While most professors try to teach their students a few tricks of the trade, Persi W. Diaconis has built his entire career around teaching tricks.

Diaconis, Leverett professor of mathematics, is a world-class sleight of hand artist and a master card player who uses his tricks to teach mathematical concepts, such as probability.

In a graduate seminar on "Topics in Mathematical Statistics," Diaconis uses a simple card game called "Say Red" to illustrate a complex mathematical theorem.

In the card game, he turns over one card at a time from the top of a randomly shuffled deck. Students must guess whether the card will be red--if it is, they win a dollar. If it's black, they lose one.

The only condition, he says, is that students must say red at least once during the game.

The game raises the question of whether the student has any advantage in guessing the color.

"[It would seem] if the first card is black you'd have some advantage [by saying red], but there's nothing you can do other than making it perfectly fair," Diaconis says, explaining that the probability a card will be red is always 50 percent.

Diaconis, 50, says his interest in things mathematical began at an early age.

"I've always been fascinated by magic tricks--there are some terrible little tricks and good tricks too," he says, adding that many card tricks can be understood by the rules of mathematics. "Even today if I have a math problem and I can translate it into the language of cards, I can solve it."

The translation of mathematical formulae into concrete objects assists Diaconis in his investigations.

Displaying a mechanical mystery bolted to the top of a bookshelf in his Science Center office, Diaconis explains that the machine eliminates the chance element in coin tossing.

"I think that coin tossing isn't random, it's physics," he says. "You can show that a very slight change in how you flip it makes for the difference between heads and tails."

A few sample tosses reveal something amiss in the machine built by the physics lab. The coin, which is supposed to come up heads every time, repeatedly turns tails.

"Last time I did it, I got 50 out of 50," Diaconis shrugs, leaving the physics problem for later contemplation.

Diaconis has spent his lifetime studying the interrelation of mathematics, probability and randomness.