774 CE

In June of this year, Japanese researchers published their findings that cedar trees in Japan indicated a surge in Carbon-14 production. This particular Carbon isotope is produced when energetic particles from space transform atmospheric nitrogen into carbon. A UCSD student found the following reference in the [The Anglo-Saxon Chronicle][]:

> A.D. 774. This year the Northumbrians banished their king, Alred, from York at Easter-tide; and chose Ethelred, the son of Mull, for their lord, who reigned four winters. This year also appeared in the heavens a red crucifix, after sunset; the Mercians and the men of Kent fought at Otford; and wonderful serpents were seen in the land of the South-Saxons.

The find won him a published [note][] in the pages of Nature. Scientists debated whether a solar flare could have been the cause, if only because the solar flare would necessarily be so large as to cause other, very obvious, and probably fatal problems. Perhaps a supernova? No, the consensus seems to be back to [solar flare][].

I would love to stumble across some historical event like this that has such convergences. (I would also like it if the humanities would adopt the DOI scheme as soon as possible.)

**DOIs** for this note:

Japanese Cedar Tree Research: [10.1038/nature11123](http://dx.doi.org/10.1038/nature11123)
The Red Crucifix: [10.1038/nature.2012.10898](http://dx.doi.org/10.1038/nature.2012.10898)
Solar Flare Explanation: [10.1038/nature11695](http://dx.doi.org/10.1038/nature11695)

[The Anglo-Saxon Chronicle]: http://avalon.law.yale.edu/medieval/ang08.asp
[note]: http://www.nature.com/news/ancient-text-gives-clue-to-mysterious-radiation-spike-1.10898
[solar flare]: http://www.nature.com/nature/journal/v491/n7426/full/nature11695.html