translation.en: So someone came up with a very clever idea, to -- instead of heating the whole cylinder and cooling the whole cylinder, what about if you put a displacer inside -- a little thing that shuttles the air back and forth.
translation.zh: 接着有人很清楚地意识到， 不需对整个缸体进行加热和冷却， 不如在缸体里充入替代物-- 使空气来回的运动。