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Chain fountain
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The chain fountain phenomenon, also known as the Mould effect, self-siphoning beads, or Newton's beads, is a physical phenomenon observed with a chain placed inside a jar. One end of the chain is pulled from the jar and is allowed to fall under the influence of gravity. This process establishes a self-sustaining flow of the chain which rises over the edge and goes down to the floor or ground beneath it, as if being sucked out of the jar by an invisible siphon. For chains with small adjacent beads, the arc can ascend into the air over and above the edge of the jar with a noticeable gap; this gap is greater when the chain falls farther.[1]
The self-siphoning effect is also observed in non-Newtonian fluids.
History
[edit]The self-siphoning phenomenon has been known for some time, and had become a topic of public discussion many times in the past. Science entertainer Steve Spangler presented this phenomenon on TV in 2009, both with beads and viscoelastic liquids.[2][3] This phenomenon is classically known as Newton's beads.[4]
The effect is most pronounced when using a long ball chain. The higher the jar containing the chain is placed above the ground, the higher the chain will rise above the jar during the "siphoning" phase. As demonstrated in an experiment, when the jar is placed 30 metres (98 ft) above the ground and the chain is sufficiently long, the arc of the chain fountain can reach a height of about 2.1 m (6 ft 11 in) above the jar.[non-primary source needed][5]
In 2011, the phenomenon with the rising chain was described as an open problem[a] for the 2012 International Young Physicists' Tournament (IYPT).[6][4]
In 2013, science presenter Steve Mould (namesake of the effect) brought the chain problem to widespread public attention.[7] In a YouTube video,[8] he demonstrated the phenomenon of self-siphoning rising beads, and he then presented his proposed explanation on a BBC show.[9] This publicity caught the attention of academics John Biggins and Mark Warner of Cambridge University.[10][11]
In 2014, Biggins and Warner published their findings on the problem in Proceedings of the Royal Society, regarding what they called the "chain fountain" or the "Mould effect".[12][13][14][7]
Explanation
[edit]A variety of explanations have been proposed as to how the phenomenon can best be explained in terms of kinematic physics concepts such as energy and momentum.[15][16][17][18]
Biggins and Warner suggest that the origin of the upward force is related to the stiffness of the chain links, and the bending restrictions of each chain joint.[7][12]
Furthermore, because the beads of the chain can drag laterally within the jar across other stationary links, the moving beads of the chain can bounce or jump vertically when they strike the immobile links. This effect contributes to the chain's movement, but is not the primary cause.[12][17]
In non-Newtonian fluids
[edit]The self-siphoning phenomena can be also observed in viscoelastic fluids[19] that are mainly composed of long polymers, like polyethylene glycol.[2][20]
See also
[edit]Notes
[edit]- ^ Statement of problem 3. String of beads: "A long string of beads is released from a beaker by pulling a sufficiently long part of the chain over the edge of the beaker. Due to gravity the speed of the string increases. At a certain moment the string no longer touches the edge of the beaker. Investigate and explain the phenomenon.")
References
[edit]- ^ Yam, Philip (2013-07-03). "Gravity-Defying, Self-Siphoning Metal Beads Explained [Video]". Scientific American.
- ^ a b Arney, Helen; Mould, Steve (2017-10-05). The Element in the Room: Science-y Stuff Staring You in the Face. Octopus. ISBN 978-1-78840-004-6.
- ^ Sick Science (2009-07-29), Newton's Beads - Cool Science Experiment, retrieved 2021-07-24
- ^ a b Martchenko, Ilya; Malinowski, Maciej; Oszmaniec, Michał (2011-10-09). "Preparation to the Young Physicists' Tournaments' 2012" (PDF). International Young Physicist Tournament.
- ^ 第1期-刘谦郎朗被吊起"命悬一杯" 撒贝宁对大炮求虐【加油!向未来20160703】 (in Chinese).
- ^ "Problems". IYPT archive. Archived (PDF) from the original on 2018-03-01.
- ^ a b c Gibney, Elizabeth (2014-01-15). "Physicists explain 'gravity-defying' chain trick". Nature. doi:10.1038/nature.2014.14523.
- ^ Mould, Steve (2013-02-20). "Self siphoning beads". YouTube.
- ^ "Amazing bead chain experiment in slow motion". YouTube. BBC Earth Unplugged. 2013-06-27.
- ^ "Understanding the chain fountain: A problem-solving partnership (w/ Video)". Phys.org. 2014-01-15.
- ^ Wade, Lizzie (2014-01-14). "Video: How the 'Chain Fountain' Defies Gravity". Science.
