The universe is massive, and humans occupy an infinitesimal part. Do we matter? In this ingenious mixture of cosmology, evolutionary biology and philosophy, Columbia Astrobiology Center director Scharf (Gravity's Engines: How Bubble-Blowing Black Holes Rule Galaxies, Stars, and Life in the Cosmos, 2012) gives a thumbs up.
Throughout history, all cultures believed that the Earth occupied the center of the universe. By the 17th century, scientists knew that it didn’t. Named in honor of the Polish astronomer who placed the sun at the heart of the solar system, the Copernican Cosmological Principle states that we do not occupy a privileged place; the Earth is just an ordinary planet orbiting an undistinguished star in a vast cosmos. Yet 20th-century observers have begun to notice that the universe seems fine-tuned in our favor. If a few constants—the strength of gravity in relation to electromagnetism, the percent of matter converted to energy in stars—were slightly different, stars would not have been able to form in the early universe, so life would never have developed. If our planet is ordinary, the universe should be full of them. This turns out to be true, with probably 20 billion in our galaxy. Sadly, these vary widely in size and composition and move in wildly irregular orbits; our well-behaved, symmetrical solar system is unusual. On the plus side, primitive organisms appeared quickly as our planet cooled. Earth’s carbon chemistry is ubiquitous throughout the cosmos, so the starter mix for life seems easy to come by.
Most readers will agree with Scharf’s complex but astute arguments that “[w]hile we cannot be at the center of what we now know to be a centerless universe, we nonetheless occupy a very interesting place in it—in time, space, and scale.”