While the National Aeronautics and Space Administration (NASA) considers future human trips to Mars and continues to build the International Space Station, some individuals in the field have pushed for even more. They believe that the key to human expansion in space does not lie in the building of colonies on planets or even the building of small space stations. Scientists such as Freeman Dyson and Gerard K. O'Neill proposed building gigantic structures for humans to live in. What makes their ideas even more unconventional is the size of their proposed structures. The structures proposed by O'Neill, known as O'Neill colonies, could be a dozen miles long and a few miles wide. Freeman Dyson's structures, called Dyson Spheres or Dyson Shells, would be the size of a planet's orbit. While it would only be a few meters thick, the size of the sphere would stretch for...