A whip crack is a tiny sonic boom, the first human-made one
Flick a long whip and a ripple races down the lash, gathering speed until the tip outruns sound itself, more than 30 times faster than the handle moved. The crack you hear is a miniature sonic boom, which makes the humble whip the first human-made object to break the sound barrier.
Most working whips are about sound and signal rather than pain. Stockwhips, the family that includes bullwhips and the Australian stockwhip, have very long lashes and short handles and are cracked to push cattle, sheep or horses away from the noise. Striking an animal with one would be too painful and too imprecise, so it is generally not done. Animals flinch from the sharp report by instinct, which is why cracking works for driving sled dogs and teams of oxen or mules.
Design details reveal the job. A bullwhip's braided thong runs 1 to 6 metres and joins its short handle in a straight line, ending in a leather fall and a cracker. The Australian stockwhip instead hangs from a longer handle by a leather joint called a keeper, so a stockman can drape it over his arm when idle; one was cracked from a rearing horse by the lone rider Steve Jefferys to open the 2000 Sydney Olympics. Old Australian bullock drivers walked beside their teams with a greenhide thong on a handle cut from spotted gum, often taller than their own shoulders.
Regional styles abound. The Florida cow whip, heavier than its Australian cousin, is now often braided from flat nylon parachute cord that keeps working when wet, and a good one cracks with a mere push of the handle, handy in thick brush. Blacksnakes, traditional in Montana and Wyoming, carry heavy shot loading and flex right to the butt. Snake whips have no internal handle and coil up small enough for an old cowboy's saddlebag or even a large pocket.
Riders use subtler tools. A crop is a short, stiff whip for English disciplines such as show jumping, while a dressage whip, up to 1.1 metres long, lets the rider tap behind the leg without letting go of the reins, refining signals rather than hurting the horse. Many competition bodies limit how whips may be used.
Source: Whip
