The Unseen World Behind The Compass Needle

by Judy Hodgkiss

The great scientists of the 19th Century, at the inspiration of Alexander von Humboldt, coalesced around the work of the “Magnetischer Verein,” the Magnetic Union, globally coordinating their studies of the varied effects produced by the earth’s magnetic field. Two American presidents enthusiastically supported the effort. This grand project to comprehend the wondrous phenomena called terrestrial magnetism, or “geomagnetism” as it is known today, proved to be the science driver of that century, as the study of electrical phenomena had been for Ben Franklin’s era. But the Verein project died by the end of the century, and is waiting to be taken up again.

John Quincy Adams, in a debate in the Congress over the establishment of the Smithsonian Institute, argued that the promotion of geomagnetic science should be one of the Smithsonian’s primary goals:

“What an unknown world of mind is yet teeming in the womb of time, to be revealed in tracing the causes of the sympathy between magnet and the pole–that unseen, immaterial spirit, which walks with us through the most entangled forests, over the most interminable wilderness, and across every region of the pathless deep, by day, by night, in the calm serene of a cloudless sky, and in the howling of the hurricane or the typhoon. Who can witness the movements of that tremulous needle, poised upon its center, still tending to the polar star, without feeling a thrill of amazement approaching to superstition?”

Later, President Abraham Lincoln spent many happy hours with America’s foremost scientist of the 19th Century, Joseph Henry, the first Secretary of the Smithsonian, participating in the geomagnetic studies and other experiments carried out by Henry at the Smithsonian, conveniently located near the White House.

Alexander von Humboldt, the world’s foremost naturalist, and a member of Friedrich Schiller’s circles in Germany, wrote, of his best-selling book on his 1804 travels to Spanish America:

“The observations on the variations of terrestrial magnetism which I have carried out during a period of 32 years in America, Europe and Asia and with comparable instruments, cover in both hemispheres…a space of 188 degrees of longitude, from 60 degrees northern latitude to 12 degrees S. I have considered the law of the decrease of the magnetic forces from the pole to the equator as the most important result of my American journey.”

Between 1829 and 1834, a young Joseph Henry completed, with the aid of Prof. James Renwick of Columbia University and the the British naval captain who had discovered geomagnetic North in the Artic, Edward Sabine, the first comprehensive magnetic survey of an American city, Albany, N.Y.; “comprehensive” meaning: documentation of the variation in declination, inclination, and intensity through the magnetic needle readings in the area, over time.

In 1834, Humboldt and Karl Gauss established the Magnetischer Verein, the Magnetic Union, to coordinate systematic studies of terrestrial magnetism globally. Three years later, the great-grandson of Ben Franklin, Alexander Dallas Bache, met with Gauss in Germany, and returned to the U.S. with the precision instruments Gauss had prepared for his use in the U.S.

So, what was all this hub-bub about?

And why did this hub-bub die out, as the above mentioned went to their graves, one by one?

The many and wondrous anomalies posed by the geomagnetic phenomena excite the most fundamental questions in the mind of the researcher. Reason enough for the oligarchy to wish to bury the subject.

In 1492, when Christopher Columbus crossed the Atlantic Ocean, somewhere near mid-way, he recorded that his ship’s compass passed from slightly to the west of true North (true North is the axis of rotation North), over to {east} of true North! Did he expect that to happen? I don’t know. There is a similar spot on the other side of the earth where the opposite occurs. Perhaps mariners in the Pacific knew of such phenomena, since China had the use of the compass since at least 1,000 AD.

This deviation of the compass needle from true North is called the “declination” of the compass; and not only does this declination go from East to West at that point noted by Columbus, but that very line of demarcation he crossed in the Atlantic, itself, shifts, wiggles and oscillates, while at the same time, over centuries, it noticably migrates in a westerly direction, at an average of .04 degrees per year. At different longitudes around the globe, lines of equal declination from geomagnetic North to geomagnetic South do not conform with lines of longitude, and are often much further off from true North than just the few degrees experienced by Columbus (from coast to coast for him, something like 10 degrees west to 10 degrees east).

(See for “movies” of such patterns, as presented by the U.S. Geological Survey. The movie for magnetic declination flashes by, decades at at time. You can click either the fully animated or the manually-controlled action movie.)

Also, there is a point on the globe midway between North and South where the compass needle will orient to the southern magnetic pole (the poles are not aligned exactly, but approximately, opposite to each other). Humboldt was the first to record this, in northern Peru.

In addition to the above, every million years or so, the north and south poles reverse themselves! Again, it was Humboldt who was the first to discover the “magnet fossils” demonstrating this, i.e., certain magnetized rocks, such as those in the German Fichtel Mountains, and later, he found in the Peruvian Andes, which, when approached with the compass, demonstrate a magnetism in the reverse direction from other magnetized rock formations in the area. Such rocks were originally formed by molten lava, which solidified with an internal magnetism aligned at a time (compared to lava flows above or below it) when the magnetic poles had a reverse polarity.

Then there is the “inclination” of the needle, measured by a “dip” needle, where your compass is designed to move vertically, swinging up and down, instead of left to right. Held over either magnetic pole, the needle would swing to an extreme, vertical position, while at the equator it would rest horizontally. A map of this phenomena shows the lines of equal inclination oscillating north-south over years, but not wiggling and swirling as much as the lines of declination do.

(Again, see the action movie at the USGS website.)

But the geomagnetic phenomena which demonstrates the most awesome anomalies, is that found in the readings of the “intensity” of the magnetic needle. The needles used by Humboldt for these measurements were large, 1 to 2 feet long, and suspended from a torsionless thread and carrying ivory scales on its two end faces. Joseph Henry described in his laboratory papers in 1833:

“Make a needle in the form of a tube, adjust glasses, suspend it by silk, and look up through the glasses as a telescope at a distant board placed at right angles to the magnetic meridian with divisions on it corresponding to the seconds and minutes of a degree. And in this way notice the variations of the needle daily and hourly.”

The number of oscillations of this free floating needle over a given time then measures an array of irregular and regular variations in the “intensity” of the magnetic force. (Again, see the movie–the one called “total intensity,” since there are sequels called “horizontal intensity,” etc., but those are irrelevant for our purposes here. Also, take note, that the system used in the movies of delineating lines of equal declination, inclination and intensity, called “isogenic,” “isocline” and “isodynamic” lines, are concepts and terms invented by Humboldt.)

Since detailed records have been kept, over the last 150 years, there has been a significant decline in the intensity of the dipole magnetic field (besides the polar magnetism, there are other more complicated field patterns, but those can be sorted out from the main dipole field). In fact, the dipole field intensity is actually decreasing at a rate of about 8 percent per century! In a few thousand years it could go to zero (as measured in gauss or tesla units); or, it could reverse itself, and start to go back up at any time. The “magnetic fossil” record, which can capture declination, inclination and intensity evidence, indicates that this kind of fluctuation, even all the way to zero, may be a frequent occurrence (frequent, as measured in thousands of years). In fact, there are indications that somewhere around 4,000-5,000 B.C., the dipole field disappeared, perhaps for 1,000 years. One might then ask: Is it possible that a global maritime culture, at the time dependent on compass navigation for ocean crossings, might have literally lost its moorings? Thereby stranding what became the American Indian, etc., in outlying areas?

These are the kinds of questions into which a new Magnetischer Verein must delve, with all the joy of a Humboldt, Gauss, Bache, or Henry–or a JQA or Abraham Lincoln.