Ball Lightning as an Optical Illusion

E. Argyle

Editor’s Note

For centuries, eyewitness accounts have attested to an elusive atmospheric phenomenon known as ball lightning: the creation during thunder storms of spherical balls of luminous energy which float through the air, persist for several seconds before abruptly disappearing, and range in size from that of a small stone to several feet in diameter. The phenomenon has been controversial, because it is difficult to study scientifically. Several reported incidents in 1970 here led Edward Argyle to suggest that ball lightning is an optical illusion due to visual afterimages. Argyle’s explanation remains one of many possibilities, and controversy over the causes or even the reality of ball lightning continues today.ft　　中文

DURING the past year there have been numerous publications on ball lightning1-9, many attempting to account for the formation, properties and behaviour of lightning balls. None have questioned the reality of the phenomenon, in spite of the lack of progress toward an understanding of these baffling objects. Serious doubt about the existence of ball lightning was expressed by Humphreys10 in 1936, and more recently by Schonland11. Both regarded the phenomenon as probably an optical illusion. Now that Altschuler et al.8 have invoked nuclear reactions to account for the lightning ball it seems appropriate to re-examine the possibility of finding an explanation in the physiology of vision.ft　　中文

The phenomenon of visual afterimages in very complex, but is predominant effect—the negative afterimage—is well known. Of less frequent occurrence is the positive afterimage, which results from the observation of a light source which is very bright relative to the surround. In this communication I shall assume that a spherical region of ionized air and white hot particles is sometimes generated at the ground end of a lightning stroke by partial vaporization of Earth, vegetation or metal, and that the luminous intensity within the sphere is high enough to create a positive afterimage in the eye of an observer. In his comprehensive survey of reports on ball lightning Rayle12 made the interesting discovery that “the number of persons reporting ball lightning observations is 44% of the number reporting observation of ordinary lightning impact points”. This can be understood by assuming that about half of all strokes to ground generate a high luminosity ball at the impact point. Indeed, this sort of assumption is required whether ball lightning is real or illusory.ft　　中文

The behaviour and apparent properties of the positive afterimage are strikingly similar to those of ball lightning. Its shape will be the same as that of the exciting source, and it well commonly be described as a ball. The apparent size of the positive afterimage will be the same as that of the exciting source only if it is “projected” by the observer to the distance of the source. If the source is outdoors, for example, but the observer focuses on the window through which it was seen, the apparent size will be reduced. Thus the relatively small size of indoor lightning balls is accounted for. Rayle12 pointed out that linear size and distance were one of the few pairs of parameters that showed a significant correlation, but he did not go on to infer the implied limited range of angular diameters.ft　　中文

The colour of positive afterimages depends more on the brightness of the source than on its colour. There is no conflict with the yellows, oranges and occasional other colours reported for ball lightning. The degree to which the size, shape, brightness and colour of the lightning ball remains constant throughout its lifetime of a few seconds is the despair of both the theoretician8,13-16 who seeks a plausible physical mechanism for it, and the experimenter3 who tries to reproduce it. On the other hand, the approximate constancy of these features is characteristic of a positive afterimage.ft　　中文

Being a cone effect, the positive afterimage will usually be formed near the centre of the retina, and the observer, wishing to examine the supposed object, will attempt the impossible task of centring it exactly. The result is a linear drift of the projected positive afterimage across the observer’s visual background, as the eye muscles try to correct the centring error. In natural circumstances this feedback motion will be combined with varying amounts of voluntary adjustment as the observer strives to make sense out of the motion.ft　　中文

Passage through physical surfaces such as a glass or metal screen is possible for positive afterimages and is reported for lightning balls3,4. In neither case is the surface burned or damaged, nor is the size, shape, colour or brightness of the ball altered by the penetration.ft　　中文

Positive afterimages last 2–10 s, depending on circumstances, and most lightning balls are reported to have a duration in the same range12. Positive afterimages disappear rather suddenly, as do lightning balls. Positive afterimages generate no sound but the typical observer finds it easy to imagine “suitable” accompanying sounds, if he has any relevant preconceptions. The ease with which most people “hear” appropriate sounds while observing natural phenomena has been documented by Beals17, who found that most of the inhabitants of northern Canada claimed to have heard the aurora borealis. The spectrum of sounds reported was persuasively narrow and differed only moderately from observer to observer. Apparently it is no more maladaptive to hear the rustling of the northern lights than it is to hear the implosive pop of a disappearing lightning ball. Curiously, the disappearance of indoor lightning balls is reported often to be violent but seldom to be damaging.ft　　中文

