Rattleback: Difference between revisions

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:''For the fictional / theorized future animal, see [[Rattleback (rodent)]].''.

[[Image:Celt_with_gemstone_turtles-01.jpg|thumb|300px|Celts are asymmetrical tops which have a preferred direction of spin. If spun in the opposite direction they become unstable and reverse their spin to the preferred direction.Rattleback]]

A '''rattleback''', also known as a "celt," "Celtic stone" or "wobblestone," is a semi-ellipsoidal [[top]] which will spin on its axis in a preferred direction. But, if spun in the opposite direction, it becomes unstable, "rattles," stops and reverses its spin to the preferred direction.

Also known as a "wobblestone" or "celt", the '''rattleback''' is a semi-[[ellipsoid]]al object that can be spun about its axis like a [[top]], but after a while reverses its spinning direction. This seems, at first sight, to violate [[conservation of angular momentum]]. Moreover, for most rattlebacks, the spinning reversal will happen when the rattleback is spun in one direction, but not when spun the other. These two peculiarities make the rattleback a physical curiosity that has excited human imagination since prehistorical times.

AlsoThis known as a "wobblestone" or "celt", the '''rattleback''' is a semispin-[[ellipsoid]]alreversal object that can be spun about its axis like a [[top]], but after a while reverses its spinning direction. Thismotion seems, at first sight, to violate the [[conservation of angular momentum|angular-momentum]] conservation law of physics. Moreover, for most rattlebacks, the spinning reversalmotion will happen when the rattleback is spun in one direction, but not when spun the other. These two peculiarities make the rattleback a physical curiosity that has excited human imagination since prehistorical times.

==History==

RattlebacksArcheologists werewho found by archeologists investigatinginvestigated ancient Celtic and Egyptian sites, andfound somecelts oldwhich Celticexhibited axesthe demonstratespin-reversal propertiesmotion. similarThe toLatin rattlebacks.word Note"[[Celt however that(tool)|celt]]" (the term "celtc" is notpronounced relatedas to"s") Celticdescribes peopleaxe- but to a Latin word for ancientand chisel-shaped [[Lithic analysis|lithic]] tools and weapons. It is pronounced with a "c" as in "ceiling".

==Physics of the rattleback==

The spin-reversal of the spinmotion follows from the growth of an[[flight instabilitydynamics|instabilities]] abouton the other axes of rotation of the rattlebackaxes, that is,are rolling (abouton the main axis) and pitching (abouton the crosswise axis).

[[Image:Rolling-pitching.png|thumb|Rolling and pitching movementsmotions]]

When there is an asymmetry in the mass distribution with respect to the plane formed by the pitching and the vertical axes, a coupling of these two instabilities arises:; one can imagine how the asymmetry in mass will deviate the rattleback when pitching, which will create some rolling. The amplified mode will differ depending on the spin direction, which explains the asymmetrical behaviour of the rattleback. Depending on whether it is rather a pitching or rolling instability that dominates, the growth rate will be very high or quite low. This explains why, due to friction, most rattlebacks only exhibit spin reversal when spun in the pitching-unstable direction, while they slow down and stop spinning before the rolling instability arises when spun in the other direction. Rattlebacks made of glass, however, were reported to be able to reverse spinning in both directions, and even to incur up to four or five successive reversals during a single experiment.

The amplified mode will differ depending on the spin direction, which explains the rattleback asymmetrical behavior. Depending on whether it is rather a pitching or rolling instability that dominates, the growth rate will be very high or quite low.

For more details on pitch and roll instabilities, see the article on [[flight dynamics]].

This explains why, due to friction, most rattlebacks spin-reversal motion only when spun in the pitching-unstable direction, while they slow down and stop spinning before the rolling instability arises when spun in the other direction. Rattlebacks made of glass, however, were reported to exhibited this motion in both directions, and incur up to four or five successive rotations during a single experiment.

