It probably describes how the human body loses muscle mass as there is no gravity to work against. Muscles that are used for standing, walking, etc. on Earth don't get the same kind of exercise in zero - gravity.
I don't think it's a straightforward true story. Usually, such shows take liberties and combine various elements to make it more captivating. Maybe there are loose connections to reality, but it's not a pure retelling of actual events.
Yes, 'Gravity' is based on some real - world aspects. It accurately depicts the harsh environment and challenges of space. For example, the zero - gravity situations and the difficulties of spacewalking are realistically presented. The movie also takes into account the physics of space, like how objects move in microgravity.
No, gravity isn't a true story. It's a physical phenomenon described by laws and principles of physics. We understand it through experiments and observations, not as a narrative with characters and events.