From: gdpusch@NO.xnet.SPAM.com   
      
   Earl Colby Pottinger  writes:   
      
   > gdpusch@NO.xnet.SPAM.com (Gordon D. Pusch) :   
   >   
   >> henry@spsystems.net (Henry Spencer) writes:   
   >>   
   >>> In article <3f64d304$0$173$edfadb0f@dread11.news.tele.dk>,   
   >>> Jens Kieffer-Olsen  wrote:   
   >>>>>> I take it that gravity on Mars being a mere 38% of that in the   
   >>>>>> experiment has little bearing on the evaporation rate?   
   >>>>> Very little.  And as a practical matter, it's virtually impossible to   
   >>>>> reproduce that anyway...   
   >>>>   
   >>>> Airplanes in free fall are used to produce brief periods of zero   
   >>>> gravity, so why not let a slight trust emulate .38G?   
   >>>   
   >>> No need for a slight thrust; emulating lunar or Martian gravity is just   
   >>> a matter of flying a slightly shallower parabola.  It's been done   
   >>> occasionally.  But the available time at reduced G is too short for   
   >>> some things; I think it would be quite a trick to get measurements of   
   >>> things like this in the time available.   
   >>   
   >> Moreover, there is ABSOLUTELY NO REASON to believe reduced gravity should   
   >> have any effect on the evaporation rate of water, any more than it would   
   >> affect the boiling point or freezing point of water.   
   >>   
   >> Gravity is quite simply UTTERLY IRRELEVANT to any process governed by   
   >> microscale physics. Gravitation is only important when bodies are large   
   >> and/or all other accelerations are small --- neither of which are true   
   >> of individual molecules of water.   
   >   
   > Sorry, you are wrong.  If a large body of water is boiling in a low pressure   
   > enviroment the portion of the water that is boiling is the water under less   
   > pressure than it's vapor pressure at it's temperture.  With a large/deep body   
   > of water the gravity in part determines how far down the water is boiling.   
   > The less the gravity, the more that boils at a time.   
      
   Look: We are =NOT= talking about "large bodies of water," we are talking   
   about _EVAPORATION FROM THE SURFACE OF DAMP SOIL_. Such phenomena are   
   VERY clearly controlled by MICROPHYSICS, SURFACE PRPERTIES, and WIND SPEED ---   
   =NONE= of which have any =INTRINSIC= dependence on surface gravity !!!   
      
   If you use a psychrometer on Mars, gravity is =NOT= one of the things   
   you will need to "correct" for !!!   
      
      
   -- Gordon D. Pusch   
      
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