Geek Trivia: Pole positions

As part of Geek Trivia's continuing efforts to highlight obscure anniversaries from the annals of science and history, I'll remind you that 174 years ago today, explorer James Clark Ross' expedition became the first group to locate the Earth's Magnetic North Pole. On June 1, 1831, Ross and his team became the first people on Earth to discover an exact position in the arctic where the dip in the planet's magnetic field is precisely 90 degrees.

The 90-degree dip means that the Earth's magnetic field lines are pointing straight up from that position (90 degrees from a level horizon)--essentially marking the exact center point of the field. Moving away from that spot, the field lines angle toward an incline, growing more pronounced as you move away from the pole. Put another way, Ross found the very site toward which all magnetic compasses were pointing, a virtual magnetic X marking the spot.

Exciting, isn't it? Well, if this milestone moment from geomagnetic orienteering doesn't get your blood pumping, consider this: Assuming you could venture to the exact geographic position that Ross' team marked in 1831, you would not be at the Earth's Magnetic North Pole. That's because the Earth's Magnetic North wanders, and various expeditions have found it in different positions, including one by famed arctic and antarctic explorer Roald Amundsen.

During the 20th century, Magnetic North headed steadily northwest at an average speed of about 11 kilometers per year--although its pace has accelerated since 1970--and it should reach Siberia sometime around the year 2050. Of course, this begs the question: How can the North Pole move northwest? Wherever the North Pole is, that's true north, right?

Wrong: As usual, science flies in the face of conventional wisdom. Setting aside the well-established fact that the Earth's magnetic poles flip about every 500 millennia or so--to say nothing of various conceptual "Norths" used by astronomers when dealing with galactic planes and satellite orbits--Magnetic North is only one of several "Norths" recognized by science. As applies to planet Earth, there are no less than four different kinds of North Poles.

What are the four types of North Poles on planet Earth typically recognized by science, three of which are different from the compass-designated Magnetic North?

Besides Magnetic North, intrepid explorers have found their way to the Geographic North Pole, Geomagnetic North Pole, and the Northern Pole of Inaccessibility. As previously mentioned, the short definition of Magnetic North is the spot on the Earth's surface toward which all magnetic compasses point.

Geographic North, by contrast, is the spot on the Earth's surface directly above the Earth's axis—think of it as the head of the pin around which the planet spins. This is the only location that can lay claim to the True North title, and it's the point of reference used to mark how far Magnetic North is "wandering" each year.

Not to be confused with the Geographic North or Magnetic North Poles is the obscure Geomagnetic North Pole. This one is a little trickier to explain, so bear with me. The Earth has a geographic axis, around which it spins. In addition, there is a magnetic axis, like a giant bar magnet, around which the Earth's magnetic field emanates.

The magnetic and geographic axes don't match up, with the magnetic axis offset from the geographic axis by about 11 degrees. If you were to extend the imaginary bar magnet so its ends touch the Earth's surface, you would have two geomagnetic poles. The pole closest to True North is the Northern Geomagnetic Pole.

Ironically, compasses don't point toward the Geomagnetic Pole because the imaginary bar magnet doesn't actually extend all the way to the Earth's surface (so to speak), with the field's endpoints actually underground.

The last North is perhaps the most bizarre. The Northern Pole of Inaccessibility is the northernmost point farthest from every possible coastline. In other words, it's the spot in the Arctic Ocean that's farthest from land on all sides.

Officially, it’s the middle of nowhere. The Pole of Inaccessibility has no magnetic or axial component. It's merely an artifact of cartography, navigation, and—of course—Geek Trivia.

Oh, migawd! They know where the middle of nowhere is and I don't actually live there! Who would have thought?!?