From: Rodneykelp605@hotmail.com   
      
   "Henry Spencer"  wrote in message   
   news:IAuAzu.M6E@spsystems.net...   
   > In article <1106458586.410851.123220@c13g2000cwb.googlegroups.com>,   
   > Cray74@gmail.com  wrote:   
   >>How hot would a nearly ideal black body object get in Mercury orbit?   
   >   
   > Mercury's average distance from the Sun is about 0.39 Earth's, so by the   
   > inverse-square law, a black body gets about 6.6x as much solar energy.   
   > However, energy radiated as heat is proportional to the fourth power of   
   > temperature, so temperature only needs to rise to 1.6x to match this.   
   > However however, that's *absolute* temperature, so a black body's   
   > temperature goes from around 300K at Earth to around 480K at Mercury,   
   > i.e. from around room temperature to around 200degC.   
   >   
   > Caution, I oversimplify in several ways.  Inverse square is not exactly   
   > right for a source of finite size and this effect is not negligible for   
   > Mercury; Mercury's orbit is noticeably elliptical and the semimajor axis   
   > is not really the average distance; and most important, Mercury is not an   
   > ideal black body in several ways, and that can make a big difference.   
   >   
   >>I've read that Mercury's daytime temperatures can spike to 800F, but my   
   >>calculation for average temperatures at Mercury orbit was 440K/328F.   
   >   
   > See above.  Your calculation's certainly in the right ballpark and is   
   > probably correct, but it's for an oversimplified model.   
   > --   
   > "Think outside the box -- the box isn't our friend."    |   Henry Spencer   
   >                                -- George Herbert       |   
   > henry@spsystems.net   
      
   What would be the temperature underground on mercury say from 20 to 100 feet   
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