Stone skipping and stone skimming are considered related but distinct activities: both refer to the art of throwing a flat stone across the water in such a way (usually sidearm) that it bounces off the surface. The objective of "skipping" is to see how many times a stone can bounce before it sinks into the water; the objective of "skimming" is to see how far a bouncing stone can travel across the water before it sinks into the water. In Japan, the practice is referred to as Mizu Kiri, which loosely translates to "water cutting". In Mizu Kiri contests, both skimming and skipping principles, as well as a throw's overall aesthetic quality, are taken into account to determine the winners.
The act of skipping stones was mentioned by Marcus Minucius Felix in his dialogue Octavius, in which he described children playing a game on the beach. Greek scholar Julius Pollux also noted the game in Onomastikon. Among the first documented evidence stone skipping as a sport was in England, where it was described as "Ducks and Drakes" in 1583. An early explanation of the physics of stone-skipping was provided by Lazzaro Spallanzani in the 18th century.
The world record for the number of skips, according to the Guinness Book of Records, is 88, by Kurt "Mountain Man" Steiner. The cast was achieved on September 6, 2013, at Red Bridge in the Allegheny National Forest, Pennsylvania. The previous record was 65 skips, by Max Steiner (no relation), set at Riverfront Park, Franklin, Pennsylvania. Before him, the record was 51 skips, set by Russell Byars on July 19, 2007, skipping at the same location. Kurt Steiner also held the world record between 2002 and 2007 with a throw of 40 skips, achieved in competition in Franklin, PA.
The Guinness World Record for the furthest distance skimmed using natural stone stands at 121.8m for men, established by Dougie Isaacs (Scotland), and 52.5m for women, thrown by Nina Luginbuhl (Switzerland). These records were made on 28 May 2018 at Abernant Lake, Llanwrtyd Wells, Powys, Wales.
The "Big Four" American stone skipping contests include (in order of establishment and participant rankings):
Former world champion Coleman-McGhee founded the North American Stone Skipping Association (NASSA) in 1989 in Driftwood, Texas. NASSA-sanctioned world championships were held from 1989 through 1992 in Wimberley, Texas. The next official NASSA World Championship is expected to be held at Platja d'en Ros beach in Cadaqués, Catalonia, Spain..
A stone skimming championship takes place every year in Easdale, Scotland, where relative distance counts as opposed to the number of skips, as tends to be the case outside of the US. Since 1997, competitors from all over the world have taken part in the World Stone Skimming Championships (WSSC) in a disused water-filled quarry on Easdale Island using sea-worn Easdale slate of maximum 3" diameter. Each participant gets three throws and the stone must bounce/skip at least twice to count (i.e. 3 water touches minimum). The WSSC for 2020-2022 were cancelled due to coronavirus concerns. The next is scheduled for Sept 2023.
Other domestic distance-based championships in the UK are currently the Welsh and British, but they were cancelled in 2020 and 2021 for reasons including the COVID-19 pandemic. The British is next due to be held in 2023. Japan holds competitions where both skimming and skipping principles, as well as a throw's overall aesthetic quality, are taken into account to determine the winners. At present, there is also a competition at Ermatingen in Switzerland and occasionally in the Netherlands (both skimming/distance-based).
2020 and 2021 Championships cancelled due to aspects of the COVID-19 pandemic.
|2002||Alastair Judkins||New Zealand|
|1997||Ian Sherriff||New Zealand|
|1993||David Rhys-Jones, Matthew Burnham, Jonathan Ford Joint winners|
2020 Championship cancelled due to the COVID-19 pandemic.
|2008||Jillian Hunter||Northern Ireland|
|1997 – present (Honorable Mention)||CC Crosby||United States|
Although stone skipping occurs at the air-water interface, surface tension has very little to do with the physics of stone-skipping. Instead, the stones are a flying wing akin to a planing boat or Frisbee, generating lift from a body angled upwards relative to a high horizontal velocity.
The same physical laws apply to stones traveling in air or in water, but the effect is only comparable to gravity when immersed in water, because of the latter fluid's higher density. The result is a characteristic bouncing or skipping motion, in which a series of extremely brief collisions with the water superficially appear to support the stone.
During each collision, the stone's horizontal velocity is approximately constant and its vertical motion can be approximated as a distorted pendulum. The stone is only partially immersed, and the lift applied at the back torques the stone towards tumbling. That torque is stabilized by the gyroscope effect: the stone-skipper imparts a perpendicular initial angular momentum much larger than the collisional impulse, so that the latter induces only a small precession in the axis of rotation.
Stones improperly oriented at the moment of collision will not rebound: the largest observed angle of attack preceding a rebound occurred at an angle of approximately 45°. Conversely, a stone making angle 20° with the water's surface may rebound even at relatively low velocities, as well as minimizing the time and energy spent in the following collision.
In principle, a stone can skip arbitrarily-long distances, given a sufficiently high initial speed and rotation. Each collision saps an approximately constant kinetic energy from the stone (a dynamical equation equivalent to Coulomb friction), as well as imparting an approximately constant angular impulse. Experiments suggest that initial angular momentum's stabilizing effect limits most stones: even "long-lived" throws still have high translational velocities when they finally sink.
The lead character of the 2001 film Amélie skips stones along the Canal Saint-Martin in Paris as a plot point, and picks up good skipping stones when she spots them.
Both texts state that rebounds are impossible beyond 45°. That value corresponds with the plots of viable combinations of impact angle and impact direction, but not the plots of viable impact angles and initial velocities, which include a rebound around 53°. No explanation for the discrepancy is given.