THE ancients referred to them as candissimi fumi (the most brilliant white fumes). The Finns called them Vindlys (the windlights) because when they appeared more brilliantly than usual they were seen as heralding the first great storm of winter.
Sometimes the French call them chevres dansantes (the dancing goats) and the Scots tell of "Lord Derwentwater's lights", because they were exceptionally bright on the night the unfortunate earl lost his head on Tower Hill for supporting the Old Pretender in the 1715 rebellion.
Here we used to call them na saighneain (the arrows of light), but now we know them better as aurora borealis, the false dawn of the north, the northern lights.
The aurorae borealis have been a common feature of the northern skies since time began. At their best they are a brilliant spectacle of restlessly moving coloured streamers, conveying an eerie aura of unearthly splendour.
In the auroral zone of maximum frequency, a region which extends from the north of Norway, south of Iceland and Greenland, over northern Canada to the north of Siberia, the phenomenon can be seen almost every night the sky is clear.
In these latitudes, the northern lights are seen on about 5 per cent of occasions when conditions otherwise are suitable, appearing low in the sky near the northern horizon as a kind of grey white glow with a sharp lower border.
The aurorae originate in the constant stream of electrically charged particles speeding earthwards from the sun. As these particles, mainly hydrogen ions and free electrons, approach the Earth, the planet's magnetic field acts like a gigantic cathode ray tube, the central core of every television set.
The charged particles are dragooned into beans, deflected towards the poles, and focused on to the Earth's upper atmosphere, which acts in this respect like a fluorescent screen. This fluorescent luminosity provides the range of red, green, pink and blue lights that the aurorae emit to provide the brilliant displays that decorate the northern sky.
The aurorae are most noticeable at times of very high solar activity when the number of sunspots is at a maximum, because it is then that the stream of charged particles from the sun is most prolific.
This solar activity follows an 11 year cycle, and the frequency and intensity of aurorae follow the same pattern. As it happens, we are currently near a sunspot minimum, so auroral activity is less remarkable now than it was, say, five years ago - and no doubt will be again in a few years.