Sunday SciKu | Radiocarbon Record

Photo by Denis Agati via Unsplash

Here’s some potentially great news, the significance of which will probably go entirely unnoticed. It requires some explanation, so hold on tight. First here’s the primer on radiocarbon and coronal mass ejections:

99% of the elemental carbon on earth is the C-12 isotope and 1% is C-13, both of which are stable. Occasionally, though, a nitrogen atom in the atmosphere gets whacked by a high-energy cosmic ray from space, knocking off a proton and turning it into the radioactive C-14. This is a continuous process, as the earth is always being showered with galactic cosmic rays, so new C-14 atoms are always being created even as they decay over time, and the amount in the atmosphere remains relatively constant.

When plants take in CO2 for photosynthesis, a trace amount of it is always C-14. Because the C-14 decays but the C-12 doesn’t, we can use the ratio between the two to determine how long ago the plant was alive. The half-life of C-14 is 5,730 years, so if only half is left, that’s how old the sample is. Carbon dating: as simple as it is amazing!

The only problem is that it turns out the atmospheric concentration of C-14 isn’t as steady as we first thought. Tree rings and stalactites show that some years in the past have seen huge anomalous spikes in C-14 production. There are only two natural phenomena we know of that could create enough high-energy particles to explain these spikes: enormous coronal mass ejections from our own sun or supernovae from distant stars.

We really want it to be the latter. My biggest worry for the future of humanity isn’t nuclear war or pandemics or climate change—it’s coronal mass ejections. Due to solar flares and magnetic field instabilities, the sun regularly flings chunks of itself out into space as superheated plasma. Usually they’re small blobs. During the solar maximum every 11 years, there are a few CMEs every day. But sometimes they’re not small at all.

If something like the 1859 Carrington Event happened today, it would wipe out not just the power grid, but many of the electrical circuits on whatever continent was sun-facing when it arrived. It would be a catastrophic disaster and take years to rebuild—but we would, with the help of the night side of the Earth, which would be spared. These happen every 150 years or so, and the last was 1921. In July 2012, one of these missed us by 9 days.

The C-14 spikes, though, are much larger, and happen every 800 years, on average. The last was the Charlemagne event of 774 AD. C-14 production was 20 times the background rate that year. And we’re overdue for one of these.

If they’re caused by distant supernovae, we just get the cosmic rays. Cancer rates might go up, air travel might be impacted, there’d be more cloud formation and more lightning for a year—but civilization would be fine.

If it came from our own sun, though, a year’s worth of this energy is compressed into a few hours of hot plasma, and all of our technology is toast. For Charlemagne’s world, with no circuits to fry, this was only a magical global aurora, and maybe a bad hair day from static electricity. For us, it would be 400 Fukushimas simultaneously. No trucks, no trains, no water pumps. No phones, no radios, no refrigerators. All gone, overnight. No factories to rebuild any of it. If you can’t imagine how that would turn out, read The Road. Humanity would survive deep in the Amazon and for clusters of doomsday preppers, and that’s about it.

But I said this was good news! And here it is:

In a paper published this week, CU Boulder geoscientist Robert Brakenridge was able to date supernova remnants to many of these C-14 spikes in the tree ring record. It really could just be option A! Carrington could be the biggest CME our sun is capable of. And the next supernova candidate, Betelgeuse, is hundreds of years off and far enough away that it wouldn’t matter much at all.

Score one for a future!


fate of the world
in a child counting
tree rings


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