The Compass and Other Magnetic Innovations

A compass is one of the most commonly used navigation instruments. We know that it always points north, but how? It contains a freely suspended magnetic element that displays the direction of the horizontal component of Earth's magnetic field at the point of observation.

The compass has been used to help people navigate for many centuries. Though located in the same part of the public imagination as sextants and telescopes, it's actually been in use for a lot longer than the sea voyages that discovered North America. The use of magnetism in inventions doesn't stop there, though; it's found in everything from telecommunications equipment and motors to the food chain.

Discovering Magnetism

Thousands of years ago, large deposits of magnetic oxides were found in the district of Magnesia in Asia Minor; their location led to the mineral receiving the name of magnetite (Fe₃O₄), which was nicknamed lodestone. In 1600, William Gilbert published "De Magnete," a paper on magnetism that details the use and properties of magnetite.

Another important natural element to magnets is ferrites, or magnetic oxides, which are stones that attract iron and other metals.

While the machines that we make with magnets are clearly inventions, these are natural magnets and should not be considered as such.

The First Compass

The magnetic compass is actually an old Chinese invention, probably first made in China during the Qin dynasty (221–206 BCE). Back then, the Chinese used lodestones (which align themselves in a north-south direction) to construct fortune-telling boards. Eventually, someone noticed that the lodestones were better at pointing out real directions, which led to the creation of the first compasses.

The earliest compasses were designed on a square slab that had markings for the cardinal points and the constellations. The pointing needle was a spoon-shaped lodestone device with a handle that would always point south. Later on, magnetized needles were used as direction pointers instead of the spoon-shaped lodestones. These appeared in the eighth century CE—again in China—and from 850 to1050.

Compasses as Navigational Aids

In the 11th century, compasses' use as navigational devices on ships became common. The magnetized-needle compasses could used when wet (in water), dry (on a pointed shaft), or suspended (on silk thread), making them valuable tools. They were employed mostly by voyagers, such as those traders who traveled to the Middle East, and early navigators looking to locate the magnetic North Pole or pole star.

The Compass Leads to Electromagnetism

In 1819, Hans Christian Oersted reported that when an electric current in a wire was applied to a magnetic compass needle, the magnet was affected. This is called electromagnetism. In 1825, British inventor William Sturgeon displayed the power of the electromagnet by lifting nine pounds with a seven-ounce piece of iron wrapped with wires through which the current of a single-cell battery was sent.

This device laid the foundation for large-scale electronic communications, as it led to the invention of the telegraph. It also resulted in the invention of the electric motor.

Cow Magnets

The use of magnets continued to evolve beyond the first compass. U.S. patent No. 3,005,458, issued to Louis Paul Longo, is the first patent issued for what is called a "cow magnet." Its goal was the prevention of hardware disease in cows. If cows happen to consume scrap pieces of metal, such as nails, when they're feeding, the foreign objects can cause internal damage to their digestive tract. Cow magnets keep the metal pieces confined to the cow's first stomach, rather than traveling to the later stomachs or intestines, where the fragments can cause the most damage.