Copy page.tpl.php to page--admin.tpl.php (note two hyphens) clear theme registry / all caches and should be good to go.

diffrent theme for admin without use theme appearance config
While learning about motion of centre of mass, I came across this statement online, 


  It is also more accurate to say that the Earth and Moon together revolve about their common center of mass. 


I am not able to understand this. Can anyone please explain this statement?
