perturbation  
noun uk/ˌpɜː.təˈbeɪ.ʃən/ us/ˌpɝː.t̬ɚˈbeɪ.ʃən/
  (WORRY)     
  [ U ] formal担心;烦恼 
worry
   (CHANGE)      
 [ C or U ] physics specialized摄动;扰动 
a small change in the regular movement of an object
  Perturbations in the orbit of the planet Uranus led to the discovery of Neptune in 1846. 天王星轨道的摄动使人们于1846年发现了海王星。