Cobretti2 said:
http://www.merriam-webster.com/dictionary/gigawatt it can be pronouced both ways. listen to the audios lol. Also power is the rate at which energy is converted (unit of power = Watts) and energy is how much is used over a period of time (unit of energy = Watthours). so he did mean power as he said needs to generate. |
Merriam-Webster is an American dictionary that is for the lay person. Non-Americans and scientists only ever pronounce it with the hard "g".
http://oxforddictionaries.com/definition/english/gigawatt
Note that it doesn't provide two different pronunciations. As for SI, have a read of the (sourced) Wikipedia section:
http://en.wikipedia.org/wiki/SI_Prefixes#Pronunciation
And I'm working from memory regarding his usage of the term, but what you should note is that he talks about charging up the flux capacitor. Now, a capacitor doesn't store power, it stores energy. When he talks of "needing 1.21 gigawatts of power", he's actually crossing wires, and mixing scientific terminology with lay terminology - he needs some amount of energy to use the capacitor, but the lay person often uses "power" in place of "energy". As an example, consider that you almost certainly refer to "how much power is left in the battery" - batteries, like capacitors, don't store power, they store energy. Power is the unit you would use to describe the rate at which the battery is charging or discharging. If Doc Brown had said "I need 1.21 gigawatts of power for 1 second", I'd have no problem - he just needs 1.21 GJ. He didn't - he said he needs 1.21 GW of power to "power the flux capacitor" (what does that even mean?).
Also, for the record, the Watt-hour isn't actually a normal unit of energy. That would be the Joule (which is, in fact, the Watt-second, if you want to use non-SI units). While the "kilowatt-hour" is a more common unit than the watt-hour, it's one of those stupid inventions of engineers because they have trouble with changing units. The kilowatt-hour is 3.6*10^6 Joules or 3.6 MJ.
