Although air molecules have an average speed of about 1,500 km/h if there is no wind the air would stay still. The reason for that is that the directions of the molecules cancel each other out.

But is there a probability that wind arise because a majority of the molecules get the same direction? Or is this only theoretically possible?

  • $\begingroup$ Please source or give background for the 1.500 km/h value, it's certainly not something most would be familiar with :-) $\endgroup$ – JeopardyTempest Feb 24 '17 at 9:24
  • $\begingroup$ (based upon this, I'm guessing you mean the European 1.500 [= 1,500 km/hr in US)? $\endgroup$ – JeopardyTempest Feb 24 '17 at 9:30
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    $\begingroup$ Molecular motion isn't an area of expertise, but getting enough molecules imbalanced would seem to be a very very very very (very) high number of standard deviations from the mean. It seems it'd be like flipping a quintillion coins and getting 51% heads. Seems like that's not asking for much, but you it is. $\endgroup$ – JeopardyTempest Feb 24 '17 at 9:37
  • $\begingroup$ no this is not possible not even in theory wind is the result of adding energy to the atmophere usualy by heating or cooling.a storm can not suddely happen in your livingroom whitout adding a lot of energy to the air. $\endgroup$ – trond hansen Feb 24 '17 at 14:50
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    $\begingroup$ I don't see why any of this makes it a bad question? $\endgroup$ – JeopardyTempest Feb 25 '17 at 0:47

This is perhaps more of a physics question than an earth science one. Thus, answering with the caveat that I am not a practicing physicist:

Yes, it's possible. But it's VERY unlikely. Without doing the maths, I'm guessing "probably won't happen in the lifetime of the universe" unlikely. The reason for this is that there are a LOT of molecules in any macro-scale parcel of air, and a huge majority of them would all have to randomly move the same way at the same time. (plus, I'm guessing there are some Newton third-law, ie action & reaction, reasons why a spontaneous mass movement wouldn't really work)

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