Q: Is Thunder the sound caused by lightning? ¶
A: Yes.
Q: Is Thunder sufficient to cause injury? ¶
A: Yes, such as internal contusion, to individuals nearby.
Q: Is Thunder seldom heard at distances over 20 kilometers? ¶
A: Yes, A very bright flash of lightning and an almost simultaneous sharp "crack" of thunder, a thundercrack, therefore indicates that the lightning strike was very near.