authority vs obstacle

authority

noun
  • A reliable, definitive source of information on a subject. 

  • Persons, regarded collectively, who occupy official positions of power; police or law enforcement. 

  • Official permission; authorisation to act in some capacity on behalf of a ruling entity. 

  • A government-owned agency that runs a revenue-generating activity for public benefit. 

  • Status as a trustworthy source of information, reputation for mastery or expertise; or claim to such status or reputation. 

  • Power or right to make or enforce rules or give orders; or a position having such power or right. 

obstacle

noun
  • Something that impedes, stands in the way of, or holds up progress, either physically or figuratively 

How often have the words authority and obstacle occurred in a corpus of books? (source: Google Ngram Viewer )