About 3,000 years ago, a potter near Jerusalem made a big jar. It was meant to hold olive oil or wine or something else valuable enough to send to the king as a tax payment. The jar's handles were stamped with a royal seal, and the pot went into the kiln.
[...] All those years ago, 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.
"It's kind of like a tape recorder," [Erez] Ben-Yosef says.
[...] When Ben-Yosef and his colleagues studied 67 jar handles spanning from the late 8th century B.C. to the late 2nd century B.C., they found that the Earth's magnetic activity has been a lot choppier than people expected.
Ben-Yosef et al. Six centuries of geomagnetic intensity variations recorded by royal Judean stamped jar handles [PNAS (2017) - Early Edition] DOI: 10.1073/pnas.1615797114
(Score: 1) by khallow on Friday February 24 2017, @11:06AM
(Score: -1, Offtopic) by Anonymous Coward on Friday February 24 2017, @06:38PM
They could change orientation but they couldn't change gender.