Ball lightning

A ball of light that appears during a thunderstorm. Known as an extremely mysterious phenomenon, it is most often around 20 centimeters in diameter and varies in color from orange to pale blue, but is bright enough to be clearly seen even during the day. It often appears near the point of a lightning strike, but not necessarily at the time of a lightning strike. It moves erratically at a speed of 2 to 3 meters per second, and sometimes enters houses. Its life span is from a few seconds to a few tens of seconds. It may make an explosion when it disappears. The effects of contact with people or objects vary, and it may leave burns or burn marks, or it may leave no trace at all. There are several theoretical hypotheses about its origin and structure, such as the plasma theory, but there is no consensus yet.

[Hiroo Misaki]

"Mysterious Luminous Object: Ball Lightning" by George Egeri, translated by Kazuma Itai (1990, Maruzen)" ▽ "The Science of Fireballs" by B.M. Smirnov, Yoshihiko Otsuki, and Hideho Okodono (1994, Kyoritsu Shuppan)

Source: Shogakukan Encyclopedia Nipponica About Encyclopedia Nipponica Information | Legend

雷雨の最中に現れる光球。きわめて不可解な現象として知られ、直径は20センチメートル程度がもっとも多く、色は橙(だいだい)から青白までさまざまであるが、昼でもはっきり見えるほど明るい。出現は落雷点付近に多いが、かならずしも落雷のときとは限らない。毎秒2～3メートルの速さで不規則に動き、ときには家の中にも入ってくる。寿命は数秒から数十秒。消滅時に爆発音をたてることもある。人や物に接触した場合の作用もまちまちで、火傷や焼痕(しょうこん)を残すこともあり、また痕跡を残さないこともある。成因や構造についてはプラズマ説などの理論的仮説がいくつかあるが、まだ定説はない。

［三崎方郎］

『ジョルジ・エゲリ著、板井一真訳『謎の発光体　球電』（1990・丸善）』▽『B・M・スミルノフ、大槻義彦、大古殿秀穂著『火の玉の科学』（1994・共立出版）』

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