Baseball Cover

A pair of identical plane regions (mirror symmetric about two perpendicular lines through the center) which can be stitchedtogether to form a baseball (or tennis ball). A baseball has a Circumference of 9 1/8 inches. The practicalconsideration of separating the regions far enough to allow the pitcher a good grip requires that the ``neck'' distance beabout 1 3/16 inches. The baseball cover was invented by Elias Drake as a boy in the 1840s. (Thompson's attribution ofthe current design to trial and error development by C. H. Jackson in the 1860s is apparently unsubstantiated, asdiscovered by George Bart.)

One way to produce a baseball cover is to draw the regions on a Sphere, then cut them out. However, it is difficultto produce two identical regions in this manner. Thompson (1996) gives mathematical expressions giving baseball covercurves both in the plane and in 3-D. J. H. Conway has humorously proposed the following ``baseball curve conjecture:'' notwo definitions of ``the'' baseball curve will give the same answer unless their equivalence was obvious from the start.

References

Thompson, R. B. ``Designing a Baseball Cover. 1860's: Patience, Trial, and Error. 1990's: Geometry, Calculus, and Computation.'' http://www.mathsoft.com/asolve/baseball/baseball.html. Rev. March 5, 1996.

• Koch Antisnowflake
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