The History of the Compass

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Podcast Transcript

One of the most important inventions of early humanity was the compass. The compass has aided human navigation around the Earth for centuries. 

Despite being a critical technology in the development of transportation, it actually took centuries between the discovery of its underlying principles and its eventual use as a practical tool for navigation. 

Even though it was discovered over 2,000 years ago, compasses are still a vital tool today. 

Learn more about the compass and how it helped humanity find its way on this episode of Everything Everywhere Daily.

Before I get into the history of the compass, I should explain a little bit about how it works. 

As I’m sure all of you are aware, a compass uses a magnetic, metallic piece of metal that will orient itself in the presence of a magnetic field.  This effect will manifest in the presence of any magnetic field, including artificially created ones.

However, unless you happen to be next to something magnetic, the metallic object will align itself with the natural magnetic field of the Earth. 

The Earth can be thought of as a giant bar magnet. Just as a bar magnet has a north and south pole, so too does the Earth. 

The magnetic north and south poles of the Earth are not the same things as the geographic poles. The geographic poles are steady, but the magnetic poles are usually some distance away from the geographic poles, and they are always moving. 

So, in summary, a compass is just a small magnet that aligns itself with a very big magnet, which happens to be the Earth. 

The compass effect, which is what I just described, was first discovered sometime during the Han Dynasty in China about 2,000 years ago. Unlike other great Chinese inventions, who discovered the compass effect and exactly when it was discovered isn’t precisely known. 

What we do know is that the Chinese found if a lodestone were hung by a string, it always point south. 

This was known as the “South Pointing Fish.”  

Here I should note the obvious, that the Chinese defined the direction in which the rock would point as being ‘south.’ Today, we usually define the direction of a compass needle as pointing ‘north.’ 

Neither of these statements are in conflict. A compass needle aligns itself along a north/south axis. So it is always both pointing north and south, and which you choose to focus on is just a matter of convention. 

Lodestone, the rock which exhibited this behavior, has a high concentration of iron, in particular the iron oxide known as magnetite.  Iron has two common types of oxides: magnetite, which is black and highly magnetic, and hematite, which is rust-colored and not as magnetic. 

Hematite has two iron and three oxygen atoms, and magnetite has three iron and four oxygen atoms. 

The Chinese discovery of the compass effect was mostly just a novelty for centuries. It was interesting that this rock would always point in a certain direction, but there was no practical use for it. 

The primary use of the “south pointing fish” was for divination in the form of geomancy and feng shui. Geomancy is simply using signs in the ground to tell fortunes. Feng shui is the ancient art of arranging things according to lines of energy, and to do so, you need to know the direction. 

Before I go further talking bout the history of the compass, I should note that the compass effect is a natural phenomenon. Unlike other Chinese inventions like the printing press or gunpowder, this was discovered, not invented.

That means that other civilizations might have discovered the effect as well.

There is some evidence that the compass effect could have been discovered by the ancient Olmec people in Central America, potentially a thousand years before the Chinese.

If they did, it was probably used for geomancy purposes like they did in China.

The next advancement after the south pointing fish was the magnetic spoon. These were literally spoons cared out of lodestone that could balance at the bottom of its bowl. The spoon would rotate until it was pointing north-south. 

However, ancient forms of fortune-telling and spoons are not why the compass is worthy of an episode. 

That has to do with navigation. 

That began with a discovery during the Tang Dynasty of the 7th century that if an iron needle was rubbed with a loadstone, then it too would become magnetized. 

A magnetized needle was far easier to use than a rock or a spoon. Moreover, a needle was small enough such that it could be made to float on water, either using the surface tension of water or floating on something light like a leaf or a piece of paper.

A floating magnetized needle is known as a wet compass. 

Likewise, the needle could be hung on a piece of silk thread, which would achieve the same purpose. This is known as a dry compass. 

Still, these magnetized needles were again first used for geomancy, not navigation.

The first evidence of magnetized needles used for navigation on land was documented in the 11th century, and the first maritime use was documented in the 12th century. 

The Chinese historian Zhu Yu wrote in his book Pingzhou Table Talks, The ship’s pilots are acquainted with the configuration of the coasts; at night they steer by the stars, and in the day-time by the sun. In dark weather they look at the south-pointing needle”

This is why the compass is known as one of the Four Great Inventions of China. 

Here I should note that the compass aided navigation, but it wasn’t responsible for navigation. Many ancient seafaring cultures didn’t have the compass, most notably the Polynesians.  If you remember back to my episode on Polynesian Navigators, they were capable of open ocean navigation without a compass. 

Nonetheless, having a compass was a huge advance. 

With a compass, you didn’t necessarily need to see the coast, or the sun, or even the stars. This could, if nothing else, prevent you from sailing in circles. 

How the compass spread beyond China is a bit of a mystery. 

The period of time between when the navigational compass appears in Chinese literature and when it appears in European literature is rather short. 

