Science

Michael Dee's research into 14C anomalies

Freak solar flares that may destroy us all

Twice in the last 1,500 years, the sun released blasts of energy no scientist ever thought possible. If that happens again, none of our satellites will survive. On the upside, scientists can use these freak solar flares to solve archaeological riddles, says Michael Dee.

Christien Boomsma

Door Christien Boomsma

10 December om 15:43 uur.
Laatst gewijzigd op 11 December 2019
om 17:08 uur.
Christien Boomsma

By Christien Boomsma

December 10 at 15:43 PM.
Last modified on December 11, 2019
at 17:08 PM.

14C and archaeology

14C is at the heart of carbon dating, the method that allows scientists to date organic materials through measuring the amount of 14C in a sample.

14C, a slightly radioactive isotope, is formed in the atmosphere where cosmic rays interact with nitrogen. It is then incorporated in plants as carbon dioxide through photosynthesis. But when the plant dies, the process stops and the 14C starts to decay.

This means that if you know how much 14C was in the atmosphere at a certain moment in time, it’s possible to calculate how old an archaeological artefact of wood or cloth might be by measuring the amount of 14C that’s left.

It must have been an awesome sight, back in the year 775. Northern lights were visible all over the globe, from Hawaii to Japan and from Tasmania to Greenland. Maybe the night sky lit up as if a giant had switched on some huge spotlights. Maybe it turned blood red. Nobody really knows.

What we do know is that something huge happened. A blast of energy hit the earth and caused neutrons to collide with nitrogen particles present in the atmosphere, creating an extra heavy form of carbon we know as 14C, or radiocarbon. This particular year, the 14C levels spiked eight times higher than usual.

Two hundred years later, in 994, it happened again. Once again, it led to a jump in 14C levels. But nobody knows what caused it. And nobody knows if it will happen again, or when.

Catastrophic effects

‘It’s a mystery’, admits Michael Dee, head of the 14C lab of the RUG. ‘The spikes were discovered only seven years ago, by a Japanese scientist called Fusa Miyake who was researching ancient tree rings. A sudden spike in the amount of radiocarbon in those rings in the year 775 AD indicated that the amount of 14C in the atmosphere had jumped in a way nobody thought possible. Of course everybody started looking to see if they could confirm them. And they did.’

A solar flare would cause absolute chaos and panic

That is worrisome, because we no longer live in the Middle Ages. There are planes now, cell phones, and the internet. An event like the one in 775 would have catastrophic effects. ‘Our whole satellite system would be wiped out in a heartbeat’, Dee says. ‘One can imagine there would be absolute chaos and panic. Everything would go down.’

It’s no surprise that scientists all over the world started a frantic investigation to find out what had happened and to discover new spikes. ‘From a hazard-preparedness point of view it seems worthwhile to know how often these storms occur’, says Dee, who has been researching the phenomenon on an ERC Starting Grant.

Superflare

He firmly believes it was the sun that caused them. He can’t prove it definitively, but other explanations come up short. ‘We’re now thinking of a superflare’, Dee says. ‘With deep space telescopes we witnessed solar storms that can be up to 10,000 times bigger than anything we’ve ever seen in our solar system.’

Nobody thought our sun to be capable of such blasts, but Dee can’t think of any other explanation. An exploding star might do it, but these occur only rarely and far away, and are therefore unlikely to affect earth. Also, one of Dee’s PhDs, Andrea Scifo, recently showed that both the events of 775 and 994 happened at the peak of the eleven-year solar cycle – the time that the sun shows increased activity.

The same goes for the largest solar storm on record, the so-called Carrington Event, in 1859. Auroras were seen even in Hawaii and the still brand new telegraph system went down because of disruptions of the earth’s magnetic field. ‘It’s interesting though that the Carrington Event did not cause a measurable spike’, Dee says. ‘Which means that those other events must have been way bigger.’

Ripples and anomalies

Surprisingly, in the last five years of research, nobody found other 14C ‘events’ in tree rings, although not for lack of searching. That doesn’t mean they didn’t happen, says Dee. ‘But they may be smaller and therefore harder to prove.’ Also, it’s a painstaking job to check the year rings of ancient wood that grew over a period of 10,000 to 15,000 years. We may have to be patient.

In the last five years of research, nobody has found other 14C events in tree rings

So Dee decided to go about it the smart way. He realized that the RUG’s 14C lab, one of the oldest in the world, sits on a lot of data. In the past, he found, carbon dating was often done in blocks of ten tree rings. Variations were small anyway, and this way, they could cut costs. ‘An event like that of 775 would be averaged out in these measurements’, he says. But what if he could get a data analyst to look at the original data again? They could analyse all the data on these decade-measurements, to see if there are little ripples and anomalies. ‘Then we might be able to guesstimate where to look’, Dee says.

That analysis was completed recently. Now, Dee has about fifteen ‘blocks’ that are most likely to deliver. A master student is currently studying one of them. ‘We might be looking at the next 775’, Dee says. ‘It is possible.’

Exact dates

But would finding one new spike – exciting though it may be – really help save the earth from solar destruction? Dee smiles, because there’s another reason that knowing when a superflare occurred is useful.

To really understand events, you need exact dates. ‘Just imagine someone writing a history of Brexit,’ he says, ‘without knowing the dates of the referendum, the withdrawal agreement or the appointment of Boris Johnson. So not knowing which event follows which.’

The trouble is, we only know fairly exactly when events happened from 650 BC onwards. Before that, it’s often an educated guess. ‘A certain king’s reign may have lasted for fifteen years, and then he was succeeded by his son, who reigned for five years, and so on. We don’t even know exactly when Tutankhamun was around.’

When you find a 775 spike in the woodwork of an ancient temple, you can pinpoint that year and start counting

Carbon dating is not much help in that respect. ‘We can estimate a time period: this object is from somewhere between 2,000 and 1,800 years ago. But a historian can usually say that just from looking at the object.’

This is where the superflares come in. ‘When you have an ancient temple and find the 775 spike in the woodwork, you can pinpoint that year and start counting the year rings up to the tree bark, which is when the tree was chopped down’, Dee says. Then it’s suddenly possible to fix a whole lot of other data that were floating before.

Progress

Here too, Dee and one of his postdocs, Margot Kuitems, believe they have made considerable progress. ‘We’ve been working on this eighth-century fortress in the south of Siberia, called Por-Bazhyn’, explains Kuitems. ‘It’s a huge clay structure on an island, surrounded by walls of twelve meters high and built by the Uyghurs. Nobody knows what it’s been used for, or if it has even been inhabited at all, because the Uyghurs are a nomadic people.’

Kuitems has been analysing the wood from the floor and believes she has found the famous spike in it. If she’s right, she’ll be one of the first people to have proven it’s possible to use those freak solar flares for good.

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