* Proved the existence of other galaxies: Before Hubble, it was believed that the Milky Way was the entire universe. Hubble observed distant objects called "nebulae" and discovered they were actually galaxies beyond our own. This completely changed our understanding of the scale of the universe.
* Developed Hubble's Law: Hubble's observations led him to discover a relationship between the distance of galaxies and their redshift (how much their light is shifted towards the red end of the spectrum). This relationship, known as Hubble's Law, provided the first strong evidence for the expansion of the universe.
* Pioneered the use of Cepheid variables: Hubble used these stars, which have a predictable relationship between their brightness and pulsation period, to determine the distances to galaxies. This technique revolutionized our understanding of galactic distances and the scale of the universe.
Hubble's groundbreaking work fundamentally changed our understanding of the universe and its vastness. The Hubble Space Telescope, named in his honor, carries on his legacy by providing incredibly detailed images and data that continue to push the boundaries of our knowledge.
