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Iron Age Potters Accidentally Recorded the Strength of Earth's Magnetic Field (npr.org)
Solandri writes: We've only been able to measure the Earth's magnetic field strength for about two centuries. During this time, there has been a gradual decline in the field strength. In recent years, the rate of decline seems to be accelerating, leading to some speculation that the Earth may be losing its magnetic field -- a catastrophic possibility since the magnetic field is what protects life on Earth from dangerous solar radiation. Ferromagnetic particles in rocks provide a long-term history which tells us the poles have flipped numerous times. But uncertainties in dating the rocks prevents their use in understanding decade-scale magnetic field fluctuations.
Now a group of archeologists and geophysicists have come up with a novel way to produce decade-scale temporal measurements of the Earth's magnetic field strength from before the invention of the magnetometer. When iron-age potters fired their pottery in a kiln to harden it, it loosened tiny ferromagnetic particles in the clay. As the pottery cooled and these particles hardened, it captured a snapshot of the Earth's magnetic field. Crucially, the governments of that time required pottery used to collect taxed goods (e.g. a portion of olive oil sold) to be stamped with a royal seal. These seals changed over time as new kings ascended, or governments were completely replaced after invasion. Thus by cross-referencing the magnetic particles in the pottery with the seals, researchers were able to piece together a history of the Earth's magnetic field strength spanning from the 8th century BCE to the 2nd century BCE. Their findings show that large fluctuations in the strength of the magnetic field over a span of decades are normal. The study has been published in the journal PNAS.
Now a group of archeologists and geophysicists have come up with a novel way to produce decade-scale temporal measurements of the Earth's magnetic field strength from before the invention of the magnetometer. When iron-age potters fired their pottery in a kiln to harden it, it loosened tiny ferromagnetic particles in the clay. As the pottery cooled and these particles hardened, it captured a snapshot of the Earth's magnetic field. Crucially, the governments of that time required pottery used to collect taxed goods (e.g. a portion of olive oil sold) to be stamped with a royal seal. These seals changed over time as new kings ascended, or governments were completely replaced after invasion. Thus by cross-referencing the magnetic particles in the pottery with the seals, researchers were able to piece together a history of the Earth's magnetic field strength spanning from the 8th century BCE to the 2nd century BCE. Their findings show that large fluctuations in the strength of the magnetic field over a span of decades are normal. The study has been published in the journal PNAS.
Sure, but how do you date when it cooled?
Since the magnetic field is declining, and losing our magnetic field would be catastrophic for life on Earth, we must therefore answer the two part question:
How is human activity causing this, and how much tax must we impose in order to make it stop?
"... to some speculation that the Earth may be losing its magnetic field -..."
Since the data ultimately suggests that fluctuations are completely normal, I submit that this also starts to explain why people are taking scientists less and less seriously.
Don't blame this on the researchers; blame this on the "science writers" (including the author of the summary here on Slashdot). The actual study - at least the abstract and the supplemental material, which was all I could read without a PNAS subscription - says no such thing and that particular wording is just a click-bait addition in order to garner more views. Science journalism - like so much journalism this day - has gone on a real decline over the past twenty years and tries to "spice up" every study rather than simply reporting the science. The end result is that scientists end up sounding inconsistent and hyperbolic ("Coffee Cures cancer!", no wait, "Coffee Causes Cancer"), when they usually are neither; it is the people reporting on their work that are to blame.
Also see for a more graphic comment on the same problem.
Before Common Era? WTF? As opposed to an "uncommon" one?
OK, I'm a (kinda) scientist, so I should maybe be "against" all the religious stuff, but I have no problem with "Before Christ" just as I have no problem with V for Volt(a) or A for Ampere. (Grant you, these were real people, and real scientists too...)
FFS, it's not like "BC" is insulting to Muslims or other people who use a different calendar (many also religion-based), since they're not aligned with the same time period. /rant
If anything, "BCE" seems more insulting, since it implies that their alternative calendars are "not common"...