Countdown

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,^[1] 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, like a spacecraft.^[2]

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.^[3]

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.^[4]^[5]

^ NASA's Launch Services Program [@@NASA_LSP] (January 31, 2015). ""L Minus" time is different from "T Minus" time."L minus" indicates how far away we are from actual liftoff& doesn't include built-in holds" (Tweet) – via Twitter.
^ "NASA Mission 'E-Minus' One Month to Comet Flyby". NASA Mission News. 2010-10-04. Archived from the original on 2016-04-13. Retrieved 2013-09-13.
^ Everett, William (1865). On the Cam: Lectures on the University of Cambridge in England. Cambridge, Massachusetts: Sever and Francis. p. 192.
^ "Spektrum der Wissenschaft - DenkMal-Frage: "Was verdankt die Raumfahrt dem Stummfilm "Die Frau im Mond" (1929) von Fritz Lang?" [Spektrum der Wissenschaft - DenkMal question: "What does space travel owe to the silent film "Woman in the Moon" (1929) by Fritz Lang?] (in German). Wissenschaft-online.de.
^ Weide, Robert (Summer 2012). "The Outer Limits". DGA Quarterly. Los Angeles, California: Directors Guild of America, Inc.: 64–71. A gallery of behind-the-scenes shots of movies featuring space travel or aliens. Page 68, photo caption: "Directed by Fritz Lang (third from right), the silent film "Woman in the Moon" (1929) is considered one of the first serious science fiction films and invented the countdown before the launch of a rocket. Many of the basics of space travel were presented to a mass audience for the first time."

[L-Minus-1] NASA's Launch Services Program [@@NASA_LSP] (January 31, 2015). ""L Minus" time is different from "T Minus" time."L minus" indicates how far away we are from actual liftoff& doesn't include built-in holds" (Tweet) – via Twitter.

[E-Minus-2] "NASA Mission 'E-Minus' One Month to Comet Flyby". NASA Mission News. 2010-10-04. Archived from the original on 2016-04-13. Retrieved 2013-09-13.

[3] Everett, William (1865). On the Cam: Lectures on the University of Cambridge in England. Cambridge, Massachusetts: Sever and Francis. p. 192.

[4] "Spektrum der Wissenschaft - DenkMal-Frage: "Was verdankt die Raumfahrt dem Stummfilm "Die Frau im Mond" (1929) von Fritz Lang?" [Spektrum der Wissenschaft - DenkMal question: "What does space travel owe to the silent film "Woman in the Moon" (1929) by Fritz Lang?] (in German). Wissenschaft-online.de.

[DGA-Quarterly-summer2012-5] Weide, Robert (Summer 2012). "The Outer Limits". DGA Quarterly. Los Angeles, California: Directors Guild of America, Inc.: 64–71. A gallery of behind-the-scenes shots of movies featuring space travel or aliens. Page 68, photo caption: "Directed by Fritz Lang (third from right), the silent film "Woman in the Moon" (1929) is considered one of the first serious science fiction films and invented the countdown before the launch of a rocket. Many of the basics of space travel were presented to a mass audience for the first time."

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