At just before 4 a.m. this morning, Gabriel and I were both woken up by a loud noise somewhere in our house. It turned out that the hook in our storage room where Gabriel hangs his commuter bike had pulled out of the wall, and the noise we'd heard was the bike falling. (Don't worry: the bike's fine!) However, we didn't realize what had happened right away, and the storage room was the last one we checked. First we looked all over the house checking for burglars / seeing what might have fallen.
Here's the brain teaser: When we got to the kitchen, we looked inside the ice box to see if the sound we'd heard might have been the "clunk" of ice settling. We saw that a chunk of ice weighing about 25 lbs had tipped over at some point last night, but we knew right away by looking at it that the ice tipping over hadn't been what had woken us up. Since the ice was askew, how could we tell just by looking at it that its fall hadn't made the noise which had woken us up?
Check back next week for the answer!