The first written mention of the compass in Europe was by the English writer Alexander Neckam who wrote in the early 13th century, The sailors, moreover, as they sail over the sea, when in cloudy whether they can no longer profit by the light of the sun, or when the world is wrapped up in the darkness of the shades of night, and they are ignorant to what point of the compass their ship’s course is directed, they touch the magnet with a needle, which (the needle) is whirled round in a circle until, when its motion ceases, its point looks direct to the north.

This description of the compass is shockingly similar to that of Zhu Yu less than a century earlier. 

The other odd thing is that evidence of the compass appeared all the way in England before it appeared in the Muslim world. By the 12th and 13th centuries, anything which came from China to Europe would have had to have come through the Caliphate. 

So, either the compass somehow skipped over the Muslim world, which seems very unlikely, or for whatever reason, it just didn’t appear in writing. 

When the Islamic world received the compass, it was used not only for navigation but also for determining the qibla, which is the direction towards Mecca, which was used for prayer. 

Around this time, the Chinese were still using wet compasses for navigation. They worked, but they had serious limitations. Water sloshed around on a ship, so it was just practically hard to use. 

In Europe, there were several innovations made to the compass. The first was a practical working dry compass. The Chinese dry compass was just a needle on a string. The European dry compass was a feely pivoting needle on a pin that could be balanced and put inside of a glass case. 

This is not too far from how most compasses are built today. 

The second big innovation was the creation of a windrose. This is the underlay of a compass that shows the cardinal directions of north-south-east-and west, including bearings in between. It is often in the shape of a star. This allowed for taking bearings in almost any direction. This eventually evolved into the fleur-de-lis which became a symbol of France and the New Orleans Saints.

Finally, for ships, the wooden box that held the needle was placed in a gimbal, which was placed in another gimbal. This allowed the compass to remain level, even when the ship was being tossed. 

There were also European wet compasses that were developed for purposes of astronomy, which didn’t have to move.

There were eventually wet navigational compasses where the liquid was contained in the box, which provided extra stability to the needle.

These European innovations to the compass eventually made their way back to China via Japan when Europeans began visiting Asia, sort of closing the loop on the compass. 

One of the things which were required to accurately use a compass was compensating for magnetic declination.  Magnetic declination was discovered by the Chinese when they were still using the south pointing fish.

Because the magnetic north pole isn’t the same as the geographic north pole, there is often a difference between where the needle points and true north. This angle difference is known as magnetic declination or magnetic deviation.

This difference changed depending on where you were. The declination in London would not be the same as in Copenhagen, for example. Moreover, because the magnetic poles wander, magnetic declination can change over time. 

This led to the creation of declination maps that could be used by navigators. 

In the 1830s, the British launched was they called the magnetic crusade, which was a worldwide effort to create a complete map of magnetic declinations. 

Magnetic compasses have advanced, but they still aren’t radically different from the compasses which existed centuries ago. The principles are still fundamentally the same. If you buy a compass today, it will probably still be a magnetic needle or card floating in a liquid for stability, encased in glass or plastic. 

One innovation used in hand compasses were sights that allowed for taking more accurate bearings. 

This was initially for military use, but it also led to the development of the sport called orienteering. 

Orienteering began in Sweden in the late 19th century as a competitive military exercise. The first large-scale meet was organized by Swedish ??Major Ernst Killander in 1919.

The sport caught on in Scandanavia and Eastern Europe and spread around the world from there. 

Today orienteering is a cross between navigation and cross-country racing. It requires both speed and accuracy. There is an orienteering world cup held every year that hosts multiple events across four disciplines: foot, mountain bike, ski, and trail orienteering.

There has been discussion for years about making orienteering an olympic sport. 

There is a good chance you have a compass on the smartphone that you are listening to this very podcast right now. It isn’t a compass with a magnetic needle, however. It uses a computer chip called a magnetometer which acts the same as a compass.

If you are using an iPhone, there is a compass application on it if you haven’t used it before.

Likewise, many aircraft have a gyroscopic compass that establishes orientation without the use of magnetism.  It achieves the same thing, but without magnetism. 

A GPS device cannot actually give you direction, it can only provide location. It can provide direction, however, if you are moving, as it can just compare the difference between two locations. 

Good old-fashioned magnetic compasses are still in regular use. Geologists have to learn how to use what is called a Brunton compass, which is designed for geology fieldwork. I had to learn to use one when I did geology field mapping one summer. 

Likewise, they can still be found in ships. I once was able to visit the bridge of an aircraft carrier while it was at sea. Despite all the advanced navigation equipment they had at their disposal, they still had a magnetic compass. 

Despite the easy access we have to GPS systems and computer maps, learning how to use a paper map and compass is a worthwhile skill to have. Having that knowledge is not only useful but will make you part of a long tradition that goes back 2000 years to ancient China.


The executive producer is Darcy Adams.

The associate producers are Thor Thomsen and Peter Bennett.

Today’s review comes from listener Scott Moffatt, over at Podcast Republic. They write, 

Gary delivers interesting stories and facts about various topics at a length that makes sure the topic doesn’t get boring. This podcast is absolutely the best of its type that I have found.

Thanks, Scott!  I’m glad you find the show to be best in breed, and I promise that I will always try to keep it not boring. 

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