I think that people use a rule of thumb when deciding what things in life are worth learning. Most people seek knowledge in one of the following three categories:

• What many other people learn (calculus, C++, and so on)
• What is easy to learn (hula-hooping, Ruby, and so on)
• What has value that is easy to appreciate (thermonuclear physics, for example, or that ridiculously loud whistle where you stick your fingers in your mouth) -- Land of Lisp. Conrad Barski.