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Location: England
Culture: The Modern World
Period: Early 19th century
Material: Metal, Glass and Wood

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A chronometer is a type of very accurate clock used to measure the time at sea so that a ship can precisely know where it is sailing. This chronometer was used on board HMS Beagle on its voyage around the world in 1831 to 1836. Charles Darwin was the scientist on this voyage, and the observations he made about geology and wildlife had an important influence on the development of his revolutionary ideas about evolution.

How did the need to measure longitude at sea lead to the standardisation of time?

The frst chronometers that could accurately keep time on board a ship were developed in the 1700s. The time on this chronometer would have been set at the time of the Greenwich Observatory in London. Knowing the time of a fixed location allowed the ship's navigator to know the difference between the ship's position and the Greenwich Meridian to determine the ship's longitude. In the 1840s the Great Western Railway used Greenwich Meantime as its standard measure of time. It replaced local time, which could vary by up to 20 minutes between towns.

• For Darwin's 25th birthday, the Beagle's captain named a mountain after him: Mt Darwin, the highest in Tierra del Fuego.

By David Thompson, curator, British Museum

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At the best of times sailing the high seas was always a precarious business and apart from fire, getting lost was probably the most hazardous event to be encountered. Sailing in sight of land presented few problems. However, sailing out of sight of land and losing position due to storms or bad judgement could mean crews dying of thirst and starvation, or ships running aground. Such were the hazards that countless numbers of ships with their crews and cargoes were being lost each year.

The problem was so bad that in 1714, the British government offered a huge prize to anyone who could devise a method of establishing longitude at sea. There were those astronomers who favoured observing the behaviour of the moon, or observing the moons of Jupiter, but achieving this with any degree of accuracy on a moving ship was perhaps a step too far.

During the eighteenth century it was to be John Harrison who proved that longitude could be found at sea using a timekeeper. He created four ground-breaking machines, the last of which, his H4, performed in what can only be described as a remarkable fashion.

While Harrison had proved that such a machine could be made and function reliably in wide ranging temperatures, humidities and in salt sea conditions, his machine was extremely expensive, costing about £500, took a number of years to make and there were precious few craftsmen in London who could actually make such a technically demanding device.

It was to be John Arnold and Thomas Earnshaw who devised new escapements and new temperature compensation systems which would enable their ‘chronometers’ to be made for as little as 30 guineas and in the space of a few months. Whilst the making of certain parts of the chronometer and indeed its final adjustment remained in the hands of the most highly-skilled makers, the simplification of the machine made all the difference.

These precision-made machines made of high quality materials to very precise tolerances quickly became an essential part of the navigation equipment on board ships.

In the early years, from the mid-1770s one aspect of the voyages of discovery was the testing of various marine chronometers to see which would prove to be the most accurate and reliable over long journeys on the high seas. In the final resort it was Thomas Earnshaw’s design which would become the standard issue timekeeper until the introduction of new technologies such as radio signals and Global Positioning System.

These life-saving machines also had another use in producing accurate charts of coastlines and were also used in mapping new and unexplored territories. If you know the time where you are by observing the sun, and you have a chronometer which shows the time at a known longitude, then, with a simple calculation, the time difference is directly equivalent to an angular difference – 360 degrees of a circle being equal to 24 hours, and so one hour is equal to 15 degrees of longitude – simple really, as long as the timekeeper is accurate enough and does not stop!

By Steve Jones, Head of the Department of Genetics, Evolution and Environment, University College London

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I’m interested in evolution and I suppose you can define evolution as biology plus time. The essential point of course is time, and I think we can only live time in this instance, time like an ever following stream and so on and it’s very hard to work out how long time has been going on, how old is our species, how old is our earth?

Until the eighteenth century everybody believed more or less Archbishop Ussher’s famous estimate based on the Bible that the world began in 4004 BC, but in the eighteenth century we began to get the first hint of how ancient the world must be, how much time there must have been. Ironically enough that was first hinted at a place – Siccer Point near Edinburgh – which I have been to.

The geologist James Hutton noticed a great break as it were in the rocks, from sandstone to slate, as he went down and he realised this must mean there was a great gap somewhere while the rocks were being laid down. And he came out with a wonderful phrase it was: ‘the mind seemed to grow giddy by looking so far into the obis of time. We find no vestige of a beginning, no prospect of an end.’ That was really a shock to discover how ancient the world was and in that gap the Atlantic Ocean had opened and closed, not once but twice we now know.

So enormously deep time, and that of course was enormously important to Charles Darwin who was on the Beagle and no doubt looked at this very object, this very chronometer because he needed time for his theory to succeed.

One of the great unread books of the 20th century was a Brief History of Time and time I suppose began 14 billion years ago at the time of the Big Bang when it all started. The age of the earth of course is immeasurably old, about 4.5 billion years. Now that is almost inconceivable. Darwin for example needed the earth to be old but he had no idea that it was that old and in fact he almost abandoned his theory because of an argument about time because Lord Kelvin the great physicist had worked out ,or so he thought from the rate was losing energy that the sun itself couldn’t be more than 30 million years old so the earth must be much younger and that really worried Darwin, but like most of the things Darwin worried about he didn’t have to worry about time at all, there’s plenty of it.