Gravitational force and universal expansion are two distinct phenomena in physics that operate on different scales and have different effects.
Gravitational Force: Gravitational force is a fundamental force of nature that acts between any two objects with mass. It is responsible for the attraction between objects and is described by Newton's law of universal gravitation or, on a larger scale, by Einstein's general theory of relativity. Gravitational force becomes significant when objects have a mass comparable to planets, stars, or other massive celestial bodies. It determines the motion of planets around the Sun, the orbits of moons around planets, and various other gravitational interactions in the universe.
Universal Expansion: Universal expansion, also known as cosmic expansion, refers to the overall expansion of the universe itself. It is a concept derived from observations in cosmology, particularly from the redshift of light from distant galaxies. According to the prevailing cosmological model, the Big Bang theory, the universe began with a hot, dense state and has been expanding ever since. The expansion is occurring at all scales and is described by Hubble's law, which states that galaxies are moving away from each other, with the velocity of recession being directly proportional to their distance. This expansion is happening on a vast cosmic scale, affecting the structure and evolution of the entire universe.
While both gravitational force and universal expansion involve the concept of gravity, they operate on different scales and have different consequences. Gravitational force acts on a local scale, determining the motion and interactions of objects with mass, while universal expansion describes the expansion of space itself on a cosmic scale, affecting the large-scale structure and evolution of the universe.