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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    $\begingroup$ Thanks for edit, but isn't important say this 1.21 GW is about the film Back to the Future? $\endgroup$ – Rodrigo May 1 '12 at 21:55
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    $\begingroup$ 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). $\endgroup$ – dmckee --- ex-moderator kitten May 1 '12 at 22:03
  • $\begingroup$ 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. $\endgroup$ – Ron Maimon May 1 '12 at 22:06
  • $\begingroup$ @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. $\endgroup$ – David Z May 2 '12 at 0:09
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    $\begingroup$ I don't know who downvoted this, but I see no issue with the question. Yes, the reference is to the movie Back to the Future, but he's asking about real world physiscs. I upvoted it back. $\endgroup$ – John May 2 '12 at 21:04

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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