Self-siphoning beads

The Mould effect or self-siphoning beads or (chain fountain) phenomenon is a counterintuitive physical phenomenon observed when one end of a chain of beads held in a jar is thrown over the edge of the jar, and is then followed by a self-sustaining stream of beads, rising from the body of the chain in the jar, up into an arch ascending into the air over the edge of the jar, and down into the outside world, as if being sucked out of the jar by an invisible siphon.

The higher the jar is placed above the ground, the higher the chain rises above the jar during the "siphoning" process. As demonstrated in an experiment, when the jar is placed 30 meters above the ground and the chain is sufficiently long, the arch of the chain fountain can reach about 2.1 meter above the opening of the jar.

The phenomenon was first brought to widespread public attention in a video made by science presenter Steve Mould. Mould's YouTube video, in which he demonstrated the phenomenon of self-siphoning beads and proposed an explanation, brought the problem to the attention of academics John Biggins and Mark Warner of Cambridge University, who published their findings about what has now been called "chain fountain" in Proceedings Of The Royal Society A.

A variety of explanations have been put forward as to how the phenomenon can best be explained in terms of basic physics concepts such as energy and momentum.

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