Universal Expansion refers to the ongoing increase in the distance between galaxies in the universe. This phenomenon is primarily driven by the initial explosion known as the Big Bang, which occurred approximately 13.8 billion years ago. As the universe expands, galaxies move away from each other, and this movement can be observed through the redshift of light, indicating that the universe is not static but dynamic. The rate of this expansion is measured by the Hubble constant, which quantifies how fast galaxies are receding based on their distance from Earth. Recent studies suggest that the expansion is accelerating, possibly due to a mysterious force called dark energy. Understanding universal expansion helps scientists learn more about the origins and fate of the universe.