Examine individual changes

'{{redirect|Cue ball|the video game|Jimmy White's 2: Cueball|the hypothetical form of matter|Q-ball}} {{Use dmy dates|date=October 2012}} [[File:Billiard ball comparison.jpg|thumb|right|200px|{{Cuegloss|Cue ball|Cue balls}} from (left to right): {{unordered list | [[Russian pyramid|Russian pool]] and [[Kaisa (billiards)|kaisa]]—68&nbsp;mm ({{frac|2|11|16}}&nbsp;in) | [[Carom billiards|Carom]]—61.5&nbsp;mm ({{frac|2|7|16}}&nbsp;in) | American-style [[Pocket billiards|pool]]—57.15&nbsp;mm ({{frac|2|1|4}}&nbsp;in) | [[Blackball (pool)|British-style]] pool (largish) —56&nbsp;mm ({{frac|2|3|16}}&nbsp;in) | [[Snooker]]—52.5&nbsp;mm ({{frac|2|1|15}}&nbsp;in) | Scaled-down pool—51&nbsp;mm (2&nbsp;in) for children's smaller tables }} Not shown: half-scale children's miniature pool—approximately 28.5&nbsp;mm ({{frac|1|1|8}}&nbsp;in).]] A '''billiard ball''' is a small, hard [[ball]] used in [[cue sports]], such as [[carom billiards]], [[Pool (cue sports)|pool]], and [[snooker]]. The number, type, diameter, color, and pattern of the balls differ depending upon the specific game being played. Various particular ball properties such as [[hardness]], [[friction coefficient]] and [[resilience]] are very important to the finer points of gameplay.{{Clarify|date=October 2008|reason=That last sentence needs elaboration.}} ==History== The earliest balls were made of wood and then later clay (the latter remaining in use well into the 20th century).{{citation needed|date=February 2010|reason=No source cited yet for composition of early balls, nor for survival of clay balls.}} Although affordable [[ox]]-bone balls were in common use in Europe,<ref name="ebay">Note: Antique ox-bone balls remain a very common item on [[eBay]].</ref> [[ivory]] was favored since at least 1627 until the early 20th century;<ref name="Shamos 1999">{{Shamos 1999}}</ref>{{rp|17}} the earliest known written reference to ivory billiard balls is in the 1588 inventory of the [[Duke of Norfolk]].<ref name="Everton 1986">{{Cite book |title=The History of Snooker and Billiards |last=Everton |first=Clive |authorlink=Clive Everton |location=Haywards Heath, UK |publisher=[[Transworld (company)|Partridge Pr.]] |page=8 |year=1986 |isbn=1-85225-013-5 |edition=rev. ver. of ''The Story of Billiards and Snooker'', 1979 |quote=11 balls of {{sic|hide=y|yvery}} }}</ref> By the mid-19th century, elephants were being slaughtered for their ivory at an alarming rate, just to keep up with the demand for high-end billiard balls – no more than eight balls could be made from a single elephant's tusks.{{citation needed|date=February 2010|reason=When sourced, this should probably be added to the article on elephants.}} The billiard industry realized that the supply of elephants (their primary source of ivory) was [[endangered species|endangered]],{{Citation needed|date=February 2010|reason=It seems just as likely that cost & human danger were the only real factors.}} as well as dangerous to obtain (the latter an issue of notable public concern at the turn of the 19th century).<ref name="Shamos 1999" />{{rp|17}} Inventors were challenged to come up with an alternative material that could be [[Manufacturing|manufactured]], with a [[United States dollar|US$]]10,000 prize being offered by a New York supplier,<ref name="Shamos 1999" />{{rp|17}} [[Michael Phelan (billiards)|Phelan]] and [[H. W. Collender|Collender]].{{Citation needed|date=February 2010|reason=Can't find reliable source for company name.