I am disappointed for reading no explanation for the J/m among our brainy membership. That maybe because there is none.
Just referring to the basic-level education, a lightning strike, as any explosive, is a short term event: it has enormous power but contains little energy. Both quantities have their units. The mentioned 20 MJ, if that is the energy in an average lighting, lasting a µs (our retina makes us to "see" it longer) stands for 20 TW, if I am not mistaken. This much power is comparable to the output of all the US energy sources combined and more. Impressive but irrelevant except for creating a sensation in popular publications. And what does all that power do? Fuse a few grains of sand if the bolt hits a sand pit. Or burn down a medieval city. Just like a match: if lit, it may lit a candle for reading or burn Chicago to the ground if used to lit the famous lantern. Once more: What is J/m? How about reaching a consensus? ☺ Stan On Wed, Aug 3, 2016 at 6:55 PM, John Altounji <phy...@msn.com> wrote: > PAR is explained here: > > http://www.vernier.com/products/sensors/solar-radiation-sensors/par-bta/ > > I also see it related to aquarium lighting like here: > > http://www.drsfostersmith.com/product/prod_display.cfm? > pcatid=30196&cmpid=03csesz&ref=3474&subref=AA&CA_6C15C=530005150000177888 > > I am not defending the author of the site below as a few symbols are not > right. > > > > John Altounji > One size does not fit all. > Social promotion ruined Education. > > *http://bit.do/tounj <http://bit.do/tounj>* > > > > *From:* Aubrecht, Gordon [mailto:aubrech...@osu.edu] > *Sent:* Wednesday, August 3, 2016 3:20 PM > *To:* John Altounji <phy...@msn.com> > *Cc:* Stanislav Jakuba <jakub...@gmail.com>; U.S. Metric Association < > usma@colostate.edu> > *Subject:* Re: [USMA 287] Puzzled > > > > Hi, folks, > > > > What is PAR? > > > > They forgot time in their last equation. > > > > They did a rotten unit job in addition. > > > > umoles? > > > > micromoles of photons? of what? (I’m a bit perplexed here) > > > > sec? > > Watts? > > KJ? > > > > Who are these people? They do not know a lot about units, it seems. (This > sort of reminds me of that Sam Cooke song *Wonderful World*—“Don’t know > much about history, don’t know much biology, don’t know much about a > science book, …”) > > > > Gordon > > > > > > On Aug 3, 2016, at 3:14 PM, John Altounji <phy...@msn.com> wrote: > > > > I found this: > > > > http://www.pnet.sr.unh.edu/subpages/radconvert.html > > > > They probably forgot the square. > > > > John Altounji > One size does not fit all. > Social promotion ruined Education. > > *http://bit.do/tounj <http://bit.do/tounj>* > > > > *From:* USMA [mailto:usma-boun...@colostate.edu > <usma-boun...@colostate.edu>] *On Behalf Of *Stanislav Jakuba > *Sent:* Wednesday, August 3, 2016 11:57 AM > *To:* U.S. Metric Association <usma@colostate.edu> > *Subject:* [USMA 286] Puzzled > > > > *Below is a quote from a scientific paper about measurements of energy in > an average lighting strike. My question: What's* MJ/m? Stan > > "The energy released by lightning is measured in megajoules, also > expressed as MJ/m." > > “For example a single megajoule is equivalent to about 200 food calories, > or the energy from leaving a microwave on for 20 minutes to cook food,” he > explains. “It can also be compared to a 60 watt lightbulb’s energy use if > left on for about four hours. It’s also the same as the kinetic energy a > car has traveling about 60 mph.” Their research found that the energy > produced by a lightning strike peaked at greater than 20MJ/m. > > _______________________________________________ > USMA mailing list > USMA@colostate.edu > https://lists.colostate.edu/cgi-bin/mailman/listinfo/usma > > > > ######################### > > Gordon Aubrecht > Professor of Physics, OSU > OSU Physics (614) 292-2574, FAX (614) 292-7557 > Marion Campus (740) 725-6250, FAX (614) 292-5817 > aubre...@mps.ohio-state.edu > > check out my web sites through my home page > http://www.physics.ohio-state.edu/~aubrecht > > Read my book Energy (Prentice-Hall, 2006) and visit the PH Energy website > http://www.pearsonhighered.com/educator/product/Companion-Website-for- > Energy-Physical-Environmental-and-Social-Impact-3E/9780131403727.page > > However beautiful the strategy, you should occasionally look at the > results.--Sir Winston Churchill > > As a rule we disbelieve all the facts and theories for which we have no > use.--William James (1842 - 1910) > > Science is not just a career or a body of facts, but, more important, a > set of cognitive and practical tools designed to understand brute reality > while overcoming the human desire to believe what we like or > find emotionally satisfying. > > —Jerry A. Coyne, in *Faith vs. Fact: Why Science and Religion Are > Incompatible *(2015) > > >
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