Edwin Powell Hubble was an American astronomer who changed our understanding of our universe and our place in it. During a series of cold nights in October 1923, Hubble observed the night sky using the powerful Hooker telescope, looking for clues about the mysteries of our universe.
This is where he first spotted a star flaring up in a nova in the M31 nebula in the constellation of Andromeda. But there was something wrong. The astronomical object M31 appeared to be much further away than was believed possible, sitting a staggering 2.5 million light-years away.
This was strange because, at the time, astronomers had estimated that our galaxy was only about 200,000 light-years across. Using the help of his "computer" (someone tasked with examining photographic plates in order to measure and catalog the brightness of stars), the astronomer Henrietta Swan Leavitt, Hubble would later discover that M31 was a galaxy, which would eventually be dubbed the Andromeda Galaxy.
This discovery demonstrated that there were galaxies outside our own. (If you haven't guessed it already, the Hubble Telescope was named after the astronomer.)
More recently, we have come to understand that there may potentially be trillions of galaxies in our universe. It is no secret that our universe is unimaginably large. However, there are some scientists out there that still think we may be thinking a little too small. Welcome to the Multiverse.