It’s hard to believe that it took until 1765 before sailors had an accurate way of measuring where they were in the world. Although a method of knowing your position relative to the equator had been around since 241 B.C. it only gave a North/South position and not an East/West one. Click on the PDF link below to see a magazine article on Navigation and the great explorers and unsung heroes who used it. Keep scrolling for a text only version of the article.
Navigation – Great Explorers & Unsung Heroes: Text only version
We are so quick to take things for granted. Each new generation is born with new technologies that have “always been there” but how often do we stop to consider how those tools and gadgets came into existence?
Those of us of a certain age will remember having to rely on an “A-Z” book of maps to find our way around cities. Nowadays there are mapping apps built into Smart Phones. Similarly it wasn’t long ago that London cab drivers had to acquire “The Knowledge” – now you can buy a car, a Sat-Nav and you’re an Uber. It seems alien for us to set out on a journey without knowing exactly how to get there – yet what would we do if we faced a journey when we didn’t know where our destination was?
Furthermore, if we did reach our new destination – would we even be able to find our way back?
Christopher Columbus led an expedition of three ships, the Nina, Pinta and Santa Maria from the coast of Spain on 3rd August 1492. His mission was to find a Western sea route to India. Traders had been profiting through importing expensive silks and spices into Europe, but the journey overland was long and perilous. Seasonal weather saw the trade routes, like the Silk Road, cut off for months at a time.
The existing sea route involved sailing around the southern tip of Africa, a place called The Cape of Good Hope because you had to hope that you might survive the journey.
But when Columbus set out he was not sailing blind – he employed navigation techniques that had been developed by a little known Greek mathematician more than 1,500 years earlier. Enter Eratosthenes.
Eratosthenes (Era-toss-ta-knees) was visiting the city of Syrene, Egypt in June 240 BCE. While he was there he went to a well to get a drink and as he looked down he noticed that there was no shadow being cast on the sides of the well. He reasoned that the lack of shadow was due to the fact that this was the Summer Solstice. He made a note of the fact, finished his visit and returned to his home city of Alexandria.
The following year, Eratosthenes prepared as the Summer Solstice approached. He waited by a tall monument in the main square, but at midday on the day of the solstice he was surprised to see that the monument was casting a shadow. He had expected that there would be no shadow – as with the well.
Eratosthenes measured the length of the shadow and set about trying to explain events.
Eratosthenes reasoned that Alexandria’s location, 500 miles further north than Syrene, must have been the cause for the difference in shadow length.
Armed with that knowledge he calculated that the angle of the shadow in Alexandria was 7.2° which compared to 0° in Syrene.
He further calculated that if the angle of 7.2° were to be multiplied by 50, the answer would equal a perfect circle of 360°.
He realised that if multiplying 7.2 x 50 gave us the 360° needed to make a circle that multiplying the 500 miles (between Alexandria and Syrene) by 50 would give us the circumference of that circle. i.e. the Earth’s circumference. His calculation of 25,000 miles was surprisingly accurate – according to our best estimates today the Earth’s circumference is around 24,812 miles.
Perhaps the most significant part of Eratosthenes’ discovery was that it made it possible to safely identify our location relative to the equator. In other words, we could finally figure out how far North or South we were. However this system had its limitations. It could only be used at midday when the sun was at its highest point in the sky, if the weather was overcast or the sea too rough you could miss your opportunity to fix your location. Perhaps more significant was that sailors still had no way to identify how far East or West they had travelled – a point that was proven when Columbus found the ‘New World’.
Columbus set out to discover a new sea route from Europe to India. He would have known where India was in relation to the Equator. He left the coast of Spain and sailed West. In October of 1492 he spotted what we know today as The Bahamas, and named the first island he arrived at San Salvador. He also visited Cuba and Hispaniola.
But Columbus initially believed that he had achieved his goal – he was convinced that he had sailed around the world and landed at a group of islands off the coast of India. This is why the islands off the coast of the Americas are still called the West Indies and also why Native American people that Columbus met were called Indians for so long.
