The story of the bombing of the Earth with cosmic radiation is written in the trees.
Specifically, when radiation hits Earth’s atmosphere, it can change any nitrogen atoms it hits to produce a form of carbon, which plants take up in turn. Connecting the peaks of this carbon isotope to tree rings could give us a reliable record of radioactive storms dating back thousands of years.
This record shows us that the largest of these events, known as the Miyake events (after the scientist who discovered them), occur about once every thousand years. However, we don’t know what causes them — and new research suggests that our groundbreaking theory, which includes giant solar flares, may be ruled out.
Without an easy way to predict these potentially devastating events, we face a serious problem.
“We need to know more because if any of them happened today it would destroy technology including satellites, internet cables, long-range power lines and transformers,” he added. said astrophysicist Benjamin Pope of the University of Queensland in Australia.
“The impact on global infrastructure would be unimaginable.”
The story of Earth’s encounters with storms of cosmic radiation is there to be deciphered if you know how to look. The main clue is a radioactive isotope of carbon called carbon-14, often referred to as radiocarbon. Compared to other natural carbon isotopes on Earth, radioactive carbon is relatively rare. It is formed only in the upper atmosphere, when cosmic rays collide with nitrogen atoms, resulting in a nuclear reaction that produces radioactive carbon.
Since cosmic rays are constantly colliding with our atmosphere, we have a constant but very small amount of stuff raining on the surface. Some are caught in tree rings. As trees add a new ring of growth each year, radiocarbon deposition can be traced back in time, giving a record of radioactivity over tens of thousands of years.
The significant rise in radiocarbon found in trees around the world indicates an increase in cosmic radiation. The cause can be several mechanisms, and solar flares are an important part of it. But there are other possible sources of radioactive storms that have not been completely ruled out. Solar flares have also not been completely ruled out.
Since interpreting tree ring data requires a comprehensive understanding of the global carbon cycle, a team of researchers led by mathematician Chengyuan Zhang of the University of Queensland set out to reconstruct the global carbon cycle, based on every piece of radiocarbon data that can be obtained. their hands on them.
“When radiation hits the atmosphere, it produces radioactive carbon-14, which filters the air, oceans, plants and animals, and produces an annual record of radiation in tree rings,” explains Chang.
“We designed the global carbon cycle to reconstruct the process over a period of 10,000 years, to better understand the scale and nature of the Miyake events.”
The results of this modeling gave the team a very detailed picture of a number of radiative events – enough to conclude that the timing and pattern do not correspond to solar flares. Radiocarbon spikes are not related to sunspot activity, which is itself related to flare activity. Some peaks lasted for several years.
There were discrepancies in the radiocarbon profiles between regions for the same event. For a major event, recorded in AD 774, some trees in some parts of the world showed sharp and sudden increases in radiocarbon over the course of a year, while others showed a slower peak over two to three years.
“Instead of a single instantaneous explosion or explosion, what we can observe is a kind of ‘storm’ or astrophysical explosion,” he added. Zhang says.
Researchers don’t know at this point what could be the cause of these eruptions, but there are a number of candidates. One of them is supernova events, from which radiation can explode into space. A supernova explosion in 774 may have occurred. Scientists have established links between radiocarbon spikes and other possible supernova events, but we know supernovae without spikes and radiocarbon spikes without related supernovae.
Other possible causes include solar superflares, but it is unlikely that an explosion strong enough to produce a radiocarbon peak of 774 CE from our sun. There may have been previously unrecorded solar activity. But the thing is that there is no simple explanation that clearly explains the cause of the events in Miyake.
This, according to the researchers, is a concern. The human world has changed drastically since AD 774; The Miyake event could now cause what scientists call a “cyber apocalypse” where infrastructure is damaged, harming the health of air travelers and even depleting the ozone layer.
“Based on the available data, there is about a 1% chance of seeing another opportunity in the next decade,” Pope says.
“But we don’t know how to predict it or the damage it might cause. These possibilities are deeply troubling and lay the groundwork for further research.”
The search was published in Proceedings of the Royal Society A: Mathematical, Physical and Engineering Sciences.