}} (This would be worth approximately ${{formatnum:{{Inflation|US|10000|1869|r=1}}}} today{{Inflation-fn|US}}.) Although not the first artificial substance to be used for the balls (e.g. [[Sorel cement]], invented in 1867, was marketed as an artificial ivory), [[John Wesley Hyatt]] invented a composition material in 1869 called [[nitrocellulose]] for billiard balls (US patent 50359, the first American patent for billiard balls). It is unclear if the cash prize was ever awarded<!--to anyone, that is-->, and there is no evidence suggesting he did in fact win it.<ref name="Shamos 1999" />{{rp|17}}<ref name="Plastiquarian">{{cite web |url= http://www.plastiquarian.com/hyatt.htm |title=Hyatt |author=<!--Staff writer(s); no by-line.--> |year=2002 |work=Plastiquarian.com |location=London |publisher=[[Plastics Historical Society]] |accessdate=26 February 2008 }} {{Dead link|date=October 2010|bot=H3llBot}}</ref> By 1870 it was commercially branded [[Celluloid]], the first industrial plastic. Unfortunately, the nature of celluloid made it volatile in production, occasionally exploding, which ultimately made this early plastic impractical.<ref name="Shamos 1999" />{{rp|17}} [[Urban legend]] has it that celluloid billiard balls themselves would occasionally explode during rough play, but no reliable sources have been found that can substantiate this. Subsequently, to avoid the problem of celluloid instability, the industry experimented with various other synthetic materials for billiard balls such as [[Bakelite]], [[Poly(methyl methacrylate)|Crystalite]] and other plastic compounds. The exacting requirements of the billiard ball are met today with balls cast from plastic materials that are strongly resistant to cracking and chipping. Currently [[Saluc]], under the brand names Aramith<ref>[http://www.saluc.com/html/billiard/index.php Aramith]</ref> and Brunswick Centennial,<ref>{{cite web|url=http://www.brunswickbilliards.com/our_rich_history/billiard_balls/index.html|title=History|work=brunswickbilliards.com}}</ref> manufactures [[phenolic resin]] balls. Other plastics and resins such as [[polyester]] (under various trade names) and clear [[Acrylic glass|acrylic]] are also used, by competing companies such as Elephant Balls Ltd.<ref>[http://www.ElephantBalls.com Elephant Balls Ltd.]</ref> and Frenzy Sports.<ref>[http://www.FrenzySports.com/productinfo.htm Frenzy Sports]</ref> Ivory balls remained in use in [[artistic billiards]] competition until the late 20th century.<ref name="Shamos 1999" />{{rp|17}} :''(See also [[Cue sports#History|Cue sports, "History"]] for more-general information on billiards history.)'' ==Types== ===Carom billiards=== [[File:Carom billiards balls.jpg|thumb|left|200px|A standard set of [[w:Carom billiards|carom billiards]] balls (61.5&nbsp;mm [{{frac|2|7|16}}&nbsp;in] diameter), including a red {{Cuegloss|Object ball|object ball}}, a plain white {{Cuegloss|Cue ball|cue ball}}, and a dotted cue ball for the opponent. Some games use an additional object ball.]] In the realm of [[carom billiards|carom]] (or carambole) games, billiard balls are the three (sometimes four) balls used to play [[straight-rail]], [[three-cushion]], [[balkline and straight rail|balkline]], and related games on pocketless [[billiards table]]s, as well as [[English billiards]] which is played on a table with pockets. The predominantly-Asian game [[Four-ball billiards|four-ball]] uses four balls (the name literally means "four-balls"). Carom balls are not numbered, and at 61–61.5&nbsp;mm (between approximately {{frac|2|3|8}} and {{frac|2|7|16}}&nbsp;in) in diameter<ref name="UMB-II-12-2">{{cite web |url= http://www.umb.org/Rules/Carom_Rules.pdf |format=PDF |title=World Rules of {{sic|hide=y|Carom Billiard|reason=Yes, UMB did leave off the "s" in "Billiards".