For Roach, space is a hostile environment, and survival teeters on the delicate balance of extremes. Too much gravity can crush organs, while too little gravity weakens bones. The cramped confinement of a module can lead to frustration, while the infinity of the expanding universe can evoke an overwhelming anxiety. In general, “Humans don’t belong in space. Everything about us evolved for life on Earth” (58). This statement is not a deterrent to space exploration, but a lens to view the impressive ingenuity and devotion that motivate scientists and astronauts to make the impossible possible.

Roach makes the risks of space travel explicit when she describes the harrowing shockwaves and centrifugal forces that can emulsify organs or sever the brain from the spinal cord. Astronauts travel at literally death-defying speeds and with unknown risks—for instance, scientists are uncertain if the human body can survive prolonged exposure to zero gravity and radiation. Because of these risks and unknowns, Roach applauds the efforts of scientists and volunteers who devote their lives to ensuring astronauts’ safety.

Roach acknowledges Jon Clark’s work in space medicine as a commitment to “protect those bodies, to keep astronauts and space tourists alive, to keep families intact” (259).