Solar Radiation Pulses Could Track Time in the Ancient World

August 17, 2016 | Erica Tennenhouse

Tree rings
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The records are preserved in tree rings.

Trees that grew during intense solar storms could help archaeologists create precise calendars of events that took place in ancient Maya and Egyptian civilizations, according to a study published in Proceedings of the Royal Society A.

To create timelines of events in these early periods, historians and archaeologists traditionally look to artefacts found in sediment layers, king lists, and other relative sequences, which provide “floating chronologies” that are not fixed to specific calendar years.

Tree-ring dating also commonly produces floating chronologies, while radiocarbon dating can be off by as much as a century. But Michael Dee and Benjamin Pope of the University of Oxford now show that tree rings contain the signatures of radiation bursts on the sun, which produce intense spikes in the radioactive isotope carbon-14 from time to time. Importantly, these spikes can be linked to real calendar dates through their appearance in known-age tree rings.

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Two well-documented bursts — one in 775 AD and the other in 994 AD — left their marks in the rings of trees from all over the world. Further, the high concentrations of carbon-14 resulting from these radiation bursts would have “been absorbed by all other growing plants at the time, including those latterly fashioned into cultural items,” the researchers write, meaning that these secret clocks potentially exist in timber that was used in construction, reeds that were made into papyrus, fibers woven into baskets, and an array of other organic materials.

The researchers hope to identify more of these carbon-14 spikes, which would allow them to anchor floating chronologies of the ancient world to absolute time on a precise scale. “It is envisaged that the method will ultimately provide important new insights into early civilization,” the researchers write.

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