Household physics question: Before I left town for 3 weeks the lock on my apartment door was loose in its encasement. I had to hold it in place while turning the key or the inner disc would rotate uselessly inside the outer ring: http://scott-shepherd.com/share/forums/lock.jpg [Broken] When I came back after Thanksgiving the lock was fixed. So, assuming no opportunistic handyman came by, I think it must have tightened as a result of contraction in the cold weather. Does this make sense? Is it a demonstrable principle that a ring contracts faster than the circumference of a disc of the same material?