- Researchers evaluated the amount of gravity a human skeleton can bear without breaking or hurting muscles.
- According to their model, humans could survive a maximum gravity of approximately 5 g (or 49 m/s²).
- People who are healthy and have developed strong lower body muscles could live normally under those harsh environments.
With the discovery of numerous new habitable exoplanets (planets outside our solar system), it’s necessary to consider physical parameters suitable for human settlement. We are talking about the fundamental parameter of a planet: gravity.
Pressure, temperature, and atmospheric composition are important aspects too, but they can be handled by modern spacesuits. It’s the gravity that plays a major role: it determines if you can stand straight and move comfortably at a normal speed from one point to another.
Recently, researchers at the University of Zagreb in Croatia evaluated the amount of gravity a human skeleton can bear without breaking or hurting muscles. By applying physical considerations to future exoplanetary biology, they deduced that ‘some’ humans could survive a maximum gravity of approximately 5 g (or 49 m/s²).
To put this into context, Earth’s gravity is 1 g (or 9.81 m/s²), which is a force experienced by a stationary object resting on Earth’s surface. If the planet has higher g, it will pull the body downward with greater force.
According to the authors, the study could be used to narrow down the search of habitable exoplanets and forecast what will happen to humans over time in space. As of January 2018, astronomers have confirmed a total of 3605 exoplanets, out of which only 469 have the mass and radii to suggest an upper limit of 5 g gravitational constant, meaning only those planets are best suited to humans.
The calculations didn’t consider any spacesuits or technology. With those, the limits can be increased significantly, but it would be quite impractical to walk around in spacesuits for the rest of your life.
How Human Body Would Change Under Strong Gravitational Force?
Using a mathematical model, they examined how human bone characteristics would change under stronger than Earth’s gravitational field (1 g). Since the pull of gravitational field is much higher when the individual is walking/running instead of resting, they concluded that 10 g pull would be enough to crack the bones of a person moving at a fast speed.
Credit: Mars Society MRDS
Although 5 g could increase the blood pressure and blood volume and could trigger fatigue, nausea and dizziness, it would be bearable. It doesn’t mean that anyone can go space and live comfortably.
They’ve carefully examined the limits at which human muscles fails to lift the body from the ground and the critical point at which skeleton breaks. Also, they modeled the leg as an inverted pendulum for the energetic expenditure of walking/running. Both methodologies suggest that athletes (with strict training) could perform regular locomotion at gravity no stronger than 5 g.
Authors mentioned that some athletes (trained for specific sports) are more likely to perform better in high gravity environments than others. People who are healthy and have developed strong lower body muscles (helps to walk) could live normally under those harsh conditions. Long distance runners, ice skaters, and cyclists would get a fair advantage in this case.