This article was originally published with the title “Cosmic (In)Significance.”

Is Earth’s Life Unique in the Universe?
To know whether life exists beyond Earth, we must come to terms with our own significance in the universe. Are we uniquely special or merely mediocre?

7-15-2014 | Caleb Scharf

Adapted from The Copernicus Complex: Our Cosmic Significance in a Universe of Planets and Probabilities, by Caleb Scharf, by arrangement with Scientific American/Farrar, Straus and Giroux, LLC (US) and Penguin Press (UK). Copyright © 2014 by Caleb Scharf.

We all reside on a small planet orbiting a single, middle-aged star that is one of some 200 billion stars in the great swirl of matter that makes up the Milky Way galaxy. Our galaxy is but one of an estimated several hundred billion such structures in the observable universe—a volume that now stretches in all directions from us for more than 270,000,000,000,000,000,000,000 (2.7 × 1023) miles.

By any paltry human standard, this is an awful lot of stuff and an awfully large amount of room. Our species has sprung into existence within the barest instant of this universe’s enormously long span of history, and it looks like there will be an even longer future that may or may not contain us. The quest to try to find our place, to discover our relevance, can seem like a monumental joke. We must be appallingly silly to imagine we can find any importance for ourselves at all.

Yet we are trying to do just that, despite our apparent mediocrity, which became evident when Renaissance scholar Nicolaus Copernicus decentralized Earth from the solar system around 500 years ago. His idea has been one of the greatest scientific guides for the past few hundred years and a critical signpost on our journey to discern the underlying structure of the cosmos and the nature of reality.

In our efforts to assess our significance, we face a conundrum: Some discoveries and theories suggest life could easily be ordinary and common, and others suggest the opposite. How do we begin to pull together our knowledge of the cosmos—from bacteria to the big bang—to explain whether or not we are special? And as we learn more about our place in the universe, what does it all imply for our efforts to find out if there are other living things out there? How do we take the next steps?

More.