One of the men instrumental in providing other galaxies exist outside our own was what?

One of the men instrumental in providing evidence for the existence of other galaxies outside our own was Edwin Hubble. In the 1920s, Hubble used observations from the Mt. Wilson Observatory to demonstrate that certain nebulae were not merely gas clouds within the Milky Way, but rather distant galaxies. His work led to the formulation of Hubble's Law, which describes the relationship between a galaxy's distance and its recessional velocity, fundamentally changing our understanding of the universe. This evidence established that the universe is vast and filled with countless galaxies beyond our own.