Cosmic Expansion

Cosmic expansion refers to the observation that the universe is stretching out over time, causing galaxies to move away from each other. Imagine the universe as a balloon with dots representing galaxies; as you blow up the balloon, the dots move farther apart. This expansion is driven by the fabric of space itself stretching, not objects rushing through space. It was first discovered through the observation that distant galaxies have their light shifted toward the red end of the spectrum, indicating they are receding. The rate of this expansion is described by the universe's expansion rate, known as the Hubble constant.