For our first episode of Our Island Universe, we decided to look at the concept of our universe as an island among many universes. And in a way, explain the name of this new series.
On the the evening of April 20, 1920 at the Smithsonian Museum of Natural History, two astronomers struggled to resolve the question of just how big is our Milky Way Galaxy, and in turn, just how big is our Universe?
The debate centered on the just how far away these “faint”, “fuzzy” so-called spiral nebulae are with respect to us. Were the faint, fuzzy patches of light relatively small but located within the Milky Way galaxy? Or were they large, exceedingly distant, “island universes” — a name that the 18th century philosopher Immanuel Kant coined to refer to external galaxies like our own Milky Way?
For more than 1,500 years our ancestors thought the Earth was at the center of the Solar System, and until the early part of the 20th century, astronomers thought that our own Galaxy was all there is! It is yet another reminder of humanity once again striving to find its place within the cosmic order of things.
A few years after the “Great Debate”, the great American astronomer Edwin Hubble resolved this question once and for all. Using a new kind of variable star discovered by Henrietta Leavitt, he was able to measure distances accurately and showed that these “Island Universes” are indeed external galaxies like our own. Just like the notion that we are at the center of our Solar System had to be abandoned by the Copernican revolution in the 16th century, we had to again recognize we occupy no special place, no privileged vantage point to view the cosmos.
Yet in the 95 years since that debate, the Universe we now understand is incredibly different, mysterious and exciting than those astronomers could have ever imagined!