Forget the earth or the sun as the center of the universe. The anthropic principle puts life at the center. The universe appears fine-tuned for life. If gravity were just slightly stronger, stars would compress tightly and burn out after a few million years rather than billions. Ergo, life would never have a chance to evolve.

Life might not have originated on Earth but rather was seeded with ancient microbes that bombarded the planet billions of years ago, an idea called Panspermia (Greek for seeds everywhere.) Therefore we are aliens.*

Excerpted from David Siegel Bernstein’s Blockbuster Science