11. The surprises include blue flame balls, apparently akin to glowing spheres of ball lightning . 12. Nearly all lightning experts agree that these objects, known as ball lightning , are real. 13. Ball lightning is one of nature's odder, and rarer, phenomena.14. The existence of ball lightning has never been unequivocally established by film or videotape. 15. About 1 percent of the population will see ball lightning in a lifetime, he estimated. 16. The International Committee on Ball Lightning ( ICBL ) held regular symposia on the subject. 17. An international symposium of scientists investigating ball lightning will be held next year in Japan. 18. This is considered by some to be one of the earliest recorded instances of ball lightning . 19. Klass initially applied his ball lightning theory cautiously and selectively in a series of magazine articles. 20. His account, in contrast, seem to be the far more mysterious phenomenon known as ball lightning .
