Abstract In the 20th century, science and technology on the human contribution to one of the most important is to liberate from the heavy manual labor people have plenty of leisure time.

• 摘要：20世纪科学技术对人类做出的最重要贡献之一，是将人类从繁重的体力劳动中解放出来，使人有了充裕的休闲时间。