钢铁做的船，为什么能浮起来？

Steel is much heavier than water. 钢铁比水重多了。 But a big steel ship floats on the sea. 可大铁船，却稳稳浮在海上。 The ship is not a solid block of steel. 船不是一块实心的铁疙瘩。 Its big belly is empty and full of air. 它肚子大大的，里面全是空气。 It pushes a lot of water out of the way. 它把好多好多水，挤到了旁边。 The pushed water weighs as much as the ship. 被挤开的水，和船一样重。 When the water holds it up, the ship stays afloat. 水的力气一托住，船就浮起来啦。