“Magnetism, you recall from physics class, is a powerful force that causes certain items to be attracted to refrigerators”*…
Concentric incision on a jar handle from Ramat Rahel, in modern-day Israel
Of all the environmental amenities that this hospitable planet provides, the magnetic field is perhaps the strangest and least appreciated. It has existed for more than three and a half billion years but fluctuates daily. It emanates from Earth’s deep interior but extends far out into space. It is intangible and mostly invisible—except when it lights up in ostentatious greens and reds during the auroras—but essential to life. The magnetic field is our protective bubble; it deflects not only the rapacious solar wind, which could otherwise strip away Earth’s atmosphere over time, but also cosmic rays, which dart in from deep space with enough energy to damage living cells. Although sailors have navigated by the magnetic field for a millennium and scientists have monitored it since the eighteen-thirties, it remains a mysterious beast. Albert Einstein himself said that understanding its origin and persistence was one of the great unsolved problems in physics…
Direct measurements of the magnetic field now span almost two hundred years, and iron-rich volcanic rocks on the ocean floor provide a lower-fidelity chronicle of its erratic behavior—including wholesale reversals in polarity—back about a hundred and fifty million years. But reconstructing the field’s behavior between these two extremes has been difficult. The trick is to find an iron-bearing object that locked in a record of the magnetic field at a well-constrained time in the past, in the way that wine of a given vintage preserves an indirect record of that year’s weather conditions…
Last Monday, in a study published in Proceedings of the National Academy of Sciences, a team of Israeli and American archeologists and geophysicists reports the most detailed reconstruction yet of the magnetic field in pre-instrumental times, using a set of ceramic jars from Iron Age Judea…
In the geophysical community, the tales told by the Judean jars may cause unrest. Both the height and the sharpness of the spike they recount push up against the limits of what some geophysicists think Earth’s outer core is capable of doing. If the eighth-century-B.C. geomagnetic jeté is real, models for the generation of the magnetic field need significant revision. Given the importance of a stable magnetic field to our electricity-dependent, communications-obsessed culture, these questions are of more than academic interest…
More on these befuddling fields at “Earth’s mysterious magnetic field, stored in a jar.”
* Dave Barry
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As we look for True North, we might send undulating birthday greetings to George Fitzgerald Smoot III; he was born on this date in 1945. An astrophysicist and cosmologist, Smoot discovered the signature of gravitational waves– ripples in space-time were first predicted by Albert Einstein– in his study of the cosmic microwave (“background”) radiation that originated with the Big Bang. He won the Nobel Prize in Physics in 2006; three years later he became the second person to run the board on the quiz show Are You Smarter than a 5th Grader?, and took home the $1 million grand prize.
