Galactic expansion refers to the process by which galaxies move away from each other over time. This phenomenon is primarily driven by the Big Bang, which occurred approximately 13.8 billion years ago, leading to the universe's continuous growth. As space itself expands, galaxies are carried along with it, resulting in an observable increase in the distance between them. Astronomers have discovered that this expansion is not uniform; some galaxies are moving faster than others due to gravitational interactions. The Hubble Space Telescope has provided crucial data, allowing scientists to measure the rate of expansion, known as the Hubble constant, and to explore the universe's ultimate fate.