Edwin Hubble revolutionized our understanding of the universe in two major ways:
- Discovering That Other Galaxies Exist
Before Hubble’s work in the 1920s, many astronomers believed that the Milky Way contained the entire universe. Using the Hooker Telescope at Mount Wilson Observatory, Hubble studied a type of star called Cepheid variables in the Andromeda “Nebula.” He determined that it was far too distant to be part of the Milky Way, proving that Andromeda was actually a separate galaxy. This discovery expanded the known universe from a single galaxy to billions. - Demonstrating the Expansion of the Universe (Hubble’s Law)
By measuring the redshift of galaxies (the way their light stretches toward the red end of the spectrum as they move away), Hubble found that the farther a galaxy is, the faster it is receding from us. This led to the formulation of Hubble’s Law, providing the first observational evidence that the universe is expanding. This was a key foundation for the Big Bang theory, which describes how the universe originated and evolved.