Why is Lightning Followed By Thunder?

The lightning and thunder must have been among the first to mystify and frighten the primitive man. The jagged tones of lightning coupled with claps and rumbles of thunder were taken for the gods being angry. Lightning and thunder were a way to punish the mart. Actually, to understand lightning and thunder we recall a fact about electricity. The things become electrically charged, either positively or negatively. We know, like poles repel each and. unlike poles attract each other. On this analogy, a positive charge has a great attraction for a negative one.

For a greater charge, this attraction becomes stronger. The strain of being kept apart becomes too great at a point, for the charge. The insulating substance, air or glass, is- overcome- or—broken down and a discharge takes place to relieve this strain or imbalance; to make the bodies electrically equal.

In the case of lightning, a cloud containing countless moisture droplets may become oppositely charged with respect to another cloud or the earth. The lightning flash occurs the moment, the air insulation is broken due to heavy electrical pressure between the two charges. Naturally, the discharge follows the line of least resistance and that is why the lightning is often zigzag. The potential or ability of air, to conduct electricity, varies with moisture, density, and temperature. Dry air is a pretty good insulator, while moist air is a fair conductor of electricity. This is the reason why lightning often stops when the rain begins to fall. The moist air as a conductor carries a charge of electricity, which may travel unseen, smoothly, and quietly.

In the case of thunder, there is a discharge of electricity, causing the air around to expand quickly and then to contract. The currents of air rush about with this expansion and contraction. The violent collisions, of these currents of air, are heard as thunder. The thunder rolls and rumbles are due to9 the sound waves which are far away and are reflected back and forth from cloud to cloud. Since light travels about 2,98,000 km. per second and the speed of sound is only 0.335 km, per second, evidently, we see the flash first and hear the thunder later.