- ^ a b c Biggins, J. S.; Warner, M. (2014). "Understanding the chain fountain". Proceedings of the Royal Society A: Mathematical, Physical and Engineering Sciences. 470 (2163) 20130689. arXiv:1310.4056. Bibcode:2014RSPSA.47030689B. doi:10.1098/rspa.2013.0689. S2CID 37699566.
- ^ Royal Society (2014-01-15). "Understanding the chain fountain". YouTube. Retrieved 2021-07-24.
- ^ Steve Mould, Investigating the "Mould Effect", TEDxNewcastle, https://www.youtube.com/watch?v=wmFi1xhz9OQ
- ^ Goodman, William (2013-06-25). "See physics phenomenon of self siphoning beads". CBS News.
- ^ Bhatia, Aatish (2013-07-01). "The physics of that gravity-defying chain of metal beads". Wired. Retrieved 2014-01-15.
- ^ a b Flekkøy, Eirik G.; Moura, Marcel; Måløy, Knut J. (2018). "Mechanisms of the Flying Chain Fountain". Frontiers in Physics. 6 84. Bibcode:2018FrP.....6...84F. doi:10.3389/fphy.2018.00084. hdl:10852/68287. ISSN 2296-424X.
- ^ Pantaleone, J. (2017-05-16). "A quantitative analysis of the chain fountain". American Journal of Physics. 85 (6): 414–421. arXiv:1910.03125. Bibcode:2017AmJPh..85..414P. doi:10.1119/1.4980071. ISSN 0002-9505. S2CID 125247401.
- ^ Graebel, William (2001-01-19). Engineering Fluid Mechanics. CRC Press. ISBN 978-1-56032-733-2.
- ^ "Gravi-Goo: A Self-Siphoning Gel". Steve Spangler. Retrieved 2024-11-13.
Bibliography
[edit]- Biggins, John Simeon; Warner, Mark (2013-11-22). "Understanding the Chain Fountain [Preprint]". Retrieved 2025-10-12.
- Mould, Steve (2013-02-20). "Self siphoning beads". Steve Mould's nerdy blog. Archived from the original on 2013-04-15.
External links
[edit]- "The Chain Fountain". Isaac Physics. Retrieved 25 April 2020.
- "Chain Fountain in Super Slow-Motion". SMU Classroom Physics Demos. Retrieved 10 September 2021.
- Hell, Timotheus (26 September 2011). "IYPT 2012 - Problem 3: String of beads (Newton's Beads)". YouTube. Retrieved 29 July 2021.
- Mould, Steve (10 October 2025). "NASA let me test my weird chain theory in space". YouTube. Retrieved 10 October 2025.
Chain fountain
View on GrokipediaHistory and Popularization
Early References
The chain fountain effect traces its origins to 19th-century investigations into the dynamics of falling chains, treated as intriguing puzzles in classical mechanics due to their counterintuitive behavior as variable-mass systems. Early explorations began with William Hopkins around 1850, who discussed such problems in private lectures at Cambridge as part of Mathematical Tripos preparation, highlighting the challenges posed by chains in motion under gravity where mass changes affect acceleration in unexpected ways. These setups were seen as anomalies akin to siphons, where the falling portion exerts a pulling force on the stationary part, defying simple expectations of free fall.[5] A more formal analysis appeared in 1856 with Peter Guthrie Tait and William John Steele's Treatise on Dynamics, which examined a uniform heavy chain with one end hanging over a smooth pulley and the other coiled on a table. They derived an acceleration of for the system, where is gravitational acceleration, attributing the reduced rate to the interaction between the moving and stationary segments—a result that puzzled contemporaries because it implied energy dissipation not immediately apparent in the idealized model. This configuration illustrated the siphon-like anomaly, with the descending chain "pulling" the coiled portion into motion, much like fluid in a siphon, though without quantitative resolution of the visual arching now associated with the fountain.[6] Arthur Cayley built on these ideas in 1857, publishing in the Proceedings of the Royal Society of London a general variational principle for a class of dynamical problems, including a chain falling link by link from a heap at the edge of a table through a hole. Cayley confirmed the acceleration of , emphasizing the selective application of Lagrangian methods to account for the impulsive forces at each link's release, which created the counterintuitive slowdown. These 19th-century treatments, confined to theoretical mechanics texts without widespread experimental illustrations, underscored the effect's puzzling nature but remained obscure curiosities. The phenomenon's dramatic visual appeal—chains seemingly defying gravity by rising before falling—went largely unappreciated until viral video demonstrations in the digital age revived interest.[7]Modern Demonstrations
In the early 21st century, the chain fountain phenomenon gained renewed attention through public demonstrations by science educators. In 2009, science entertainer Steve Spangler showcased the effect in a video demonstration using a string of beads that appeared to rise and loop upward as it was pulled from a container, captivating audiences and highlighting its counterintuitive nature.[8] This presentation, part of Spangler's broader efforts to popularize physics experiments, played a key role in sparking widespread interest among teachers, students, and online viewers by framing it as a mesmerizing display of inertia and motion.[9] The phenomenon received further prominence in 2013 when science communicator Steve Mould featured it in a YouTube video titled "The Chain Fountain," which amassed millions of views and introduced the term "Mould effect" to describe the self-siphoning behavior.