what he had done in his observatory. Spot the moons through a telescope with one eye and chart their position on a scale with the other. Except, in the spring of 1617, standing on the deck of a ship in Livorno’s port, the rocking of the waves prevented him from sighting the moons.
September saw Galileo sat strapped to a floating platform on the deck of a ship in Livorno’s port. As the waves knocked the boat, Galileo remained stable, with his eye fixed on the sky. The Spanish weren’t convinced and, again, rejected the astronomer’s proposal, saying his charts weren’t sufficiently accurate. It would be more than a decade before Galileo revived the celatone.
By 1636, Galileo was an old man, nearly blind from his years of stargazing. After having been found to be “vehemently suspect of heresy” over his support of Copernican astronomy, the Vatican hadn’t allowed the astronomer to leave his house in three years. There, locked indoors, he wrote a letter to the States General of the United Provinces of the Netherlands. The country was offering a prize of 30,000 florins (about £193,500) to whomever could provide sailors a method to guide themselves any time by day or night.
Galileo again wheeled out his celatone design, but this time the wearer was fixed to a chair within a bronze hemisphere. That was positioned inside another, slightly larger, hemisphere with a layer of oil in between that allowed the operator to roll with the sea’s waves. Along with the seat, the charts of Jupiter’s moons’ movements, and the celatone, Galileo added a clock which, unlike others of the era, kept time using a weighted pendulum.
The Dutch Fleet Admiral, Laurens Raeal, rejected the proposal, saying “[seamen are] rude people, men only superficially acquainted with mathematics and astronomy … and who still find insuperable the problem of using your discovery on a moving ship, continually being tossed about”. The Dutch court offered Galileo a consolation prize of a gold chain, which he rejected.
Galileo thought his tomes of charts, complex stabilising platforms, and helmet mounted telescopes would solve the problem of longitude. Instead it was the pendulum clock, 100 years after his death, that would hold the answer. Galileo’s clock launched a line of clockmakers, each iterating on the design of their predecessors, that led to John Harrison, inventor of the marine chronometer. in 1772 Harrison was awarded £23,065 for finally finding the solution to the longitude problem.
Today, the celatone is largely forgotten. But not entirely.
Steampunk designer Matthew Dockrey has revived the device for an exhibition at the Royal Observatory that opens Easter 2014. Longitude Punk’d challenged designers to build a steampunk longitude machine based on designs submitted to Britain’s Board of Longitude between 1714 and 1828. Dockrey’s celatone isn’t based on Galileo’s designs but Samuel Parlour’s, an Englishman who tried to develop Galileo’s helmet into ‘an apparatus to render a telescope manageable on ship-board’. You can see Dockrey’s beautiful, brass machine for yourself in this gallery.
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