Rattleback
Encyclopedia
A rattleback, also known as an "anagyre", "celt
", "Celtic stone", "rebellious celt", "rattlerock", "spin bar", "wobble stone" or "wobblestone" and by the product names "ARK," "Bizzaro Swirls," "RATTLEBACKS," "Space Pet" and "Space Toy," 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.
This spin-reversal motion seems, at first sight, to violate the angular-momentum
conservation law of physics. Moreover, for most rattlebacks, the motion will happen when the rattleback is spun in one direction, but not when spun in the other. Some exceptional rattlebacks will reverse when spun in either direction.
This makes the rattleback a physical curiosity that has excited human imagination since prehistorical times.
ic and Egyptian
sites
in the 19th century found celts which exhibited the spin-reversal motion. The antiquarian
word "celt
" (the "c" is pronounced as "s") describes adze
-, axe
-, chisel
- and hoe
-shaped lithic
tools and weapons.
The first modern descriptions of these celts were published in the 1890s when Sir Gilbert Thomas Walker FRS
wrote his "On a curious dynamical property of celts" for the Proceedings of the Cambridge Philosophical Society in Cambridge, England, and "On a dynamical top" for the Quarterly Journal of Pure and Applied Mathematics in Somerville, Mass.
Additional examinations of rattlebacks were published in 1909 and 1918, and by the 1950s and 1970s, several more examinations were made. But, the popular fascination with the objects has increased notably since the 1980s when no fewer than 28 examinations were published.
s are described as stone with various measurements, most which are sold currently as novelty puzzles and toys are described as plastic with measurements of 3.75 inches long x 0.75 inches wide x 0.4375 inches high. Carved wooden rattlebacks are described with a measurement of 5.5 to 6 inches in length. One plastic rattleback made and sold by Charles W. Sherburne is described as 12 inches in length. Glass rattlebacks, and those made of spoons http://www.exo.net/~pauld/TomTits2000/europetrip/technorama%20lecture/technoramalecture.html, are described as being tested with unreported measurements. Larger rattlebacks, and those of other materials, aren't yet reported.
Two rattleback design types exist. They have either an asymmetrical base with a skewed rolling axis, or a symmetrical base with offset weighting at the ends.
on the other rotation axes, that are rolling (on the main axis) and pitching (on the crosswise axis).
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 rattleback's 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.
This explains why, due to friction, most rattlebacks appear to exhibit spin-reversal motion only when spun in the pitching-unstable direction, also known as the strong reversal direction. When the rattleback is spun in the "stable direction", also known as the weak reversal direction, friction and damping often slow the rattleback to a stop before the rolling instability has time to fully build. Some rattlebacks, however, exhibit "unstable behavior" when spun in either direction, and incur several successive spin reversals per spin.
Other ways to add motion to a rattleback include tapping by pressing down momentarily on either of its ends, and rocking by pressing down repeatedly on either of its ends.
Celt (tool)
Celt is an archaeological term used to describe long thin prehistoric stone or bronze adzes, other axe-like tools, and hoes.-Etymology:The term "celt" came about from what was very probably a copyist's error in many medieval manuscript copies of Job 19:24 in the Latin Vulgate Bible, which became...
", "Celtic stone", "rebellious celt", "rattlerock", "spin bar", "wobble stone" or "wobblestone" and by the product names "ARK," "Bizzaro Swirls," "RATTLEBACKS," "Space Pet" and "Space Toy," is a semi-ellipsoidal top
Top
A top is a toy that can be spun on an axis, balancing on a point. This motion is produced in the most simple forms of top by twirling the stem using the fingers. More sophisticated tops are spun by by holding the axis firmly while pulling a string or twisting a stick or pushing an auger as shown...
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.
- Behold the mysterious celt,
- with a property that amuses.
- One way it will spin,
- the other way it refuses.
This spin-reversal motion seems, at first sight, to violate the angular-momentum
Angular momentum
In physics, angular momentum, moment of momentum, or rotational momentum is a conserved vector quantity that can be used to describe the overall state of a physical system...
conservation law of physics. Moreover, for most rattlebacks, the motion will happen when the rattleback is spun in one direction, but not when spun in the other. Some exceptional rattlebacks will reverse when spun in either direction.
This makes the rattleback a physical curiosity that has excited human imagination since prehistorical times.