==References==

Boardman, Allan J. "The mysterious celt." ''Fine Woodworking'', vol. 53, pp. 68-9. The Taunton Press Inc. Newtown, Conn. July/August 1985.

H. K. Moffatt, ''Talk for the 50th anniversary of the Journal of Fluid Mechanics'', Cambridge, 21 July 2006.

[[Hermann Bondi|Bondi, Sir Hermann]], [[Order of the Bath|KCB]] [[Royal Society|FRS]]. "The rigid body dynamics of unidirectional spin." ''Proceedings of the Royal Society of London for the Improvement of Natural Knowledge'', vol. A405, pp. 265-74. London. 1986.

A. B. Pippard, [http://www.iop.org/EJ/abstract/0143-0807/11/1/112 How to make a celt or rattleback], ''Eur. J. Phys.'' 11:1, 63-64, 1990. (The rattleback is made with a part of a glass wine bottle and a metal bar fixed at a small angle to the rolling axis)

Crabtree, Harold. ''An elementary treatment of the spinning tops and gyroscopic motion''. pp. 7, 54, plate I. Longmans, Green & Co. London. 1909.

Allan J. Boardman,The Mysterious Celt, ''Fine Woodworking'', July/August 1985

Crane Ph.D., H. Richard. "How things work: The rattleback revisited." ''The Physics Teacher'', vol. 29(5), pp. 278-9. American Association of Physics Teachers. College Park, Md. 1991.

Edge Ph.D., Ronald D. and Richard Lee Childers Ph.D.. "String and sticky tape: Curious celts and riotous rattlebacks." ''The Physics Teacher'', vol. 37(2), p. 80. American Association of Physics Teachers. College Park, Md. 1999.

Elliott, W.A. ''The inside story of the whirlygig!'' W.A. Elliott Co., Toronto.

Elliott, W.A. ''The Tate's compass''. W.A. Elliott Co., Toronto. 1982.

Freeman, Ira B. "What is Trevelyan's rocker?" ''The Physics Teacher'', vol. 12, p. 382. American Association of Physics Teachers. College Park, Md. 1974.

Gray, Andrew. ''Treatise of gyrostatics and rotational motion''. Macmillan Publishers Ltd. London. 1918.

Magnus, Karl. ''The stability of rotations of a non-symmetrical body on a horizontal surface''. Festschrift Szabo, pp. 19-23, Berlin. 1971.

McGeer Ph.D., Tad and Leigh Hunt Palmer Ph.D. "Wobbling, toppling and forces of contact." ''American Journal of Physics'', vol. 57, pp. 1089-98. American Association of Physics Teachers. College Park, Md. 1989.

H.Moffatt KPh.D. Moffatt[[Royal Society|FRS]], ''Henry Keith. "Talk for the 50th anniversary." of the ''Journal of Fluid Mechanics'', Cambridge, 21University JulyPress. Cambridge, England. 2006.

Satterly D.Sc. [[Royal Society of Canada|FRSC]], John. "Induced rocking." ''American Journal of Physics'', vol. 26, pp. 625-7. American Association of Physics Teachers. College Park, Md. 1958.

Satterly D.Sc. [[Royal Society of Canada|FRSC]], John. "Rocking experiment with two degrees of freedom." ''American Journal of Physics'', vol. 21, 267-73. American Association of Physics Teachers. College Park, Md. 1953.

Satterly D.Sc. [[Royal Society of Canada|FRSC]], John. "Three interesting instances of rocking." ''American Journal of Physics'', vol. 23, pp. 14-26. American Association of Physics Teachers. College Park, Md. 1955.

Satterly D.Sc. [[Royal Society of Canada|FRSC]], John. "Vibrational dynamics with lenses, mirrors and prisms." ''American Journal of Physics'', vol. 23, pp. 562-81. American Association of Physics Teachers. College Park, Md. 1955.

Sherburne, Charles W. "Scientific demonstration toy." U.S. Design 210,947. Filed: Nov. 12 1995. Patented: May 7, 1968. San Pedro, Calif.

