Why Does a Bullwhip Make Such a Loud Cracking Sound?

The serious-sounding crack generated when a bullwhip is sharply flicked is, in fact, a small sonic boom. The tip of the whip, known as the “cracker,” was thought to be the source of the menacing crack -- historically used as a means of getting the attention of livestock, and, in some cruel applications, unfortunate humans. However, researchers have since determined that it is the uncoiling of the loop during the whipping action that makes the snapping noise and gets your attention.

"The crack of a whip comes from a loop traveling along the whip, gaining speed until it reaches the speed of sound and creates a sonic boom," wrote University of Arizona researcher Alain Goriely in the scholarly journal Physical Review Letters. Though some parts of the whip, including the tip, travel at faster speeds, "it is the loop itself that generates the sonic boom."

Cracking the whip, then and now:

• Whipcracking originated among the Germanic peoples of Bavaria and various alpine areas in Austria and Hungary. This tradition is still part of the Bavarian culture and is sometimes used in traditional musical performances.
• In past centuries, Bavarian carriage drivers used elaborate whipcracking sequences to signal their approach. The particular cadences identified the approaching coach.
• Today, whipcracking is more of a performing art. It is an entertaining exhibition activity at rodeo shows in the United States, a competitive sport in Australia, and an increasingly popular pastime in the United Kingdom.