}} |at=Chapter II ("Equipment"), Article 12 ("Balls, Chalk"), Section 2 |work=UMB.org |author=<!--Staff writer(s); no by-line.--> |publisher=[[Union Mondiale de Billard]] |location=Sint-Martens-Latem, Belgium |date=1 January 1989 |archiveurl=//web.archive.org/web/20070928031638/http://www.umb.org/Rules/Carom_Rules.pdf |archivedate=2007-09-28 |accessdate=5 March 2007 }} Officially but somewhat poorly translated version, from the French original.</ref> are larger than pool balls. The 61.5&nbsp;mm size are more common. They are typically colored as follows: :* Red {{Cuegloss|Object ball|object ball}} (or, uncommonly, blue; two object balls are used in some games) :* White {{Cuegloss|Cue ball|cue ball}} for player 1 :* White with a spot (or sometimes yellow) cue ball for player 2 <br style="clear:left;" /> ===International pool=== {{anchor|American-style pool}}[[File:Billiard Balls and Rack.jpg|thumb|right|200px|Classic-style pool balls {{Cuegloss|Rack|racked}} for a game of [[ten-ball]], just before the {{Cuegloss|Break|break shot}}.]] [[File:Billiards balls.jpg|right|thumb|200px|Modern-style pool balls]] Pool balls are used to play various [[Pool (cue sports)|pool]] (pocket billiards) games, such as [[eight-ball]], [[nine-ball]] and [[one-pocket]]. In North America, they are sometimes referred to simply as "billiard balls" (except among carom players), and in the UK they are commonly referred to as [[kelly pool]] or American balls. These balls, used the most widely throughout the world, are considerably smaller than carom billiards balls, slightly larger than British-style pool balls and substantially larger than those for snooker. According to [[World Pool-Billiard Association|WPA]]/[[Billiard Congress of America|BCA]] equipment specifications, the weight may be from 5.5 to 6&nbsp;oz. (156–170&nbsp;g) with a diameter of 2.25&nbsp;in. (57.15&nbsp;mm), plus or minus 0.005&nbsp;in. (0.127&nbsp;mm).<ref name="WPAequipspec">{{cite web |url= http://www.wpa-pool.com/web/WPA_Tournament_Table_Equipment_Specifications |archiveurl= https://web.archive.org/web/20130928165510/http://www.wpa-pool.com/web/WPA_Tournament_Table_Equipment_Specifications |archivedate=2013-09-28 |title=WPA Tournament Table & Equipment Specifications |work=WPA-Pool.com |publisher=World Pool-Billiard Association |date=November 2001}} ([http://www.wpa-pool.com/web/WPA_Tournament_Table_Equipment_Specifications PDF version]).</ref><ref name="BCAbook">{{cite book | year = 2004 | title = Billiards: The Official Rules and Records Book | publisher = [[Billiards Congress of America]] | location = [[Colorado Springs, Colorado|Colorado Springs]] | page = 5 | isbn = 978-1-878493-14-9 | author = BCA Rules Committee }}</ref> The balls are numbered and colored as follows: {{ordered list|type=none <!--This orders them properly, but suppresses display of the list numbers, which are added manually, because most browsers do not allow the auto-generated numbers to be copy-pasted!--> | {{0|1}}1.&nbsp;&nbsp;Yellow | {{0|1}}2.&nbsp;&nbsp;Blue | {{0|1}}3.&nbsp;&nbsp;Red | {{0|1}}4.&nbsp;&nbsp;Purple (pink in some ball sets) | {{0|1}}5.&nbsp;&nbsp;Orange | {{0|1}}6.&nbsp;&nbsp;Green | {{0|1}}7.&nbsp;&nbsp;Brown or maroon (tan in some ball sets) | {{0|1}}8.&nbsp;&nbsp;Black | {{0|1}}9.&nbsp;&nbsp;Yellow and white <!-- --> | 10.&nbsp;&nbsp;Blue and white | 11.&nbsp;&nbsp;Red and white | 12.&nbsp;&nbsp;Purple and white (pink and white in some ball sets) | 13.&nbsp;&nbsp;Orange and white | 14.&nbsp;&nbsp;Green and white | 15.