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电影里的火箭倒计时，竟然是真的？揭秘这个发射程序的由来和好处
你是否曾经看过电影里火箭发射的场面？你是否曾经听到过“十、九、八……三、二、一，点火！”的声音？你是否知道这种倒计时的方式是从哪里来的呢？
宇宙知识探秘148/345
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