How can humanity expand its presence beyond Earth using existing physical principles and advanced engineering? Nigel Calder, a prominent science writer and former editor of New Scientist, synthesizes concepts from physics, biology, and engineering to propose a framework for space colonization. He examines the feasibility of large-scale orbital habitats and interstellar travel, grounding his projections in the scientific understanding of the late 20th century. The text argues that the limitations to space expansion are primarily economic and political rather than strictly physical.

Experts recognize this work as a significant synthesis of space colonization concepts popular during the late 1970s and early 1980s. Readers frequently note the accessible prose style that makes complex orbital mechanics and biological constraints understandable for a general audience.