&nbsp;&nbsp;Brown, or maroon, and white (tan and white in some ball sets) | {{0|1}}{{lidot2}}{{Cuegloss|Cue ball|Cue ball}}, white (sometimes with one or more spots) }} In [[baseball pocket billiards]], the ball set is extended to 21 balls, in which the 16 ball is black and white, while balls 17 through 21 have no special design, but look exactly like balls 9 through 13, respectively, except for their numbers. Note that balls 1 through 7 are often referred to as {{Cuegloss|Solids|solids}} and 9 through 15 as {{Cuegloss|Stripes|stripes}} though there are many other colloquial terms for each {{Cuegloss|Suit|suit}} of balls (highs and lows, etc.). Though it looks similar to the solids, the 8 ball is not considered a solid. Some games such as nine-ball do not distinguish between stripes and solids, but rather use the numbering on the balls to determine which {{Cuegloss|Object ball|object ball}} must be pocketed. In other games such as [[three-ball]] neither type of marking is of any consequence. In [[eight-ball]], [[straight pool]], and related games, all sixteen balls are employed. In the games of [[seven-ball]], [[nine-ball]], [[ten-ball]] and related, only object balls 1 through 7, 9 and 10, respectively (plus the cue ball) are used. Some balls used in televised pool games are colored differently in order to make them distinguishable on television monitors. Specifically, the 4 ball is colored pink instead of dark purple, and the 12 is white with a pink stripe, to make it easier to distinguish their color from the black 8 ball, and similarly the 7 and 15 balls use a light tan color instead of a deep brown. The TV is also the genesis of the "measle" cue ball with numerous spots on its surface so that {{Cuegloss|Spin|spin}} placed on it is evident to viewers. Coin-operated pool tables such as those found at [[Bar (establishment)|bars]] historically have often used either a larger ("grapefruit") or denser ("rock", typically ceramic) cue ball, such that its extra weight makes it easy for the cue ball return mechanism to separate it from object balls (which are captured until the game ends and the table is paid again for another game) so that the cue ball can be returned for further play, should it be accidentally pocketed. Rarely in the US, some pool tables use a smaller cue ball instead. Modern tables usually employ a magnetic ball of regulation or near-regulation size and weight, since players have complained for many decades that the heavy and often over-sized cue balls do not "play" correctly.<!--R. Givens's "Eight-ball Bible" can be cited on these points, but my copy is missing. -SMcCandlish--> ===British-style pool (blackball)=== [[File:Blackball kick shot.jpg|left|thumb|250px|Playing blackball, with its distinctive red and yellow {{Cuegloss|Group|groups}}.]] In WPA [[Blackball (pool)|blackball]] (and its predecessor [[World Eight-ball Pool Federation|WEPF]] or ''English eight-ball pool'' (not to be confused with the games of [[eight-ball]] or [[English billiards]]), fifteen object balls again are used, but fall into two unnumbered {{Cuegloss|Group|groups}}, the {{Cuegloss|Red ball|reds}} (or less commonly {{Cuegloss|Blue ball|blues}}) and {{Cuegloss|Yellow ball|yellows}}, with a white cue ball, and black 8 ball. Aside from the 8, shots are not {{Cuegloss|Call-shot|called}} since there is no reliable way to identify particular balls to be pocketed. Because they are unnumbered they are wholly unsuited to certain pool games, such as nine-ball, in which ball order is important. They are noticeably smaller than the American-style balls, and with a cue ball that is slightly smaller than the object balls, while the table's {{Cuegloss|Pocket|pockets}} are tighter to compensate. Neither the WPA nor the WEPF (publicly) define ball or even table dimensions, though presumably league and tournament organizers are given some guidelines