DESC: Take a tour of the world through more than 190 maps. Get instant vocabulary help with a dictionary and thesaurus. A perfect reference source for home, school, and work. How is a sandbar formed? What are the four main islands of Japan? How long does it take for Jupiter to orbit the Sun? Find these answers and more in the Encyclopedia Britannica Ready Reference. More than 25,000 articles on just about every aspect of life and human endeavor.