History
Archeologists who investigated ancient CeltCelt
The Celts were a diverse group of tribal societies in Iron Age and Roman-era Europe who spoke Celtic languages.The earliest archaeological culture commonly accepted as Celtic, or rather Proto-Celtic, was the central European Hallstatt culture , named for the rich grave finds in Hallstatt, Austria....
ic and Egyptian
Ancient Egypt
Ancient Egypt was an ancient civilization of Northeastern Africa, concentrated along the lower reaches of the Nile River in what is now the modern country of Egypt. Egyptian civilization coalesced around 3150 BC with the political unification of Upper and Lower Egypt under the first pharaoh...
sites
Archaeology
Archaeology, or archeology , is the study of human society, primarily through the recovery and analysis of the material culture and environmental data that they have left behind, which includes artifacts, architecture, biofacts and cultural landscapes...
in the 19th century found celts which exhibited the spin-reversal motion. The antiquarian
Antiquarian
An antiquarian or antiquary is an aficionado or student of antiquities or things of the past. More specifically, the term is used for those who study history with particular attention to ancient objects of art or science, archaeological and historic sites, or historic archives and manuscripts...
word "celt
Celt (tool)
Celt is an archaeological term used to describe long thin prehistoric stone or bronze adzes, other axe-like tools, and hoes.-Etymology:The term "celt" came about from what was very probably a copyist's error in many medieval manuscript copies of Job 19:24 in the Latin Vulgate Bible, which became...
" (the "c" is pronounced as "s") describes adze
Adze
An adze is a tool used for smoothing or carving rough-cut wood in hand woodworking. Generally, the user stands astride a board or log and swings the adze downwards towards his feet, chipping off pieces of wood, moving backwards as they go and leaving a relatively smooth surface behind...
-, axe
Axe
The axe, or ax, is an implement that has been used for millennia to shape, split and cut wood; to harvest timber; as a weapon; and as a ceremonial or heraldic symbol...
-, chisel
Chisel
A chisel is a tool with a characteristically shaped cutting edge of blade on its end, for carving or cutting a hard material such as wood, stone, or metal. The handle and blade of some types of chisel are made of metal or wood with a sharp edge in it.In use, the chisel is forced into the material...
- and hoe
Hoe (tool)
A hoe is an ancient and versatile agricultural tool used to move small amounts of soil. Common goals include weed control by agitating the surface of the soil around plants, piling soil around the base of plants , creating narrow furrows and shallow trenches for planting seeds and bulbs, to chop...
-shaped lithic
Lithic analysis
In archaeology, lithic analysis is the analysis of stone tools and other chipped stone artifacts using basic scientific techniques. At its most basic level, lithic analyses involve an analysis of the artifact’s morphology, the measurement of various physical attributes, and examining other visible...
tools and weapons.
The first modern descriptions of these celts were published in the 1890s when Sir Gilbert Thomas Walker FRS
Gilbert Walker
Sir Gilbert Thomas Walker, CSI, FRS, was a British physicist and statistician of the 20th century. He is best known for his groundbreaking description of the Southern Oscillation, a major phenomenon of global climate, and for greatly advancing the study of climate in general.He was born in...
wrote his "On a curious dynamical property of celts" for the Proceedings of the Cambridge Philosophical Society in Cambridge, England, and "On a dynamical top" for the Quarterly Journal of Pure and Applied Mathematics in Somerville, Mass.
Additional examinations of rattlebacks were published in 1909 and 1918, and by the 1950s and 1970s, several more examinations were made. But, the popular fascination with the objects has increased notably since the 1980s when no fewer than 28 examinations were published.
Size and materials
While rattleback artifactArtifact (archaeology)
An artifact or artefact is "something made or given shape by man, such as a tool or a work of art, esp an object of archaeological interest"...
s are described as stone with various measurements, most which are sold currently as novelty puzzles and toys are described as plastic with measurements of 3.75 inches long x 0.75 inches wide x 0.4375 inches high. Carved wooden rattlebacks are described with a measurement of 5.5 to 6 inches in length. One plastic rattleback made and sold by Charles W. Sherburne is described as 12 inches in length. Glass rattlebacks, and those made of spoons http://www.exo.net/~pauld/TomTits2000/europetrip/technorama%20lecture/technoramalecture.html, are described as being tested with unreported measurements. Larger rattlebacks, and those of other materials, aren't yet reported.