Walgate Ph.D., Robert. "Tops that like to spin one way." ''Nature'', vol. 323, p. 204. Nature Publishing Group, London. 1986.

[[Jearl Walker|Walker Ph.D., Jearl]]. "The mysterious 'rattleback': A stone that spins in one direction and then reverses." ''Scientific American'', pp. 172-84. Scientific American Inc. New York. 1979.

[[Jearl Walker|Walker Ph.D., Jearl]]. "Rattlebacks and tippe tops; Roundabout: The physics of rotation in the everyday world." ''Scientific American'', pp. 33-8, 66. Scientific American Inc. New York. 1985.

[[Gilbert Walker|Walker FRS, Sir Gilbert Thomas]]. "On a curious dynamical property of celts." ''Proceedings of the Cambridge Philosophical Society'', vol. 8, pp. 305-6. Cambridge, England. 1892/5.

[[Gilbert Walker|Walker FRS, Sir Gilbert Thomas]]. "On a dynamical top." ''Quarterly Journal of Pure and Applied Mathematics'', vol. 28, pp. 175-84. International Press. Somerville, Mass. 1896.

Wheeler Ph.D., Nicholas A. ''Rattlebacks -- How do they work?'' Reed College Department of Physics. Portland, Ore.

==External links==

*4Physics.com: [http://www.4physics.com:8080/phy_demo/rattleback.htm ''The amazing rattleback!'']

"Torque of the Devil" http://www.physics.brown.edu/physics/demopages/Demo/solids/demos/torque.html

http://www.4physics.com:8080/phy_demo/rattleback.htm

*Bondi, Sir Hermann. KCB FRS. [http://links.jstor.org/sici?sici=0080-4630(19860609)405%3A1829%3C265%3ATRBDOU%3E2.0.CO%3B2-M "The rigid body dynamics of unidirectional spin."] ''Proceedings of the Royal Society of London for the Improvement of Natural Knowledge'', vol. A405, pp. 265-74. 1986.

Physics demo instructions http://www.sfu.ca/physics/ugrad/courses/teaching_resources/demoindex/mechanics/mech1q/celt.html

"Torque*Brown of the Devil"University: [http://www.physics.brown.edu/physics/demopages/Demo/solids/demos/torque.html ''Torque of the devil''.] physics demonstration.

Building a Rattleback: http://www.123too.com

*Brown University: [http://www.physics.brown.edu/physics/demopages/Demo/solids/demos/1q6016.html ''To demonstrate a puzzling mechanical device with unidirectional rotational behavior''.] physics demonstration.

Sources of Rattlebacks:

*Grand Illusions: [http://www.grand-illusions.com/acatalog/info_63.html ''Russian rattleback''.]

http://www.physlink.com//estore/cart/BizzaroSwirls.cfm

*Keath, Ed. [http://www.grand-illusions123too.com/toyshop/russian_rattleback/ ''Turning a celt''.]

*PhysLink.com: [http://www.physlink.com//estore/cart/BizzaroSwirls.cfm "Bizzaro swirls -- Rattleback."] Science eStore.

*Pippard, A.B. [http://www.iop.org/EJ/abstract/0143-0807/11/1/112 "How to make a celt or rattleback."] ''European Journal of Physics'', vol. 11, pp. 63-4. Institute of Physics. 1990.

*Simon Fraser University: [http://www.sfu.ca/~closari/projects/ensc100/index.htm ''Rattleback''.] Engineering Science 100 Tutorial Group Nu. Canada.

Physics*Simon demoFraser instructionsUniversity: [http://www.sfu.ca/physics/ugrad/courses/teaching_resources/demoindex/mechanics/mech1q/celt.html ''Celt''.] physics demonstration.

*Singmaster, David. [http://www.g4g4.com/MyCD5/SOURCES/SOURCE4.DOC ''Celts -- Rattlebacks''.] South Bank University. London. 2004.

[[de:Keltischer Wackelstein]]

[[pl:Kamień celtycki]]

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