The book goes into great depth and makes "rather difficult to support humans" the focus of the entire first 2 parts of the book. Space is indeed rather difficul

The book goes into great depth and makes "rather difficult to support humans" the focus of the entire first 2 parts of the book. Space is indeed rather difficult to support humans. The third part of the book is a 'what if they actually survived and continued to survive, fast forward 5000 years". In reality, there would be no survivors in left space, but I appreciated the final third part of the book all the same because I enjoy the fiction part of science fiction just as much as I do the science part.