The psychological principle for imagining odour is the same as for sound but fewer individuals have strong odour expectations and in only a few cases are odours reported. An appropriate odour would be one the observer associates with electrical apparatus, if he has some familiarity with it; or with deeper metaphysical concomitants of danger and mystery, such as fire and brimstone, if his associations tend to the supernatural. Such are the reported odours of ball lightning18.ft　　中文

In bright daylight positive afterimages are a rare occurrence. But in subdued light, as during a thunderstorm, especially if the observer is indoors, a positive afterimage is readily formed by any source as intense as a frosted light bulb. Considering that lightning is primarily an outdoor phenomenon it is remarkable how many lightning balls are seen indoors. This strange fact can be understood if positive afterimages are involved.ft　　中文

That the unsuspecting observer of a chance natural phenomenon can be misled by a positive afterimage is more than speculation. Two of the eyewitnesses to the passage of the Revelstoke bolide19 reported independently that the meteor had landed on low ground in the middle distance, and had bounced several times before going out. It is more likely that these observers each followed a positive afterimage down to zero elevation after the bolide passed behind distant mountains. At ground level a conflict between positive afterimage drift and physical anticipations led to an unstable situation in which the positive afterimage oscillated briefly before disappearing.ft　　中文

There are a few reports which indicate the release of large amounts of energy from the lightning ball. In the most famous of these cases, described by Goodlet20, water in a rain barrel was heated by a lightning ball. If ball lightning is an optical illusion it will be necessary to categorize this and similar reports as unreliable. To do so would not be unreasonable in view of the many observations on record.ft　　中文

Final resolution of the question of the nature of ball lightning will no doubt depend more on the outcome of further experimentation than on the collection of more observer reports. Fortunately, the question of the reality of ball lightning is amenable to laboratory investigation. I have found it easy to simulate the lightning ball by using light bulbs, strobe-flash lamps and photographic flash bulbs as intense sources for the generation of drifting positive afterimages. This qualitative work requires verification, however. It is hoped that a laboratory equipped for psychovisual studies will take up the problem and report on the degree to which descriptions of “artificial” ball lightning resemble those of the natural phenomenon that are recorded in the scientific literature.ft　　中文

(230, 179-180; 1971)

Edward Argyle: Dominion Radio Astrophysical Observatory, Penticton, British Columbia.

Received December 7; revised December 20, 1970.

References:

  1. Lowke, J. J., Uman, M. A., and Lieberman, R. W., J. Geophys. Res., 74, 6887 (1969).

  2. Jennison, R. C., Nature, 224, 895 (1969).

  3. Powell, J. R., and Finklestein, D., Amer. Sci., 58, 262 (1970).

  4. Covington, A. E., Nature, 226, 252 (1970).

  5. Bromley, K. A., Nature, 226, 253 (1970).

  6. Felsher, M., Nature, 227, 982 (1970).

  7. Hill, E. L., Amer. Sci., 58, 479 (1970).

  8. Altschuler, M. D., House, L. L., and Hildner, E., Nature, 228, 545 (1970).

  9. Zimmerman, P. D., Nature, 228, 853 (1970).

  10. Humphreys, W. J., Proc. Amer. Phil. Soc., 76, 613 (1936).

  11. Schonland, B., The Flight of Thunderbolts (Clarendon Press, Oxford, 1964).

  12. Rayle, W. D., NASA Technical Note TN D-3188 (Washington, DC, 1966).

  13. Bruce, C. E. R., Nature, 202, 996 (1964).

  14. Singer, S., Nature, 198, 745 (1963).

  15. Hill, E. L., J. Geophys. Res., 65, 1947 (1960).

  16. Wooding, E. R., Nature, 199, 272 (1963).

  17. Beals, C. S., J. Roy. Astron. Soc. Canad., 27, 184 (1933).

  18. Barry, J. D., J. Atmos. Terr. Phys., 29, 1095 (1967).

  19. Folinsbee, R. E., Douglas, J. A. V., and Maxwell, J. A., Geochim. Cosmochim. Acta, 31, 1625 (1967).

  20. Goodlet, B. L., J. Inst. Elec. Eng., 81, 1 (1937).