Along twelve kilometres of a quiet valley in central Norway, lights appear. White, yellow or red, above and below the horizon, sometimes hanging still, sometimes crossing the sky at enormous speed, lasting seconds or more than an hour. Reports go back to the 1930s and the peak was extraordinary: between December 1981 and mid-1984 they were being seen fifteen to twenty times a week. It is down to ten or twenty sightings a year now. In 1998 an automatic measurement station went in to record them, which makes this one of the very few phenomena of its kind with a permanent instrument pointed at it. Proposed explanations include misidentified aircraft and headlights, burning mine dust carrying titanium and scandium, dust plasma from radon decay, piezoelectricity in quartz rock, and the valley working as a natural battery. None has settled it.
Hessdalen, Norway
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