Erratic but repeated, the Earth has been hit by mysterious bursts of radiation. The cause is unclear, but a recurrence would be devastating.
Roughly once every thousand years, mysterious and potentially devastating astrophysical events have left their mark on tree rings across the globe. That’s what Australian researchers have determined, who now warn that the probability of something like this happening again in the next decade is over one percent.
“The consequences for global infrastructure would be unimaginable,” warns University of Queensland physicist Benjamin Pope. Modern technology such as satellites, internet cables, power lines, and transformers would be destroyed. At the same time, however, it is still unclear what the events, the traces of which he and his team investigated, were all about. The last one was over 1200 years ago.
The research team analyzed the so-called Miyake events, named after the discoverer of the first immense accumulation of the carbon isotope C-14 in the annual rings of trees. This occurs when radiation hits the Earth’s atmosphere. Around the year 774, huge amounts of it were suddenly produced when an immense amount of radiation hit the earth. At the same time, there is as good as no evidence that the event was visible to people at the time. An immense gamma-ray burst may have been the cause. In the meantime, further Miyake events have been found on the basis of tree rings. Something similar happened around 7176 BC, 5410 BC, 5259 BC, 663 BC, and around 993.
So far, solar flares have been thought to be the most likely explanation, Pope writes. However, the new analysis would raise doubts. Their work did not show a consistent connection to the solar cycle, and various characteristics would speak against an astrophysical – but also against a geophysical – explanation. While some were arguably short-lived, others would have lasted for years. It is all the more important to find out what exactly caused the immense increase in C-14 in each case. The fact that we still don’t know what it is about and therefore cannot predict such an event is “very disturbing”. Overall, the finds are extremely alarming and further research is urgently needed.
Research now published in the Proceedings of the Royal Society A indicates that the event occurred two years before a solar maximum during Charlemagne’s lifetime, while the two occurred at a minimum in the sixth millennium BC. Unlike previous studies, the team did not find sufficient evidence that the magnitude of the C-14 increase depends on latitude. They still think it is possible that the finding of a sometimes longer-lasting radiation burst can be explained by biological or atmospheric processes. But if it is confirmed, at least some traces should not be due to an explosion in space, but rather some kind of storm.