The weakening of the Earth’s magnetic field is not new, and there is no reason to assume that it indicates a polar reversal, according to Israeli archeologists and geophysicists who examined dozens of jars from the Judean Kingdom dating from the 8th century BCE to the 2nd century CE.
Using fragments of storage jars they found, the scientists managed to reconstruct the ancient magnetic field strength.
The discovery means that the magnetic field that protects the Earth from radiation is not in danger of collapse, said Dr. Erez Ben-Yosef of Tel Aviv University.
The new findings have just been published in the journal Proceedings of the National Academy of Sciences.
“The period spanned by the jars allowed us to procure data on the Earth’s magnetic field during that time – the Iron Age through the Hellenistic Period in Judea,” he said. “The typology of the stamp impressions, which correspond to changes in the political entities ruling this area, provides excellent age estimates for the firing of these artifacts.”
The study was conducted, in addition to Ben-Yosef, by Prof.Oded Lifschits and graduate student Mike Millman of the archeology department at Tel Aviv University and Dr. Ron Sha’ar of the Hebrew University of Jerusalem, in collaboration with the laboratory of the Scripps Research Institute of San Diego.
“The magnetic field that allows the existence of life on Earth as we know it,” said Ben-Yosef. “This field protects us from cosmic radiation and solar wind, is used in many animals to navigate and has a direct impact on many more processes in nature, such as the creation of isotopes in the atmosphere.
However, this magnetic field was and remains a scientific puzzle that is shrouded in secrecy. Albert Einstein defined the understanding of the source field one of the five most important mysteries in physics.”
Einstein, who was on the first board of governors of the Hebrew University of Jerusalem, would likely have been pleased that the study concluded there is no reason for alarm.
According to conventional theory, the magnetic field was created in the outer core of the Earth, at a depth of more than 2,900 kilometers and a temperature of more than 4,000 degrees.
The nucleus consists mostly of liquid iron. The movement of iron, which is an electrically conductive material, produces a magnetic field as a result of the Earth’s rotation on its axis.
Since the mid-19th century, measurements have been taken directly from the field strength – but these measurements have indicated weakness.
From the time measurements were first carried out by Carl Friedrich Gauss in 1835, the Earth has lost 10% of its magnetic field, noted Ben-Yosef. “In addition, we know the weakening of the field is associated with the rare phenomenon of a polar reversal. The field was down nearly to zero during the reversal of the magnetic poles, and there are scholars who believe the current decline in intensity as the start of such a reversal.”
The inversion theory is in the minds of many laymen and feeds more than a few conspiracy theories. While most scientists think there will not be a catastrophe even in the case of a reversal of the poles, there are some researchers who believe that we cannot exist without a magnetic field. Obviously, he continued, all of these questions lead to the question of what the magnetic field strength was before the measurements began.
To measure the magnetic field, they use used ancient geological or archeological materials that “recorded” the magnetic field when it was formed.
These materials, like basalt, contain magnetic particles that arranged themselves according to the magnetic field at the time that the material cooled.
In general, archeological finds like pottery, bricks, roof tiles and kilns allow a more accurate source of geological materials in magnetic fields during the 10,000 years since man learned to use fire.
“In this study, we used the primary archeological research conducted during the ancient Judean kingdom,” said Ben-Yosef.
From the 8th century BCE to the 2nd century CE, the Judean bureaucratic system operated in an orderly way. It used to stamp the storage jar handles differently, as “for the king.
These stamps allow us to tailor an exact date for field strength recorded in jars to within a few decades, and thus reconstruct 600 years of ancient magnetic fields – a database of unprecedented magnitude.”
The jars of the Judean Kingdom were sent to investigators at the magnetic lab at Scripps.
The results show that there is no reason to fear the weakening of the magnetic field, since it was much weaker in the recent past but has recovered since then.
“We learned that the intensity of the magnetic field dropped 20% within 30 years, so the weakening of 10% during 180 years should not cause any special concern, Ben-Yosef said.
“This study shows us that the field is volatile. In fact, new findings reinforce previous findings we published in 2009 indicating that 3,000 years ago, the magnetic field’s strength was 2.5 times stronger than it is now – the strongest field in the history of the Earth, a phenomenon we call the Iron Age Geomagnetic Spike.”
In addition to the contribution of the new database to understanding the Earth’s magnetic field, the researchers hope it will also lead to better understanding of local archeology.
“This is a two-way window,” Ben-Yosef said. “We can take a pitcher from 630 BCE to measure the magnetic properties and thereby calculate the strength of the magnetic field of the ancient Earth – or we can take a pitcher whose age we do not know and use the magnetic field of the ancient world to date it. Our vision is to establish a database on the ancient magnetic field, which would be an additional tool for archeological dating in our region, similar to carbon 14 dating.”
Ben-Yosef said the team is now working on enhancing the archeomagnetic database for the Levant, one of the most archeologically rich regions on the planet, to better understand the geomagnetic field and establish a robust dating reference.
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