The existence of gravity in the universe is attributed to the curvature of spacetime fabric, which is a consequence of the energy and mass within the universe. According to the theory of general relativity proposed by Albert Einstein, the presence of mass or energy warps the spacetime, causing objects to move along curved paths. This curvature of spacetime is what we experience as gravity.

In simple terms, imagine placing a heavy ball on a trampoline. The ball creates a dip or curvature in the trampoline, and if you place a smaller object near the heavy ball, it will roll down the slope of the curvature towards the heavy ball. This is analogous to how massive objects like planets and stars cause a curvature of spacetime, influencing the motion of other objects in their vicinity.

The more mass an object has, the greater the curvature of spacetime it creates. This curvature extends throughout the universe, affecting the movement and interactions of all matter and energy. Gravity, therefore, is an inherent property of spacetime, resulting from the distribution and presence of mass and energy within the universe.