The problem of how to calculate how far East or West a ship had travelled would continue to plague navigators for centuries. In the 1600’s it was established that using ‘time’ might provide the key, but the clock makers lacked the technological ability to fashion a timepiece accurate enough to be used. Furthermore, the watches and clocks of the day were fragile and required delicate handling. They did not fare well aboard ships where changes in temperature and humidity played havoc on their accuracy. The salt water alone would cause most clocks to rust and seize. It took a declaration by King George I to invigorate efforts to solve this problem.
After a declaration by king George I, the Board of Longitude was created after an Act of Parliament in 1714. There were a series of rewards set out for anybody that could create a timepiece that could accurately measure time at sea. The rewards were scaled from £10,000 – £20,000 (which is roughly equivalent to £1.3M to £2.6M today).
Despite many takers and international efforts there was no immediate progress in achieving this goal. This was despite the involvement of the greatest minds of the day, like Sir Isaac Newton.
It took until 1736, more than 20 years before the first watches were given sea-trials, but none was able to deliver the level of accuracy needed. King George I never actually saw the watch that would fill the brief he had commissioned, nor did his son, King George II. But finally, after 51 years of work, John Harrison delivered the H4 (Harrison #4) to King George III in 1765.
Over the 5 decades Harrison was paid £23,653 which equates to around £3M, however, he spent most of the money he was paid on his watches.
At the subsequent sea-trials, Harrison’s watch proved its worth and proved to be one of the most significant navigational leaps in human history.
When sailors left Greenwich docks in London they ensured that their ship’s watch was set to match Greenwich Meridian Time (GMT).
The sailors would calculate the angle of the sun at their location when the ship’s watch read noon. By calculating the angle of the sun they could work out how far East or West they were from Greenwich London by using the principals that were introduced by Eratosthenes. The globe above is divided into 15° lines of longitude or meridians. Each meridian represents one hour of time ahead of or behind Greenwich Meridian Time.
British Sailors could now plot their positions on two axis, how far North or South they were from the Equator and how far East or West they were from London. It is incredible to look back and realise just how significant a development this was and how great an advantage that British Sailors held over the ships of other nations. Harrison’s watch was a huge factor in the building of the British Empire.
While the rest of the world’s sailors were still forced to rely on navigating by the sun while depending on trade winds, the British were able to develop the quickest and most efficient sea routes. Furthermore, they lost fewer ships at sea – before Harrison’s watch just getting back to a safe port was almost as dangerous as finding new land!
These new techniques were employed by sailors like James Cook who would go on to map huge swathes of the southern oceans. Cook is also credited with discovering Australia, Tasmania and much of the Antipodean nations – but perhaps he was merely the first man to make it back and tell the tale!
The two axis grid reference system for navigation is still critical to our everyday lives. It was only with the advent of submarines and aeroplanes during the 20th Century that we began to need a third axis to account for depth / height.
One final note to this article is a lesson from history on the importance of Equality and Diversity.
John Harrison was a normal chap. He had no titles, he was not an aristocrat – no blue blood. But when the King announced the challenge to create a watch, Harrison opted to try his luck.
In Britain there was an eagerness for new ideas and new thinking – this was what fuelled the Industrial Revolution. Ideas were judged on their merits and if they worked their inventors could achieve life changing rewards. Even the lowliest born of men could rise through the ranks of society on merit.
At the same time that Harrison was developing his watch in Britain, the French had a polar opposite view to new ideas. If a peasant had an idea it stood to reason that it must be a bad idea. As far as the French Aristocracy were concerned, it was only men of noble blood that could ever conceive of good ideas. Their Universities and Academies were filled with the sons of lords and kings. If you were born poor you invariably died poor.
After Harrison’s watch was adopted by the British Navy in the late 1700’s, the British would become the dominant maritime force of the day and the British Empire expanded to become the largest that the world had ever seen.
While the British were expanding their empire and growing through the Industrial Revolution, the French were engaged in a revolution of their own. Fed up at the treatment they were receiving at the hands of the aristocracy, the French rose up and overthrew the monarchy. Heads rolled and the French Republic was born under the motto, “Liberte, Fraternitie, Egalite” or “Freedom, Fraternity and Equality”.
If people are denied equal opportunity they may be left with no choice but to rise up. There are countless examples running throughout history, from the Jews in Egypt right through to the civil rights marches of the 60’s. We have seen numerous major landmarks including the 1975 Sex Discrimination act and the Equalities Act of 2010 but for some reason the lesson still isn’t being learned by all.