According to Albert Einstein's theory of general relativity, mass and energy deform or curve the fabric of space-time. This deformation is what we commonly refer to as "bending" of space-time. The concept can be understood through the following explanation:
In the theory of general relativity, space and time are not considered separate entities but are unified into a four-dimensional continuum called space-time. Mass and energy are associated with a property called "stress-energy," which includes not only the mass of an object but also its momentum and the energy it possesses.
Mass and energy cause the curvature of space-time by creating a gravitational field. The presence of mass or energy in a region of space-time causes a deformation in the surrounding space-time geometry. This deformation is similar to how a heavy object placed on a rubber sheet would cause the sheet to bend and warp.
The curvature of space-time affects the motion of objects within it, including the path of light. Objects and light follow the curvature of space-time, which is influenced by the distribution of mass and energy in the vicinity. The bending of space-time is what we perceive as the force of gravity.
To visualize this, imagine a massive object, such as a star, placed in space-time. The presence of the star causes the surrounding space-time to curve inward towards it. If another object, such as a planet or a satellite, moves near the star, it will follow a curved path determined by the shape of the curved space-time.
The bending of space-time due to mass and energy is a fundamental concept in general relativity and has been experimentally confirmed in various ways, such as through the bending of starlight by the Sun's gravity during a solar eclipse.
It's important to note that the explanation provided here is a simplified description of a complex topic. The mathematics of general relativity provides a more precise and detailed understanding of how mass and energy bend space-time, involving concepts like tensors, the Einstein field equations, and the geodesic equation.