Why Does This Thing Point North?

Alex Johnson

Alex Johnson
Content Writer

Magnets, huh? How do they work? Before 1600—or 2009, if you were a member of the Insane Clown Posse—nobody really knew.

Either an early Chinese compass, or a Swedish Fish that’s way past date.

Sure, people had observed the effects of magnetism; they had even developed the compass. The Chinese manuscript Wu Ching Tsung Yao describes an “iron fish” that pointed south (and thus, you know, also north) when suspended in water, and that was written all the way back in AD 1040.1

Even earlier, the ancient Greek philosophers Socrates and Thales of Miletus had written about the properties of lodestone, which is naturally magnetized magnetite—a very common form of iron oxide, and the most strongly magnetic mineral found in nature.23

But all the way up through most of the 16th century, that’s all we really had. Despite the fact that magnetic compasses were already serving as the cornerstone of nautical navigation—expanding trade, exploration, and imperialism beyond the familiar safety of the known world—nobody knew how or why they worked.

Thankfully, someone came around and finally did some long overdue homework for the rest of us.

William Gilbert and De Magnete

That special someone was William Gilbert, a middle-class English physician and natural philosopher who I guess was pretty smart, since he started studying at Cambridge University when he was 14.

William Gilbert, shown here not sure what he’s wearing because he can’t see himself below that neck ruff.

Gilbert ran a successful medical practice, but it would appear that neither his material success nor his ability to enhance the physical well-being of his fellow citizens could fill a void that festered deep inside his soul. No, that void could only be filled by one thing: knowing how the f*ck magnets worked. At least, that’s how his story plays out in my head.4

To remedy this long-standing ignorance, Gilbert wrote a groundbreaking, six-volume treatise: De Magnete, Magneticisque Corporibus, et de Magno Magnete Tellure.

Reader, if you don’t understand Latin, then (a) we aren’t so different, you and I; and (b) it means “On the Magnet, Magnetic Bodies, and the Great Magnet of the Earth.”

What follows are a couple of the most noteworthy discoveries of Gilbert’s magnum opus.5

Mindblower #1: Static Electricity and Magnetism Aren’t the Same Thing

What we now call static electricity, or the “triboelectric effect,” was once known as the “amber effect.” It happens when amber and some other materials (e.g., balloons, your head) acquire a static charge through friction. This was common knowledge but, again, people didn’t get why it happened, or how it worked exactly.6

A big, honking pile of elektron.

Common belief held that the amber effect and magnetism were examples of the same mysterious sticky-magic phenomenon. But Gilbert theorized—correctly—that these effects were distinct from one another.7 As such, he provided some new terminology. To the ancient Greeks, amber was known as elektron. Gilbert determined that the force observed between elektron and other materials was something different, and coined the phrase “electrick force.”8

Mindblower #2: The Earth is a Magnet, Man

For his most important experiment, Gilbert created a versorium. This instrument consisted of a metal needle and a spherical piece of lodestone called a terrella, or “little Earth.” The terrella, being a magnet itself, had its own north and south poles. It also included imperfections and pittings. Here, Gilbert describes the terrella:
“Let there be a loadstone [sic] somewhat imperfect in some part, and impaired by decay (such as one we had with a certain part corroded to resemble the Atlantic or great Ocean).”9

Gilbert had guessed that compasses rarely pointed to true north (what we now call “declination”) because the Earth was not a perfect sphere, and because its surface is far from uniform. He did, however, incorrectly presume that Earth’s magnetism was directly correlated with its axis of rotation—this appeared to be too much of a coincidence at the time for him to think otherwise. But, given how little was understood about magnetism, it’s understandable why Gilbert may have overlooked the possibility that rotation wasn’t tied to magnetism. Plus, this was a time when adventurous theories about the Earth’s rotation needed to agree with the church, unless you wanted to publish and perish via burning at the stake.

Gilbert would also use his versorium to test another known phenomenon. In 1581, Robert Norman had discovered that compass needles not only pointed northward for some reason, but that they also experienced a “magnetic dip” where the needle was not quite horizontal, but rather was attracted downward, toward the Earth itself—but the reason for this, too, had been a mystery.

Gilbert used his versorium to test his hypothesis on declination, as well as the magnetic dip phenomenon. He suspended the metal needle so that it could freely interact with the terrella’s magnetic field.

