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parallaxmore about parallax

parallax

 

  2  definitions  found 
 
  From  Webster's  Revised  Unabridged  Dictionary  (1913)  [web1913]: 
 
  Parallax  \Par"al*lax\,  n.  [Gr.  ?  alternation,  the  mutual 
  inclination  of  two  lines  forming  an  angle,  fr  ?  to  change  a 
  little,  go  aside,  deviate;  ?  beside,  beyond  +  ?  to  change: 
  cf  F.  parallaxe.  Cf  {Parallel}.] 
  1.  The  apparent  displacement,  or  difference  of  position,  of 
  an  object,  as  seen  from  two  different  stations,  or  points 
  of  view. 
 
  2.  (Astron.)  The  apparent  difference  in  position  of  a  body 
  (as  the  sun,  or  a  star)  as  seen  from  some  point  on  the 
  earth's  surface,  and  as  seen  from  some  other  conventional 
  point,  as  the  earth's  center  or  the  sun. 
 
  {Annual  parallax},  the  greatest  value  of  the  heliocentric 
  parallax,  or  the  greatest  annual  apparent  change  of  place 
  of  a  body  as  seen  from  the  earth  and  sun;  as  the  annual 
  parallax  of  a  fixed  star. 
 
  {Binocular  parallax},  the  apparent  difference  in  position  of 
  an  object  as  seen  separately  by  one  eye,  and  then  by  the 
  other  the  head  remaining  unmoved. 
 
  {Diurnal},  or  {Geocentric},  {parallax},  the  parallax  of  a 
  body  with  reference  to  the  earth's  center.  This  is  the 
  kind  of  parallax  that  is  generally  understood  when  the 
  term  is  used  without  qualification. 
 
  {Heliocentric  parallax},  the  parallax  of  a  body  with 
  reference  to  the  sun,  or  the  angle  subtended  at  the  body 
  by  lines  drawn  from  it  to  the  earth  and  sun;  as  the 
  heliocentric  parallax  of  a  planet. 
 
  {Horizontal  parallax},  the  geocentric  parallx  of  a  heavenly 
  body  when  in  the  horizon,  or  the  angle  subtended  at  the 
  body  by  the  earth's  radius. 
 
  {Optical  parallax},  the  apparent  displacement  in  position 
  undergone  by  an  object  when  viewed  by  either  eye  singly. 
  --Brande  &  C. 
 
  {Parallax  of  the  cross  wires}  (of  an  optical  instrument), 
  their  apparent  displacement  when  the  eye  changes  its 
  position,  caused  by  their  not  being  exactly  in  the  focus 
  of  the  object  glass. 
 
  {Stellar  parallax},  the  annual  parallax  of  a  fixed  star. 
 
  From  WordNet  r  1.6  [wn]: 
 
  parallax 
  n  :  the  apparent  displacement  of  an  object  as  seen  from  two 
  different  points  that  are  not  on  a  line  with  the  object




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