[10] Mould explicitly linked the demonstration to the classic "Newton's beads" analogy, where a falling chain of beads resists collapsing fully due to momentum, emphasizing the shared principles of chain dynamics and drawing parallels to historical puzzles in mechanics.[11] This video not only popularized the effect in digital media but also prompted initial scientific curiosity by challenging viewers to explain the upward arch without external forces. Concurrently, the chain fountain was formalized as a research problem in academic circles through its inclusion in the 2012 International Young Physicists' Tournament (IYPT), listed as Problem 3: "String of beads."[12] The problem described releasing a long string of beads from a beaker, observing the chain's tendency to form an upward loop due to gravity, and tasked participants with investigating the underlying mechanisms.[13] As an unsolved challenge, it stimulated early discussions and experiments among young physicists worldwide, bridging popular demonstrations with structured scientific inquiry.[14]Recent Research Milestones
The chain fountain phenomenon gained renewed scientific attention following its popularization through demonstrations by science communicator Steve Mould, which spurred theoretical and experimental investigations.[15] A pivotal milestone came in 2014 with the publication of the first rigorous theoretical model by John S. Biggins and Mark Warner in Proceedings of the Royal Society A, explaining the fountain's formation through the dynamics of chain motion and momentum transfer from the stationary pile.[1] Building on this foundation, a 2018 study in Frontiers in Physics by E. G. Flekkøy, Marcel Moura, and K. J. Måløy utilized numerical simulations and controlled experiments to elucidate the momentum transfer mechanisms driving the arch-like rise, identifying subtle interactions at the chain's pickup point as key to the effect's persistence.[3] In 2021, Dragos-Victor Anghel revisited the phenomenon in Journal of Physics: Conference Series, analyzing the siphoning dynamics and arguing that chain inertia, rather than purely gravitational influences, primarily sustains the fountain, thereby refining earlier hypotheses on force balances.[16] A significant experimental advancement occurred in 2025 when NASA astronaut Don Pettit conducted a microgravity test of the chain fountain aboard the International Space Station, in collaboration with Steve Mould; the results showed the chain maintaining its arched shape and flow without significant gravitational pull, refuting models overly reliant on Earth-bound gravity and confirming the role of intrinsic chain dynamics in the effect.[17]Phenomenon Description
Experimental Setup
The chain fountain effect is typically observed using a simple apparatus consisting of a container, such as a 1-liter plastic beaker or tall pot, elevated above a lower surface like a smooth floor or table. A long chain, often a nickel-plated brass ball chain with 4.5 mm diameter beads connected by short 2 mm rods, is piled loosely inside the container in a random or patterned configuration to minimize tangling. One end of the chain is draped over the rim of the container and extended downward toward the lower surface, with the setup designed to allow the chain to flow freely upon release without external interference.[3] Key parameters include the total chain length, which ranges from 1 to 5 meters for classroom demonstrations to ensure visibility of the arch formation, though longer chains up to 50 meters are used in detailed studies to achieve pronounced effects. The height of the container above the receiving surface, typically 1 to 4 meters, is crucial to provide sufficient drop for the chain to accelerate and form the characteristic structure, while the initial pile must occupy the container without overflowing the rim. The receiving surface should be flat and unobstructed to allow the chain to accumulate without rebounding or altering the flow dynamics.[3] Variations in the setup often involve the type of chain, such as rigid-linked chains versus more flexible bead strings, where the maximum bending angle (e.g., 63° for typical ball chains) influences the stability of the pile and flow. Initial pile configurations can be adjusted, for instance, by distributing the chain at multiple points within a bumpy-bottomed container spaced at bead diameters to prevent clumping, ensuring repeatable and tangle-free initiation of the effect. These modifications stem from early demonstrations adapted for controlled observations.[3]Observed Behavior
In the chain fountain experiment, a long beaded chain is initially piled loosely in a tall pot or beaker elevated above a lower surface, with one end draped over the rim and allowed to fall freely under gravity to the lower surface. The chain starts stationary in the container, but as the hanging portion accelerates downward, the pile inside begins to lift and flow toward the rim, spontaneously forming a smooth, self-supporting arch that rises above the container's edge before arcing over and connecting to the descending segment.[18] This arch typically reaches heights of 10 to 20 cm above the rim in standard tabletop demonstrations using beaded chains of moderate length, creating a persistent "fountain" shape that maintains its form without any external structural support as the chain continues to uncoil and exit the pot.[19] The visual effect is marked by the chain's segments moving upward in a coordinated, looping trajectory, contrasting sharply with the expected behavior of material simply spilling over the edge.[3] The counterintuitive nature of the phenomenon lies in the chain's apparent resistance to gravity, as if "climbing" out of the container against the pull of free fall, rather than collapsing or flowing directly downward.[20] The fountain persists steadily until the chain is depleted from the pot, at which point the motion transitions to ordinary free fall of the remaining length, with no further arch formation.[18]Underlying Physics
