Evening Republican, Volume 21, Number 239, Rensselaer, Jasper County, 24 October 1917 — Why Thunder Rumbles. [ARTICLE]

Why Thunder Rumbles.

Thunder is the sound made by the lightning, which in turn, is a momentary electric current through the air. The air in the path of this current is heated very quickly, expands and hits the surrounding air. This causes a sound wave to travel outward from al) parts of this path. Sound goes at the rate of 1,090 feet per second in air being more than this in heated air. The rumble is made by only one flash But as this has a'path all of whose points are not the same distance froir the observer, the sound made at the more distant pointe gets in a little later than that made at those nearby. All thunder has some rumble, for the path could not be the same distance at all pointe unless it were circular, with the observer in the center of the air.