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Travel - April 23, 2021

Fixing the Longitude Drawback

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Navigation on the open ocean is extraordinarily tough. It’s a talent that takes years to grasp. 

Even with years of talent, an skilled mariner was nonetheless capable of floor their ship on an unseen reef, underwater rocks, or a sandbar, as a result of they didn’t know their exact location. 

The principle drawback, which was unsolved for hundreds of years, was figuring out your longitude.

Study extra concerning the longitude drawback, and the way it was finally solved, on this episode of All the things All over the place Day by day. 


In an earlier episode, I spoke concerning the navigational achievements of the  Polynesians. They managed to discover the Pacific Ocean with out the usage of any superior navigational instruments. Furthermore, they sailed giant outrigger ships that sat very excessive within the water. 

Not solely did they’ve superior data of reefs and the right way to navigate them, however their ships, at excessive tide may usually simply sail proper over them. 

European navigators weren’t so fortunate. That they had a lot bigger ships that sat a lot decrease within the water. If there was an underwater hazard resembling a rock or a reef, and so they had been to unknowingly hit it, the outcomes could possibly be devastating. 

In truth, this occurred much more usually than most individuals understand. Simply for instance, Sable Island which is a big sand bar off the coast of Nova Scotia is estimated to have brought about a minimum of 350 shipwrecks and presumably as many as 500. 

This was only one island. There have been many different such hazards throughout which ships needed to keep away from. 

This was one of many the explanation why correct mapping was so vital. There have been many voyages the place a cartographer was despatched alongside to deliver again info to enhance their maps. 

Nonetheless, the most effective map on the planet doesn’t imply something in the event you don’t know the place you’re. 

This was the issue that beset sailors. 

To know the place you had been, you wanted to know two issues: your latitude and your longitude. 

Latitude, that are the imaginary horizontal strains across the Earth, was a somewhat simple drawback to unravel. As a result of the Earth rotates round its poles, and since there’s a star within the northern hemisphere the place the pole is, it’s doable to find out your latitude by realizing the angle between the pole star and the horizon. 

This was completed by way of a sextant which was a tool that would measure angles. 

For those who add to this the usage of a compass, you possibly can know your route, however that was it.

There was no approach, nevertheless, to find out your longitude.

Longitude strains are the imaginary vertical strains that go from north to south pole. As a result of the Earth is at all times rotating, it’s close to unattainable to get a repair in your longitude primarily based on the celebrities. 

This drawback was so vital that the British Parliament handed the Longitude Act 1714 which provided a prize to anybody who may remedy the issue. 

The prize was between £10,000 and £20,000 relying on the accuracy of the approach. In modern-day cash, that may be between $2 to $4 million {dollars}. Cash went so much additional again then. 

The important thing to figuring out longitude was time. For those who knew the native time and the time at a hard and fast location, you possibly can decide the distinction in time, and therefore the distinction in longitude. 

The approach that everybody thought would win out was an astronomical approach. 

One of many concepts was the strategy of Lunar distance. The moon strikes throughout the celebrities at a price of about 0.5 levels per hour. When you’ve got good tables, a great measurement, and did the calculations, you possibly can decide your native time. 

One other approach was to make use of the moons of Jupiter. As a result of the 4 main moons of Jupiter orbited at a particular price, in the event you knew the place of the moons, once more with some excellent tables, you possibly can decide the time. 

The issue with these methods is that they didn’t actually work on the deck of a ship that was pitching and rolling on the ocean. You may’t use a telescope in that kind of atmosphere. 

Furthermore, if the moon wasn’t out, or Jupiter wasn’t within the sky on the proper time of the 12 months, or if there have been clouds, the methods wouldn’t work. 

The primary British Astronomer Royal in 1675 was principally commissioned to work on this drawback and develop tables on the observatory in Greenwich.

These astronomical methods did really work on land. For those who had been in say Newfoundland or Kingstown, you possibly can work out the longitude of that spot with respectable accuracy, and that helped in mapmaking.

Nonetheless, it did nothing for aiding navigators on a ship. 

The answer which finally received out was the event of an correct clock. 

Initially, nobody thought {that a} clock would work as a result of early clocks required the usage of a pendulum. A pendulum clock on a rocking ship was about as ineffective as attempting to make astronomical observations on a ship with a telescope. 

An English clockmaker by the identify of John Harrison knew that constructing a chronograph was the important thing to fixing the issue of latitude. The trick was engineering a clock that would work at sea, but nonetheless, stay correct. 

Harrison spent 40 years engaged on 5 totally different clocks. His first clock, which was examined on a voyage in 1736, was capable of decide the longitude of a ship to inside 60 miles. Good however not nice.

Through the years he saved continuously bettering his clocks. His remaining model seemed like a really giant pocket watch. 

He has solved many issues related to maintaining time on a ship, together with the movement of the ship and adjustments in temperature.

His remaining clock, which was examined in 1772 by King George III himself, was discovered to be correct to inside ? of 1 second per day. Greater than correct sufficient to assert the prize.

Nonetheless, he by no means did technically declare the prize. The astronomer royal was on the board overseeing the prize, and the board was very biased towards any non-astronomical answer. In the long run, Harrison did gather the equal of the prize, however by no means the acknowledgment of parliament. 

All of the clocks within the British Navy had been synchronized to the Greenwich Observatory, which is the rationale why the Prime Meridian is there, and why Greenwich Imply Time, now known as Coordinated Common Time or UTC, is centered on Greenwich. 

In truth, in the event you go to the Greenwich observatory as we speak, you possibly can see the primary 4 Harrison timepieces. All of them nonetheless work as we speak. It’s also possible to hear the cannon which is fired at midday every single day, which was used so ships may synchronize their clocks. 

The early clocks had been costly, however they proved their price. Captain Cook dinner used a clock similar to Harrison’s fifth clock on his second and third voyages, and he had solely glowing issues to say about them.

Within the nineteenth century, the clocks continued to get higher and cheaper, and in consequence, navigation turned higher and safer. Because the clocks had been put in on extra ships, the variety of disasters involving ships working aground plummeted, and crusing turned a lot safer.

Finally, because the telegraph turned widespread, time indicators can be despatched alongside the wire. Because the sign was nearly instantaneous, measurements of longitude between factors turned much more exact. 

Telegraphs didn’t do a lot for ships, however when wi-fi communication was developed, it allowed ships to get time indicators wirelessly, which improved the precision of their measurements. 

In 1912, a convention was held in Paris to coordinate international wi-fi time indicators on totally different frequencies, permitting ships to get correct time info nearly wherever on the globe. 

The pursuit of longitudinal measurement culminated within the improvement of the World Positioning System, which permits for pinpoint measurement wherever on Earth. The event of GPS is a subject which I went into a lot larger element in a earlier episode. 

For those who’ve ever traveled or bought one thing which was made abroad, you could have been the beneficiary of the answer to the issue of longitude. An issue solved by one decided English clockmaker within the 18th century. 

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