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In connection with a related question on Science Fiction & Fantasy Stack Exchange page: does this number 1.21 GW make any sense? What is 1.21 GWatts? With what can you compare it? Can the lightning really produce this amount of power?

Are there any idea of why this number was used in a physical sense?

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Thanks for edit, but isn't important say this 1.21 GW is about the film Back to the Future? – Rodrigo May 1 '12 at 21:55
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Note that Watts is power, not energy and that short enough time scales can mean that high power does not imply a lot of energy (see for example sub-nanosecond pulsed lasers). – dmckee♦ May 1 '12 at 22:03
There is no reason, it just sounded nice. It's probably taken by dividing the energy released in a lightning stroke and dividing by the time of the flash, so it is probably a roughly accurate amount of power in the lightning. – Ron Maimon May 1 '12 at 22:06
@Rodrigo: no, not for asking about it in a physics context. In any case, most people will probably either recognize the source of the number or click through to the question on SFF. – David Zaslavsky♦ May 2 '12 at 0:09
this site says that "jiggawatts" is the mispronunciation for gigawatt...funny... www.urbandictionary.com/define.php?term=jiggawatt – user8673 May 2 '12 at 9:09
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There is no deep reason, it just sounded nice (the one-two-one number-palindrome plus the techie sounding mispronounciation "jigga-watts"). It's a number taken by dividing the energy released in a lightning stroke (a few million joules according to Wikipedia) and dividing by the time of the flash (in the millisecond range), so that the total power is in the billions of Watts. It is not the absurdly precise value of 1.21 GW given in the movie, however.

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Actually, Ron, I'm pretty sure that at the time whe Back to the Future came out, "jigga-watts" was the correct pronunciation - "giga" as in its cognate English word "gigantic." Even then it was used only by a very small number of computer types, engineers, and scientists. When "gigga bite" disk drives appeared, the parallel to "gig" and "giggle" quickly drove "jigga" (already endangered) to extinction. Scientific words also mutate oddly in spelling from time to time. If you don't believe me, just Googol it... :) – Terry Bollinger May 2 '12 at 1:27
@TerryBollinger: Except I'm old enough to remember people heckling the pronounciation "jigga" in the late eighties, so it wasn't common usage. "Giga" was pronounced with a hard G in the US, but it wasn't used often, as you said, so there were a lot of people who made the false analogy with gigantic. – Ron Maimon May 2 '12 at 2:08
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There is a discussion of the pronunciation on the wiki page: en.wikipedia.org/wiki/Giga-#Pronunciation It seems that the "jigga" pronunciation was indeed common and preferred in the '80s, if we believe the references. I can't claim to be old enough to know what was correct, but my advisor confirmed for me that some people did say jigga in the 80s. – Logan Maingi May 2 '12 at 2:32
to add to the trivia giga comes from the greek "gigas" which means "giant", but pronounced as "gamma" is pronounced ( in greek a softer sound between g and j). Webster says giant comes from: "Middle English giaunt, from Anglo-French geant, from Latin gigant-, gigas, from Greek", so both are correct and it is a matter of fashion. – anna v May 2 '12 at 5:31
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I once talked to a Greek restaurant owner about how to pronounce "gyros," hoping I could be enlightened between [k=hard g] "kee roes," "kie roes," "jee roes," and "jie roes." Result: He liked all four equally. Sigh. – Terry Bollinger May 2 '12 at 23:45

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