Scientists Discover Ancient Pottery Contains a Magnetic “Clock” That Can Reveal Its Past

Scientists at the University of California, San Diego have discovered that ancient pottery may contain a magnetic "clock" that can reveal its past. The method uses the residual magnetic signal in clay, which is preserved when the pottery is fired. This signal, known as viscous remanent magnetization, can be used to determine how long ago an artifact was made. In experiments, clay objects more than 1,000 years old retained the magnetic signature until temperatures exceeded 234°F (112°C), while modern objects lost the signal at lower temperatures. The study, published in the Proceedings of the National Academy of Sciences, could help archaeologists and museums authenticate artifacts and detect forgeries.

• The study tested 26 modern objects and 19 ancient specimens.
• The ancient objects retained the magnetic signal until 234°F.
• The technique uses the property of clay particles that become less stable over time.
• The method could help law enforcement identify forgeries in antiquities fraud cases.

The research could provide a new forensic tool for museums and archaeologists to authenticate artifacts. The technique is based on the idea that the magnetic signal in ancient pottery can be used to determine its age. The method is based on the principle of thermal remanent magnetization, which is the orientation of magnetic particles in clay when it is fired. The secondary signal, viscous remanent magnetization, accumulates over time and can be used to determine how long ago the artifact was made. The study found that the magnetic signal in ancient pottery could only be erased by heating it above 234°F, while modern objects lost the signal at lower temperatures. The study also tested the method on three disputed artifacts, and the results were consistent with them being genuine. The technique has limitations, as it does not reveal the exact date of manufacture and the 234°F threshold cannot be applied to all objects. The researchers envision magnetic testing as a new line of evidence for authenticating artifacts.

AI-generated summary of the original article — see the source for the full story.