The shape was popularized by Danish poet and scientist Piet Hein (1905–1996). Supereggs of various materials, like the one shown, were sold as novelties or "executive toys" in the 1960s. A 1-ton superegg made of steel and aluminium was placed outside Kelvin Hall in Glasgow in 1971, on occasion of a lecture by Piet Hein.
The superegg is a super-ellipsoid whose horizontal cross-sections are circles. It is defined by the implicit equation
where r is the horizontal radius at the "equator" (the widest part), and h is one half of the height. The exponent p determines the degree of flattening at the tips and equator. Hein's choice was p = 2.5 (the same he used for the Sergels Torg roundabout), and r/h = 3/4.
The definition can be changed to have a strict equality rather than inequality; this changes the superegg to being a surface of revolution rather than a solid.
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- Gardner, Martin (1977). "Piet Hein's Superellipse". Mathematical Carnival. A New Round-Up of Tantalizers and Puzzles from Scientific American. New York: Vintage Press. pp. 240–254. ISBN 978-0-394-72349-5.
- "Superegg" in the Internet Encyclopedia of Science
- Piet Heins Superellipse (in Danish)
- Weisstein, Eric W. "Superegg." From MathWorld--A Wolfram Web Resource. http://mathworld.wolfram.com/Superegg.html