Under general relativity, gravity is not a force. Instead it is a distortion of spacetime. Objects in free-fall move along geodesics (straight lines) in spacetime, as seen in the inertial frame of reference on the right. When standing on Earth we experience a frame of reference that is accelerating upwards, causing objects in free-fall to move along parabolas, as seen on the left.

Source: Gravity is not a force

Fascinating.