G-Forces are a form of acceleration that causes the accelerating object to experience a force acting in the opposite direction to the acceleration. In the Bioastronautics Data Book from NASA in 1973, the authors wrote, “ Few units of measurement have been more misused and misunderstood than the unit ‘G’.” And that’s because the term “G” doesn’t represent actual gravity, but the apparent forces of gravity- it tells us how much force is acting on an object.
How much gravity can the human body take? In the early 20th century, we thought the limit was 18Gs based on observational data of plane crashes. But when scientists actually tested this by strapping a man to a rocket, they found he was able to survive 46.2 Gs! He was injured, but survived. We still haven’t found an official upper limit.