• Entry
  • Reader's guide
  • Entries A-Z
  • Subject index

The moon, a natural satellite of the earth, was formed at approximately the same time as the earth, roughly 4.6 billion years ago. The origin of the moon remains the subject of debate; differing theories have been advanced, each with its ...

Loading
  • Loading...
locked icon

Sign in to access this content

Get a 30 day FREE TRIAL

  • Watch videos from a variety of sources bringing classroom topics to life
  • Read modern, diverse business cases
  • Explore hundreds of books and reference titles