Kinematic Aspects
The chain in a fountain configuration follows a distinct trajectory divided into three primary segments. It begins in a stationary pile within the container, where the chain links are at rest. From the pile, the chain transitions into a rising segment that lifts upward, undergoing a curved deflection at the rim of the container due to the geometric constraint of the edge. This curved portion smoothly connects to a straight falling segment that descends vertically toward the ground, maintaining a consistent linear path thereafter.[21][22] Velocity profiles along the chain exhibit characteristic variations across these segments. In the falling straight segment, the chain propagates at an approximately uniform speed, reflecting steady downward motion without significant acceleration or deceleration. Conversely, in the rising segment, the chain experiences deceleration attributable to the inertia of the links as they are set into motion from rest, resulting in a progressive slowdown during ascent. These velocity changes contribute to the observed arch formation as a kinematic outcome of the trajectory.[21][3] Geometric factors play a crucial role in shaping the overall motion. The radius of curvature at the rim directly influences the height of the rising arch, with a smaller radius typically leading to a more pronounced lift due to the tighter bend constraining the path. Basic kinematic descriptions model positions as functions of time; for instance, in the rising or lowering phases of similar chain motions, the position vector can be expressed as , where is the radius, is the characteristic speed, and is time, illustrating the parametric evolution of the trajectory.[21][22]Dynamic Forces
In the chain fountain, the primary dynamic forces governing the motion include gravitational force, internal tension within the chain, and contact forces at the pot's rim. Gravity provides the driving force by pulling the chain downward, while tension transmits momentum along the chain links. Contact forces at the rim, arising from interactions between the chain and the container edge, redirect the chain's path and contribute to the upward deflection observed in the fountain. These forces interact to produce the characteristic arching behavior without violating conservation laws.[1] Tension propagates along the chain with distinct variations between segments. In the falling segment, tension is relatively high, particularly near the top where it must support the weight of the descending chain and provide the net force to accelerate the system, decreasing toward the bottom due to the cumulative effect of gravity on the length below. In contrast, tension in the stationary pile is low or negligible, as the chain there experiences minimal motion and primarily rests under its own weight until beads are successively engaged. This gradient in tension ensures smooth propagation of motion from the pile to the falling part.[1] At the rim, the chain undergoes redirection as it transitions from the horizontal pile to the vertical fall, involving normal and frictional contact forces from the pot edge. The normal force acts perpendicular to the rim surface, pushing the chain outward and contributing to the separation from the edge that forms the arched fountain. Frictional forces, though often small in smooth setups, act tangentially to oppose sliding and help manage the change in direction, effectively redirecting the chain's linear momentum into a curved path. These interactions prevent the chain from simply draping over the rim and instead impart the upward component essential to the phenomenon.[23][21] Gravity exerts a uniform downward force on every segment of the chain, proportional to its mass per unit length, which drives the overall descent and energy release but challenges the rising portion of the fountain. This downward pull is balanced in the arched bend by a dynamic lift arising from the net effect of rim contact forces and tension, enabling the chain to rise above the rim despite gravitational opposition. Without this balance, the fountain would collapse into a simple siphon.[1] Basic free-body diagrams illustrate these forces on representative chain elements:- Element in the pile (stationary bead being engaged): Gravity acts downward; low tension pulls upward from the adjacent moving link; a reaction force from the stationary pile provides an upward push to initiate motion, arising from the pile's inertia resisting the acceleration of the bead.[1]
- Element at the rim (bead in the bend): Incoming and outgoing tensions act along the chain directions; gravity pulls downward; normal force from the rim pushes radially outward; frictional force opposes tangential motion.[23][21]
- Element in the fall (descending bead): High tension acts upward from the chain above; gravity pulls downward, resulting in net acceleration; air resistance is typically negligible.