in this regard. Most manufacturers that supply this market provide sets that range from 2&nbsp;inch (5.08&nbsp;cm) up to {{frac|2|3|16}}&nbsp;inch (56&nbsp;mm), often with a slightly smaller cue ball, e.g. {{frac|1|7|8}}&nbsp;inches (4.76&nbsp;cm) for a 2&nbsp;inch set. The most common object ball diameters are 2&nbsp;inch and {{frac|2|1|8}} inch (54&nbsp;mm). The yellow-and-red sets are sometimes commercially referred to as "casino sets" (they were formerly used for televised eight-ball championships,<ref name="Shamos 1999"/>{{rp|45}} most often held in casinos). The use of such sets, however, pre-dates television, as they were used for B.B.C. Co. Pool, the forerunner of modern eight-ball, at least as early as 1908.<ref name="Shamos 1999" />{{rp|24}} {{Clear|left}} ===Snooker=== [[File:Set of Snookerballs.png|thumb|right|300px|Complete set of snooker balls.]] Ball sets for the sport of [[snooker]] look at first glance like a mixture of American- and British-style pool balls. There are twenty-two balls in total, arranged as a rack of fifteen unmarked reds, six {{Cuegloss|Colour ball|colour balls}} placed at various predetermined spots on the table, and a white cue ball. ''(See [[snooker]] for more information on ball setup.)'' The colour balls are sometimes numbered American-style, with their point values, for the amateur/home market, as follows: {{ordered list|type=none|start=2 <!--This orders them properly, but suppresses display of the list numbers, which are added manually, because most browsers do not allow the auto-generated numbers to be copy-pasted!--> | 2.&nbsp;&nbsp;{{Cuegloss|Yellow ball|Yellow}} | 3.&nbsp;&nbsp;{{Cuegloss|Green ball|Green}} | 4.&nbsp;&nbsp;{{Cuegloss|Brown ball|Brown}} | 5.&nbsp;&nbsp;{{Cuegloss|Blue ball|Blue}} | 6.&nbsp;&nbsp;{{Cuegloss|Pink ball|Pink}} | 7.&nbsp;&nbsp;{{Cuegloss|Black ball|Black}} MADE BY STONE ONLY!! }} Snooker balls are technically standardized at 52.5&nbsp;mm (approximately {{frac|2|1|15}}&nbsp;in) in diameter within a tolerance of plus or minus 0.05&nbsp;mm (0.002&nbsp;in.) No standard weight is defined, but all balls in the set must be the same weight within a tolerance of 3 g.<ref name="WSAequipspec">[http://www.worldsnooker.com/equipment.htm "Equipment"], World Snooker Association, publication date unknown (Retrieved 28 January 2007), London, UK.</ref> However, many sets are actually {{frac|2|1|16}}&nbsp;in. (a little under 52.4&nbsp;mm), even from major manufacturers. Snooker sets are also available with considerably smaller-than-regulation balls (and even with ten instead of fifteen reds) for play on smaller tables (down to half-size), and are sanctioned for use in some amateur leagues. Sets for [[American snooker]] are typically {{frac|2|1|8}}&nbsp;in. (54&nbsp;mm), with the numbered colour balls. ===Other games=== [[File:Russian billiards ball at a corner pocket.jpg|thumb|left|150px|Russian pyramid ball at a corner pocket. The relative size of the ball and the pocket makes the game very challenging.]] Various other games have their own variants of billiard balls. [[Russian pyramid]] use a set of fifteen numbered but otherwise all-white balls, and a red or yellow cue ball, that may be even larger than carom billiards balls, at 68&nbsp;mm (2¹¹⁄₁₆&nbsp;in) or 72&nbsp;mm (2⁴⁄₅ in). The related Finnish/Russian game [[kaisa (billiards)|kaisa]] has the same pocket and ball dimensions but it has only five balls: one yellow, two reds and two cue balls, one for each player.<ref name="BVRP">{{Cite web |url= http://www.billiardsvillage.com/russian-pyramid.html |title=Russian Billiards|work=BilliardsVillage.com |author=<!--Staff writer; no byline.