Everything we know about how planets form and how life first appears leads us to believe that the human civilization that exists on Earth is not an anomaly. The presence of alien life should be amply demonstrated, but we don’t. Who is present where? Wade Roush, a science and technology writer, tackles one of science’s biggest open questions in this installment of the MIT Press Essential Knowledge series: are there other planets with life, intelligent or not?
This conundrum, first posed by the eminent physicist Enrico Fermi, has been the subject of decades of discussion, conjecture, and, more recently, some actual science. Roush outlines the issue in its historical and contemporary context and provides a synopsis of the most recent research from astronomers and astrobiologists. He talks about the long history of alien skepticism (humans have debated the idea for thousands of years), the development of SETI (the Search for Extraterrestrial Intelligence) as a scientific field in the 1960s, and how scientists use radio and optical techniques to scan for signals, as well as advancements in astrobiology (the study of how life might arise in non-Earthlike environments) and exoplanet research (the discovery of planets outside our solar system). Finally, he analyzes potential solutions to the Fermi paradox and offers ideas for refocusing SETI efforts that would improve the likelihood of doing so—and discovering extraterrestrial life.