Gilbert’s versorium yielded results that explained both mysteries. When the needle was moved around the terrella, it acted like the compass needle did around Earth. The needle pointed toward the terrella’s magnetic pole, and was attracted downward, toward the center of the terrella, reproducing the magnetic dip effect. The needle also varied slightly in its direction as it moved around the corroded, imperfect surface of the terrella—much as a compass angles slightly toward nearby continents, while pointing truer toward magnetic north when in open sea.

Gilbert’s versorium.

Gilbert was convinced: the Earth is a giant magnet. It was his most important discovery. He also demonstrated it to Queen Elizabeth and her court, and I’ll bet it blew their f*cking minds.10

Not Perfect, but Pretty, Pretty, Pretty Good

Gilbert’s De Magnete wasn’t right about everything. He didn’t challenge the idea that the universe revolved around the Earth—though, he didn’t explicitly support it, either. He had some weird theories about magnetism being Earth’s soul, and built a sort of magnetism philosophy.11

But, to be fair to Gilbert, he didn’t go full Gwyneth Paltrow, either, and criticized some of the popular holistic magnet magic of the time, writing, “The application of loadstones to all sorts of headaches no more cures them (as some make out) than would an iron helmet or a steel cap.”12

Besides, it was the tail end of the 16th century, and, as mentioned, heliocentrism wasn’t even a popular theory yet. So Gilbert did pretty well, all things considered.

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Notes 📌

  1. Vardalas, John. (2013, November 8). Retrieved from http://theinstitute.ieee.org/tech-history/technology-history/a-history-of-the-magnetic-compass
  2. Vardalas, John. (2013, November 8). Retrieved from http://theinstitute.ieee.org/tech-history/technology-history/a-history-of-the-magnetic-compass
  3. Geology.com. (Accessed March 9, 2018). Retrieved from https://geology.com/minerals/magnetite.shtml
  4. Magnet Academy. (Accessed March 9, 2018). William Gilbert. Retrieved from https://nationalmaglab.org/education/magnet-academy/history-of-electricity-magnetism/pioneers/william-gilbert
  5. Or “great work.” I guess I do know some Latin.
  6. Magnet Academy. (Accessed March 9, 2018). William Gilbert. Retrieved from https://nationalmaglab.org/education/magnet-academy/history-of-electricity-magnetism/pioneers/william-gilbert
  7. Magnet Academy. (Accessed March 9, 2018). William Gilbert. Retrieved from https://nationalmaglab.org/education/magnet-academy/history-of-electricity-magnetism/pioneers/william-gilbert
  8. Stern, David P. (2004, November 29). The Great Magnet, the Earth. Retrieved from http://www.phy6.org/earthmag/dmglist.htm
  9. Stern, David P. (2004, November 29). The Great Magnet, the Earth. Retrieved from http://www.phy6.org/earthmag/dmglist.htm
  10. Stern, David P. (2004, November 29). The Great Magnet, the Earth. Retrieved from http://www.phy6.org/earthmag/dmglist.htm
  11. The Galileo Project. (Accessed March 9, 2018). William Gilbert (1544-1603). Retrieved from http://galileo.rice.edu/sci/gilbert.html
  12. Stern, David P. (2004, November 29). The Great Magnet, the Earth. Retrieved from http://www.phy6.org/earthmag/dmglist.htm

Additional Resources

  • Encyclopædia Britannica. (Accessed March 9, 2018). Retrieved from https://www.britannica.com/biography/William-Gilbert
  • Geology.com. (Accessed March 9, 2018). Retrieved from https://geology.com/minerals/magnetite.shtml
  • Magnet Academy. (Accessed March 9, 2018). William Gilbert. Retrieved from https://nationalmaglab.org/education/magnet-academy/history-of-electricity-magnetism/pioneers/william-gilbert
  • Stern, David P. (2004, November 29). The Great Magnet, the Earth. Retrieved from http://www.phy6.org/earthmag/dmglist.htm
  • The Galileo Project. (Accessed March 9, 2018). William Gilbert (1544-1603). Retrieved from http://galileo.rice.edu/sci/gilbert.html
  • Vardalas, John. (2013, November 8). Retrieved from http://theinstitute.ieee.org/tech-history/technology-history/a-history-of-the-magnetic-compass

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