--> |year=2007 |accessdate=2008-08-14 }}</ref> [[Bumper pool]] requires four white and four red object balls, and two special balls, one red with a white spot and the other the opposite; all are usually {{frac|2|1|8}} inch (approximately 52.5&nbsp;mm) in diameter.<br style="clear:both;" /> ===Training balls=== [[File:Jim Rempe practice ball.jpg|thumb|right|The [[Jim Rempe]] Training Ball]] Several brands of practice balls exist, which have systems of spots, stripes, differently-colored halves and/or targeting rings. For example, Saluc markets several practice ball systems, including the [[Jim Rempe]] Training Ball, a {{Cuegloss|Cue ball|cue ball}} marked with rings and targets on the surface of the ball so that the practicing player can better judge the effects of very particular amounts of {{Cuegloss|Sidespin|sidespin}}, {{Cuegloss|Topspin|topspin}}, {{Cuegloss|Backspin|backspin}} and other forms of cue ball control, and learn better control of [[Cue stick|cue]] {{Cuegloss|Stroke|stroke}}.<ref name="Saluc 1">{{Cite web|url= http://www.saluc.com/html/index.php?idlien=17 |title=Product Line &gt; Training Balls|year=2005|work=Saluc.com|publisher=[[Saluc|Saluc S.A.]]|location=Callenelle, Belgium|accessdate=2008-02-18}} {{Dead link|date=October 2010|bot=H3llBot}}</ref> Various competing products, such as several other Saluc models<ref name="Saluc 1" /> and Elephant Practice Balls,<ref name="Elephant">{{Cite web|url= http://www.elephantballs.com/store/products/22 |title=Elephant Practice Balls|year=2007|work=ElephantBalls.com|publisher=Elephant Balls, Ltd.|location=Columbus, Ohio|accessdate=2008-02-18}}</ref> use a similar aiming system. Some such sets consist of just a special cue ball and manual, while others also include an object ball marked for aiming practice. ===Novelty balls=== [[File:Striped 8 ball.jpg|thumb|left|200px|A striped "[[referee]]" 8 ball from a set of [[American football]] team logo balls.]] [[File:Novelty billiard balls.jpg|thumb|right|200px|Various novelty [[pocket billiards]] balls. Clockwise from the top: Red and white balls and markers from a proprietary game called Starball; an [[Elvis Presley]] commemorative cue ball from [[Graceland]]; a [[leopard]]-patterned 9 ball; colorful balls from a [[poker]]-themed set; regular balls and the small "jack" from a miniature [[bocce]] set used on a table instead of a lawn or court.]] There is a market for specialty cue balls and even entire ball sets, featuring sports team logos, cartoon characters, animal pelt patterns, etc. Entrepreneurial inventors also supply a variety of novelty billiard games with unique rules and balls, some with playing card markings, others with stars and stripes, and yet others in sets of more than thirty balls in several suits. Marbled-looking and glittery materials are also popular for home tables. There are even [[blacklight]] sets for playing in near-dark. There are also [[practical joke]] cue and 8 balls, with off-center weights in them that make their paths curve and wobble. Miniature sets in various sizes (typically {{frac||2|3}} or {{frac||1|2}} of normal size) are also commonly available, primarily intended for under-sized toy tables. Even an egg-shaped ball has been patented<ref>U.S. Patent No. 7,468,002</ref> and marketed under such names as Bobble Ball and Tag Ball.