CAMBRIDGE—Some people line up at stores or hit the treadmill after Thanksgiving. Others—about 2,000 of them—packed the gymnasium bleachers at the Massachusetts Institute of Technology to watch a jar of honey make a slow, halting roll down a ramp until it finally nudged a blue ball to fall into a giant netted-off area full of mousetraps that sprung almost instantaneously, launching dozens of ping-pong balls into the air.
The Friday After Thanksgiving (FAT) chain reaction is an annual tradition that has exploded since its modest beginnings in the hallway of the MIT Museum 16 years ago. Nowadays, teams plan their contraptions days or weeks in advance. Family members become engineering collaborators as they work to build and design an array of interconnected mouse traps, cardboard tubes, dominoes, robots, toy trains, balloons, and balls of all kinds. Full story for BostonGlobe.com subscribers.
Carolyn Y. Johnson can be reached at cjohnson@globe. com.