Some researchers know that these fluctuations are due to the bureaucracy of Judah, an ancient kingdom located around Jerusalem now. From the 8th century BC to the 2nd century BC, there were administrative seals on clay pots that changed with the political situation. People burn these pots without knowing it, and the heating action locks the information of the earth's magnetic field in the minerals in the clay. Because these stamps provide accurate information about when these cans were launched, this study can observe the geomagnetic changes in the past 600 years in detail.
"This is a system in which the King of Jerusalem can effectively collect taxes," said Erez Ben Yosef, an archaeologist at Tel Aviv University, referring to the stamps. We actually benefit from a good bureaucratic system, that is, the ancient IRS. "[7 The earth changed in the blink of an eye]
Magnetic Earth The Earth is surrounded by a magnetic field, which is produced by the movement of iron in the liquid outer core. Ben Yosef told Life Science that the direct observation in this field is only 180 years. He said that the magnetic field had weakened by about 10%. Some researchers think that the magnetic field may be in the process of overturning, so the magnetic north direction becomes the magnetic south direction, and vice versa.
This new study reveals a faster change in magnetic field strength. Ben Joseph and his colleagues reported in today's (February 13) Proceedings of the National Academy of Sciences that the earthquake intensity rose sharply at the end of the 8th century BC and declined rapidly after 732 BC. The researchers found that in the short period of 365,438+0 years from 732 BC, the magnetic field intensity decreased by 27%. From the 6th century BC to the 2nd century BC, this field was generally stable and declined slightly.
"Our research shows that this field is very unstable," Ben Yosef said. It fluctuates quite quickly, so there is nothing to worry about, "as far as the current decline is concerned, he said. (This does not mean that the magnetic field will not flip in the near future; The new research only focuses on the strength of the magnetic field, not the directionality. Ben Yosef said that the research results do show that there is no reason to worry that the decline of oilfield strength in more than a century 10% is abnormal. )
At least in the Levant, which means. All the pottery in the study came from this area, including Syria, Jordan, Israel, Palestine, Lebanon and nearby areas. This means that researchers can't be sure whether the same fluctuation has happened elsewhere. Because scientists are not sure about the exact location of pottery in the Levant, they can't say the geomagnetic direction at that time, but only its intensity. [Photo: Tomb and metal tools from South Levant]
The clay in the mysterious multi-family pottery pot contains ferromagnetic minerals or iron-containing minerals. When clay is heated, the electrons in these minerals are arranged according to the earth's magnetic field-imagine a series of iron filings arranged in an arc around a bar magnet. Once cooled, the magnetic mode will be permanently locked. The same process happens when lava cools, so researchers can also study volcanic rocks to detect changes in the magnetic field.
Printed pottery handle from Israeli settlement Ramat Rahel. The magnetic minerals used in pottery are sealed during heating, revealing the history of the earth's magnetic field. (provided by Oded Li)