Cosmological distance ladder

The cosmological distance ladder is a method astronomers use to measure vast distances in the universe by stacking different techniques, each suited for specific ranges. It starts with nearby objects, like measuring distances within our galaxy using parallax (apparent shift) as Earth moves. Then, it uses these measurements to calibrate brighter methods, like observing variable stars called Cepheids. These, in turn, help determine distances to farther galaxies by analyzing their brightness. By combining these steps, scientists build a "ladder" that extends from our neighborhood to the most distant parts of the universe, enabling us to understand its scale and expansion.