Aurora Borealis Tiberii

Every now and then, it turns out the journalists get it right. An excerpt from an item in the Telegraph last week:

Solar winds are plumes of electrically charged particles spewed out by the Sun that occasionally hit Earth. The planet’s protective magnetic field pushes these particles to the poles, where they react with oxygen and nitrogen atoms in the atmosphere to produce light. These eerily beautiful curtains of light are the aurora borealis and australis (or Northern and Southern Lights).

Sometimes a particularly violent solar blast known as a Coronal Mass Ejection (CME) means the auroras are visible at lower latitudes. In AD37, according to the historian Seneca, the Emperor Tiberius saw a vivid red light in the sky and dispatched battalions to the seaport at Ostia, “in the belief that it was burning”. In London in 1839, fire brigades rushed north to put out a conflagration that turned out to be an aurora. The same thing happened in January 1938, when the Associated Press reported that a “ruddy glow led many to think half the city was ablaze”.

Now when I saw the mention of “the historian Seneca”, my alarm bells went off, but thanks to amicus noster John McMahon (who pointed me in the right direction and so gets the traditional tip o’ the pileus), it turns out the source for this actually is Seneca’s Quaestiones Naturales. Here’s the relevant bit via the Latin Library (1.15.5):

Inter haec licet ponas et quod frequenter in historiis legimus caelum ardere uisum, cuius nonnumquam tam sublimis ardor est, ut inter sidera ipsa uideatur, nonnumquam tam humilis, ut speciem longinqui incendii praebeat. Sub Tiberio Caesare cohortes in auxilium Ostiensis coloniae cucurrerunt tamquam conflagrantis, cum caeli ardor fuisset per magnam partem noctis parum lucidus, <ut> crassi fumidique ignis.

FWIW, plenty of news outlets (e.g. the Huffington Post) last week were suggesting we might be able to see the Northern Lights much further south due to solar flare activity, but I didn’t see any such thing …


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