<br style="clear:both;" /> ==In popular culture== [[File:8 ball face.jpg|thumb|A [[Magic 8 Ball]]]] [[File:USS Sam Rayburn (SSBN-635) missile hatches.jpg|thumb|upright|[[Ballistic missile submarine]] {{USS|Sam Rayburn|SSBN-635|6}} displays a billiard motif on her missile hatches]] The 8 ball is frequently used iconically in Western, especially American, culture. It can often be found as an element of T-shirt designs, album covers and names, tattoos, household goods like paperweights and cigarette lighters, belt buckles, etc. A classic toy is the [[Magic 8-Ball]] "oracle". [[Don and Ron Harris|A wrestler]], [[Eightball & MJG|a rapper]], and [[8-Ball (band)|a rock band]] have all independently adopted the name. The term "8 ball" is also [[slang]] both for {{frac||1|8}}&nbsp;[[Ounce|oz.]] of [[cocaine]] or [[crystal methamphetamine|crystal meth]], and for a bottle of [[Olde English 800]] [[malt liquor]]. It has also been used to refer to African-Americans, particularly those of darker skin tones, as in the film ''[[Full Metal Jacket]]''. The expression "behind the eight (ball)" is used to indicate a [[dilemma]] from which it is difficult to extricate oneself. The term derives from the game [[kelly pool]].<ref name="IEOB">{{cite book | last = Shamos | first = Michael Ian | year = 1993 | title = The Illustrated Encyclopedia of Billiards | publisher = Lyons & Burford | location = New York City | pages = 85, 128 and 168 | isbn = 1-55821-219-1}}</ref><ref>{{cite journal | last = Jewett | first = Bob |date=February 2002 | title = 8-Ball Rules: The many different versions of one of today's most common games | journal = Billiards Digest Magazine | pages = Pages 22–23}}</ref><ref>Ralph Hickok (2001). [http://www.hickoksports.com/history/billiard.shtml Sports History: Pocket Billiards]. Retrieved 22 February 2007.</ref><ref>Billiard Congress America (1995–2005) [http://www.bca-pool.com/aboutus/history/start.shtml A Brief History of the Noble Game of Billiards] by Mike Shamos. Retrieved 22 February 2007.</ref><ref name="Mizerak">{{cite book | author= Steve Mizerak and Michael E. Panozzo | title = Steve Mizerak's Complete Book of Pool | publisher = Contemporary Books | location = [[Chicago|Chicago, Ill]] | pages = 127–8 | year = 1990 | isbn = 0-8092-4255-9}}</ref> Because the [[Collision#Billiards|collisions between billiard balls]] are nearly [[Elastic collision|elastic]], and the balls roll on a surface that produces low [[rolling friction]], their behavior is often used to illustrate [[Newton's laws of motion]]. Idealized, frictionless billiard balls are a staple of [[Mathematics|mathematical]] theorems and [[physics]] models, and figure in [[dynamical billiards]], [[scattering theory]], [[Lissajous knots]], [[billiard ball computing]] and [[Reversible cellular automaton|reversible cellular automata]], [[Polchinski's paradox]], [[contact dynamics]], [[collision detection]], the [[illumination problem]], [[Ultracold atom|atomic ultracooling]], [[quantum mirage]]s and elsewhere in these fields. "Billiard balls" or "pool balls" is the name given to balls used in [[stage magic]] tricks, especially the classic "[[multiplying billiard balls]]". Though obviously derived from real billiard balls, today they are usually smaller, for easier manipulation and hiding, but not so small and light that they are difficult to [[juggle]], as the magic and juggling disciplines have often overlapped since their successful combination by pioneers like [[Paul Vandy]]. The phrase "as smooth as a billiard ball" is sometimes applied to describe a [[Baldness|bald person]], and the term "cue ball" is also slang for someone who sports a [[shaved head]]. ==References== {{reflist}} ===Patents=== * {{US patent|0050359}}—''Billiard ball ca. 1865'' * {{US patent|0076765}}—''Billiard ball ca. 1868'' * {{US patent|0088634}}—''Billiard ball ca. 1869'' * {{US patent|0114945}}—''Billiard ball ca. 1871'' {{Cue sports nav}} {{DEFAULTSORT:Billiard Ball}} [[Category:Cue sports equipment|Ball, billiard]] [[Category:Balls]] [[Category:Game equipment]]'