Some people aren’t afraid to think big! Just trying to fully grasp the magnitude of some of the articles in these Wikipedia categories can put you in a solemn mood.

• http://en.wikipedia.org/wiki/Category:Planetary_engineering
• http://en.wikipedia.org/wiki/Category:Futurology
  
• http://en.wikipedia.org/wiki/Category:Megastructures

I especially like some of the writing in these and other Wiki articles.

A choice expert from User:Beowulf314159 in the article on the Matrioshka Brain:

The idea of the matrioshka brain violates none of the currently known laws of physics, although the engineering details of building such a structure would be staggering, as such a project would require the “disassembly” of significant portions (if not all) of the planetary system of the star for construction materials.
…

The possible uses of such an immense computational resource tax the imagination.