I just wanted to see some paradoxes that have come up for special relativity. They're fun to look over and catch where the flaws are. Post your own or any you find! Note that I know the solutions to the one's I'm posting. Oh, don't post any solutions to the paradoxes visibly, please. 1: The twin paradox Had to be mentioned. 2: The train paradox There's a bomb attached to the front of a train. When the front of the train enters a tunnel which is the same length as the train, the bomb is armed. When the back of the train enters the tunnel the bomb explodes. Since the train is contracted according to the tunnel, the bomb explodes, but since the tuneel is contracted according to the train the bomb doesn't explode. 3: T and U paradox A T shaped object is heading towards a U shaped object (open side of U facing the bottom bar of the T, the top bars of the U are the same length as the bottom bar of the T). There is a detonator on the inside of the U at the bottom. The T hits the U. According to the T the U is shorter so the bomb explodes. According to the U the T is shorter so the bomb doesn't explode. (argh! acceleration + rigids!) 4: Sled paradox A sled is moving at high speed next to a wall and is then (according to the sled frame) pushed (almost instantly) through a hole in the wall the same length as the sled. According to the wall frame the sled won't fit! 5: Barn-Pole paradox You run towards a barn carrying a pole the same length as the barn. When you are inside the barn the doors at both ends are shut then reopened. According to the barn frame you are contracted and there's plenty of time to shut the doors. According to your frame the barn is contracted and the pole can't fit entirely inside the barn!