If we want to colonize another world, it will be crucial to find a planet with a gravitational field where humans can survive and flourish. If the gravity is too great, our blood will be pulled down into our legs, our bones may break, and we may even be helplessly pressed to the ground. Before we even think about landing on a new planet, we should know the gravitational limit of the human body.
This was researched by professors and scientists from the University of Zagreb in Croatia. The team first calculated the compressive strength of a human bone. Based on the average bone of a mammal, they calculated that the human skeleton can withstand a gravitational force more than 90 times that of the Earth. But this is the case when someone stands still. When we start to run, the load on our bones, when they flex and bend, increases tenfold. This means that we could be running across a planet with a gravitational field about ten times that of the Earth before our bones begin to crack.
Realistic targets for humans
The researchers say that the load on your legs and core muscles in a strong gravitational field feels very similar to carrying a large weight on your shoulders. Because of that, they decided to analyze the deeds of Hafþór Júlíus Björnsson – one of the strongest people on our planet. The Icelandic man is most easily recognized as Sir Gregor “The Mountain” Clegane from the Game of Thrones TV series, but he has also won Arnold Strongman Classic, Europe’s Strongest Man, and World’s Strongest Man competitions. One of his most impressive records is taking a few steps with a giant 1430 pound (~650 kg) log on his back. Based on his strength, it is believed that he would be able to take a short walk on an exoplanet with a gravitational field around 4.6 times ours.
The team estimated that it would be more realistic for ordinary people to target an exoplanet with a gravitational force three to four times that of the Earth – and they would still need rigorous training to achieve the level of muscle strength of elite athletes.
This study should help us focus on finding more appropriate habitable exoplanets. “Now we know that there is no point in hoping to settle planets with high g-values,” said the lead author Nikola Poljak.
Many of the rocky exoplanets we find are much larger than our own planet. Astronomers call them super-earths. Without going there it’s difficult to determine what the gravity of another world is, because the density may vary from world to world, but usually, even if the planet is slightly larger, it will have a much stronger gravitational pull.