In the heart of the Black Mountains just outside of Morganton, North Carolina, there have long been legends of strange lights that appear from time to time, particularly around the area of Brown Mountain.
Legends about these purported "ghost lights" led the U.S. Geological Survey to investigate the matter in 1922, sending George Mansfield to the area to complete a scientific investigation of the lights and their potential causes, which were deemed mostly to be the headlights on trains in the distance. Some will note that, despite the plausibility of the locomotive origin of the lights, an electrical outage followed by a period of train inactivity that hit the region after the USGS study produced no fewer reports of the lights. Today, leading theories as to the cause of unexplained illuminations seen in the area range from natural plasmas (much like ball lightning), to pranksters camping along Table Rock and adjacent ridges, armed with Roman candles and Chinese lanterns.
Brown Mountain is unusual as far as the "ghost light" phenomenon goes, because it involves reports of objects that reappear within a given area over time; if continuing reports of such observations are to be believed, the lights -- whatever their cause -- have hardly waned any in the last century. However, in most cases, reports of unusual illuminative phenomenon are seldom as predictable as those seen at Brown Mountain, and hence the difficulty we find in attempting to study them scientifically. Since, without an ability to predict where and when strange luminous manifestations may occur, it becomes all the more difficult to equip oneself with the proper tools needed to render conclusions about their cause.
Legends associated with "ghost lights" are rife throughout rural areas, particularly in the American South. Within my own family's history, stories have cropped up from time to time which suggest ominous characteristics attributed to their appearance. One example recalled from my childhood had involved my great grandfather on my father's side of the family, who died under mysterious circumstances while only in his early twenties. Shortly before his death, his widow recalled that he described being followed home by a large, dark-colored dog on several subsequent nights (this is reminiscent of the legendary "black schuck", a ghost dog described for centuries in the folklore of East Anglia).
However, more interesting than the strange dog he described had been an unusual light that purportedly followed him along his walk home one evening. According to my great grandmother's story, he observed this strange ball of light as it followed him a short distance away for several minutes, before it finally dissipated in several directions, and vanished in a quick flash. Within a few days, great granddad Hanks had passed away, after the onset of a strange feverish condition shortly after a long period of labor in the South Carolina cotton mill where he was employed that summer.
While this story from my own family history may possess all the characteristics of your typical rural country "ghost story", there may be a simpler explanation for why some appearances of anomalous illuminations have been popularly associated with misfortune. Throughout the centuries, a number of traditions around the world have warned that deadly earthquakes were often preceded by the appearance of odd ghost lights; researchers Robert Theriault and John Derr, contributors to a paper on “earthquake lights” published in 2014 titled Prevalence of Earthquake Lights Associated with Rift Environments, note that such superstitions may indeed have been influenced by actual observations of luminous plasmas produced by tectonic stress that occurs leading up to an earthquake.
Hence, in older times, when strange lights that might be recognized as "earthquake lights" today would appear, it seemed reasonable to assume that their appearance would foreshadow dangerous things yet to come.
In a sense, there appears to be some factual basis for why reports of strange lights might have often been seen as harbingers of misfortune in the past, and especially the evidence of a devastating earthquake yet to come. In turn, modern scientists like Theriault and Derr hope to employ the study of strange illuminations in nature in ways that might help predict real-world threats like earthquakes and tsunamis.
Of course, broadening our understanding of such things as earthquake lights may not "solve" the stories of those like great granddad Hanks, whose own observation of a strange light seemed to occur right before his death. Whether or not there had been any connection between the two may never be proven or understood fully. However, the persistence of belief in "ghost lights" as a warning of untimely things to come can indeed be more easily understood today, especially with the help of science that helps prove, to an extent, that those who claimed to witness such things in the past weren't merely being superstitious: in fact, some of them may actually have been right.