How much stronger would gravity have to be before humans would find it impossible to walk? That question could face humanity if it ever embarks on the colonization of exoplanets – planets orbiting stars other than the Sun. Now, using relatively simple calculations, Nikola Poljak, Dora Klindzic and Mateo Kruljac at the University of Zagreb in Croatia have proposed an upper limit on exoplanet gravity that would allow a trained athlete to live comfortably on a distant world.
Astrobiologists often consider the potential habitability of newly-discovered exoplanets by measuring the properties of their atmospheres. However, as the Apollo Moon missions proved, humans can use technology to survive in a distant hostile atmosphere. Gravity, however, is an environmental factor that humans would find extremely difficult (if not impossible) to control. Indeed, the three researchers argue that gravity should be a crucial parameter when evaluating whether humans could survive on a distant world.
In their study, the physicists considered how the performance of various systems in a trained athlete’s body would change when subjected to gravitational fields stronger than the Earth’s field (gᴇ). They first calculated the maximum stress a typical human skeleton could withstand while running. Inputting various properties of human bone into their equations, they ascertained an upper limit of 10gᴇ before bones begin to break.
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