火箭問題??

火箭升空, 需要有很多人的共同合作, 有很多儀器及程序同步運作, 倒數, 就是要所有相關的人員和程序同步運作, 發射之後, 倒數鐘會開始計時, 以記錄這次升空任務的所用時間.

Timing is very important in rocket launch. It is first to synchronize opearations of different systems, e.g. disconnection of support rig in launch pad, noise reduction, fuel pumping, firing, etc. Also, there is a so called best launch window for every launch. That is the best time to launch a rocket (including space shuttle) after considering weather, wind speed and direction, vsibility, and even interference of solar wind. But most important is the best launch window can help the rocket to save fuel. For example, if a space shuttle is to launched to the International Space Station (ISS). If it is launched too early, it will take the space shuttle more time to reach the ISS. If it is launched too late, it will miss the ISS and have to turn 1 more round about the earth to catch the ISS (becuase ISS or satelllite is roatating about the earth at a speed different from earth's spin speed). In other word, good launch can make the rocket reach its target with best fuel efficiency.

是興奮所致的。

例如倒數2008年，人們也是上街倒數，齊來見證這個時刻。