In the imploding tank car story, hot steam gas at atmospheric pressure was put inside a steel tank car, and the valve closed overnight. Gradually the steam condensed and cooled down, severely lowering the pressure inside the tank, and then atmospheric pressure squeezed the tank car.
But my question is, why does the implosion take place so suddenly and rapidly? Why doesn't the tank car implode slowly and gradually as the pressure continuously drops inside (ie. the dent slowly grows)?
Compare this with, say, an empty water bottle. When you suck the air out, the bottle continuously deforms and flattens out, it doesn't retain its shape and then suddenly collapse. How are the two containers designed differently?