<P> A countdown is a sequence of backward counting to indicate the time remaining before an event is scheduled to occur . NASA commonly employs the terms `` L - minus '' and `` T - minus '' during the preparation for and anticipation of a rocket launch , and even `` E-minus '' for events that involve spacecraft that are already in space , where the `` T '' could stand for `` Test '' or `` Time '' , and the `` E '' stands for `` Encounter '' , as with a comet or some other space object . Other events for which countdowns are commonly used include the detonation of an explosive , the start of a race , the start of the New Year , or any anxiously anticipated event . An early use of a countdown once signaled the start of a Cambridge University rowing race . One of the first known associations with rockets was in the 1929 German science fiction movie Frau im Mond ( English : Woman in the Moon ) written by Thea von Harbou and directed by Fritz Lang in an attempt to increase the drama of the launch sequence of the story 's lunar - bound rocket . </P>
<P> A countdown is a sequence of backward counting to indicate the time remaining before an event is scheduled to occur . NASA commonly employs the terms `` L - minus '' and `` T - minus '' during the preparation for and anticipation of a rocket launch , and even `` E-minus '' for events that involve spacecraft that are already in space , where the `` T '' could stand for `` Test '' or `` Time '' , and the `` E '' stands for `` Encounter '' , as with a comet or some other space object . Other events for which countdowns are commonly used include the detonation of an explosive , the start of a race , the start of the New Year , or any anxiously anticipated event . An early use of a countdown once signaled the start of a Cambridge University rowing race . One of the first known associations with rockets was in the 1929 German science fiction movie Frau im Mond ( English : Woman in the Moon ) written by Thea von Harbou and directed by Fritz Lang in an attempt to increase the drama of the launch sequence of the story 's lunar - bound rocket . </P>
where does the phrase t minus come from
where does the phrase t minus come from
NASA
NASA