“All those years ago,” NPR reported earlier this week, “as potters continued to throw clay, the molten iron that was rotating deep below them tugged at tiny bits of magnetic minerals embedded in the potters’ clay. As the jars were heated in the kiln and then subsequently cooled, those minerals swiveled and froze into place like tiny compasses, responding to the direction and strength of the Earth’s magnetic field at that very moment.”
Archaeologist Erez Ben-Yosef, one of the researchers on the project, has compared the process to a terrestrial “tape recorder,” and a particularly sensitive one at that: the resulting jars “provide an unprecedented look at the planet’s magnetic field over those six centuries, one that’s much harder to get from rocks.”
These accidental indices also indicate that the Earth’s magnetic field at the time was much stronger than expected; ominously, this “astonishing geomagnetic spike,” as mentioned above, could happen again. Indeed, the jars have “given scientists a glimpse of how intense the magnetic field can get—and the news isn’t good for a world that depends on electrical grids and high-tech devices,” Annalee Newitz writes for Ars Technica.
“The researchers note that this geomagnetic spike is similar to another that occurred in the 10th century BCE,” Newitz adds. “Data from the 10th century spike and this 8th century one indicate that such events were probably localized, not global. That said, they write that ‘the exact geographic expanse of this phenomenon has yet to be investigated, and the fact that these are very short-lived features that can be easily missed suggests that there is much more to discover.’”
This vision—of highly localized, mysterious geomagnetic storms frying electronics from below—is not only a great plot device for some burgeoning scifi novelist, it could also almost undoubtedly be weaponized: subterranean geomagnetic warfare against an entire region of the planet, short-circuiting every electrical device in sight.
Of course, it’s also worth noting that this would still be happening: that is, today’s ceramics should still be “recording” the Earth’s magnetic field, even without any corresponding spike in that field’s strength. An invisible terrestrial forcefield is thus still inscribing itself inside objects in your kitchen cabinet or standing on your breakfast table. Everyday knick-knacks in retail stores around the world are still archives of planetary magnetism.
This also makes me wonder what other types of artifacts—clay figurines from nomadic Arctic tribes, mud bricks from central Africa—might also house geomagnetic records yet to be analyzed by modern technology. So what else might be discovered someday?
I’m reminded of the possibility that space weather—or “fossils of spacetime”—might be frozen into the built environment in the form of GPS glitches: hidden inside minute structural errors in large building projects, such as freeways, dams, and bridges, there might be evidence that our solar system is passing through “cosmic kinks” of dark matter.