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Lecture for Students: Colm Mulcahy

MAA Lecture for Students: Colm Mulcahy

Mathemagic at MathFest

by Robert Schneider

One might be forgiven for erroneously thinking he or she had walked into a rock concert rather than a mathematical lecture: the large conference room was packed, with even the standing room filling up. The chatter from nearly five hundred attendees had risen to a crescendo when the Irish "mathemagician," Professor Colm Mulcahy of Spelman College, took the stage. Author of the MAA?s bi-monthly online article Card Colm (a pun on the speaker?s first name, which is pronounced "column"), Dr. Mulcahy proceeded to charm and mystify, drawing from a repertoire of card tricks, apparent mind-reading feats, one-liners and mathematical wizardry.

Student LectureIn keeping with the format of a magic show, the speaker extracted volunteers from the audience and, in a swirl of banter, drew them into his baffling routines, which fell broadly in the ?pick a card, any card? category. One trick climaxed with the volunteer receiving a cookie?clearly baked in advance?decorated with the ace of hearts, the image of her chosen card. The speaker subsequently revealed how he executed each trick, including theoretical background, going against sacred magical tradition; however, having invented most of the tricks himself using ideas from diverse branches of mathematics, Dr. Mulcahy?s disclosure of his secrets should lie beyond reproach from fellow magicians.

This correspondent was doubly amazed after seeing the routines explained mathematically, often thinking, "How on Earth can such a theorem be true?" or "Who on Earth would think of turning this theorem into a card trick?" For while the magic show itself was composed of illusions designed to deceive the audience, there was a sense of real magic at work in the mathematics behind the tricks.

It goes without saying that many members of the audience, drawn to MathFest by the magic of mathematics, gained a new appreciation of the mathematics of magic.