Space travel is not normal. Humans did not evolve to spend extended time in microgravity environments without having to use their muscles to stand upright, all while being bathed in cosmic radiation, and it shows in the health of astronauts: Extended stays on the International Space Station leave crew members with less bone and muscle mass, along with changes in metabolic and genetic markers associated with getting older.

“We don't really as humans understand aging, but we have these biomarkers that we can test,” Jeremy Sabo, a Ph.D. candidate in biochemistry and molecular biology at Oklahoma State University tells Inverse. “It turns out that microgravity pretty much increases the rate of all biomarker-measured aging-related things.”

Not good. Space travel needs to be extremely rapid as well as safe. We aren't nearly there yet. To read more, click here.