When Clifford Stoll speaks, you can't help but listen. Full of restless energy, he jumps from one topic to the next, darting back and forth across the stage. You may not be sure where he's going, but the ride is always part of the adventure.

An astronomer (though his astronomy career took a turn when he noticed a bookkeeping error that ultimately led him to track down a notorious hacker), researcher and internationally recognized computer security expert -- who happens to be a vocal critic of technology -- Stoll makes a sharp, witty case for keeping computers out of the classroom. Currently teaching college-level physics to eighth graders at a local school, he stays busy in his spare time building Klein bottles.