Science Frontiers ONLINE No. 119: Sep-Oct 1998Issue Contents

### Curious Effects Department

The spinning-egg water-sprinkler. It is generally known that you can separate fresh eggs from hard-boiled eggs by spinning them like a top. If they are hard-boiled they will spin on one of the ends. The fluid contents of fresh eggs, however, will slosh around and prevent top action. O.K.! this is not very curious, so we'll place a hard-boiled egg in a flat pan containing a thin layer of water and give it a spin. Not only does the egg spin on end but a layer of water creeps up the side of the egg. When the water is about half way up the side of the egg it breaks up into droplets and sprays out horizontally like a rotating lawn sprinkler.

No mysterious forces are involved, nor are there spooky quantum mechanics effects. The major forces operating are gravity, centrifugal force, and adhesion between the egg surface and the water. As the film of water creeps up the egg, the centrifugal force increases and overcomes the force of adhesion. Then, water droplets spray outward.

(Gutierrez, Gustavo, et al; "Fluid Flow up the Wall of a Spinning Egg," American Journal of Physics, 66:442, 1998.)

Creating fluid corners in kitchen sinks. When a smooth column of water from your kitchen faucet hits the sink, it flows out radially. At a calculable radius, its height suddenly rises. This smooth, circular ridge is called a "hydraulic jump." Here, some of the kinetic energy of the falling water is converted into the potential energy of the deeper layer of water. Nothing particularly mysterious here.

But, if a liquid more viscous than water is used, the circular ridge is transformed into a neat polygon with surprisingly sharp corners. Different flow rates create different polygons. Polygons with as many as 14 corners have been observed. Interestingly, identical flow rates can result in different stable polygons. See the referenced article for all the math.

(Ellegaard, Clive, et al; "Creating Corners in Kitchen Sinks," Nature, 392:767, 1998.)

 A spinning hard-boiled egg creates a water sprinkler.

From Science Frontiers #119, SEP-OCT 1998. © 1998-2000 William R. Corliss

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 "A sourcebook of unexplained phenomena is therefore a valuable addition to a collection of scientific literature. William R. Corliss has provided this in the past with his source books of scientific anomalies in several subjects, and now he has provided it for astronomy. He has done an excellent job of collecting and editing a large amount of material, taken in part from scientific journals and in part from scientific reporting in the popular or semi-scientific press." -- "The Mysterious Universe: A Handbook of Astronomical Anomalies", reviwed by Thomas Gold, Cornell University, in Icarus, vol.41, 1980 "An interesting, systematic presentation of unusual weather [..] This book is recommended for a general audience" --"Corliss, William R., Tornados, Dark Days, Anomalous Precipitation, and Related Weather Phenomena, Sourcebook Project, 1983.", revieweed in Choice, September 1983 "..the science is necessarily somewhat speculative, but Corliss's symthesis is based on reputable sources." -- "Corliss, William R. (Compiler). Lightning, Auroras, Nocturnal Lights, and Related Luminous Phenomena" reviwed by Joseph M. Moran, Univ. of Wisconsin in Science Books and Films, Sep/Oct 1983 "Before opening the book, I set certain standards that a volume which treads into dangerous grounds grounds like this must meet. The author scrupulously met, or even exceeded those standards. Each phenomenon is exhaustively documented, with references to scientific journals [..] and extensive quotations" -- "Book Review: The moon and planets: a catalog of astronomical anomalies", The Sourcebook Project, 1985., Corliss, W. R., Journal of the Royal Astronomical Society of Canada, Vol. 81, no. 1 (1987), p. 24., 02/1987