Some of you had some interesting responses to my last puzzle. Several of you (rightly) chose to not post your answer publicly, but instead emailed them to me. And so I've decided to backstep a bit, and to offer a more deterministic puzzle. This is better suited for those who not only wish to remain inside the box, but also want to be reminded of where the box's walls are.
You have eight billiard balls. One of them is defective in that it weighs more than the others. How do you tell, using a balance, which ball is defective in only two weighings?
While it's probably possible to google the answer. Please give it an honest try on your own.