My favorite thing along these lines is a question from my undergrad special relativity textbook: A pole vaulter carrying a 40m pole is running at a speed such

My favorite thing along these lines is a question from my undergrad special relativity textbook: A pole vaulter carrying a 40m pole is running at a speed such that to an observer, he appears contracted by ½. He runs through a barn of length 20m and the doors at each end of the barn are closed simultaneously. But to the pole vaulter, the barn appears contracted by ½ and thus appears to be 10m long to him. What does he see when the doors are closed?