According to Einstein's theory of general relativity, mass and energy can cause the curvature of spacetime. This theory describes gravity as the curvature of spacetime caused by the presence of mass and energy, rather than a force acting at a distance as described by Newton's theory of gravity.
In the framework of general relativity, the presence of mass and energy curves the fabric of spacetime, similar to how a heavy object placed on a stretched rubber sheet would cause it to curve. This curvature is what we perceive as the force of gravity.
The concept can be visualized by imagining a massive object, like a star or a planet, placed on a flat, elastic sheet representing spacetime. The object creates a depression in the sheet, causing nearby objects to roll towards it. This represents the gravitational attraction between masses.
In this curved spacetime, objects with mass or energy follow the paths dictated by the curvature. The paths of objects are not straight lines in this curved spacetime, but rather the shortest paths, known as geodesics, which are influenced by the curvature caused by mass and energy.
The degree of curvature depends on the mass and energy distribution in spacetime. The more massive an object, the greater its curvature, and the stronger its gravitational influence. For example, the intense curvature around black holes is so significant that it can trap light itself, creating an event horizon.
In summary, according to general relativity, mass and energy cause spacetime to curve, and this curvature is what we experience as the force of gravity. The theory provides a framework for understanding how mass and energy interact with the geometry of the universe.