Two rattleback design types exist. They have either an asymmetrical base with a skewed rolling axis, or a symmetrical base with offset weighting at the ends.
Physics
The spin-reversal motion follows from the growth of instabilitiesFlight dynamics
Flight dynamics is the science of air vehicle orientation and control in three dimensions. The three critical flight dynamics parameters are the angles of rotation in three dimensions about the vehicle's center of mass, known as pitch, roll and yaw .Aerospace engineers develop control systems for...
on the other rotation axes, that are rolling (on the main axis) and pitching (on the crosswise axis).
The amplified mode will differ depending on the spin direction, which explains the rattleback's 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.
This explains why, due to friction, most rattlebacks appear to exhibit spin-reversal motion only when spun in the pitching-unstable direction, also known as the strong reversal direction. When the rattleback is spun in the "stable direction", also known as the weak reversal direction, friction and damping often slow the rattleback to a stop before the rolling instability has time to fully build. Some rattlebacks, however, exhibit "unstable behavior" when spun in either direction, and incur several successive spin reversals per spin.
Other ways to add motion to a rattleback include tapping by pressing down momentarily on either of its ends, and rocking by pressing down repeatedly on either of its ends.
Myths
Rattlebacks have been misdescribed and misused as:- A tool of divinationDivinationDivination is the attempt to gain insight into a question or situation by way of an occultic standardized process or ritual...
— CyclomancyCyclomancyCyclomancy is a form of divination based on spinning an object and deriving predictions or conclusions from the object's final resting direction. In some traditions, a wheel or top is spun on a surface marked with letters or symbols, and those that fall closest to the device's pointer are consulted... - Influenced by magicMagic (paranormal)Magic is the claimed art of manipulating aspects of reality either by supernatural means or through knowledge of occult laws unknown to science. It is in contrast to science, in that science does not accept anything not subject to either direct or indirect observation, and subject to logical...
- An expression of the object's AnimismAnimismAnimism refers to the belief that non-human entities are spiritual beings, or at least embody some kind of life-principle....
- Influenced by the Fourth Dimension
- A demonstration of perpetual motionPerpetual motionPerpetual motion describes hypothetical machines that operate or produce useful work indefinitely and, more generally, hypothetical machines that produce more work or energy than they consume, whether they might operate indefinitely or not....
"free energySecond law of thermodynamicsThe second law of thermodynamics is an expression of the tendency that over time, differences in temperature, pressure, and chemical potential equilibrate in an isolated physical system. From the state of thermodynamic equilibrium, the law deduced the principle of the increase of entropy and...
" - Influenced by Earth's magnetic fieldEarth's magnetic fieldEarth's magnetic field is the magnetic field that extends from the Earth's inner core to where it meets the solar wind, a stream of energetic particles emanating from the Sun...
- An accurate test of judicial guilt
- Influenced by the Coriolis effectCoriolis effectIn physics, the Coriolis effect is a deflection of moving objects when they are viewed in a rotating reference frame. In a reference frame with clockwise rotation, the deflection is to the left of the motion of the object; in one with counter-clockwise rotation, the deflection is to the right...
- A "Tate's" compass ("He who has a Tate's is lost.")
External links
- Bondi KCB FRS, Sir Hermann. "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.
- Brown University: Torque of the devil. physics demonstration.
- Brown University: To demonstrate a puzzling mechanical device with unidirectional rotational behavior. physics demonstration.
- Doherty, Paul. Scientific Explorations. Spoon Rattleback. 2000.
- Flinn Scientific Inc. "Celt Spoon."
- Krasnoukhov, Dr. Vladimir and Anatoli Kalinin. Stubborn Turtles.
- Pippard, A.B. "How to make a celt or rattleback." European Journal of Physics, vol. 11, pp. 63–4. Institute of Physics. 1990.
- Sanderson, Jonathan. Activity of the Week: Rattleback.
- Simon Fraser University: Rattleback. Engineering Science 100 Tutorial Group Nu. Burnaby, British Columbia, Canada.
- Simon Fraser University: Celt. physics demonstration. Burnaby, British Columbia, Canada.
- Singmaster, David. Celts -- Rattlebacks. South Bank University. London. 2004.
- University of Cambridge Millennium Mathematics Project "Boomerangs and Gyroscopes."
- Aleksei V Borisov, Ivan S Mamaev Institute of Computer Science, Izhevsk, Russian Federation Strange attractors in rattleback dynamics