According to Einstein's theory of general relativity, the force experienced during free fall is not a force in the traditional sense, but rather a manifestation of the curvature of spacetime caused by massive objects. In other words, gravity is not a force that pulls us down; instead, it is the curvature of spacetime that determines the motion of objects in its vicinity.
In the theory of general relativity, massive objects like planets or stars curve the fabric of spacetime around them. When an object, such as a person or a spacecraft, is in free fall, it is following a geodesic, which is the path that objects naturally take through curved spacetime.
From the perspective of someone in free fall, they are weightless, as there is no force acting on their body to resist the motion. They are essentially following the curvature of spacetime created by the nearby massive object.
To understand this concept, consider the example of an astronaut in space near a planet. When the astronaut is far from the planet and not influenced by its gravity, they will experience a sense of weightlessness, as there is no gravitational force acting on them. However, as they approach the planet, they will enter its gravitational field, and their trajectory will start curving toward the planet. During this free fall towards the planet, the astronaut will feel weightless because they are simply following the curvature of spacetime around the planet.
In summary, Einstein's theory of general relativity explains that the experience of gravity during free fall is not due to a force pulling us down, but rather the effect of the curvature of spacetime caused by massive objects.