A group has found an item (an artifact, some piece of supposedly incomprehensible technology, etc.). The group, most likely including the smart guy, starts discussing how it will take quite a bit of time and research to discover the item's purpose and/or how to use it. Meanwhile, another person in the group (often The Hero, but not necessarily) is fiddling around with the item, and unlocks/activates/arms/whatevers the device, interrupting and possibly upsetting the others in the group. Note that sometimes the activation isn't necessarily a good thing. Examples of Chance Activation include: