This is in the running for coolest gift ever: The Reverse Geocache Puzzle Box (”“You are — how you say in English? — a BASTARD!”). Here’s a nice video overview. See also this variation, the Woodpecker Puzzle Cache and these wind-up birds.

A meeting of mathemagical tricksters:

Gary Foshee, a collector and designer of puzzles from Issaquah near Seattle walked to the lectern to present his talk. It consisted of the following three sentences: “I have two children. One is a boy born on a Tuesday. What is the probability I have two boys?”

The event was the Gathering for Gardner earlier this year, a convention held every two years in Atlanta, Georgia, uniting mathematicians, magicians and puzzle enthusiasts. The audience was silent as they pondered the question.

“The first thing you think is ‘What has Tuesday got to do with it?’” said Foshee, deadpan. “Well, it has everything to do with it.” And then he stepped down from the stage.

I haven’t read the rest yet because I want to puzzle over it awhile longer. (via kottke)

Beautiful, relaxing fun: Auditorium (via ze)

How do you synchronize five metronomes? Why, with a board and two soda cans, of course!

Y'gotta love any description of a physics puzzler that includes this:

Hamstrung by their lack of access to guar gum or competitive swimmers, Newton's and Huygens' work was mainly theoretical. Cussler's demonstration shows that Huygens was right, at least for human-sized projectiles.

Got there via a roundabout route, from this Jason Kottke page relaying a Cecil Adams answer to a plane-on-a-conveyor-belt problem.