Summary:
- In 1923, astronomer Edwin Hubble made a groundbreaking discovery that revealed the vastness of the universe. He observed a specific type of star called a Cepheid variable, which allowed him to measure the distance to distant galaxies.
- Hubble's discovery showed that the Milky Way galaxy was not the entire universe, but just one of many galaxies in an immense cosmic expanse. This challenged the prevailing view at the time that the universe was limited to our own galaxy.
- Hubble's work laid the foundation for our modern understanding of the expanding universe and the Big Bang theory, which explains the origin and evolution of the entire observable universe.